A smallholder farmer holds fertilizer in her hands.
Photo: ©C. de Bode/CGIAR

On-farm nitrogen management practices have global reverberations

A new meta-study confirms that nitrous oxide emissions can be reduced by boosting nitrogen productivity, crop yield and use of “4Rs” - right source, right timing, right placement and right application.

An international team of scientists, in their new publication: Meta-analysis of yield and nitrous oxide outcomes for nitrogen management in agriculture, has strengthened our understanding of how better fertilizer management could help minimize nitrous oxide (N2O) emissions while still achieving high crop yields. In this meta-analysis research, the results of multiple scientific studies are statistically combined.

To meet the world’s growing demand for food, farmers need fertile soil. Nitrogen, an essential element in plant fertilizer, can have extremely deleterious effects on the environment when not managed effectively. Numerous studies have confirmed that improving nitrogen use in agriculture is key to securing a food-secure future and environmental sustainability.

“Society needs nuanced strategies based upon tailored nutrient management approaches that keep nitrogen balances within safe limits,” said Tai M Maaz, researcher at the University of Hawaiʻi at Mānoa and lead author of the study.

When farmers apply nitrogen fertilizer to their crop, typically only 30 to 40 per cent of it is taken up by the plant and the rest is lost in the environment. One by-product is  nitrous oxide (N2O), one of the most potent greenhouse gases in the atmosphere. Global agriculture is a major contributor of greenhouse gas emissions, especially those derived from nitrous oxide emissions.

Although farmers are now commonly told to practice fertilizer rate reduction, or simply put, to apply less fertilizer, there are cases where that strategy is either not possible or not advisable.

Alternative predictors of emissions


The study found that output indicators such as partial nitrogen balance (PNB), an indicator for the amount of nitrogen prone to loss, and partial factor productivity (PFP), a measure of input-use efficiency, predicted nitrous oxide emissions as well as or better than the application rate alone. This means that in some cases, where nitrogen rate reduction is not possible, nitrous oxide emission can still be reduced by increasing yield through implementing improved fertilizer management practices, such as the “4Rs:” right source, right timing, right placement and right application rate.

Tek B. Sapkota, climate scientist at the International Maize and Wheat Improvement Center (CIMMYT) and co-author of the study, emphasized that “rate reduction is still important in the cropping systems where the current level of nitrogen application is excessively high. But, when comparing the systems at the same nitrogen application rates, nitrous oxide emission can be reduced by increasing yield.”

“The 4R nutrient management practices must be tailored to specific regions to help close yield gaps and maintain environmental sustainability: the win-win scenario. The future will require public and private institutions working together to disseminate such nutrient management information for specific cropping systems in specific geographies,” said Sapkota, who is also a review editor of the Intergovernmental Panel on Climate Change (IPCC) sixth assessment report.

The article was a collaborative effort from the International Maize and Wheat Improvement Center (CIMMYT), the University of Hawaiʻi , the Environmental Defense Fund, Plant Nutrition Canada and the African Plant Nutrition Institute. It was funded by the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).

(CGIAR/wi)

Read the full study:
Tai M. Maaz, et al.: Meta‐analysis of yield and nitrous oxide outcomes for nitrogen management in agriculture; Global Change Biology, April
2021, https://doi.org/10.1111/gcb.15588


More information: 
CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS)

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