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CIMMYT

Less fertilizer, same crop yields

Low Emissions Development

Nitrogen fertilizers are a significant source of the greenhouse gas nitrous oxide (N2O). But farmers are often reluctant to reduce their fertilizer rates for fear of reducing crop yields and losing income. In the case of spring wheat fields in Mexico, however, CCAFS and the International Maize and Wheat Improvement Centre (CIMMYT) have found that applying less nitrogen fertilizer can significantly curtail N2O emissions without reducing yield.

CIMMYT

These findings are particularly important for Mexico, as 80% of wheat production in the country comes from irrigated conditions, where excess nitrogen fertilizer is applied.

The researchers, working in collaboration with Michigan State University, measured N2O outputs from irrigated spring wheat in northwest Mexico fertilized at 5 nitrogen rates during 2 growing seasons. Emissions of N2O increased following soil management activities, especially the application of nitrogen fertilizer, and particularly when this input exceeded crop requirements.

Below average emissions of N2O were measured when the volume of fertilizer used was not enough to produce a good crop. However, substantially higher than average emissions were found when an excess of fertilizer was applied – more than was needed to produce an optimum yield. This exponential response, consistent with other crops, suggests large decreases in N2O emissions are possible with lower nitrogen inputs and without any negative impact on yield.

“With fertilizer use patterns in the Yaqui Valley a likely gauge for high-productivity irrigated cereal systems elsewhere, our results provide evidence for a win–win–win scenario – large reductions in agricultural greenhouse gas emissions, increased farmer incomes and maintained or even improved productivity.” Ivan Ortiz-Monasterio, Senior Scientist in the Wheat Program at CIMMYT

The Mexico study used these findings to inform management strategies for mitigating N2O emissions without compromising productivity and economic returns. It also explored opportunities for farmers to take advantage of global carbon markets, and generate income from any improvements in nitrogen management they adopt.