Field and Stream Demonstrations for Evaluating Sediment and Nutrient Reduction Efficiency of Agricultural Conservation Practices through Long-Term Meta-Analyses.

Research projects designed to evaluate the environmental response of agricultural management and conservation practice adoption are often constrained to two or three crop years. Resulting data are typically used as inputs into computer models designed to simulate or quantify the impact on soil and water quality. Short-term data sets may not capture all contributing factors within the holistic agricultural landscape system, resulting in unrealistic expectations or inaccurate estimations. Research and monitoring programs developed to guide watershed management decision-making have limitations for measuring the water quality response to adopting in-field conservation practices or altering crop management due to the lag time between conservation implementation and observed water quality effect. To overcome these limitations while establishing confidence and collaboration with agricultural producers, the Minnesota Department of Agriculture (MDA) manages long-term, on-farm demonstration projects to promote a better understanding of conservation practice effectiveness and water quality impact at both field and watershed scales. The MDA maintains nearly 40 automated monitoring stations to collect hydrologic, nutrient and sediment data from edge-of-field, sub-surface and in-stream locations. Statewide program meta-analyses results provide insight on the annual patterns of surface water runoff and subsurface drain flow under varying management conditions, which can influence future selection and sizing of conservation practices to meet water quality goals. Data since 2010 have indicated that sites annually average 20 surface runoff events, and over 115 days of flow in subsurface drains. Although approximately half of the annual surface runoff volume occurred when soils were frozen, most sediment loss was during May and June from one or two storm events. Data collected at these demonstration sites are providing direct feedback to landowners and crop advisors regarding the influence land management decisions have on water quality, while providing input for model validation and improved conservation practice efficiency information to researchers and water managers.