Soil Carbon Spatial Variability Patterns in Conventional and Organic Cropping Systems at Different Depths.

Spatial variability of soil carbon (C) needs to be taken into account for accurate predictions of the contributions to C sequestration due by different management practices on field and farm scales. The objective is to quantify effects of management practices and topographical features on spatial variability of total soil C at 0-5 cm and 20-30 cm depths. The study was conducted at the Long Term Ecological Research (LTER) site, at Kellogg Biological Station, in southwest Michigan. Treatments used in the study were conventional chisel-plow (CT) and an organic-based chisel plow (CT-cover) management systems. We collected approximately 200 soil samples from each treatment at both depths for total soil C measurements. Spatial variability characterization was conducted using geostatistical techniques. C content at the surface (0-5 cm depth) was found to be more spatially variable as compared to C content below plowing depth (20-30 cm). CT-cover tended to have greater variability and stronger spatial correlation than CT. Variability characteristics of the total soil C in the studied plots were strongly affected by topographical gradients. The detailed results will be presented and discussed.