In many regions around the world, too much fertilization is used – with negative consequences for ecosystems, the climate and health. However, as a study now shows, many countries could use significantly less nitrogen fertilizer without losing crop yields. Because the nitrate excess often brings only minimal benefits for the yield. In order to change that, politics in particular offers a number of starting points, as the researchers found.
Plants need nitrogen to grow, which is why this nutrient is usually added as a nitrate fertilizer in agriculture. This should ensure stable yields and replace the nutrients that were removed from the soil by the crops. However, in common practice in many places far more nitrate is applied to the fields in the form of fertilizers and liquid manure than the plants can absorb. As a result, there is an excess of nitrogen compounds in the soil, in water bodies and also in groundwater – with negative consequences for the ecosystem, for the climate and also for human health.
Does the increase in yield justify common fertilization practices?
Given these negative consequences, the question arises of how much nitrogen fertilizer really needs to be. According to popular assumption, many arable soils require such fertilization in order to grow crops with sufficiently high yields. Otherwise – so the argument goes – there is a risk of too large a profit gap. It describes the difference between the possible and the actually achieved yield. David Wüpper from ETH Zurich and his colleagues have now investigated whether fertilization practice in different countries is actually geared towards minimizing the yield gap and which economic and political factors may influence fertilization practice in different countries.
For their study, the researchers determined for the first time the overall effect of almost all countries in the world on their nitrogen pollution and crop yields. It turned out that national policy is actually a decisive factor when it comes to the use of nitrogen fertilizers in agriculture. And it is often these influences that drive up the amount of fertilizer used and the associated pollution – without significantly increasing crop yields. The comparative analyzes showed that countries such as Germany, France, South Korea, the USA or Austria cause an average of 35 percent less nitrogen pollution than some of their neighboring countries with similar soil and climate conditions. Nevertheless, their earnings gap is only one percent larger, as Wüpper and his team report.
Above all, politics offers starting points
According to the scientists, this means that many countries could reduce their fertilizer use without risking major crop losses. They identify the reasons for the unnecessary use of nitrogen and nitrogen pollution, among other things, in the quality of institutions, economic development, the size of the population, but also how high the share of agriculture in the overall economy of a country is. Direct subsidies, with which a state makes nitrogen fertilizers cheaper, as well as indirect grants, regulations and laws, the training of farmers, the use of technologies or trade structures are also relevant.
All of this suggests that national governments could be a powerful lever in containing the problem, the researchers say. One possible approach is, for example, the price of nitrogen fertilizer: in countries where too much of it is used, the fertilizer would have to become correspondingly more expensive, for example through the introduction of a nitrogen tax or other political instruments. In poorer countries such as sub-Saharan Africa, on the other hand, prices could be reduced through subsidies. Because there, a lack of nitrogen fertilizer leads to considerable reductions in yields and contributes to malnutrition of the population.
In the industrialized and emerging countries characterized by overfertilization, incentives for farmers to make their production more environmentally friendly could also be effective – for example by promoting more efficient production processes or financial compensation for reduced yields. New technologies can also help to save on fertilizer: “The keyword is precision agriculture, in which, for example, fertilizer is only applied where it is actually needed,” explains Wüpper’s colleague Robert Finger. “This can increase the efficiency of use and reduce environmental problems without shrinking production.” As the researchers emphasize, however, consumer behavior can also have a regulating effect: the waste of food and high meat consumption increase the pressure on agriculture to produce more and more.
Source: Swiss Federal Institute of Technology Zurich; Professional article: Nature Food, doi: 10.1038 / s43016-020-00185-6