Fertilizer source and tillage effects on yield-scaled nitrous oxide emissions in a corn cropping system

Authors: Venterea, Rodney - Rod; MAHARJAN, BIJESH - University Of Minnesota; Dolan, Michael

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2011
Publication Date: 9/1/2011
Citation: Venterea, R.T., Maharjan, B., Dolan, M.S. 2011. Fertilizer source and tillage effects on yield-scaled nitrous oxide emissions in a corn cropping system. Journal of Environmental Quality. 40(5):1521-1531.

Interpretive Summary: Corn production consumes approximately 50% of all nitrogen (N) fertilizers applied to agricultural crops in the U.S. and therefore represents a large potential source of emissions of the potent greenhouse gas nitrous oxide (N2O) relative to other crops. Quantification of N2O emissions resulting from alternative corn production management regimes is therefore essential to developing effective N2O mitigation strategies. The objective of the current study was to quantify growing season N2O emissions occurring under multiple management practices in a corn cropping system in Minnesota over three consecutive growing seasons. Three different fertilizer application regimes, each designed to conserve fertilizer N, were applied to both an intensively-tilled and an untilled cropping system, and N2O emissions were measured using chambers on approximately 35 dates each season. Tillage treatments had been in place for more than 17 years. Fertilizer treatments consisted of conventional granular urea (GU), polymer-coated urea (PCU), and urea amended with nitrification and urease inhibitors (UI), each using 146 kg N ha-1 applied 4 to 5 weeks after planting. A control treatment which received only 4.5 kg N ha-1 at planting was also examined. Overall, tillage had no effect on cumulative growing season N2O emissions. Fertilizer-induced emissions calculated as the difference in emissions between each fertilized treatment and the control were < 0.35% of applied fertilizer N in all cases, which is low relative to most literature values. The UI treatment showed some potential for reducing N2O emissions compared to GU, although the effect was not consistent across years or tillage treatments. These results suggest that post-plant fertilizer applications are a potentially effective strategy for maintaining fertilizer-induced N2O emissions well below the value of 1% that is commonly assumed. This information will be useful to corn producers and environmental policy-makers and regulators interested in identifying practices that minimize N2O emissions.

Technical Abstract: Corn production consumes approximately 50% of all nitrogen (N) fertilizers applied to agricultural crops in the U.S. and therefore represents a large potential source of emissions of the potent greenhouse gas nitrous oxide (N2O) relative to other crops. Quantification of N2O emissions resulting from alternative corn production management regimes is therefore essential to developing effective N2O mitigation strategies. The objective of the current study was to quantify growing season N2O emissions occurring under multiple management practices in a corn cropping system in Minnesota over three consecutive growing seasons. Three different fertilizer application regimes, each designed to conserve fertilizer N, were applied to both an intensively-tilled and an untilled cropping system, and N2O emissions were measured using chambers on approximately 35 dates each season. Tillage treatments had been in place for more than 17 years. Fertilizer treatments consisted of conventional granular urea (GU), polymer-coated urea (PCU), and urea amended with nitrification and urease inhibitors (UI), each using 146 kg N ha-1 applied 4 to 5 weeks after planting. A control treatment which received only 4.5 kg N ha-1 at planting was also examined. Overall, tillage had no effect on cumulative growing season N2O emissions. Fertilizer-induced emissions calculated as the difference in emissions between each fertilized treatment and the control were < 0.35% of applied fertilizer N in all cases, which is low relative to most literature values. The UI treatment showed some potential for reducing N2O emissions compared to GU, although the effect was not consistent across years or tillage treatments. These results suggest that post-plant fertilizer applications are a potentially effective strategy for maintaining fertilizer-induced N2O emissions well below the value of 1% that is commonly assumed.