Soil Organic Carbon Dynamics in the Conversion From Native Tallgrass Prairie to Agriculture in North Central Kansas.

Land use change and soil management directly affect the level and dynamics of soil organic carbon (SOC). This study is designed to understand and quantify the effects of soil and vegetation management on SOC pools, in sites converted from tallgrass prairie to annual agriculture. The long term and short term effects of the conversion of prairie to agriculture are being investigated in the two components of this research. The long term effects of land use change on SOC pools are being analyzed by sampling five farms that contain both virgin annually harvested tallgrass prairie remnants and conventional agricultural fields on the same soil types. This study also assessed the initial effects of soil and vegetation management on SOC pools on an experimental site converted directly, through herbicide application, from annually harvested tallgrass prairie meadow to no-till (NT) annual agriculture. All treatments were laid out in a replicated complete block design (n = 3), established in 2004. Management effects on SOC pools were assessed by determining changes in total SOC, particulate organic matter (POM) and microbial biomass C (MBC) to a depth of 1m. The POM and MBC were used as indices of change in labile pools of SOC. The POM is strongly influenced by land use and soil management, and the POM fraction is a good indicator of subtle changes in SOM over relatively short periods of time. POM was sampled using a sized base fractionation of SOM in the particle sizes 250-53 micrometers. The MBC was sampled using a chloroform fumigation extraction technique. Total SOC concentration to 1m was assessed by the dry combustion analysis. Samples were taken as cores to 0-10, 10-20, 20-40, 40-60, 60-80 and 80-100cm depths in May and June of 2008. Results will be presented at the SSSA meeting in November 2009.