Effects of residue management and controlled traf®c on carbon dioxide and water loss

Management of crop residues and soil organic matter is of primary importance in maintaining soil fertility and productivity and in minimizing agricultural impact on the environment. Our objective was to determine the effects of traf®c and tillage on short-term carbon dioxide (CO2) and water (H2O) ̄uxes from a representative soil in the southeastern Coastal Plain (USA). The study was conducted on a Norfolk loamy sand (FAO classi®cation, Luxic Ferralsols; USDA classi®cation, ®ne-loamy siliceous, thermic Typic Kandiudults) cropped to a corn (Zea mays L.) Ð soybean (Glycine max (L.) Merr) rotation with a crimson clover (Trifolium incarnatum L.) winter cover crop for eight years. Experimental variables were with and without traf®c under conventional tillage (CT) (disk harrow twice, chisel plow, ®eld cultivator) and no tillage (NT) arranged in a splitplot design with four replicates. A wide-frame tractive vehicle enabled tillage without wheel traf®c. Short-term CO2 and H2O ̄uxes were measured with a large portable chamber. Gas exchange measurements were made on both CT and NT at various times associated with tillage and irrigation events. Tillage-induced CO2 and H2O ̄uxes were larger than corresponding ̄uxes from untilled soil. Irrigation caused the CO2 ̄uxes to increase rapidly from both tillage systems, suggesting that soil gas ̄uxes were initially limited by lack of water. Tillage-induced CO2 and H2O ̄uxes were consistently higher than under NT. Cumulative CO2 ̄ux from CT at the end of 80 h was nearly three times larger than from NT while the corresponding H2O loss was 1.6 times larger. Traf®c had no signi®cant effects on the magnitude of CO2 ̄uxes, possibly re ̄ecting this soil's natural tendency to reconsolidate. The immediate impact of intensive surface tillage of sandy soils on gaseous carbon loss was larger than traf®c effects and suggests a need to develop new management practices for enhanced soil carbon and water management for these sensitive soils. # 1999 Elsevier Science B.V. All rights reserved.