Benefits of Crop Rotation for Reducing Nitrous Oxide Emissions.

Nitrous oxide emissions are influenced by management practices, indigenous soil properties as well as climatic factors.  The influence of the previous crop in the rotation has been demonstrated; however there is not very much information available concerning the overall impacts of crop rotation on nitrous oxide emissions and N dynamics.  Therefore, a 4-year study was conducted to determine the effects of crop rotation (corn-oats-alfalfa-alfalfa, C-O-A-A) and phase of the rotation on nitrous oxide emissions, N uptake and crop yields as compared to monoculture corn. Nitrous oxide emissions were measured from static chambers on a weekly basis during each growing season.  The 4-year average N₂O emissions were 16.5% greater in the corn phase of the C-O-A-A rotation (9.25 kg N ha^-1) as compared to continuous corn (7.94 kg N ha^-1). However, the oats phase of the rotation had about 1/3 of the N₂O emissions as the corn phase (3.1 kg N ha^-1) and both alfalfa years had even lower N₂O emissions (1.1 and 1.3 kg N ha^-1). The net result was that the N₂O emissions averaged over all 4 phases of the rotation were 3.7 kg N ha^-1 which was about ½ of the continuous corn N₂O emissions. Rotation corn also had considerably greater corn yields (10.2 t ha^-1) and N uptake (73.0 kg N ha^-1) as compared to continuous corn with a yield of 6.82 t ha^-1 and N uptake of 123 kg N ha^-1 over the 4-yr period. Hence improved soil quality with crop rotation enhanced N utilization by crops and reduced N₂O emissions compared to monoculture cropping.