Rye Cover Crop Effects On Nitrous Oxide Emissions From a Corn-Soybean System.

Agricultural activities are a major source nitrous oxide emitted to the atmosphere. Development of management practices to reduce these emissions is needed.   Non-leguminous cover crops are efficient scavengers of residual soil nitrate, but their effects on nitrous oxide emissions have not been well documented.  This study quantified soil nitrous oxide emissions over an 8 year period from a corn/soybean production system with and without a rye winter cover crop.   In two of the 8 years direct nitrous oxide emissions were significantly reduced (P>0.1) in the treatment that included the cover crop.  When direct soil nitrous oxide emissions were averaged over the study period, no significant cover crop effect was observed.  Indirect emissions, estimated using the IPCC default protocol and measurements of nitrate leaching losses, were significantly reduced (P = 0.057) in the presence of the rye cover crop.   We conclude that a winter rye cover crop has limited potential to reduce nitrous oxide emissions in a corn/soybean system in central Iowa.