Potential of nitrogen management strategies to mitigate nitrous oxide emissions in corn

Effective management of nitrogen (N) in corn (Zea mays L.) cropping systems can positively affect production and mitigate environmental impacts such as nitrous (N₂O) emissions. The goal was to quantify N₂O emissions and the response of corn to application of N employing diverse management approaches (soil test and sensor-based approaches) to identify effective N management strategies. In 2016 and 2017, a corn study was established on a Belvue silt loam soil at the Ashland Bottoms Research Farm south of Manhattan, KS (39º 08’ N lat, 96º 37’ W long). In 2017, an additional site on a Eudora silt loam was added at the Kansas River Valley Experiment Field northwest of Topeka, KS (39º 04’ N lat, 95º 46’ W long). The study was a randomized complete block design comprised of five treatments replicated four times. Nitrogen treatments were stream applied as 28% N in the form of urea ammonium nitrate and included: Check, Soil Test, Split-Soil Test, Sensor, and Aerial NDVI. Nitrous oxide emissions were measured throughout the growing season using a static chamber method. Cumulative emissions ranged between 0.03 – 0.14 kg N₂O-N ha⁻¹. There were no significant differences among treatment cumulative emissions at any of the three site-years. Manhattan grain yields ranged from 6.2 – 11.3 and 1.9 – 6.7 Mg ha⁻¹ in 2016 and 2017, respectively. Yield was not significantly across the four N management strategies in 2016, but in 2017 Split-Soil Test was significantly higher than Sensor. Topeka grain yields ranged from 8.0 – 15.2 Mg ha⁻¹. Soil Test and Split-Soil Test were significantly higher than Sensor and Aerial NDVI. Treatments receiving nitrogen yielded higher than the Check for all site-years. Yield-scaled nitrous oxide emissions (YSNE) were not significantly different at Manhattan in 2016 and Topeka in 2017. Check was significantly higher than the N management strategies at Manhattan in 2017. Emissions factor (EF) was ≥0.07 percent for all site-years on continuously tilled, low organic matter, river bottom silt loam soils with surface applied N fertilizer at agronomic N rates, which is markedly lower than the IPCC default value of one percent. Results between site-years were variable, which may stem from differences in site characteristics and water availability. Further investigation is needed to assess the ability of N management strategies to increase corn yield and lower N₂O emissions.