Wisconsin Phosphorus Index
The Wisconsin Phosphorus (P) Index (WPI) is a planning tool for managing cropland and pastureland. It uses information that is readily available to farmers to quantify the risk of phosphorus delivery to surface water in runoff from a specific field under varying management conditions. The WPI algorithms are based on Wisconsin research and have been validated with field runoff monitoring by UW-Extension (Discovery Farms) and UW-Platteville (Pioneer Farm). The WPI can be used to target areas that are contributing the greatest amount of P to local surface water and also to evaluate the runoff P reduction potential of alternative management strategies.
Outcomes
The WPI is referenced in state runoff standards that apply to all agricultural land in Wisconsin as a tool that should be used for evaluating the risk of phosphorus in runoff from cropland and pastures. The WPI is calculated automatically in the SnapPlus nutrient management planning software, so farmers planning manure and fertilizer applications for cropped fields will automatically receive an indication of the relative risk of their field-level management practices contributing to phosphorus in runoff. Agricultural nonpoint runoff projects are using the WPI for targeting conservation efforts and estimating reductions in phosphorus runoff. The WPI is part of the state's new Watershed Adaptive Management and Water Quality Trading Programs.
Focus Areas
Project Leader
Laura Good
Associate Scientist
- Department/Unit
- Soil Science
- School or College
- College of Agricultural and Life Sciences