Key Takeaways
- NC State University researchers completed a three-year study on nitrogen-related emissions from corn fields in North Carolina.
- The study evaluated dual urease and nitrification inhibitors across 18 farms with different soil types.
- Results showed consistent reductions in ammonia emissions, while nitrous oxide outcomes varied by soil texture.
- Yield impacts were generally small, even with reduced nitrogen application rates.
- Findings may inform future incentive programs and carbon crediting discussions.
NC State University Conducts Multi-Year Study on Fertilizer Emissions
Researchers at NC State University are gaining new insights into how enhanced efficiency fertilizers affect nitrous oxide and ammonia emissions in corn production. Since 2023, the study has examined 18 farms across North Carolina, from Greensboro to the coastal plain, focusing on environmental outcomes and potential economic implications for growers.
The research is led by Alex Woodley, associate professor in the Department of Crop and Soil Sciences and faculty affiliate of the N.C. Plant Sciences Initiative. The project, known as the Beyond Yield study, is funded by the U.S. Department of Agriculture’s Natural Resources Conservation Service and involves collaboration with multiple NC State faculty members.
Conventional nitrogen fertilizers are widely used to boost crop yields, but only an estimated 40–60% of applied nitrogen is absorbed by plants. Unused nitrogen can be converted into nitrous oxide, a potent greenhouse gas, or ammonia, which can negatively affect air and water quality.
How Enhanced Efficiency Fertilizers Were Evaluated by NC State Researchers
Dual Inhibitors and Field Monitoring
The study focused on fertilizers treated with a dual urease and nitrification inhibitor. These additives slow the conversion of urea and ammonium, allowing nitrogen to remain available in the root zone for a longer period.
Woodley’s team conducted weekly measurements in paired corn plots, comparing fields with and without inhibitors. The results showed that ammonia emissions were reduced on nearly every farm where inhibitors were applied. Nitrous oxide emissions, however, varied significantly depending on soil type.
“With nitrous oxide, on heavy-texture soil, like clay and loam, where it gets wetter and saturated longer, we saw the inhibitors work,” Woodley said. “But on really sandy soils, we saw less effectiveness.”
Yield and Economic Implications for Farmers
Limited Yield Differences Observed by NC State Researchers
The research also examined whether reducing nitrogen application rates affected crop yields. In many cases, yields from half-rate nitrogen applications were comparable to those from full-rate applications, regardless of inhibitor use.
“In a lot of the cases, what we found is the yields aren’t very different between that half application versus the full application,” Woodley said.
From a purely agronomic perspective, the added cost of inhibitors may not always be offset by yield gains. To further assess the financial implications, the research team is working with NC State agricultural economist Rod Rejesus to model economic outcomes, including potential carbon credit scenarios.
Policy Relevance and Future Applications
Woodley noted that while inhibitors may not currently justify their cost based solely on yield, they could play a role if incentive programs or subsidies are introduced.
“What this research will do is allow farmers to have a couple things on paper,” he said. “It can also potentially unlock economic incentives in the future for more sustainable nitrogen use.”
As the team prepares to publish its findings, the study is expected to provide data for both growers and policymakers evaluating strategies to reduce agricultural emissions while maintaining farm profitability.
