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Spatio-temporal Analysis Of Atrazine Degradation And Associated Attributes In Eastern Colorado Soils
1D. Zach, 2M. Stromberger, 3R. Khosla, 4D. Shaner
1.
2. Colorado State University
3. Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523
4. USDA-ARS, Water Management Research, Fort Collins, CO 80526-8119

Atrazine catabolism is an example of a rapidly evolved soil microbial adaptation. In the last 20 years, atrazine-degrading bacteria have become globally distributed, and many soils have developed enhanced capacities to degrade atrazine, reducing its half-life from 60 to a few days or less. While the presence of atrazine-degrading bacteria determine a soil's potential to catabolize atrazine, the actual manifestation of enhanced atrazine degradation is likely regulated by soil physicochemical properties and management strategies that are spatially and temporally heterogeneous and control bacterial expression of atrazine degradation enzymes. In this study, we collected soils from eastern Colorado and analyzed them for atrazine dissipation time (DT50), soil physical and chemical properties, and the presence of an atrazine degradation gene, atzC. Management practices, including atrazine use history, were also recorded. We assessed the spatial distribution scale of atrazine degradation activity and applied Classification and Regression Tree (CART) analysis to develop a prediction model for atrazine degradation based on management practice and soil predictor variables. Soils that rapidly degraded atrazine (DT50 < 3 days) were correctly classified by the CART prediction model 80% of the time based on atrazine use history, soil pH, and soil organic matter content. While the spatial distribution of atrazine degradation was predicted from atrazine use history and soil chemistry, we predict that the temporal dynamics of atrazine degradation within a field are controlled by microbial properties, such as the presence and amount of atzC. This study will advance the application of spatial and classification techniques in the field of soil ecology and will further our understanding of soil abiotic and management factors which regulate a rapidly evolved soil microbial activity.

Keyword: atrazine, atzC, soil ecology, classification and regression tree