Effects of residue management and controlled traffic on carbon dioxide andwater loss

Management of crop residues and soil organic matter is of primary importanc e in maintaining soil fertility and productivity and in minimizing agricult ural impact on the environment. Our objective was to determine the effects of traffic and tillage on short-term carbon dioxide (CO2) and water (H2O) f luxes from a representative soil in the southeastern Coastal Plain (USA). T he study was conducted on a Norfolk loamy sand (FAO classification, Luxic F erralsols; USDA classification, fine-loamy siliceous, thermic Typic Kandiud ults) cropped to a corn (Zea mays L.)- soybean (Glycine maw (L.) Merr) rota tion with a crimson clover (Trifolium incarnatum L.) winter cover crop for eight years. Experimental variables were with and without traffic under con ventional tillage (CT) (disk harrow twice, chisel plow, field cultivator) a nd no tillage (NT) arranged in a split-plot design with four replicates. A wide-frame tractive vehicle enabled tillage without wheel traffic. Short-te rm CO2 and H2O fluxes were measured with a large portable chamber. Gas exch ange measurements were made on both CT and NT at various times associated w ith tillage and irrigation events. Tillage-induced COP and H2O fluxes were larger than corresponding fluxes from untilled soil. Irrigation caused the CO2 fluxes to increase rapidly from both tillage systems, suggesting that s oil gas fluxes were initially limited by lack of water. Tillage-induced CO2 and H2O fluxes were consistently higher than under NT. Cumulative CO2 flux from CT at the end of 80 h was nearly three times larger than from NT whil e the corresponding H2O loss was 1.6 times larger. Traffic had no significa nt effects on the magnitude of CO:! fluxes, possibly reflecting this soil's natural tendency to reconsolidate. The immediate impact of intensive surfa ce tillage of sandy soils on gaseous carbon loss was larger than traffic ef fects and suggests a need to develop new management practices for enhanced soil carbon and water management for these sensitive soils. (C) 1999 Elsevi er Science B.V. All rights reserved.