Evaluating greenhouse gas emissions in an irrigated cropping system

In a paper recently published in the Soil Science Society of America Journal, researchers report nitrous oxide (N₂O), carbon dioxide (CO2), and methane (CH4) emissions from a dairy forage rotation (silage corn-barley-alfalfa) in south-central Idaho that received various nitrogen sources, including granular urea, an enhanced-efficiency fertilizer (SuperU), dairy manure, or composted dairy manure.

During corn production, the team found that cumulative N₂O emissions were 53% lower with SuperU when compared with granular urea, and crop yields were unaffected. But when SuperU was used the following year with barley, cumulative N₂O emissions were the same as those from granular urea. Overall, N₂O-N emission losses as a percentage of total N applied were very low. Carbon dioxide emissions were greatest from the manure treatment during the first two years, while CH4 emissions were negative, with no differences among the N treatments.

This work demonstrates that SuperU can reduce N₂O emissions from irrigated cropping systems, but the results suggest that there is a crop-dependent effect. The study is currently being replicated for confirmation.