Influence of crop rotation and aggregate size on carbon dioxide production and denitrification

The influence of soil and crop management practices on soil aggregation is well documented; however very little information is available on the impact of aggregation on biological processes such as greenhouse gas emissions. Soils (Ap horizon of a Brookston clay loam) were sampled in the spring of 2002 from two treatments in a long-term study (established in 1959). The treatments included continuous corn ( Zea mays L.) and the corn phase of a 4-year crop rotation which included corn–oats ( Avena sativa L.)–alfalfa ( Medicago sativa L.)–alfalfa. The continuous corn (CC) treatment was plowed every fall whereas the rotation corn (RC) treatment was plowed 2 out of the 4 years (in the fall following second year alfalfa and following corn). The objectives were to determine the impact of crop rotation and continuous corn on aggregate size distribution, and the influence of aggregate size on CO 2 and N 2O production through denitrification. The soil samples were separated into six aggregate size fractions (