Tillage and inorganic nitrogen source effects on nitrous oxide emissions from irrigated cropping systems.

Nitrogen fertilization is essential for optimizing crop yields; however, it increases N 2 O emissions. The study objective was to compare N 2 O emissions resulting from application of commercially available enhanced-efftciency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn (Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha -1 when in corn, 56 kg N ha -1 when in dry bean (Phaseolus vulgaris L.), and 157 kg N ha -1 when in barley (Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn-dry bean (NT-CDb), and no-till corn-barley (NT-CB). In the NT-CC and CT-CC systems, a controlled-release, polymer-coated urea (ESN) and dry granular urea were compared. In the NT-CDb and NT-CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N 2 O emissions from urea and ESN application were not different under CT-CC, but ESN reduced N 2 O emissions 49% compared with urea under NT-CC. Compared with urea, SuperU reduced N 2 O emissions by 27% in dry bean and 54% in corn in the NT-CDb rotation and by 19% in barley and 51% in corn in the NT-CB rotation. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N 2 O emissions from irrigated systems.

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