EFFECT OF PREVIOUS CROP RESIDUE ON SOIL SURFACE CARBON DIOXIDE FLUX IN MAIZE

Abstract

Information regarding carbon (C) cycling in terrestrial ecosystems will become increasingly important as measures to offset rising atmospheric carbon dioxide (CO2) levels are explored. This study focused on the effect of previous crop on soil surface CO2 flux in maize (Zea mays L.). Maize grown in a continuous cropping system exhibited greater soil CO2 flux than maize following soybean [Glycine max (L.) Merrill] in rotation, and this difference was greatest early in the growing season. The higher flux measured in continuous maize (CM) was attributed to greater amounts of maize residue returned to the soil after the previous growing season as compared with the soybean residue returned to the soil in the maize-soybean (MS) rotation. Soil CO2 flux integrated during a 50-day sampling period during the 2001 growing season was 3089 kg C ha−1 for CM and 2505 kg C ha−1 for maize following soybean. Soil CO2 integrated during an 82-day sampling period during the 2002 growing season was higher in CM (4098 kg C ha−1) than in maize following soybean (3901 kg C ha−1). This pattern was reversed during a 247-day sampling period after maize harvest, when integrated soil CO2 flux was higher in the MS rotation (4915 kg C ha−1) than in CM (4823 kg C ha−1), presumably because of the considerably greater amount of residue returned to the soil by maize following soybean in the fall of 2002. Estimated annual soil CO2 flux based on an 11-month sampling period in 2002 to 2003 was 9786 kg C ha−1 year−1 for the CM and 9667 kg C ha−1 year−1 for maize following soybeans.