Location: Agroecosystem Management Research
Project Number: 3042-11210-003-03-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jul 1, 2015
End Date: Apr 30, 2019
Nutrient exports from agroecosystems have severe health and ecological impacts including stream eutrophication and low dissolved oxygen which can extend from local watersheds to oceans. Scientists, lawmakers, and stake-holders have worked together to develop nutrient reduction strategies for reducing losses from agroecosystems, thereby mitigating impacts on downstream ecosystems and municipalities. A nutrient reduction plan for Mississippi River Basin watersheds was recently adopted by the State of Tennessee with the participation of landowners, government, NGOs, and other stake-holders. A key provision in the plan calls for the evaluation of science-based nutrient reduction strategies such as adjusting fertilizer timing and application rates, employing winter cover crops, and no-till practices. To link ecosystem processes and management actions at diverse spatial and temporal scales, we propose to evaluate the biological and environmental factors that regulate the storage, transformation, and loss of nitrogen (N) from actively managed agroecosystems. Our goal is to isolate the key biotic and abiotic controls on the biogeochemical mechanisms that regulate the storage, transformation, and ultimately, loss of N. Our proposed research will advance the goal of the Program Priority Area to evaluate the physical and biogeochemical processes affecting the fate and transport, transformation, movement, and storage of N. Specific objectives are to: 1) Determine seasonal changes to the structure and function of microbial assemblages involved in soil N transformations as a result of active management practices. 2) Assess management practices in terms of mitigating N export from agroecosystems. This will include gaseous losses, leaching, and runoff. 3) Predict the long-term consequences for nutrient retention, with respect to how these management practices are altering agroecosystem function.
We will utilize fully replicated, existing long-term (>25 y) experimental plots in West Tennessee at Jackson, TN that employ management practices that have been recommended in nutrient reduction strategies which include: fertilizer addition, cover crop rotation, and no-till practices. We will be able to identify those practices either most in need of validation, or most readily adoptable by producers. We will measure losses (gaseous, runoff, leaching) and soil transformations of inorganic, soil organic, and microbial N to reconstruct N cycles under the various management practices. Using molecular techniques, we will characterize the structure and function of microbial populations responsible for key N transformations. We will use process-based models (e.g. EPIC, APEX) to scale-up and forecast the impact of the various nutrient export reduction strategies.