Achieving Water Quality Goals through a Focused Implementation Strategy.

A watershed project in southwest Wisconsin used a focused implementation approach to achieve measured reductions in phosphorus loads at the watershed outlet following three years of practice implementation.  The project first focused on a watershed that was small enough to be able to do a complete inventory, approximately a HUC-12-size.  Within the watershed the project focused on areas with higher estimated phosphorus losses.  Farmers on “focus farms” implemented a variety of practices selected both to fit within their operations and to bring modeled phosphorus losses below a target threshold.  During and after implementation, the land use inventory was updated and modeled phosphorus losses recalculated. Documenting changes from nutrient management planning was difficult, while tillage changes were more apparent.  

In-stream phosphorus loads were reduced in the project watershed compared to a reference watershed.  Measuring against baseline conditions without a reference watershed, the project's effectiveness would have been obscured by regional land use trends, such as conversion of grassland to row crops, that led to greater runoff losses.  Sediment finger-printing showed that stream banks contributed about 30% of the particulate-bound P  load, demonstrating that eroding stream banks within this watershed should be addressed along with upland areas.

Implementation of phosphorus reduction practices on focus-farm fields and pastures exceeded the Wisconsin agricultural runoff standards which are based on estimated runoff phosphorus loads. Although the project was designed to reduce phosphorus loads, total and dissolved phosphorus concentrations were also reduced.  The project watershed meets Wisconsin's new in-stream phosphorus concentration standards.