Jun 10, 2014 11:36 AM EDT
Climate Change: Too Much Fertilizer May Speed Up Global Warming
Applying more precise amounts of nitrogen-based fertilizer could help combat climate change, according to a recent study.
Researchers from Michigan State University found that emissions of nitrous oxide, a greenhouse gas produced in the soil after nitrogen-based fertilizer is added, rise faster than previously expected when fertilizer rates exceed crop needs.
Researchers said nitrogen-based fertilizers spur greenhouse gas emissions by stimulating microbes in the soil to produce more nitrous oxide. Nitrous oxide is the third most important greenhouse gas, behind only carbon dioxide and methane, and also destroys stratospheric ozone. Agriculture accounts for around 80 percent of human-caused nitrous oxide emissions worldwide, which have increased substantially in recent years, primarily due to increased nitrogen fertilizer use.
"Our specific motivation is to learn where to best target agricultural efforts to slow glbal warming," Phil Robertson, senior author of the study and director of MSU's Kellogg Biological Station Long-term Ecological Research Program, said in a statement. "Agriculture accounts for 8 to 14 percent of all greenhouse gas production globally. We're showing how farmers can help to reduce this number by applying nitrogen fertilizer more precisely."
Researchers said the production of nitrous oxide can be greatly reduced if the amount of fertilizer crops need is exactly the amount that's applied to farmers' fields. Simply put, when plant nitrogen needs are matched with the nitrogen that's supplied, fertilizer has substantially less effect on greenhouse gas emission.
Iurii Shcherbak, lead author of the study, noted that the research also informs fertilizer practices in underfertilized areas such as sub-Saharan Africa.
"Because nitrous oxide emissions won't be accelerated by fertilizers until crop nitrogen needs are met, more nitrogen fertilizer can be added to underfertilized crops with little impact on emissions," he said.
Adding less nitrogen to overfertilized crops elsewhere, however, would deliver major reductions to greenhouse gas emissions in those regions.
Researchers said the study provides support for expanding the use of carbon credits to pay farmers for better fertilizer management. Carbon credits for fertilizer management are now available to United States corn farmers.
The findings were recently published in the Proceedings of the National Academy of Sciences.
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