Evaluating conservation practice effectiveness with a paired watershed approach
Gary Feyereisen
Reducing nitrate-N tile drainage losses from corn-soybean agriculture while maintaining productivity is an ongoing major challenge. Conservation practices are typically developed at the plot and field scale, so performance evaluation at a small watershed scale is needed. Producer input is necessary to optimize results for a given situation. The proposed research calls for a small watershed scale evaluation of conservation measures chosen and implemented with producer input. A paired-watershed analysis technique will be used. Water flow and quality relationships between two adjacent watersheds will be made for a few years; this is calibration. Then an organized effort will be made to implement conservation measures on one of the watersheds with subsequent years’ monitoring known as the treatment period.
The Faribault County SWCD with other state and regional agencies, and national, state, and local funding, installed a unique, three-bed, small-watershed-scale bioreactor at the outlet of CD62 in 2016. ARS, with assistance from the Minnesota Department of Agriculture (MDA), set up monitoring of flow and water quality from the watershed outlet and the bioreactor inlet and outlets (fig. 2). Data collection is in the sixth year. Additionally, ARS, with assistance of the Minnesota Corn Growers Association and MDA, established similar monitoring on the adjacent watershed, CD30, and is in the second year of data collection at that site. The work proposed for 2022 supports continued data collection for calibration. Additions this year include measurement of dissolved chloride (Cl-) from the two watersheds and collection of soil moisture content data with dissemination to producer-cooperators. Evaluation of a unique watershed-scale woodchip bioreactor, which is installed at the outlet of one of the study watersheds, will continue. The installation is the largest known one of its kind in the US and is being used to determine if community scale bioreactors offer advantages to the typical field scale.
The research is designed to evaluate the performance of conservation practices to reduce nitrate-nitrogen (N) loads from corn-soybean agriculture at a small-watershed scale under real world conditions. The ultimate goal of the research is to demonstrate significant water quality improvements while maintaining or enhancing profitability of corn-soybean production. Results from the project will be disseminated via one-on-one interaction between the project principals and the handful of producers in the watersheds, as well as at least one group meeting, news outlets as appropriate, and scientific publication when sufficient data have been collected.
