Microbial Changes Associated with Renovated Soils: Nutrient Cycling in Subtropical Agroecosystems

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The proposed research is in two phases: phase I will focus on mechanisms controlling microbial changes associated with the renovation of soils in a detailed, specific controlled fashion in a greenhouse or growth chamber system. Phase II will focus on carbon and nitrogen dynamics, as well as associated microbial changes, in the Piedmont landscape using stable isotopes. The objectives of this research are: 1. To measure the uptake and the percentage of nitrogen recovered by the summer grain crop as affected by time, erosion/texture levels, surface placed residues, and aggregate formation and stabilization in the Piedmont agroecosystems. 2. To gain a better understanding of the internal, dynamic cycling of nitrogen by using an isotope tracer, 15N, to measure microbial nitrogen as well as other pools at specific time intervals. 3. To measure the effect of fertilizer N on residue N retention and release and how this process affects mineralization - immobilization turnover rates.