Process-Level Interactions in Agricultural Ecosystems

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The investigators propose to study the interactions of key nutrient cycling processes in terrestrial ecosystems. The main objectives of this research are to examine the effects of different temporal interactions on nutrient availability in agricultural ecosystems and to examine the dynamics of these interactions within the soil profile. Specific to the newly proposed research are 1) a focus on water as a primary determinant of nutrient turnover; 2) a focus on soil pores of biological origin as regulators of water movement in the soil profile; 3) a focus on specific pathways of N loss from the system, and 4) a focus on quantitative modeling. Hypotheses about interactions among processes at several different scales will be tested. Soil lysimeters will be installed for tilled, no-tilled, and never tilled agricultural plots. 15N will be used to examine seasonal dynamics. Several replicated soil catenas sites will be used to address questions related to spatial variation in N turnover for plants, microbial biomass and inorganic N pools. Initially at these sites the PI's will track wetting fronts, root turnover, and soil solution concentrations of biologically important ions. Simulation modeling will be used to build a quantitative predictive models of how these processes interact to regulate nutrient availability to plants in a landscape perspective. The investigators are well qualified to perform the proposed research and the facilities at the Kellogg Center are more than adequate.