Pasture Termination Impacts on Soil Organic Matter and Physical Properties in Transition to Cropping in North Carolina.

Pasture Termination Impacts on Soil Organic Matter and Physical Properties in Transition to Cropping in North Carolina

Bonetti, J de A⁽¹⁾ and Franzluebbers, A J⁽²⁾

Abstract- How pasture is terminated in a crop-livestock system can affect the stock of organic matter as a result of tillage management. Our objective was to determine short-term changes in soil organic matter and physical properties in a crop-livestock system with 6-year-old cool- and warm-season pastures terminated by three tillage systems. Cool-season pasture was tall fescue (Schedonorus arundinaceus Schreb.) located on finer textured soil than warm-season pasture composed of native species (Andropogon gerardii, Panicum virgatum, Sorghastrum nutans and Tripsacum dactyloides). In April 2016, pastures were terminated by (i) disk tillage, (ii) plow tillage and (ii) no-tillage with chemical spray. Soil was collected before termination in February 2016 and immediately after termination in April 2016 at depths of 0-5, 5-10, 10-20 and 20-30 cm. Soil organic C and N, particle organic C and N, soil microbial biomass, mineralizable C and N, bulk density, and total porosity will be determined. Preliminarily, bulk density ranged from 1.33 to 1.66 Mg m^-3 following warm-season pasture and 1.42 to 1.76 Mg m^-3 following cool-season pasture. Mineralizable C during 3 days was similar between cool- and warm-season pastures soil, but soil microbial biomass C was greater after cool- than warm-season pastures. A strong relationship occurred between mineralizable C and soil microbial biomass C (r²=0.93). We hope to unravel specific interactions among microbial biomass C, substrate availability, decomposition, and biophysical of soil structure.