By using fertilizer more efficiently, farmers can reduce emissions while maintaining yields.
Somewhere in the hall of fame of transformational inventions, there is a space reserved for synthetic nitrogen fertilizers. By supplying the nitrogen needed for plant growth on a mass-produced scale, these fertilizers enable crops to produce yields that were unthinkable for most of human history. Today, they are central features of much of modern agriculture. They are also major contributors to climate change.
Nitrogen fertilizers produce greenhouse gases at every stage of their life cycle, from the natural gas used to manufacture them, to the production process itself, and finally when fertilizer is applied to the field. The emissions in this final stage come in the form of nitrous oxide, a greenhouse gas nearly 300 times more potent than carbon dioxide.
Nitrous oxide emissions from fertilizer application are a growing problem in Canada, having risen almost 90% between 2005 and 2021. They represent an increasing share of emissions from agriculture too, jumping from 10 per cent to 17 per cent of the sector’s emissions in the same period.
For this reason, the Government of Canada has set a goal to reduce nitrous oxide emissions from fertilizer use by 30 per cent below 2020 levels by 2030. Contrary to some reports, the target is purely voluntary and the government will not require farmers to use less fertilizer. Instead, research suggests that the government’s target can be achieved through more efficient farming techniques that reduce emissions while preserving crop yields.
Using nitrogen more efficiently
Nitrous oxide emissions are partly the result of inefficiency. Nitrogen is applied to fields in such large quantities that much of it is never absorbed by crops. Instead, this “excess nitrogen” is transformed into nitrous oxide by microbes in the soil, runs off into bodies of water, leaches into the soil or is emitted into the atmosphere, where it contributes to toxic algae blooms and poor water quality, produces air pollution, and accelerates climate change.
Compared to other countries, Canada uses nitrogen fertilizers relatively efficiently. But it has become slightly less efficient in recent years. In 2020, Canada’s “nitrogen use efficiency” was about 64 per cent, meaning that 36 per cent of nitrogen in farm soils was not absorbed by crops. In comparison, agriculture in the United States has become somewhat more nitrogen efficient, while relatively inefficient China has gotten noticeably better.
The good news is that because nitrous oxide emissions are partly the result of inefficiency, it should be possible to optimize nitrogen fertilizer use in ways that reduce emissions—and other harms—without threatening crop yields.
More efficient farming can hit the federal target
Techniques that maximize the nitrogen absorbed by crops and minimize the amount emitted into the atmosphere are often described as “beneficial management practices,” or BMPs. Farmers and the fertilizer industry have a framework called the “4Rs” to describe some of these practices, so-named because it refers to using the right source of fertilizer, at the right rate, the right time, and in the right place.
The “right source” could mean using fertilizers that reduce nitrogen loss, known as enhanced efficiency fertilizers, or replacing some synthetic fertilizer with manure. Farmers can help identify the “right rate” by testing the level of nitrogen in their soils. They can choose the “right time” by applying fertilizers when there is a lower risk of runoff, or at different stages during the growing season. And they can apply fertilizer in the “right place” by spreading fertilizer in bands, or strips, across the field.
Research indicates that the 4Rs, combined with other beneficial management practices, can reduce enough nitrous oxide emissions to hit, or even exceed, the federal target. The problem is that these practices aren’t being adopted widely enough. A recent survey showed that while a few practices are relatively common—many canola growers, for example, have reduced the risk of runoff by applying their fertilizer in the spring rather than in the fall—some of the most effective management practices are not. Enhanced efficiency fertilizers offer some of the greatest potential for reducing nitrous oxide emissions, but they represented only about 15 per cent of the nitrogen used on Canadian farms in 2021.
Policy can offer stronger incentives to reduce emissions
There are a few ways that policymakers can give farmers stronger incentives to adopt these techniques.
One of the biggest obstacles to change is a lack of information. Because farming practices, weather, crop mixes and soil types vary across Canada, the “right” combination of management practices will be different for every farmer. Government can help bridge this information gap, including by funding the expansion of lab capacity so that farmers can regularly test the nitrogen in their soil, and sharing the cost of agronomy services that calculate the costs and benefits of different practices.
Those benefits aren’t limited to emissions reduction. In the long term, beneficial management practices should also lead to healthier soil and lower fertilizer costs, all of which is beneficial for farmers’ yields and margins. Survey data show that farmers have reported increased returns after adopting 4R management plans.
Policy can give farmers other incentives to optimize their use of nitrogen fertilizers. Part of the solution may be more funding, since extension services (like agronomists), enhanced efficiency fertilizers, and precision agriculture technology are all expensive. In some cases, it might be appropriate for governments to set conditions for accessing these funds, like requiring farmers to prepare nutrient management plans. And governments need better metrics to credit farmers for their efforts, since the methodology of Canada’s national inventory doesn’t yet measure some of the emissions reductions from beneficial management practices.
The federal government will have an opportunity to advance some of these solutions when it releases its sustainable agriculture strategy. It should publish the metrics it will use to track progress toward its target, such as the deployment of enhanced efficiency fertilizers. It can clarify how it will reconcile its desire for rising agriculture exports with the need for emissions reductions. And it can address the understandable anxiety about its fertilizer emissions target by stating the truth: Canada can grow food and cut emissions at the same time.
Ross Linden-Fraser is a Senior Research Associate with the Canadian Climate Institute.