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N loss to drain flow and N2O emissions from a corn-soybean rotation with winter rye N loss to drain flow and N20 emmissions from a corn-soybean rotation with winter rye

K. Gillette, R.W. Malone, T.C. Kaspar, L. Ma, T.B. Parkin, D.B. Jaynes, Q.X. Fang, J.L. Hatfield, G.W. Feyereisen, K.C. Kersebaum
Science of the total environment 2017 v.618 no. pp. 982-997
Glycine max, Root Zone Water Quality Model, Zea mays, coasts, corn, cover crops, crop rotation, emissions factor, fertilizers, field capacity, greenhouse gas emissions, hypoxia, leaching, mineralization, nitrates, nitrogen, nitrogen content, nitrogen cycle, nitrous oxide, rain, rye, soil water, soil water content, soybeans, subsurface drainage, winter, Iowa
Anthropogenic perturbation of the global nitrogen cycle and its effects on the environment such as hypoxia in coastal regions and increased N2O emissions is of increasing, multi-disciplinary, worldwide concern, and agricultural production is a major contributor. Only limited studies, however, have simultaneously investigated NO(3)− losses to subsurface drain flow and N(2)O emissions under corn-soybean production. We used the Root Zone Water Quality Model (RZWQM) to evaluate NO(3)− losses to drain flow and N(2)O emissions in a corn-soybean system with a winter rye cover crop (CC) in central Iowa over a nine year period. The observed and simulated average drain flow N concentration reductions from CC were 60% and 54% compared to the no cover crop system (NCC). Average annual April through October cumulative observed and simulated N(2)O emissions (2004–2010) were 6.7 and 6.0kgN(2)O-Nha−1yr−1 for NCC, and 6.2 and 7.2kgNha−1 for CC. In contrast to previous research, monthly N(2)O emissions were generally greatest when N loss to leaching were greatest, mostly because relatively high rainfall occurred during the months fertilizer was applied. N(2)O emission factors of 0.032 and 0.041 were estimated for NCC and CC using the tested model, which are similar to field results in the region. A local sensitivity analysis suggests that lower soil field capacity affects RZWQM simulations, which includes increased drain flow nitrate concentrations, increased N mineralization, and reduced soil water content. The results suggest that 1) RZWQM is a promising tool to estimate N(2)O emissions from subsurface drained corn-soybean rotations and to estimate the relative effects of a winter rye cover crop over a nine year period on nitrate loss to drain flow and 2) soil field capacity is an important parameter to model N mineralization and N loss to drain flow.