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id	title	slug	type	status	content	archieml	archieml_update_statistics	published_at	updated_at	gdocSuccessorId	authors	excerpt	created_at_in_wordpress	updated_at_in_wordpress	featured_image	formattingOptions	markdown	wpApiSnapshot
44720	Can we reduce fertilizer use without sacrificing food production?	reducing-fertilizer-use	post	publish	<!-- wp:html --> <div class="blog-info"> <p>Our World in Data presents the data and research to make progress against the world’s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href="https://ourworldindata.org/fertilizers" target="_blank" rel="noopener">Fertilizers</a></strong> and <strong><a href="https://ourworldindata.org/crop-yields" target="_blank" rel="noopener">Crop Yields</a></strong>.</p> <p>Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.</p> </div> <!-- /wp:html --> <!-- wp:owid/summary --> <!-- wp:paragraph --> <p>Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>When they're overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p> <!-- /wp:paragraph --> <!-- /wp:owid/summary --> <!-- wp-block-tombstone 44888 --> <!-- wp:paragraph --> <p>One of the world’s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). <a href="https://www.nature.com/articles/nature25785">Pursuing sustainable productivity with millions of smallholder farmers</a>. <em>Nature</em>, 555(7696), 363-366.{/ref} They were successful. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use <em>decreased</em> by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn’t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>It’s often assumed that fertilizer use – alongside the pollution it creates – and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world’s soils, we could produce our own. Their innovation (the <a href="https://en.wikipedia.org/wiki/Haber_process">Haber-Bosch process</a>) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. <em>Nature Geoscience</em>, 1(10), 636-639.<br><br>Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that <a href="https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed">every second person</a> reading this has them to thank for being alive today.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p><a href="http://ourworldindata.org/fertilizers">Fertilizers</a> help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What’s less obvious is that this has a large environmental benefit. Higher <a href="http://ourworldindata.org/crop-yields">crop yields</a> mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we <a href="https://ourworldindata.org/grapher/land-sparing-by-crop">would need</a> almost three times as much farmland today (to meet food production in 2019). Crop yield gains have ‘saved’ 1.7 billion hectares of land. That’s equal to an area the size of the USA and Brazil combined.{/ref}  This means we can protect forests and maintain natural habitats.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>But it’s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p> <!-- /wp:paragraph --> <!-- wp:heading {"level":3} --> <h3>There are large differences in fertilizer use across the world</h3> <!-- /wp:heading --> <!-- wp:columns {"className":"is-style-side-by-side"} --> <div class="wp-block-columns is-style-side-by-side"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called ‘limiting nutrients’. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>There are 100-fold differences between countries. In many of the world’s poorest countries – particularly across Sub-Saharan Africa – farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By ‘football’, I mean ‘soccer’.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>This has led to a divided world:</p> <!-- /wp:paragraph --> <!-- wp:list --> <ul><li>In many poorer countries we need <em>more</em> fertilizers. Improvements in crop yields have been slow, and <a href="https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap">large yield gaps</a> could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). <a href="https://www.nature.com/articles/nature11420">Closing yield gaps through nutrient and water management</a>. <em>Nature</em>, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.<br><br>This is why it’s damaging for agencies, such as the United Nations Development Programme to continually <a href="https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20">promote the message</a> that the less fertilizer, the better. It’s not good for humans, or the environment.<br></li><li>But, as we will see, many countries are <em>overapplying</em> nitrogen. They could cut back without negatively affecting their crop yields.</li></ul> <!-- /wp:list --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:columns {"className":"is-style-side-by-side"} --> <div class="wp-block-columns is-style-side-by-side"><!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:heading {"level":3} --> <h3>Nitrogen use efficiency: balancing yields and the need for nutrient inputs</h3> <!-- /wp:heading --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>Using lots of fertilizer wouldn’t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn’t.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the ‘nitrogen use efficiency’ (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was <em>not</em> used by the crops.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Soon we will see that some countries have a <em>very</em> high NUE – greater than 100%. You might assume that this is good news. In fact, it’s often the opposite. This means they are <em>undersupplying</em> nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil – a process called ‘nitrogen mining’. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). <a href="https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta">50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland</a>. <em>Environmental Research Letters</em>, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE – less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/nitrogen-use-efficiency" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:owid/additional-information --> <!-- wp:heading {"level":3} --> <h3><strong>How nitrogen use efficiency has changed over time</strong></h3> <!-- /wp:heading --> <!-- wp:columns {"className":"is-style-sticky-right"} --> <div class="wp-block-columns is-style-sticky-right"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>We can also look at the <em>change</em> in NUE over time, which shows us some interesting differences between countries. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen <em>outputs</em>: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen <em>inputs</em>: added in the form of fertilizers, manure, or natural soil uptake.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably <em>undersupplying</em> nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields <em>are</em> increasing, but they need increasing amounts of nitrogen to achieve this. It’s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move <em>back</em> along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It’s increasing yields whilst <em>reducing</em> the amount of fertilizers used. NUE is improving.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields <em>and</em> apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- /wp:owid/additional-information --> <!-- wp:heading {"level":3} --> <h3>We can reduce nitrogen pollution without a decline in yields</h3> <!-- /wp:heading --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>We might assume that all countries could achieve the same high NUE. But, maybe it’s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can’t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>How can we better understand which countries are doing well in these yield-fertilizer trade-offs?</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in <em>Nature</em>.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href="https://www.nature.com/articles/s43016-020-00185-6">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country’s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they <em>should</em> be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a ‘natural experiment’ where the environmental conditions are held constant, and policy decisions are the changeable variable.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:image {"id":44723,"sizeSlug":"full","linkDestination":"none"} --> <figure class="wp-block-image size-full"><img src="https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png" alt="" class="wp-image-44723"/><figcaption>Discontinuities in vegetation at country borders{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href="https://www.nature.com/articles/s43016-020-00185-6">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref}</figcaption></figure> <!-- /wp:image --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p><strong>They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields – increasing yield gaps by only 1%.</strong></p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains <em>relative to their neighbors</em>. Positive values – shown in orange and red – mean a country causes <em>more</em> pollution than necessary for the yields that it achieves. Negative values – shown in blue – means a country causes <em>less</em>.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>There are a couple of important points we need to keep in mind. All of these values are measured <em>relative to a country’s neighbors</em>. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:heading {"level":3} --> <h3>How can we use nitrogen more efficiently?</h3> <!-- /wp:heading --> <!-- wp:columns --> <div class="wp-block-columns"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today’s middle-income countries kickstarted their ‘Green Revolution’ and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). <a href="https://doi.org/10.2499/p15738coll2.133652.%7B/ref">https://doi.org/10.2499/p15738coll2.133652.</a>{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement ‘precision farming’, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929">Precision farming at the nexus of agricultural production and the environment</a>. Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). <a href="https://www.pnas.org/content/114/24/6148.short">Opinion: Smart farming is key to developing sustainable agriculture</a>. <em>Proceedings of the National Academy of Sciences</em>, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there’s an opportunity to improve how efficiently plants use it too.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Let’s not forget that one of the most promising solutions – and one we often overlook – is the simplest and oldest of all. Legumes – crops such as beans, peas and lentils – perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called ‘biological fixation’. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes – either on their own, or alongside other crops – is one of the easiest ways that we can bring nitrogen into the soil.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Finally, there’s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.  Large policy changes and technological advancements are often needed to make a large difference, but we shouldn’t underestimate the impact that education can make.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn’t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- wp:separator {"className":"is-style-wide"} --> <hr class="wp-block-separator is-style-wide"/> <!-- /wp:separator --> <!-- wp:heading {"level":5} --> <h5>Explore more of our work at <em>Our World in Data</em></h5> <!-- /wp:heading --> <!-- wp:owid/prominent-link {"title":"Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers?","linkUrl":"http://ourworldindata.org/excess-fertilizer","mediaId":44782,"mediaUrl":"https://owid.cloud/app/uploads/2021/09/excess-fertilizer.png","mediaAlt":"","className":"is-style-thin"} --> <!-- wp:paragraph --> <p></p> <!-- /wp:paragraph --> <!-- /wp:owid/prominent-link --> <!-- wp:owid/prominent-link {"title":"Fertilizers Data Explorer","linkUrl":"ourworldindata.org/explorers/fertilizers","mediaId":39373,"mediaUrl":"https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png","mediaAlt":"COVID-19 data explorer","className":"is-style-thin"} --> <!-- wp:paragraph --> <p>Explore fertilizer use and its impacts across the world in our data explorer.</p> <!-- /wp:paragraph --> <!-- /wp:owid/prominent-link --> <!-- wp:owid/prominent-link {"title":"Crop Yields Data Explorer","linkUrl":"ourworldindata.org/explorers/crop-yields","mediaId":39373,"mediaUrl":"https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png","mediaAlt":"COVID-19 data explorer","className":"is-style-thin"} --> <!-- wp:paragraph --> <p>Explore crop yields across the world in our data explorer.</p> <!-- /wp:paragraph --> <!-- /wp:owid/prominent-link -->	{ "id": "wp-44720", "slug": "reducing-fertilizer-use", "content": { "toc": [], "body": [ { "type": "text", "value": [ { "text": "Our World in Data presents the data and research to make progress against the world\u2019s largest problems.", "spanType": "span-simple-text" }, { "spanType": "span-newline" }, { "text": "This blog post draws on data and research discussed in our entries on ", "spanType": "span-simple-text" }, { "children": [ { "url": "https://ourworldindata.org/fertilizers", "children": [ { "text": "Fertilizers", "spanType": "span-simple-text" } ], "spanType": "span-link" } ], "spanType": "span-bold" }, { "text": " and ", "spanType": "span-simple-text" }, { "children": [ { "url": "https://ourworldindata.org/crop-yields", "children": [ { "text": "Crop Yields", "spanType": "span-simple-text" } ], "spanType": "span-link" } ], "spanType": "span-bold" }, { "text": ".", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "type": "text", "value": [ { "text": "Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. ", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "When they're overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries ", "spanType": "span-simple-text" }, { "children": [ { "text": "can", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " reduce fertilizer use without sacrificing food production.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "callout", "title": "Summary", "parseErrors": [] }, { "type": "text", "value": [ { "text": "One of the world\u2019s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). ", "spanType": "span-simple-text" }, { "url": "https://www.nature.com/articles/nature25785", "children": [ { "text": "Pursuing sustainable productivity with millions of smallholder farmers", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", 555(7696), 363-366.{/ref} They were successful.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use ", "spanType": "span-simple-text" }, { "children": [ { "text": "decreased", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn\u2019t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "It\u2019s often assumed that fertilizer use \u2013 alongside the pollution it creates \u2013 and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world\u2019s soils, we could produce our own. Their innovation (the ", "spanType": "span-simple-text" }, { "url": "https://en.wikipedia.org/wiki/Haber_process", "children": [ { "text": "Haber-Bosch process", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ") at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature Geoscience", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", 1(10), 636-639.", "spanType": "span-simple-text" }, { "spanType": "span-newline" }, { "spanType": "span-newline" }, { "text": "Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that ", "spanType": "span-simple-text" }, { "url": "https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed", "children": [ { "text": "every second person", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " reading this has them to thank for being alive today.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "url": "http://ourworldindata.org/fertilizers", "children": [ { "text": "Fertilizers", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What\u2019s less obvious is that this has a large environmental benefit. Higher ", "spanType": "span-simple-text" }, { "url": "http://ourworldindata.org/crop-yields", "children": [ { "text": "crop yields", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we ", "spanType": "span-simple-text" }, { "url": "https://ourworldindata.org/grapher/land-sparing-by-crop", "children": [ { "text": "would need", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " almost three times as much farmland today (to meet food production in 2019). Crop yield gains have \u2018saved\u2019 1.7 billion hectares of land. That\u2019s equal to an area the size of the USA and Brazil combined.{/ref} \u00a0This means we can protect forests and maintain natural habitats.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But it\u2019s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries ", "spanType": "span-simple-text" }, { "children": [ { "text": "can", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " reduce fertilizer use without sacrificing food production.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "There are large differences in fertilizer use across the world", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called \u2018limiting nutrients\u2019. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "There are 100-fold differences between countries. In many of the world\u2019s poorest countries \u2013 particularly across Sub-Saharan Africa \u2013 farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By \u2018football\u2019, I mean \u2018soccer\u2019.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This has led to a divided world:", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "list", "items": [ { "type": "text", "value": [ { "text": "In many poorer countries we need ", "spanType": "span-simple-text" }, { "children": [ { "text": "more", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " fertilizers. Improvements in crop yields have been slow, and ", "spanType": "span-simple-text" }, { "url": "https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap", "children": [ { "text": "large yield gaps", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). ", "spanType": "span-simple-text" }, { "url": "https://www.nature.com/articles/nature11420", "children": [ { "text": "Closing yield gaps through nutrient and water management", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.", "spanType": "span-simple-text" }, { "spanType": "span-newline" }, { "spanType": "span-newline" }, { "text": "This is why it\u2019s damaging for agencies, such as the United Nations Development Programme to continually ", "spanType": "span-simple-text" }, { "url": "https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20", "children": [ { "text": "promote the message", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " that the less fertilizer, the better. It\u2019s not good for humans, or the environment.", "spanType": "span-simple-text" }, { "spanType": "span-newline" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But, as we will see, many countries are ", "spanType": "span-simple-text" }, { "children": [ { "text": "overapplying", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " nitrogen. They could cut back without negatively affecting their crop yields.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "parseErrors": [] }, { "left": [ { "url": "https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland", "type": "chart", "parseErrors": [] } ], "type": "sticky-right", "right": [ { "url": "https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU", "type": "chart", "parseErrors": [] } ], "parseErrors": [] }, { "text": [ { "text": "Nitrogen use efficiency: balancing yields and the need for nutrient inputs", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "left": [ { "type": "text", "value": [ { "text": "Using lots of fertilizer wouldn\u2019t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn\u2019t.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the \u2018nitrogen use efficiency\u2019 (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was ", "spanType": "span-simple-text" }, { "children": [ { "text": "not", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " used by the crops.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Soon we will see that some countries have a ", "spanType": "span-simple-text" }, { "children": [ { "text": "very", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " high NUE \u2013 greater than 100%. You might assume that this is good news. In fact, it\u2019s often the opposite. This means they are ", "spanType": "span-simple-text" }, { "children": [ { "text": "undersupplying", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil \u2013 a process called \u2018nitrogen mining\u2019. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). ", "spanType": "span-simple-text" }, { "url": "https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta", "children": [ { "text": "50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". ", "spanType": "span-simple-text" }, { "children": [ { "text": "Environmental Research Letters", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE \u2013 less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "sticky-right", "right": [ { "url": "https://ourworldindata.org/grapher/nitrogen-use-efficiency", "type": "chart", "parseErrors": [] } ], "parseErrors": [] }, { "type": "gray-section", "items": [ { "text": [ { "text": "Additional information", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "expandable-paragraph", "items": [ { "left": [ { "type": "text", "value": [ { "text": "We can also look at the ", "spanType": "span-simple-text" }, { "children": [ { "text": "change", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " in NUE over time, which shows us some interesting differences between countries.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen ", "spanType": "span-simple-text" }, { "children": [ { "text": "outputs", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ": the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen ", "spanType": "span-simple-text" }, { "children": [ { "text": "inputs", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ": added in the form of fertilizers, manure, or natural soil uptake.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably ", "spanType": "span-simple-text" }, { "children": [ { "text": "undersupplying", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields ", "spanType": "span-simple-text" }, { "children": [ { "text": "are", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " increasing, but they need increasing amounts of nitrogen to achieve this. It\u2019s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move ", "spanType": "span-simple-text" }, { "children": [ { "text": "back", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It\u2019s increasing yields whilst ", "spanType": "span-simple-text" }, { "children": [ { "text": "reducing", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " the amount of fertilizers used. NUE is improving.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields ", "spanType": "span-simple-text" }, { "children": [ { "text": "and", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "sticky-right", "right": [ { "url": "https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA", "type": "chart", "parseErrors": [] } ], "parseErrors": [] } ], "parseErrors": [] } ], "parseErrors": [] }, { "text": [ { "text": "We can reduce nitrogen pollution without a decline in yields", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "left": [ { "type": "text", "value": [ { "text": "So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark.\u00a0", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "We might assume that all countries could achieve the same high NUE. But, maybe it\u2019s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can\u2019t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "How can we better understand which countries are doing well in these yield-fertilizer trade-offs?", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ".{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). ", "spanType": "span-simple-text" }, { "url": "https://www.nature.com/articles/s43016-020-00185-6", "children": [ { "text": "Countries influence the trade-off between crop yields and nitrogen pollution", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature Food", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", ", "spanType": "span-simple-text" }, { "children": [ { "text": "1", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": "(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country\u2019s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they ", "spanType": "span-simple-text" }, { "children": [ { "text": "should", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a \u2018natural experiment\u2019 where the environmental conditions are held constant, and policy decisions are the changeable variable.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "sticky-right", "right": [ { "alt": "", "size": "wide", "type": "image", "filename": "nitrogen-pollution-discontinuity.png", "parseErrors": [] } ], "parseErrors": [] }, { "left": [ { "type": "text", "value": [ { "text": "Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. ", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "children": [ { "text": "They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields \u2013 increasing yield gaps by only 1%.", "spanType": "span-simple-text" } ], "spanType": "span-bold" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains ", "spanType": "span-simple-text" }, { "children": [ { "text": "relative to their neighbors", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ". Positive values \u2013 shown in orange and red \u2013 mean a country causes ", "spanType": "span-simple-text" }, { "children": [ { "text": "more", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " pollution than necessary for the yields that it achieves. Negative values \u2013 shown in blue \u2013 means a country causes ", "spanType": "span-simple-text" }, { "children": [ { "text": "less", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ".", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "There are a couple of important points we need to keep in mind. All of these values are measured ", "spanType": "span-simple-text" }, { "children": [ { "text": "relative to a country\u2019s neighbors", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ". A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "sticky-right", "right": [ { "url": "https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution", "type": "chart", "parseErrors": [] } ], "parseErrors": [] }, { "text": [ { "text": "How can we use nitrogen more efficiently?", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today\u2019s middle-income countries kickstarted their \u2018Green Revolution\u2019 and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). ", "spanType": "span-simple-text" }, { "url": "https://doi.org/10.2499/p15738coll2.133652.%7B/ref", "children": [ { "text": "https://doi.org/10.2499/p15738coll2.133652.", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": "{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement \u2018precision farming\u2019, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). ", "spanType": "span-simple-text" }, { "url": "https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929", "children": [ { "text": "Precision farming at the nexus of agricultural production and the environment", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). ", "spanType": "span-simple-text" }, { "url": "https://www.pnas.org/content/114/24/6148.short", "children": [ { "text": "Opinion: Smart farming is key to developing sustainable agriculture", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". ", "spanType": "span-simple-text" }, { "children": [ { "text": "Proceedings of the National Academy of Sciences", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there\u2019s an opportunity to improve how efficiently plants use it too.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Let\u2019s not forget that one of the most promising solutions \u2013 and one we often overlook \u2013 is the simplest and oldest of all. Legumes \u2013 crops such as beans, peas and lentils \u2013 perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called \u2018biological fixation\u2019. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes \u2013 either on their own, or alongside other crops \u2013 is one of the easiest ways that we can bring nitrogen into the soil.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Finally, there\u2019s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.\u00a0 Large policy changes and technological advancements are often needed to make a large difference, but we shouldn\u2019t underestimate the impact that education can make.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn\u2019t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "Explore more of our work at ", "spanType": "span-simple-text" }, { "children": [ { "text": "Our World in Data", "spanType": "span-simple-text" } ], "spanType": "span-italic" } ], "type": "heading", "level": 4, "parseErrors": [] }, { "url": "http://ourworldindata.org/excess-fertilizer", "type": "prominent-link", "title": "Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers?", "description": "", "parseErrors": [] }, { "url": "ourworldindata.org/explorers/fertilizers", "type": "prominent-link", "title": "Fertilizers Data Explorer", "description": "Explore fertilizer use and its impacts across the world in our data explorer.", "parseErrors": [] }, { "url": "ourworldindata.org/explorers/crop-yields", "type": "prominent-link", "title": "Crop Yields Data Explorer", "description": "Explore crop yields across the world in our data explorer.", "parseErrors": [] } ], "type": "article", "title": "Can we reduce fertilizer use without sacrificing food production?", "authors": [ "Hannah Ritchie" ], "excerpt": "Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.", "dateline": "September 9, 2021", "subtitle": "Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.", "sidebar-toc": false, "featured-image": "reducing-fertilizer.png" }, "createdAt": "2021-08-31T12:33:41.000Z", "published": false, "updatedAt": "2021-09-09T15:04:21.000Z", "revisionId": null, "publishedAt": "2021-09-09T11:33:00.000Z", "relatedCharts": [], "publicationContext": "listed" }	{ "errors": [ { "name": "unexpected wp component tag", "details": "Found unhandled wp:comment tag list" }, { "name": "too many figcaption elements after archieml transform", "details": "Found 7 elements after transforming to archieml" }, { "name": "unexpected wp component tag", "details": "Found unhandled wp:comment tag image" }, { "name": "unhandled html tag found", "details": "Encountered the unhandled tag hr" }, { "name": "unexpected wp component tag", "details": "Found unhandled wp:comment tag separator" } ], "numBlocks": 37, "numErrors": 5, "wpTagCounts": { "html": 6, "list": 1, "image": 1, "column": 14, "columns": 7, "heading": 6, "paragraph": 49, "separator": 1, "owid/summary": 1, "owid/prominent-link": 3, "owid/additional-information": 1 }, "htmlTagCounts": { "p": 51, "h3": 5, "h5": 1, "hr": 1, "ul": 1, "div": 22, "figure": 1, "iframe": 5, "figcaption": 1 } }	2021-09-09 11:33:00	2024-02-28 13:49:24	1GRGhCB7C0ypB7Jl0WC1ePIeB6OUOHE_0gXcQquXWB9E	[ "Hannah Ritchie" ]	Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.	2021-08-31 12:33:41	2021-09-09 15:04:21	https://ourworldindata.org/wp-content/uploads/2021/09/reducing-fertilizer.png	{}	Our World in Data presents the data and research to make progress against the world’s largest problems. This blog post draws on data and research discussed in our entries on [Fertilizers](https://ourworldindata.org/fertilizers) and [Crop Yields](https://ourworldindata.org/crop-yields). Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work. <Callout title="Summary"/> One of the world’s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). [Pursuing sustainable productivity with millions of smallholder farmers](https://www.nature.com/articles/nature25785). _Nature_, 555(7696), 363-366.{/ref} They were successful. In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use _decreased_ by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn’t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices. It’s often assumed that fertilizer use – alongside the pollution it creates – and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think. To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen. For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world’s soils, we could produce our own. Their innovation (the [Haber-Bosch process](https://en.wikipedia.org/wiki/Haber_process)) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. _Nature Geoscience_, 1(10), 636-639. Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that [every second person](https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed) reading this has them to thank for being alive today. [Fertilizers](http://ourworldindata.org/fertilizers) help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What’s less obvious is that this has a large environmental benefit. Higher [crop yields](http://ourworldindata.org/crop-yields) mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we [would need](https://ourworldindata.org/grapher/land-sparing-by-crop) almost three times as much farmland today (to meet food production in 2019). Crop yield gains have ‘saved’ 1.7 billion hectares of land. That’s equal to an area the size of the USA and Brazil combined.{/ref} This means we can protect forests and maintain natural habitats. But it’s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries _can_ reduce fertilizer use without sacrificing food production. ## There are large differences in fertilizer use across the world Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called ‘limiting nutrients’. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium. If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart. There are 100-fold differences between countries. In many of the world’s poorest countries – particularly across Sub-Saharan Africa – farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By ‘football’, I mean ‘soccer’.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year. This has led to a divided world: * In many poorer countries we need _more_ fertilizers. Improvements in crop yields have been slow, and [large yield gaps](https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap) could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). [Closing yield gaps through nutrient and water management](https://www.nature.com/articles/nature11420). _Nature_, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics. This is why it’s damaging for agencies, such as the United Nations Development Programme to continually [promote the message](https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20) that the less fertilizer, the better. It’s not good for humans, or the environment. * But, as we will see, many countries are _overapplying_ nitrogen. They could cut back without negatively affecting their crop yields. <Chart url="https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland"/> <Chart url="https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU"/> ## Nitrogen use efficiency: balancing yields and the need for nutrient inputs Using lots of fertilizer wouldn’t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn’t. To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the ‘nitrogen use efficiency’ (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was _not_ used by the crops. A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant. Soon we will see that some countries have a _very_ high NUE – greater than 100%. You might assume that this is good news. In fact, it’s often the opposite. This means they are _undersupplying_ nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil – a process called ‘nitrogen mining’. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run. Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). [50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland](https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta). _Environmental Research Letters_, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment. But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE – less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds. <Chart url="https://ourworldindata.org/grapher/nitrogen-use-efficiency"/> ## Additional information We can also look at the _change_ in NUE over time, which shows us some interesting differences between countries. In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen _outputs_: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen _inputs_: added in the form of fertilizers, manure, or natural soil uptake. The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably _undersupplying_ nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time. Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it. I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields _are_ increasing, but they need increasing amounts of nitrogen to achieve this. It’s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move _back_ along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It’s increasing yields whilst _reducing_ the amount of fertilizers used. NUE is improving. In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields _and_ apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis. <Chart url="https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA"/> ## We can reduce nitrogen pollution without a decline in yields So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark. We might assume that all countries could achieve the same high NUE. But, maybe it’s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can’t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others. How can we better understand which countries are doing well in these yield-fertilizer trade-offs? An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in _Nature_.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). [Countries influence the trade-off between crop yields and nitrogen pollution](https://www.nature.com/articles/s43016-020-00185-6). _Nature Food_, _1_(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country’s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they _should_ be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a ‘natural experiment’ where the environmental conditions are held constant, and policy decisions are the changeable variable. The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture. <Image filename="nitrogen-pollution-discontinuity.png" alt=""/> Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref} Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields – increasing yield gaps by only 1%. Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains _relative to their neighbors_. Positive values – shown in orange and red – mean a country causes _more_ pollution than necessary for the yields that it achieves. Negative values – shown in blue – means a country causes _less_. There are a couple of important points we need to keep in mind. All of these values are measured _relative to a country’s neighbors_. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example. China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields. We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist. <Chart url="https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution"/> ## How can we use nitrogen more efficiently? You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today’s middle-income countries kickstarted their ‘Green Revolution’ and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). [https://doi.org/10.2499/p15738coll2.133652.](https://doi.org/10.2499/p15738coll2.133652.%7B/ref){/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today. One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts. Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them. We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit. One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement ‘precision farming’, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). [Precision farming at the nexus of agricultural production and the environment](https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929). Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). [Opinion: Smart farming is key to developing sustainable agriculture](https://www.pnas.org/content/114/24/6148.short). _Proceedings of the National Academy of Sciences_, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there’s an opportunity to improve how efficiently plants use it too. Let’s not forget that one of the most promising solutions – and one we often overlook – is the simplest and oldest of all. Legumes – crops such as beans, peas and lentils – perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called ‘biological fixation’. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes – either on their own, or alongside other crops – is one of the easiest ways that we can bring nitrogen into the soil. Finally, there’s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear. Large policy changes and technological advancements are often needed to make a large difference, but we shouldn’t underestimate the impact that education can make. Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn’t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions. #### Explore more of our work at _Our World in Data_ ### Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers? http://ourworldindata.org/excess-fertilizer ### Fertilizers Data Explorer Explore fertilizer use and its impacts across the world in our data explorer. ourworldindata.org/explorers/fertilizers ### Crop Yields Data Explorer Explore crop yields across the world in our data explorer. ourworldindata.org/explorers/crop-yields	{ "id": 44720, "date": "2021-09-09T12:33:00", "guid": { "rendered": "https://owid.cloud/?p=44720" }, "link": "https://owid.cloud/reducing-fertilizer-use", "meta": { "owid_publication_context_meta_field": { "latest": true, "homepage": true, "immediate_newsletter": true } }, "slug": "reducing-fertilizer-use", "tags": [], "type": "post", "title": { "rendered": "Can we reduce fertilizer use without sacrificing food production?" }, "_links": { "self": [ { "href": "https://owid.cloud/wp-json/wp/v2/posts/44720" } ], "about": [ { "href": "https://owid.cloud/wp-json/wp/v2/types/post" } ], "author": [ { "href": "https://owid.cloud/wp-json/wp/v2/users/17", "embeddable": true } ], "curies": [ { "href": "https://api.w.org/{rel}", "name": "wp", "templated": true } ], "replies": [ { "href": "https://owid.cloud/wp-json/wp/v2/comments?post=44720", "embeddable": true } ], "wp:term": [ { "href": "https://owid.cloud/wp-json/wp/v2/categories?post=44720", "taxonomy": "category", "embeddable": true }, { "href": "https://owid.cloud/wp-json/wp/v2/tags?post=44720", "taxonomy": "post_tag", "embeddable": true } ], "collection": [ { "href": "https://owid.cloud/wp-json/wp/v2/posts" } ], "wp:attachment": [ { "href": "https://owid.cloud/wp-json/wp/v2/media?parent=44720" } ], "version-history": [ { "href": "https://owid.cloud/wp-json/wp/v2/posts/44720/revisions", "count": 9 } ], "wp:featuredmedia": [ { "href": "https://owid.cloud/wp-json/wp/v2/media/44780", "embeddable": true } ], "predecessor-version": [ { "id": 44890, "href": "https://owid.cloud/wp-json/wp/v2/posts/44720/revisions/44890" } ] }, "author": 17, "format": "standard", "status": "publish", "sticky": false, "content": { "rendered": "\n<div class=\"blog-info\">\n<p>Our World in Data presents the data and research to make progress against the world\u2019s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href=\"https://ourworldindata.org/fertilizers\" target=\"_blank\" rel=\"noopener\">Fertilizers</a></strong> and <strong><a href=\"https://ourworldindata.org/crop-yields\" target=\"_blank\" rel=\"noopener\">Crop Yields</a></strong>.</p>\n<p>Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.</p>\n</div>\n\n\n\t<div class=\"wp-block-owid-summary\">\n\t\t<h2>Summary</h2>\n\t\t\n\n<p>Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. </p>\n\n\n\n<p>When they’re overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>\n\n\n\t</div>\n\n\n<p>One of the world\u2019s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., … & Dou, Z. (2018). <a href=\"https://www.nature.com/articles/nature25785\">Pursuing sustainable productivity with millions of smallholder farmers</a>. <em>Nature</em>, 555(7696), 363-366.{/ref} They were successful. </p>\n\n\n\n<p>In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use <em>decreased</em> by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn\u2019t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.</p>\n\n\n\n<p>It\u2019s often assumed that fertilizer use \u2013 alongside the pollution it creates \u2013 and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.</p>\n\n\n\n<p>To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen. </p>\n\n\n\n<p>For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world\u2019s soils, we could produce our own. Their innovation (the <a href=\"https://en.wikipedia.org/wiki/Haber_process\">Haber-Bosch process</a>) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. <em>Nature Geoscience</em>, 1(10), 636-639.<br><br>Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that <a href=\"https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed\">every second person</a> reading this has them to thank for being alive today.</p>\n\n\n\n<p><a href=\"http://ourworldindata.org/fertilizers\">Fertilizers</a> help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What\u2019s less obvious is that this has a large environmental benefit. Higher <a href=\"http://ourworldindata.org/crop-yields\">crop yields</a> mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we <a href=\"https://ourworldindata.org/grapher/land-sparing-by-crop\">would need</a> almost three times as much farmland today (to meet food production in 2019). Crop yield gains have \u2018saved\u2019 1.7 billion hectares of land. That\u2019s equal to an area the size of the USA and Brazil combined.{/ref}  This means we can protect forests and maintain natural habitats.</p>\n\n\n\n<p>But it\u2019s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.</p>\n\n\n\n<p>We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>\n\n\n\n<h3>There are large differences in fertilizer use across the world</h3>\n\n\n\n<div class=\"wp-block-columns is-style-side-by-side\">\n<div class=\"wp-block-column\">\n<p>Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called \u2018limiting nutrients\u2019. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.</p>\n\n\n\n<p>If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.</p>\n\n\n\n<p>There are 100-fold differences between countries. In many of the world\u2019s poorest countries \u2013 particularly across Sub-Saharan Africa \u2013 farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By \u2018football\u2019, I mean \u2018soccer\u2019.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.</p>\n\n\n\n<p>This has led to a divided world:</p>\n\n\n\n<ul><li>In many poorer countries we need <em>more</em> fertilizers. Improvements in crop yields have been slow, and <a href=\"https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap\">large yield gaps</a> could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). <a href=\"https://www.nature.com/articles/nature11420\">Closing yield gaps through nutrient and water management</a>. <em>Nature</em>, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.<br><br>This is why it\u2019s damaging for agencies, such as the United Nations Development Programme to continually <a href=\"https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20\">promote the message</a> that the less fertilizer, the better. It\u2019s not good for humans, or the environment.<br></li><li>But, as we will see, many countries are <em>overapplying</em> nitrogen. They could cut back without negatively affecting their crop yields.</li></ul>\n</div>\n\n\n\n<div class=\"wp-block-column\"></div>\n</div>\n\n\n\n<div class=\"wp-block-columns is-style-side-by-side\">\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\n<h3>Nitrogen use efficiency: balancing yields and the need for nutrient inputs</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>Using lots of fertilizer wouldn\u2019t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn\u2019t.</p>\n\n\n\n<p>To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the \u2018nitrogen use efficiency\u2019 (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was <em>not</em> used by the crops.</p>\n\n\n\n<p>A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant. </p>\n\n\n\n<p>Soon we will see that some countries have a <em>very</em> high NUE \u2013 greater than 100%. You might assume that this is good news. In fact, it\u2019s often the opposite. This means they are <em>undersupplying</em> nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil \u2013 a process called \u2018nitrogen mining\u2019. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.</p>\n\n\n\n<p>Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). <a href=\"https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta\">50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland</a>. <em>Environmental Research Letters</em>, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.</p>\n\n\n\n<p>But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE \u2013 less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/nitrogen-use-efficiency\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\t<block type=\"additional-information\" default-open=\"false\">\n\t\t<content>\n\n<h3><strong>How nitrogen use efficiency has changed over time</strong></h3>\n\n\n\n<div class=\"wp-block-columns is-style-sticky-right\">\n<div class=\"wp-block-column\">\n<p>We can also look at the <em>change</em> in NUE over time, which shows us some interesting differences between countries. </p>\n\n\n\n<p>In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen <em>outputs</em>: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen <em>inputs</em>: added in the form of fertilizers, manure, or natural soil uptake.</p>\n\n\n\n<p>The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably <em>undersupplying</em> nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.</p>\n\n\n\n<p>Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it. </p>\n\n\n\n<p>I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields <em>are</em> increasing, but they need increasing amounts of nitrogen to achieve this. It\u2019s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move <em>back</em> along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It\u2019s increasing yields whilst <em>reducing</em> the amount of fertilizers used. NUE is improving.</p>\n\n\n\n<p>In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields <em>and</em> apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n</content>\n\t</block>\n\n\n<h3>We can reduce nitrogen pollution without a decline in yields</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark. </p>\n\n\n\n<p>We might assume that all countries could achieve the same high NUE. But, maybe it\u2019s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can\u2019t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.</p>\n\n\n\n<p>How can we better understand which countries are doing well in these yield-fertilizer trade-offs?</p>\n\n\n\n<p>An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in <em>Nature</em>.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href=\"https://www.nature.com/articles/s43016-020-00185-6\">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country\u2019s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they <em>should</em> be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a \u2018natural experiment\u2019 where the environmental conditions are held constant, and policy decisions are the changeable variable.</p>\n\n\n\n<p>The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"2578\" height=\"624\" src=\"https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png\" alt=\"\" class=\"wp-image-44723\" srcset=\"https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png 2578w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-400x97.png 400w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-800x194.png 800w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-150x36.png 150w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-768x186.png 768w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-1536x372.png 1536w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-2048x496.png 2048w\" sizes=\"(max-width: 2578px) 100vw, 2578px\" /><figcaption>Discontinuities in vegetation at country borders{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href=\"https://www.nature.com/articles/s43016-020-00185-6\">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref}</figcaption></figure>\n</div>\n</div>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}</p>\n\n\n\n<p>Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. </p>\n\n\n\n<p><strong>They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields \u2013 increasing yield gaps by only 1%.</strong></p>\n\n\n\n<p>Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains <em>relative to their neighbors</em>. Positive values \u2013 shown in orange and red \u2013 mean a country causes <em>more</em> pollution than necessary for the yields that it achieves. Negative values \u2013 shown in blue \u2013 means a country causes <em>less</em>.</p>\n\n\n\n<p>There are a couple of important points we need to keep in mind. All of these values are measured <em>relative to a country\u2019s neighbors</em>. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.</p>\n\n\n\n<p>China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.</p>\n\n\n\n<p>We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\n<h3>How can we use nitrogen more efficiently?</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today\u2019s middle-income countries kickstarted their \u2018Green Revolution\u2019 and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). <a href=\"https://doi.org/10.2499/p15738coll2.133652.%7B/ref\">https://doi.org/10.2499/p15738coll2.133652.</a>{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.</p>\n\n\n\n<p>One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.</p>\n\n\n\n<p>Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.</p>\n\n\n\n<p>We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.</p>\n\n\n\n<p>One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement \u2018precision farming\u2019, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). <a href=\"https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929\">Precision farming at the nexus of agricultural production and the environment</a>. Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). <a href=\"https://www.pnas.org/content/114/24/6148.short\">Opinion: Smart farming is key to developing sustainable agriculture</a>. <em>Proceedings of the National Academy of Sciences</em>, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there\u2019s an opportunity to improve how efficiently plants use it too.</p>\n\n\n\n<p>Let\u2019s not forget that one of the most promising solutions \u2013 and one we often overlook \u2013 is the simplest and oldest of all. Legumes \u2013 crops such as beans, peas and lentils \u2013 perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called \u2018biological fixation\u2019. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes \u2013 either on their own, or alongside other crops \u2013 is one of the easiest ways that we can bring nitrogen into the soil.</p>\n\n\n\n<p>Finally, there\u2019s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.  Large policy changes and technological advancements are often needed to make a large difference, but we shouldn\u2019t underestimate the impact that education can make.</p>\n\n\n\n<p>Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn\u2019t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\"></div>\n</div>\n\n\n\n<hr class=\"wp-block-separator is-style-wide\"/>\n\n\n\n<h5>Explore more of our work at <em>Our World in Data</em></h5>\n\n\n <block type=\"prominent-link\" style=\"is-style-thin\">\n <link-url>http://ourworldindata.org/excess-fertilizer</link-url>\n <title>Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers?</title>\n <content>\n\n<p></p>\n\n</content>\n <figure><img width=\"768\" height=\"301\" src=\"https://owid.cloud/app/uploads/2021/09/excess-fertilizer-768x301.png\" class=\"attachment-medium_large size-medium_large\" alt=\"\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/09/excess-fertilizer-768x301.png 768w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-400x157.png 400w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-800x314.png 800w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-150x59.png 150w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-1536x603.png 1536w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer.png 1600w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n </block>\n\n <block type=\"prominent-link\" style=\"is-style-thin\">\n <link-url>http://ourworldindata.org/explorers/fertilizers</link-url>\n <title>Fertilizers Data Explorer</title>\n <content>\n\n<p>Explore fertilizer use and its impacts across the world in our data explorer.</p>\n\n</content>\n <figure><img width=\"768\" height=\"404\" src=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png\" class=\"attachment-medium_large size-medium_large\" alt=\"COVID-19 data explorer\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png 768w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-400x210.png 400w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-800x421.png 800w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-150x79.png 150w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png 1200w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n </block>\n\n <block type=\"prominent-link\" style=\"is-style-thin\">\n <link-url>http://ourworldindata.org/explorers/crop-yields</link-url>\n <title>Crop Yields Data Explorer</title>\n <content>\n\n<p>Explore crop yields across the world in our data explorer.</p>\n\n</content>\n <figure><img width=\"768\" height=\"404\" src=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png\" class=\"attachment-medium_large size-medium_large\" alt=\"COVID-19 data explorer\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png 768w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-400x210.png 400w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-800x421.png 800w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-150x79.png 150w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png 1200w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n </block>", "protected": false }, "excerpt": { "rendered": "Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.", "protected": false }, "date_gmt": "2021-09-09T11:33:00", "modified": "2021-09-09T16:04:21", "template": "", "categories": [ 1 ], "ping_status": "closed", "authors_name": [ "Hannah Ritchie" ], "modified_gmt": "2021-09-09T15:04:21", "comment_status": "closed", "featured_media": 44780, "featured_media_paths": { "thumbnail": "/app/uploads/2021/09/reducing-fertilizer-150x59.png", "medium_large": "/app/uploads/2021/09/reducing-fertilizer-768x301.png" } }

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Can we reduce fertilizer use without sacrificing food production?

reducing-fertilizer-use

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<div class="blog-info"> <p>Our World in Data presents the data and research to make progress against the world’s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href="https://ourworldindata.org/fertilizers" target="_blank" rel="noopener">Fertilizers</a></strong> and <strong><a href="https://ourworldindata.org/crop-yields" target="_blank" rel="noopener">Crop Yields</a></strong>.</p> <p>Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.</p> </div>    <p>Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. </p>   <p>When they're overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>     <p>One of the world’s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). <a href="https://www.nature.com/articles/nature25785">Pursuing sustainable productivity with millions of smallholder farmers</a>. <em>Nature</em>, 555(7696), 363-366.{/ref} They were successful. </p>   <p>In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use <em>decreased</em> by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn’t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.</p>   <p>It’s often assumed that fertilizer use – alongside the pollution it creates – and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.</p>   <p>To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen. </p>   <p>For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world’s soils, we could produce our own. Their innovation (the <a href="https://en.wikipedia.org/wiki/Haber_process">Haber-Bosch process</a>) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. <em>Nature Geoscience</em>, 1(10), 636-639.<br><br>Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that <a href="https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed">every second person</a> reading this has them to thank for being alive today.</p>   <p><a href="http://ourworldindata.org/fertilizers">Fertilizers</a> help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What’s less obvious is that this has a large environmental benefit. Higher <a href="http://ourworldindata.org/crop-yields">crop yields</a> mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we <a href="https://ourworldindata.org/grapher/land-sparing-by-crop">would need</a> almost three times as much farmland today (to meet food production in 2019). Crop yield gains have ‘saved’ 1.7 billion hectares of land. That’s equal to an area the size of the USA and Brazil combined.{/ref}  This means we can protect forests and maintain natural habitats.</p>   <p>But it’s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.</p>   <p>We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>   <h3>There are large differences in fertilizer use across the world</h3>   <div class="wp-block-columns is-style-side-by-side"> <div class="wp-block-column"> <p>Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called ‘limiting nutrients’. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.</p>   <p>If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.</p>   <p>There are 100-fold differences between countries. In many of the world’s poorest countries – particularly across Sub-Saharan Africa – farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By ‘football’, I mean ‘soccer’.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.</p>   <p>This has led to a divided world:</p>   <ul><li>In many poorer countries we need <em>more</em> fertilizers. Improvements in crop yields have been slow, and <a href="https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap">large yield gaps</a> could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). <a href="https://www.nature.com/articles/nature11420">Closing yield gaps through nutrient and water management</a>. <em>Nature</em>, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.<br><br>This is why it’s damaging for agencies, such as the United Nations Development Programme to continually <a href="https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20">promote the message</a> that the less fertilizer, the better. It’s not good for humans, or the environment.<br></li><li>But, as we will see, many countries are <em>overapplying</em> nitrogen. They could cut back without negatively affecting their crop yields.</li></ul> </div>   <div class="wp-block-column"></div> </div>   <div class="wp-block-columns is-style-side-by-side"> <div class="wp-block-column"> <iframe src="https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> </div>   <div class="wp-block-column"> <iframe src="https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> </div> </div>   <h3>Nitrogen use efficiency: balancing yields and the need for nutrient inputs</h3>   <div class="wp-block-columns"> <div class="wp-block-column"> <p>Using lots of fertilizer wouldn’t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn’t.</p>   <p>To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the ‘nitrogen use efficiency’ (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was <em>not</em> used by the crops.</p>   <p>A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant. </p>   <p>Soon we will see that some countries have a <em>very</em> high NUE – greater than 100%. You might assume that this is good news. In fact, it’s often the opposite. This means they are <em>undersupplying</em> nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil – a process called ‘nitrogen mining’. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.</p>   <p>Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). <a href="https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta">50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland</a>. <em>Environmental Research Letters</em>, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.</p>   <p>But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE – less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.</p> </div>   <div class="wp-block-column"> <iframe src="https://ourworldindata.org/grapher/nitrogen-use-efficiency" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> </div> </div>    <h3><strong>How nitrogen use efficiency has changed over time</strong></h3>   <div class="wp-block-columns is-style-sticky-right"> <div class="wp-block-column"> <p>We can also look at the <em>change</em> in NUE over time, which shows us some interesting differences between countries. </p>   <p>In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen <em>outputs</em>: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen <em>inputs</em>: added in the form of fertilizers, manure, or natural soil uptake.</p>   <p>The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably <em>undersupplying</em> nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.</p>   <p>Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it. </p>   <p>I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields <em>are</em> increasing, but they need increasing amounts of nitrogen to achieve this. It’s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move <em>back</em> along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It’s increasing yields whilst <em>reducing</em> the amount of fertilizers used. NUE is improving.</p>   <p>In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields <em>and</em> apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis.</p> </div>   <div class="wp-block-column"> <iframe src="https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> </div> </div>    <h3>We can reduce nitrogen pollution without a decline in yields</h3>   <div class="wp-block-columns"> <div class="wp-block-column"> <p>So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark. </p>   <p>We might assume that all countries could achieve the same high NUE. But, maybe it’s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can’t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.</p>   <p>How can we better understand which countries are doing well in these yield-fertilizer trade-offs?</p>   <p>An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in <em>Nature</em>.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href="https://www.nature.com/articles/s43016-020-00185-6">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country’s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they <em>should</em> be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a ‘natural experiment’ where the environmental conditions are held constant, and policy decisions are the changeable variable.</p>   <p>The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.</p> </div>   <div class="wp-block-column"> <figure class="wp-block-image size-full"><img src="https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png" alt="" class="wp-image-44723"/><figcaption>Discontinuities in vegetation at country borders{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). <a href="https://www.nature.com/articles/s43016-020-00185-6">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref}</figcaption></figure> </div> </div>   <div class="wp-block-columns"> <div class="wp-block-column"> <p>Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}</p>   <p>Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. </p>   <p><strong>They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields – increasing yield gaps by only 1%.</strong></p>   <p>Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains <em>relative to their neighbors</em>. Positive values – shown in orange and red – mean a country causes <em>more</em> pollution than necessary for the yields that it achieves. Negative values – shown in blue – means a country causes <em>less</em>.</p>   <p>There are a couple of important points we need to keep in mind. All of these values are measured <em>relative to a country’s neighbors</em>. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.</p>   <p>China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.</p>   <p>We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.</p> </div>   <div class="wp-block-column"> <iframe src="https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> </div> </div>   <h3>How can we use nitrogen more efficiently?</h3>   <div class="wp-block-columns"> <div class="wp-block-column"> <p>You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today’s middle-income countries kickstarted their ‘Green Revolution’ and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). <a href="https://doi.org/10.2499/p15738coll2.133652.%7B/ref">https://doi.org/10.2499/p15738coll2.133652.</a>{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.</p>   <p>One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.</p>   <p>Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.</p>   <p>We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.</p>   <p>One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement ‘precision farming’, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929">Precision farming at the nexus of agricultural production and the environment</a>. Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). <a href="https://www.pnas.org/content/114/24/6148.short">Opinion: Smart farming is key to developing sustainable agriculture</a>. <em>Proceedings of the National Academy of Sciences</em>, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there’s an opportunity to improve how efficiently plants use it too.</p>   <p>Let’s not forget that one of the most promising solutions – and one we often overlook – is the simplest and oldest of all. Legumes – crops such as beans, peas and lentils – perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called ‘biological fixation’. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes – either on their own, or alongside other crops – is one of the easiest ways that we can bring nitrogen into the soil.</p>   <p>Finally, there’s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.  Large policy changes and technological advancements are often needed to make a large difference, but we shouldn’t underestimate the impact that education can make.</p>   <p>Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn’t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.</p> </div>   <div class="wp-block-column"></div> </div>   <hr class="wp-block-separator is-style-wide"/>   <h5>Explore more of our work at <em>Our World in Data</em></h5>    <p></p>     <p>Explore fertilizer use and its impacts across the world in our data explorer.</p>     <p>Explore crop yields across the world in our data explorer.</p>

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                        "text": "Our World in Data presents the data and research to make progress against the world\u2019s largest problems.",
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                        "text": "This blog post draws on data and research discussed in our entries on ",
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                                "url": "https://ourworldindata.org/fertilizers",
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                                        "text": "Fertilizers",
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                                "url": "https://ourworldindata.org/crop-yields",
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                                        "text": "Crop Yields",
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                        "text": "Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.",
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                                "text": "Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. ",
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                                "text": "When they're overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries ",
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                                "text": " reduce fertilizer use without sacrificing food production.",
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                        "text": "One of the world\u2019s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). ",
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                        "url": "https://www.nature.com/articles/nature25785",
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                                "text": "Pursuing sustainable productivity with millions of smallholder farmers",
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                        "text": ", 555(7696), 363-366.{/ref} They were successful.\u00a0",
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                        "text": "In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use ",
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                                "text": "decreased",
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                        "text": " by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn\u2019t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.",
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                        "text": "It\u2019s often assumed that fertilizer use \u2013 alongside the pollution it creates \u2013 and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.",
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                        "text": "To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen.\u00a0",
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                        "text": "For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world\u2019s soils, we could produce our own. Their innovation (the ",
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                                "text": "Haber-Bosch process",
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                        "text": ") at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. ",
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                                "text": "Nature Geoscience",
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                        "text": ", 1(10), 636-639.",
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                        "text": "Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that ",
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                                "text": "every second person",
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                        "text": " reading this has them to thank for being alive today.",
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                        "text": " help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What\u2019s less obvious is that this has a large environmental benefit. Higher ",
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                                "text": "crop yields",
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                        "text": " mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we ",
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                                "text": "would need",
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                        "text": " almost three times as much farmland today (to meet food production in 2019). Crop yield gains have \u2018saved\u2019 1.7 billion hectares of land. That\u2019s equal to an area the size of the USA and Brazil combined.{/ref} \u00a0This means we can protect forests and maintain natural habitats.",
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                        "text": "But it\u2019s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.",
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                        "text": "We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries ",
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                        "text": " reduce fertilizer use without sacrificing food production.",
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                        "text": "There are large differences in fertilizer use across the world",
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                        "text": "Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called \u2018limiting nutrients\u2019. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.",
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                        "text": "If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.",
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                        "text": "There are 100-fold differences between countries. In many of the world\u2019s poorest countries \u2013 particularly across Sub-Saharan Africa \u2013 farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By \u2018football\u2019, I mean \u2018soccer\u2019.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.",
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                        "text": "This has led to a divided world:",
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                                "text": "In many poorer countries we need ",
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                                        "text": "more",
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                                "text": " fertilizers. Improvements in crop yields have been slow, and ",
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                                "url": "https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap",
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                                        "text": "large yield gaps",
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                                "text": " could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). ",
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                                "url": "https://www.nature.com/articles/nature11420",
                                "children": [
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                                        "text": "Closing yield gaps through nutrient and water management",
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                                "text": ". ",
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                                "text": ", 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.",
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                                "text": "This is why it\u2019s damaging for agencies, such as the United Nations Development Programme to continually ",
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                            {
                                "url": "https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20",
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                                        "text": "promote the message",
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                                "text": " that the less fertilizer, the better. It\u2019s not good for humans, or the environment.",
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                                "text": "But, as we will see, many countries are ",
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                                "text": " nitrogen. They could cut back without negatively affecting their crop yields.",
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                        "text": "Nitrogen use efficiency: balancing yields and the need for nutrient inputs",
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                                "text": "Using lots of fertilizer wouldn\u2019t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn\u2019t.",
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                                "text": "To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the \u2018nitrogen use efficiency\u2019 (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was ",
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                                "text": " used by the crops.",
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                                "text": "A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant.\u00a0",
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                                "text": "Soon we will see that some countries have a ",
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                                "text": " high NUE \u2013 greater than 100%. You might assume that this is good news. In fact, it\u2019s often the opposite. This means they are ",
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                                        "text": "undersupplying",
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                                "text": " nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil \u2013 a process called \u2018nitrogen mining\u2019. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.",
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                                "text": "Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). ",
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                            {
                                "url": "https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta",
                                "children": [
                                    {
                                        "text": "50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland",
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                                "text": ". ",
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                                        "text": "Environmental Research Letters",
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                                "text": ", 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.",
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                                "text": "But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE \u2013 less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.",
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                                "text": "Additional information",
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                                                "text": "We can also look at the ",
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                                                "text": " in NUE over time, which shows us some interesting differences between countries.\u00a0",
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                                                "text": "In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen ",
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                                                "text": ": the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen ",
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                                                "text": ": added in the form of fertilizers, manure, or natural soil uptake.",
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                                                "text": "The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably ",
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                                                "text": " nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.",
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                                                "text": "Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it.\u00a0",
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                                                "text": "I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields ",
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                                                "text": " increasing, but they need increasing amounts of nitrogen to achieve this. It\u2019s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move ",
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                                                "text": " along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It\u2019s increasing yields whilst ",
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                                                "text": "In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields ",
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                        "text": "We can reduce nitrogen pollution without a decline in yields",
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                                "text": "So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark.\u00a0",
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                                "text": "We might assume that all countries could achieve the same high NUE. But, maybe it\u2019s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can\u2019t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.",
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                                "text": "How can we better understand which countries are doing well in these yield-fertilizer trade-offs?",
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                                "text": "An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in ",
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                                "text": ".{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). ",
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                                        "text": "Countries influence the trade-off between crop yields and nitrogen pollution",
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                                "text": "(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country\u2019s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they ",
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                                "text": " be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a \u2018natural experiment\u2019 where the environmental conditions are held constant, and policy decisions are the changeable variable.",
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                                "text": "The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.",
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                                "text": "Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}",
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                                "text": "Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. ",
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                                "text": "Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains ",
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                                "text": ". Positive values \u2013 shown in orange and red \u2013 mean a country causes ",
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                                "text": "There are a couple of important points we need to keep in mind. All of these values are measured ",
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                                "text": ". A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.",
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                                "text": "China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.",
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                                "text": "We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.",
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                        "text": "How can we use nitrogen more efficiently?",
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                        "text": "You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today\u2019s middle-income countries kickstarted their \u2018Green Revolution\u2019 and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). ",
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                        "text": "{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.",
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                        "text": "One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.",
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                        "text": "Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.",
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                        "text": "We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.",
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                        "text": "One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement \u2018precision farming\u2019, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). ",
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                        "url": "https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929",
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                                "text": "Precision farming at the nexus of agricultural production and the environment",
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                        "text": ". Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). ",
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                        "url": "https://www.pnas.org/content/114/24/6148.short",
                        "children": [
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                                "text": "Opinion: Smart farming is key to developing sustainable agriculture",
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                        "text": ". ",
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                        "text": ", 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there\u2019s an opportunity to improve how efficiently plants use it too.",
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                        "text": "Let\u2019s not forget that one of the most promising solutions \u2013 and one we often overlook \u2013 is the simplest and oldest of all. Legumes \u2013 crops such as beans, peas and lentils \u2013 perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called \u2018biological fixation\u2019. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes \u2013 either on their own, or alongside other crops \u2013 is one of the easiest ways that we can bring nitrogen into the soil.",
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                        "text": "Finally, there\u2019s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.\u00a0 Large policy changes and technological advancements are often needed to make a large difference, but we shouldn\u2019t underestimate the impact that education can make.",
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                        "text": "Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn\u2019t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.",
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                        "text": "Explore more of our work at ",
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2021-09-09 11:33:00

2024-02-28 13:49:24

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    "Hannah Ritchie"
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Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.

2021-08-31 12:33:41

2021-09-09 15:04:21

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Our World in Data presents the data and research to make progress against the world’s largest problems. This blog post draws on data and research discussed in our entries on **[Fertilizers](https://ourworldindata.org/fertilizers)** and **[Crop Yields](https://ourworldindata.org/crop-yields)**. Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work. <Callout title="Summary"/> One of the world’s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., ... & Dou, Z. (2018). [Pursuing sustainable productivity with millions of smallholder farmers](https://www.nature.com/articles/nature25785). _Nature_, 555(7696), 363-366.{/ref} They were successful. In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use _decreased_ by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn’t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices. It’s often assumed that fertilizer use – alongside the pollution it creates – and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think. To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen. For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world’s soils, we could produce our own. Their innovation (the [Haber-Bosch process](https://en.wikipedia.org/wiki/Haber_process)) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. _Nature Geoscience_, 1(10), 636-639. Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that [every second person](https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed) reading this has them to thank for being alive today. [Fertilizers](http://ourworldindata.org/fertilizers) help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What’s less obvious is that this has a large environmental benefit. Higher [crop yields](http://ourworldindata.org/crop-yields) mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we [would need](https://ourworldindata.org/grapher/land-sparing-by-crop) almost three times as much farmland today (to meet food production in 2019). Crop yield gains have ‘saved’ 1.7 billion hectares of land. That’s equal to an area the size of the USA and Brazil combined.{/ref} This means we can protect forests and maintain natural habitats. But it’s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries _can_ reduce fertilizer use without sacrificing food production. ## There are large differences in fertilizer use across the world Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called ‘limiting nutrients’. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium. If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart. There are 100-fold differences between countries. In many of the world’s poorest countries – particularly across Sub-Saharan Africa – farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By ‘football’, I mean ‘soccer’.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year. This has led to a divided world: * In many poorer countries we need _more_ fertilizers. Improvements in crop yields have been slow, and [large yield gaps](https://ourworldindata.org/explorers/crop-yields?tab=map&country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&Crop=Cassava&Metric=Yield+gap) could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., & Foley, J. A. (2012). [Closing yield gaps through nutrient and water management](https://www.nature.com/articles/nature11420). _Nature_, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics. This is why it’s damaging for agencies, such as the United Nations Development Programme to continually [promote the message](https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20) that the less fertilizer, the better. It’s not good for humans, or the environment. * But, as we will see, many countries are _overapplying_ nitrogen. They could cut back without negatively affecting their crop yields. <Chart url="https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland"/> <Chart url="https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU"/> ## Nitrogen use efficiency: balancing yields and the need for nutrient inputs Using lots of fertilizer wouldn’t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn’t. To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the ‘nitrogen use efficiency’ (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was _not_ used by the crops. A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant. Soon we will see that some countries have a _very_ high NUE – greater than 100%. You might assume that this is good news. In fact, it’s often the opposite. This means they are _undersupplying_ nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil – a process called ‘nitrogen mining’. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run. Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., & Garnier, J. (2014). [50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland](https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta). _Environmental Research Letters_, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment. But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE – less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds. <Chart url="https://ourworldindata.org/grapher/nitrogen-use-efficiency"/> ## Additional information We can also look at the _change_ in NUE over time, which shows us some interesting differences between countries. In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen _outputs_: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen _inputs_: added in the form of fertilizers, manure, or natural soil uptake. The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably _undersupplying_ nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time. Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it. I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields _are_ increasing, but they need increasing amounts of nitrogen to achieve this. It’s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move _back_ along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It’s increasing yields whilst _reducing_ the amount of fertilizers used. NUE is improving. In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields _and_ apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis. <Chart url="https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA"/> ## We can reduce nitrogen pollution without a decline in yields So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark. We might assume that all countries could achieve the same high NUE. But, maybe it’s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can’t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others. How can we better understand which countries are doing well in these yield-fertilizer trade-offs? An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in _Nature_.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., & Finger, R. (2020). [Countries influence the trade-off between crop yields and nitrogen pollution](https://www.nature.com/articles/s43016-020-00185-6). _Nature Food_, _1_(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country’s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they _should_ be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a ‘natural experiment’ where the environmental conditions are held constant, and policy decisions are the changeable variable. The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture. <Image filename="nitrogen-pollution-discontinuity.png" alt=""/> Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref} Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. **They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields – increasing yield gaps by only 1%.** Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains _relative to their neighbors_. Positive values – shown in orange and red – mean a country causes _more_ pollution than necessary for the yields that it achieves. Negative values – shown in blue – means a country causes _less_. There are a couple of important points we need to keep in mind. All of these values are measured _relative to a country’s neighbors_. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example. China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields. We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist. <Chart url="https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution"/> ## How can we use nitrogen more efficiently? You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today’s middle-income countries kickstarted their ‘Green Revolution’ and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). [https://doi.org/10.2499/p15738coll2.133652.](https://doi.org/10.2499/p15738coll2.133652.%7B/ref){/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today. One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts. Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them. We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit. One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement ‘precision farming’, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., & Walter, A. (2019). [Precision farming at the nexus of agricultural production and the environment](https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929). Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., & Buchmann, N. (2017). [Opinion: Smart farming is key to developing sustainable agriculture](https://www.pnas.org/content/114/24/6148.short). _Proceedings of the National Academy of Sciences_, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there’s an opportunity to improve how efficiently plants use it too. Let’s not forget that one of the most promising solutions – and one we often overlook – is the simplest and oldest of all. Legumes – crops such as beans, peas and lentils – perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called ‘biological fixation’. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes – either on their own, or alongside other crops – is one of the easiest ways that we can bring nitrogen into the soil. Finally, there’s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear. Large policy changes and technological advancements are often needed to make a large difference, but we shouldn’t underestimate the impact that education can make. Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn’t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions. #### Explore more of our work at _Our World in Data_ ### Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers? http://ourworldindata.org/excess-fertilizer ### Fertilizers Data Explorer Explore fertilizer use and its impacts across the world in our data explorer. ourworldindata.org/explorers/fertilizers ### Crop Yields Data Explorer Explore crop yields across the world in our data explorer. ourworldindata.org/explorers/crop-yields

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        "rendered": "\n<div class=\"blog-info\">\n<p>Our World in Data presents the data and research to make progress against the world\u2019s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href=\"https://ourworldindata.org/fertilizers\" target=\"_blank\" rel=\"noopener\">Fertilizers</a></strong> and <strong><a href=\"https://ourworldindata.org/crop-yields\" target=\"_blank\" rel=\"noopener\">Crop Yields</a></strong>.</p>\n<p>Many thanks to David Wuepper, Paul West and Luis Lassaletta for providing data for this article. Thanks to Max Roser for feedback on this work.</p>\n</div>\n\n\n\t<div class=\"wp-block-owid-summary\">\n\t\t<h2>Summary</h2>\n\t\t\n\n<p>Fertilizers can increase crop yields. This not only offers important benefits for farmer incomes and food security, but also produces environmental benefits by reducing our demands for farmland. Many countries would benefit from using more fertilizer. </p>\n\n\n\n<p>When they&#8217;re overapplied, they can also become an environmental pollutant. We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. But the research shows that this is not necessarily true. Farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>\n\n\n\t</div>\n\n\n<p>One of the world\u2019s biggest and most impressive studies shows us that simple interventions can produce large results. In a decade-long trial, researchers worked with 21 million smallholder farmers across China to see if they could increase crop yields while also reducing the environmental impacts of farming.{ref}Cui, Z., Zhang, H., Chen, X., Zhang, C., Ma, W., Huang, C., &#8230; &amp; Dou, Z. (2018). <a href=\"https://www.nature.com/articles/nature25785\">Pursuing sustainable productivity with millions of smallholder farmers</a>. <em>Nature</em>, 555(7696), 363-366.{/ref} They were successful.&nbsp;</p>\n\n\n\n<p>In the decade from 2005 to 2015, average yields of maize, rice and wheat increased by around 11%. At the same time, nitrogen fertilizer use <em>decreased</em> by around one-sixth. By producing more crops and needing less fertilizer, this experiment provided an economic return of US$12.2 billion. This wasn\u2019t achieved through major technological innovations or policy changes: it involved educating and training farmers on good management practices.</p>\n\n\n\n<p>It\u2019s often assumed that fertilizer use \u2013 alongside the pollution it creates \u2013 and crop yields present an inevitable trade-off. To increase yields, you need more and more fertilizer. This large-scale study suggests this trade-off is not always as extreme as we might think.</p>\n\n\n\n<p>To be clear: fertilizers are vital for global food production. There are few innovations that have transformed the world as much as synthetic nitrogen.&nbsp;</p>\n\n\n\n<p>For most of human history, food production was limited by the amount of reactive nutrients that were available for crops. This all changed with Fritz Haber and Carl Bosch. Rather than relying on the scarce nitrogen that exists naturally within the world\u2019s soils, we could produce our own. Their innovation (the <a href=\"https://en.wikipedia.org/wiki/Haber_process\">Haber-Bosch process</a>) at the beginning of the 20th century enabled the lives of billions of people.{ref}Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., &amp; Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. <em>Nature Geoscience</em>, 1(10), 636-639.<br><br>Smil, V. (2004). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press.{/ref} Estimates suggest that <a href=\"https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed\">every second person</a> reading this has them to thank for being alive today.</p>\n\n\n\n<p><a href=\"http://ourworldindata.org/fertilizers\">Fertilizers</a> help us to achieve higher crop yields. This is an obvious net positive for humans: farmers can produce and earn more, and the world has more food. What\u2019s less obvious is that this has a large environmental benefit. Higher <a href=\"http://ourworldindata.org/crop-yields\">crop yields</a> mean we need to use less land for farming.{ref}If crop yields had remained at their levels in 1961, we <a href=\"https://ourworldindata.org/grapher/land-sparing-by-crop\">would need</a> almost three times as much farmland today (to meet food production in 2019). Crop yield gains have \u2018saved\u2019 1.7 billion hectares of land. That\u2019s equal to an area the size of the USA and Brazil combined.{/ref} &nbsp;This means we can protect forests and maintain natural habitats.</p>\n\n\n\n<p>But it\u2019s true that alongside the environmental benefits, there are also some downsides. Not all of the nitrogen we use is used by the crops. The rest runs off the soils and into the natural environment: fertilizing the rivers and lakes and thereby upsetting the balance of ecosystems and causing biodiversity loss.</p>\n\n\n\n<p>We might assume that there is nothing we can do: that to achieve higher yields we need more inputs and therefore necessarily cause more pollution. In this article I show that farmers in many countries <em>can</em> reduce fertilizer use without sacrificing food production.</p>\n\n\n\n<h3>There are large differences in fertilizer use across the world</h3>\n\n\n\n<div class=\"wp-block-columns is-style-side-by-side\">\n<div class=\"wp-block-column\">\n<p>Crops, like any organism, need nutrients to grow. When particular nutrients are lacking, they fail or grow at a much slower rate. These are called \u2018limiting nutrients\u2019. What nutrient is the most limiting varies across the world: some soils lack nitrogen, while others lack phosphorus or potassium.</p>\n\n\n\n<p>If a soil is lacking nutrients naturally we can add our own. This can be in the form of synthetic fertilizers, or organic additions such as manure. There are very large differences in how much fertilizer is applied across the world. We see this in the charts below: first as a map of average fertilizer use per hectare of cropland; and second, with the breakdown by nutrient in the bar chart.</p>\n\n\n\n<p>There are 100-fold differences between countries. In many of the world\u2019s poorest countries \u2013 particularly across Sub-Saharan Africa \u2013 farmers apply only a few kilograms of fertilizer per hectare. For context, one hectare is about 1.5-times the size of a football pitch.{ref}By \u2018football\u2019, I mean \u2018soccer\u2019.{/ref} Contrast this with countries such as China, Brazil, the UK or Egypt, where farmers apply hundreds of kilograms per year. They apply as much in a few days as some farmers do in an entire year.</p>\n\n\n\n<p>This has led to a divided world:</p>\n\n\n\n<ul><li>In many poorer countries we need <em>more</em> fertilizers. Improvements in crop yields have been slow, and <a href=\"https://ourworldindata.org/explorers/crop-yields?tab=map&amp;country=IND~USA~ITA~GBR~NGA~LKA~BRA~PER~AGO&amp;Crop=Cassava&amp;Metric=Yield+gap\">large yield gaps</a> could be closed through more and better management of inputs.{ref}Mueller, N. D., Gerber, J. S., Johnston, M., Ray, D. K., Ramankutty, N., &amp; Foley, J. A. (2012). <a href=\"https://www.nature.com/articles/nature11420\">Closing yield gaps through nutrient and water management</a>. <em>Nature</em>, 490(7419), 254-257.{/ref} This is not only good for farmers, but also for the environment: for the reasons above, closing yield gaps is one of the best ways we can prevent habitat loss across the tropics.<br><br>This is why it\u2019s damaging for agencies, such as the United Nations Development Programme to continually <a href=\"https://twitter.com/_HannahRitchie/status/1432284322896171012?s=20\">promote the message</a> that the less fertilizer, the better. It\u2019s not good for humans, or the environment.<br></li><li>But, as we will see, many countries are <em>overapplying</em> nitrogen. They could cut back without negatively affecting their crop yields.</li></ul>\n</div>\n\n\n\n<div class=\"wp-block-column\"></div>\n</div>\n\n\n\n<div class=\"wp-block-columns is-style-side-by-side\">\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/fertilizer-use-per-hectare-of-cropland\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/fertilizer-per-hectare?country=OWID_WRL~CHN~USA~GBR~IND~BRA~NGA~European+Union~GHA~ECU\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\n<h3>Nitrogen use efficiency: balancing yields and the need for nutrient inputs</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>Using lots of fertilizer wouldn\u2019t necessarily be a bad thing if all of it was used by the crops. Unfortunately, most of it isn\u2019t.</p>\n\n\n\n<p>To capture this, we can look at the ratio of nitrogen in harvested products (our crops) compared to our inputs (fertilizers or manure); this ratio is called the \u2018nitrogen use efficiency\u2019 (NUE). A NUE of 60% would mean that the amount of nitrogen in our crops was 60% of the nitrogen that was added to them as inputs. The remaining 40% of nitrogen was <em>not</em> used by the crops.</p>\n\n\n\n<p>A low NUE is bad. This means very little of the nitrogen we add is taken up by the crops. A NUE of 20% would mean that 80% of the applied nitrogen became a pollutant.&nbsp;</p>\n\n\n\n<p>Soon we will see that some countries have a <em>very</em> high NUE \u2013 greater than 100%. You might assume that this is good news. In fact, it\u2019s often the opposite. This means they are <em>undersupplying</em> nitrogen, but continue to try to grow more and more crops. Instead of utilizing readily available nutrients, crops have to take nitrogen from the soil \u2013 a process called \u2018nitrogen mining\u2019. Over time this depletes soils of their nutrients which will be bad for crop production in the long-run.</p>\n\n\n\n<p>Globally, NUE has been stubbornly low, at 40% to 50% since 1980.{ref}Lassaletta, L., Billen, G., Grizzetti, B., Anglade, J., &amp; Garnier, J. (2014). <a href=\"https://iopscience.iop.org/article/10.1088/1748-9326/9/10/105011/meta\">50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland</a>. <em>Environmental Research Letters</em>, 9(10), 105011.{/ref} This is surprisingly low. It means that less than half of the nitrogen we apply to our crops is actually taken up by them. The rest is excess that leaks into the natural environment.</p>\n\n\n\n<p>But there are very large differences in NUE across the world, as shown in the map. Some countries achieve low NUE \u2013 less than 40%. Both India and China, for example, have an efficiency of only one-third. Some countries, though, do much better. France, Ireland, the UK, and the US, have an efficiency greater than two-thirds.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/nitrogen-use-efficiency\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\t<block type=\"additional-information\" default-open=\"false\">\n\t\t<content>\n\n<h3><strong>How nitrogen use efficiency has changed over time</strong></h3>\n\n\n\n<div class=\"wp-block-columns is-style-sticky-right\">\n<div class=\"wp-block-column\">\n<p>We can also look at the <em>change</em> in NUE over time, which shows us some interesting differences between countries.&nbsp;</p>\n\n\n\n<p>In the chart we see the ratio of nitrogen inputs and outputs as a connected scatter plot. On the y-axis we have nitrogen <em>outputs</em>: the amount of nitrogen that is harvested in the crops. On the x-axis we have nitrogen <em>inputs</em>: added in the form of fertilizers, manure, or natural soil uptake.</p>\n\n\n\n<p>The grey line indicates where nitrogen use efficiency would be 100%, meaning all of the nitrogen that was added was taken up by the crop. In reality, this is probably bad news. As we discussed earlier, they are probably <em>undersupplying</em> nitrogen. Instead of utilizing synthetic inputs, crops have to take nitrogen from the soil which can deplete their soils over time.</p>\n\n\n\n<p>Ideally, we want a value that gets higher on the y-axis: a larger yield from our crops but does not move further and further to the right (which would indicate that more and more inputs are needed to achieve this). If a country is moving further away from the grey line, it is becoming increasingly inefficient. We want countries to move towards it.&nbsp;</p>\n\n\n\n<p>I have highlighted some interesting country patterns. We see that countries such as India, China, and Egypt are becoming less efficient. Yields <em>are</em> increasing, but they need increasing amounts of nitrogen to achieve this. It\u2019s a diminishing return curve. They are moving further from the central grey line. France gives us an interesting counter-example. In recent years it has started to move <em>back</em> along the x-axis to lower nitrogen inputs. It has slowly increased yields at the same time. It\u2019s increasing yields whilst <em>reducing</em> the amount of fertilizers used. NUE is improving.</p>\n\n\n\n<p>In the bottom-left corner we see Nigeria. Many countries in Sub-Saharan Africa cluster close to the origin. They get low yields <em>and</em> apply only small amounts of nitrogen to their crops. For food security, they need to quickly move up the y-axis.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/nitrogen-output-vs-nitrogen-input-to-agriculture?country=CHN~IND~USA~NGA~EGY~FRA\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n</content>\n\t</block>\n\n\n<h3>We can reduce nitrogen pollution without a decline in yields</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>So, nitrogen efficiency rather than just fertilizer use seems like a better sustainably metric for us to benchmark.&nbsp;</p>\n\n\n\n<p>We might assume that all countries could achieve the same high NUE. But, maybe it\u2019s still unfair to compare countries across the world in this way. Differences in climate, vegetation, and soil types mean we can\u2019t achieve the same yields with the same inputs everywhere. Some countries might have more favorable environmental conditions than others.</p>\n\n\n\n<p>How can we better understand which countries are doing well in these yield-fertilizer trade-offs?</p>\n\n\n\n<p>An interesting way to tackle this question is to look at the discontinuities of yields and nitrogen pollution at international borders. This is the approach that David Wuepper and his colleagues took in a recent study, published in <em>Nature</em>.{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., &amp; Finger, R. (2020). <a href=\"https://www.nature.com/articles/s43016-020-00185-6\">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref} By looking at the discontinuities of yields, nitrogen balances and inputs across borders the researchers investigated the role that each country\u2019s agricultural policies play. This is because the environmental conditions, climate and soil qualities should be very similar just across the border. Technically they <em>should</em> be able to achieve a similar level of NUE, and similar yields. If there are large differences in yields or pollution between one country and its neighbor, we would therefore assume there are important country-specific effects playing a role. It mimics a \u2018natural experiment\u2019 where the environmental conditions are held constant, and policy decisions are the changeable variable.</p>\n\n\n\n<p>The contrast at the border between Kazakhstan and China; and Turkey and Syria provide good examples of this. We can see this in the aerial shots. The conditions for growing crops on either side should be similar. But China and Turkey have much more vegetation than their neighbors as a result of nutrient inputs and how they manage agriculture.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"2578\" height=\"624\" src=\"https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png\" alt=\"\" class=\"wp-image-44723\" srcset=\"https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity.png 2578w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-400x97.png 400w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-800x194.png 800w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-150x36.png 150w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-768x186.png 768w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-1536x372.png 1536w, https://owid.cloud/app/uploads/2021/08/nitrogen-pollution-discontinuity-2048x496.png 2048w\" sizes=\"(max-width: 2578px) 100vw, 2578px\" /><figcaption>Discontinuities in vegetation at country borders{ref}Wuepper, D., Le Clech, S., Zilberman, D., Mueller, N., &amp; Finger, R. (2020). <a href=\"https://www.nature.com/articles/s43016-020-00185-6\">Countries influence the trade-off between crop yields and nitrogen pollution</a>. <em>Nature Food</em>, <em>1</em>(11), 713-719.{/ref}</figcaption></figure>\n</div>\n</div>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>Using satellite imagery and geospatial datasets these researchers could measure four key metrics at high-resolution across hundreds of thousands of cross-country borders: cropland nitrogen balances, nitrogen pollution, yield gaps (the amount that yields could be increased with better management of nutrients), and the natural vegetation potential. They found cross-border differences in the first three metrics, but not in natural vegetation potential. This is important because it means our assumption that the environmental conditions on either side of borders is similar, is a valid one.{ref}In the few cases that natural vegetation potential did vary across borders, this was corrected for in the results.{/ref}</p>\n\n\n\n<p>Across this large global dataset, the researchers found that the discontinuity in nitrogen pollution across borders was much larger than the discontinuity in yield gaps. Their results suggest that globally there is massive potential to reduce nitrogen pollution without impacting crop yields. </p>\n\n\n\n<p><strong>They conclude that nitrogen pollution could be reduced by around 35% if polluting countries became as efficient as their neighbors. This would have little impact on crop yields \u2013 increasing yield gaps by only 1%.</strong></p>\n\n\n\n<p>Their results also allow us to understand what countries are using nitrogen inefficiently. The map here shows how countries compare in levels of nitrogen pollution versus their yield gains <em>relative to their neighbors</em>. Positive values \u2013 shown in orange and red \u2013 mean a country causes <em>more</em> pollution than necessary for the yields that it achieves. Negative values \u2013 shown in blue \u2013 means a country causes <em>less</em>.</p>\n\n\n\n<p>There are a couple of important points we need to keep in mind. All of these values are measured <em>relative to a country\u2019s neighbors</em>. A country might have a good score because their neighbor gets very low yields: South Korea is a good example. Or a country scores well because its neighbor uses nitrogen inefficiently: Mongolia is a good example.</p>\n\n\n\n<p>China has the highest score of 170%. This means it causes 170% more nitrogen pollution than is necessary to achieve its level of crop yields. Brazil, Mexico, Colombia, and Thailand also create a lot of pollution. These are the countries that are overapplying nitrogen the most: they could probably reduce fertilizer use significantly without affecting their crop yields.</p>\n\n\n\n<p>We often assume that more pollution is an unavoidable cost of trying to close yield gaps. But this trade-off does not always exist.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<iframe src=\"https://ourworldindata.org/grapher/yield-gap-vs-nitrogen-pollution\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n</div>\n</div>\n\n\n\n<h3>How can we use nitrogen more efficiently?</h3>\n\n\n\n<div class=\"wp-block-columns\">\n<div class=\"wp-block-column\">\n<p>You might notice that most of the largest polluters are middle-income countries. During the 1960s and 1970s, many of today\u2019s middle-income countries kickstarted their \u2018Green Revolution\u2019 and achieved large increases in food production. Governments offered subsidies for farmers to use fertilizers and other inputs. This made fertilizers cheap and reduced the incentives for farmers to use it efficiently.{ref}Kurdi, Sikandra; Mahmoud, Mai; Abay, Kibrom A.; and Breisinger, Clemens. 2020. Too much of a good thing? Evidence that fertilizer subsidies lead to overapplication in Egypt. MENA RP Working Paper 27. Washington, DC: International Food Policy Research Institute (IFPRI). <a href=\"https://doi.org/10.2499/p15738coll2.133652.%7B/ref\">https://doi.org/10.2499/p15738coll2.133652.</a>{/ref} This cheap fertilizer is one of the reasons that these countries massively overapply nitrogen today.</p>\n\n\n\n<p>One way that governments can therefore reduce nitrogen pollution is to adjust the ratio of fertilizer prices to the return on agricultural products. They can adjust subsidies to make it costly for farmers to overuse fertilizers. Instead, they could re-allocate these financial resources towards practices that have positive environmental impacts.</p>\n\n\n\n<p>Another option is to invert the financial incentives: rather than subsidizing fertilizers, you could tax them.</p>\n\n\n\n<p>We might want to make fertilizers more expensive for countries that overuse them. But we actually want to do the opposite for countries with large yield gaps. As we saw earlier, many countries across Sub-Saharan Africa use barely any fertilizer at all. They achieve very poor yields as a result. Providing subsidies for fertilizers and other inputs would be of massive benefit.</p>\n\n\n\n<p>One of the challenges of putting fertilizer on your crops is that it can be hard to know where it is needed. Some parts of your field might be lacking in nitrogen while others have more than enough. Often the easiest and quickest solution is to apply it everywhere, especially if fertilizers are heavily subsidized and cheap. But with emerging technologies, we can do better. Thanks to information from drones or satellite imagery, we can implement \u2018precision farming\u2019, which allows us to see exactly where fertilizers are needed the most.{ref}Finger, R., Swinton, S. M., El Benni, N., &amp; Walter, A. (2019). <a href=\"https://www.annualreviews.org/doi/abs/10.1146/annurev-resource-100518-093929\">Precision farming at the nexus of agricultural production and the environment</a>. Annual Review of Resource Economics, 11, 313-335.{/ref} Plant breeding technologies could also offer new opportunities.{ref} Walter, A., Finger, R., Huber, R., &amp; Buchmann, N. (2017). <a href=\"https://www.pnas.org/content/114/24/6148.short\">Opinion: Smart farming is key to developing sustainable agriculture</a>. <em>Proceedings of the National Academy of Sciences</em>, 114(24), 6148-6150.{/ref} We can try to improve how efficient we are at using nitrogen, but there\u2019s an opportunity to improve how efficiently plants use it too.</p>\n\n\n\n<p>Let\u2019s not forget that one of the most promising solutions \u2013 and one we often overlook \u2013 is the simplest and oldest of all. Legumes \u2013 crops such as beans, peas and lentils \u2013 perform their own magic when it comes to nitrogen. They have the ability to capture nitrogen in the atmosphere and transform it into reactive nitrogen on their own. This is called \u2018biological fixation\u2019. Unlike most other crops where we have to add additional nitrogen, they create it by themselves. Growing more legumes \u2013 either on their own, or alongside other crops \u2013 is one of the easiest ways that we can bring nitrogen into the soil.</p>\n\n\n\n<p>Finally, there\u2019s a lot that we can do by training farmers to adopt sustainable management practices. The 21-million-farmer study in China makes this clear.&nbsp; Large policy changes and technological advancements are often needed to make a large difference, but we shouldn\u2019t underestimate the impact that education can make.</p>\n\n\n\n<p>Many view crop yields and environmental pollution as an unavoidable trade-off. It doesn\u2019t have to be. We can reduce pollution a lot without reducing crop yields. Less pollution, more food, higher farmer returns, and less farmland make this a problem with multiple wins if we can implement the right solutions.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\"></div>\n</div>\n\n\n\n<hr class=\"wp-block-separator is-style-wide\"/>\n\n\n\n<h5>Explore more of our work at <em>Our World in Data</em></h5>\n\n\n    <block type=\"prominent-link\" style=\"is-style-thin\">\n        <link-url>http://ourworldindata.org/excess-fertilizer</link-url>\n        <title>Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers?</title>\n        <content>\n\n<p></p>\n\n</content>\n        <figure><img width=\"768\" height=\"301\" src=\"https://owid.cloud/app/uploads/2021/09/excess-fertilizer-768x301.png\" class=\"attachment-medium_large size-medium_large\" alt=\"\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/09/excess-fertilizer-768x301.png 768w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-400x157.png 400w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-800x314.png 800w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-150x59.png 150w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer-1536x603.png 1536w, https://owid.cloud/app/uploads/2021/09/excess-fertilizer.png 1600w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n    </block>\n\n    <block type=\"prominent-link\" style=\"is-style-thin\">\n        <link-url>http://ourworldindata.org/explorers/fertilizers</link-url>\n        <title>Fertilizers Data Explorer</title>\n        <content>\n\n<p>Explore fertilizer use and its impacts across the world in our data explorer.</p>\n\n</content>\n        <figure><img width=\"768\" height=\"404\" src=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png\" class=\"attachment-medium_large size-medium_large\" alt=\"COVID-19 data explorer\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png 768w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-400x210.png 400w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-800x421.png 800w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-150x79.png 150w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png 1200w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n    </block>\n\n    <block type=\"prominent-link\" style=\"is-style-thin\">\n        <link-url>http://ourworldindata.org/explorers/crop-yields</link-url>\n        <title>Crop Yields Data Explorer</title>\n        <content>\n\n<p>Explore crop yields across the world in our data explorer.</p>\n\n</content>\n        <figure><img width=\"768\" height=\"404\" src=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png\" class=\"attachment-medium_large size-medium_large\" alt=\"COVID-19 data explorer\" loading=\"lazy\" srcset=\"https://owid.cloud/app/uploads/2021/01/data_explorer-featured-768x404.png 768w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-400x210.png 400w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-800x421.png 800w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured-150x79.png 150w, https://owid.cloud/app/uploads/2021/01/data_explorer-featured.png 1200w\" sizes=\"(max-width: 768px) 100vw, 768px\" /></figure>\n    </block>",
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    "excerpt": {
        "rendered": "Some countries need more fertilizers to increase crop yields. But some could cut back without sacrificing food production.",
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    "date_gmt": "2021-09-09T11:33:00",
    "modified": "2021-09-09T16:04:21",
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    "ping_status": "closed",
    "authors_name": [
        "Hannah Ritchie"
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    "modified_gmt": "2021-09-09T15:04:21",
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