Tuesday, November 14, 2006

Effect of Crop Rotation, Tillage, and Soil Series on Soil Organic Carbon Sequestration.

Ronald Follett, USDA-ARS, Soil Plant Nutrient Research, 2150 Centre Ave, Bldg D, Suite 100, Fort Collins, CO 80526-8119, Stephen Del Grosso, Agricultural Research Service of USDA, Natural Resources Research Center, 2150 Centre Avenue, BLDG D, Fort Collins, CO 80526, and James Wallace, Colonial Soil & Water Conservation District, PO Box 190, 2502 New Kent Hwy, Quinton, VA 23141.

Farm fields in eastern Virginia with corn-soybean and corn-small grain-soybean rotations from multiple farms were sampled to depths of 0-10 and 10-20 cm to measure soil organic carbon (SOC) sequestration for ‘complete no-till’ (no-till) vs. ‘conventional-till’ (conv-till) (tillage prior to small grain).  Cropping sequences include combinations of corn, small grain, and soybean for 3 coarse-textured soils. Soil samples were analyzed for SOC and soil bulk density.  Extensive prior information (past 5 years) on crop rotations, nutrients applied, tillage, and crop yields were collected for each field.  Tillage significantly affected SOC in the 0-10 and in the 0-20 cm depth increments.  Soil series was different in the 10-20 cm depth increment and there was a soil by depth interaction when both depths were considered.  Importantly, the data collected allow the ‘DAYCENT’ computer model to be calibrated to these soils.  Corresponding weather records were obtained for the same 5-year period from the Richmond climate station and model simulations were run for each field.  Use of the DAYCENT model provides a practical method to project rates of SOC sequestration and N2O emissions into the future under no-till and conv-till systems.  DAYCENT can also provide information that may be useful should carbon (C) trading or C markets develop for agricultural producers.  A SOC increase is projected for each of the soil series with that for the Alta Vista being the largest.  SOC sequestration increased for both no-till and conv-till to 10 years but the increase was larger for no-till.