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.10 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.11 Plant breeding technologies could also offer new opportunities.12 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.

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