Nitrous Oxide Emissions From Anhydrous Ammonia, Urea, and ESN Fertilizers in Illinois.

Nitrous oxide (N₂O) has a large global warming potential (GWP) and agricultural applications of nitrogen (N) contribute to N₂O emissions. The objective of the study was to investigate the potential to reduce N₂O emissions using different N sources. The study was conducted near Urbana, Illinois on highly productive mollisols during 2009 to 2011 using as N sources: anhydrous ammonia (AA); urea; and the polymer coated urea, ESN. In addition to an unfertilized check, corn (Zea mays L.) received 110 kg N ha^-1 in 2009 and 180 kg N ha^-1 in 2010 and 2011. Nitrous oxide fluxes were measured one to three times per week early in the growing season and less frequently at the end of the season using vented non-steady state closed chambers. Regardless of N source, N₂O-N emissions were largest immediately after substantial (>20 mm) single or 2-3 day cumulative rains during June and July, dropping to near background levels thereafter. Emission differences for treatments occurred in 2010, which was the only year with high N₂O-N emissions. In 2010, cumulative emissions in kg N₂O-N ha^-1 were lowest for the check (2.21) followed by ESN (9.77), and ESN was significantly lower than urea (14.07) and AA (16.89). Across years and N sources the fertilized plots emitted 4.3 times more N₂O-N than the check. Across years, mean cumulative emission for ESN was 4.95 kg N₂O-N ha^-1and 39% lower than AA, while urea emitted intermediate amounts. Across years the check had the lowest grain yield, but no differences in yield occurred between N sources. However, N₂O-N emissions per unit of corn yield for ESN were similar to the check and 45% lower than for AA, with urea produced intermediate values. The data indicate that ESN can maintain high-corn yield levels while mitigating N₂O-N emissions relative to AA.