Effects of Agronomic and Conservation Management Practices On Organic Matter and Associated Properties in Claypan Soils.

Organic matter plays several important roles in the biogeochemistry of soil and impacts the sustainability and profitability of agroecosystems. Retention and transformation of soil organic matter (SOM) are affected by agronomic and conservation management practices. The primary objective of this study is to characterize the effects of several management practices on the quantity and quality of SOM in the central claypan region of Missouri, USA. Practices evaluated in this study include crop cover, tillage, residue, amendment, prairie restoration and vegetative buffer strip installation. This study utilizes contemporary soil samples from (1) ten long–term agriculture experiment (LTAE) plots under various management regimens, (2) an experimental agricultural watershed with grass and tree-grass contour buffers, and (3) virgin (never cultivated) native prairie soil. Bulk density, soil organic carbon (SOC), total nitrogen (TN), water-extractable organic carbon (WEOC), o-diphenol oxidase and dehydrogenase enzyme activity, and aggregate stability (AS) will be determined on all soils. Preliminary results indicate a significant reduction in AS, SOC and TN in the following order: virgin prairie > restored prairie > amended no-tillage > amended conventional tillage > unamended conventional tillage. We hypothesize that WEOC and the ratio of dehydrogenase to o-phenol oxidase activity will follow the same pattern. Overall, this study has the potential to elucidate changes in both the quantity and quality of SOM as the result of long-term agricultural management practices.