Evaluation of the Kansas P-Index with CEAP National Assessment Data.

The Kansas phosphorus index (KSPI) is a tool that incorporates multiple factors to evaluate the risk of phosphorus loss from a field. Although the KSPI has been used for several years, its ability to predict P loss has not been evaluated over a wide range of soils and cropping systems due to lack of data availability.  The objective of this research is to evaluate the KSPI by comparing it to independently modeled  P loss estimates.  The long-term average annual phosphorus loss was predicted for over 980 locations within Kansas using the Agricultural Policy/Environmental Extender (APEX) model as part of the Natural Resource Conservation Services CEAP National Assessment. The KSPI was used to assess the risk of phosphorus loss for these same locations and compared to APEX predictions. The data were segmented based on management and geographic location. Results of this study are expected show variations in KSPI performance due to large differences in climate and soils within the state of Kansas.  Results of this study will help improve the quality of the KSPI, increasing its value as a phosphorus conservation tool for producers and decreasing the amount of phosphorus lost to surface water.