A more comprehensive and consistent system for modeling phosphorus loss is now available, thanks to work by scientists at the U.S. Department of Agriculture.

The Phosphorus Index was originally a simple management tool developed to gauge the risk of phosphorus losses from agricultural fields. The original index has since been modified by individual states to incorporate local variations in soils, climate, management, and water quality goals. This resulted in widely different state-by-state phosphorus indices that were sometimes defined more by political boundaries than by watersheds or other regional variations.

To reduce these state-by-state discrepancies, Vadas and colleagues developed the Annual Phosphorus Loss Estimator (APLE), a user-friendly spreadsheet program that predicts field-scale phosphorus loss in runoff for a whole year. The revamped program can also be used in many different states to quantify field-scale phosphorus loss and soil phosphorus changes over 10 years for a given set of runoff, erosion, and management conditions.