Evaluation of the Kansas Phosphorous Index Using Apex Model Data.

The phosphorus index is a tool that incorporates multiple factors to evaluate the risk of phosphorus loss from agricultural field. The integrity of the phosphorus index has come into question due to continued occurrence of excess phosphorus in surface waters of agricultural watersheds. The objective of this research is to evaluate the Kansas phosphorus index. The methods of evaluating the phosphorus index involve comparing phosphorus index ratings to modeled data. The long-term average annual phosphorus loss was predicted for over 200 locations within Kansas using the Agricultural Policy/Environmental Extender (APEX) model as part of the Natural Resource Conservation Service Conservation Effects Assessment Project (CEAP) National Assessment. The Kansas phosphorus index was used to assess the risk of phosphorus loss for these same locations. The modeled data and risk of phosphorus loss from the phosphorus index were then compared. The data was also segmented based on management and geographic location. Results of this study are expected to have variations most likely due to large differences in climate and soils within the state of Kansas. Results of this study will hopefully help to improve the quality of the phosphorus index, making it a valuable phosphorus conservation tool for producers and decrease the amount of phosphorus lost to surface water.