The Wisconsin Phosphorus (P) Index is a nutrient management planning tool for assessing the risk of P contamination of surface water through runoff from individual agricultural fields. In the current draft NRCS Nutrient Management Standard 590, the P Index is one of two options for planning applications of animal manure P. If the P Index is used for planning, manure applications can be made as long as the assessed risk of P delivery to nearby surface water over the crop rotation remains within an acceptable range. The other option uses soil test P as the sole indicator of the pollution potential of a field, and it restricts manure P applications at high soil test P levels. Planning with the P Index gives producers with high soil test P fields the ability to choose management options appropriate to their operations to maintain each field’s P loss risk at an acceptable level.