Cereal Rye Decomposition Dynamics on Topographically Varied Terrain Under a Corn/Soybean Rotation.

After termination, incorporated rye cover crop residue becomes a ‘green manure’, adding carbon and returning previously accumulated nutrients back into the soil. Decomposition of cover crop residue is an important source of C and N in soil. The decomposition rates differ at different topographical forms due to differences in soil properties. The objective of this study was to examine the decomposition dynamics of an incorporated cereal rye cover crop, and to quantify how factors such as topography, soil temperature, and soil moisture affect this process. Litterbags containing cereal rye were buried at 10cm depth at three different topographical positions of summit, slope, and depression, at two locations in south and southwestern Michigan. Soil moisture and soil temperature were monitored continuously at the same depth. Over the course of 64 days, the bags were removed at losses of litter mass were assessed. We found that topography had a significant effect on decomposition rate (k) over the course of the study (p=0.014). this was associated both with soil temperature and soil water content dynamics. Specifically, soil temperature was consistently higher in summit and slope areas than in depression areas. Soil moisture content was persistently higher in the depression. We assume that the differences in both water content and temperature at the topographical location affected the activity of decomposing microorganisms.