Assessment of Alternative Soil Management Practices on N sub(2)O Emissions from US Agriculture

The NGAS model, which estimates nitrification nitrous oxide flux from soil, was coupled with a N and carbon cycling scheme to simulate annual N sub(2)O emissions from 2639 cropland sites in the US. The emission mitigation potential of returning marginal cropland to perennial grass was also assessed by contrasting simulated emissions from 306 Conservation Reserve Program grassland areas with those from nearby cropland sites. Initial conversion of agricultural land to no-till showed higher N sub(2)O emissions/ha relative to conventional tillage. Spy, wheat, and corn cultivation areas contributed 68% of total emissions under both no-till and conventional tillage scenarios. Conversion of 10.5 million ha of cropland to grassland offers an emissions mitigation potential of 31 Gg N sub(2)O-N/yr.