A MORE comprehensive and consistent system for modeling phosphorus loss is now available, thanks to work by scientists with the U.S. Department of Agriculture's Agricultural Research Service (ARS).
The Phosphorus Index was originally a simple management tool developed to gauge the risk of phosphorus losses from agricultural fields. It has since been modified by individual states to incorporate local variations in soils, climate, management and water quality goals, resulting 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, ARS scientist Peter Vadas at the ARS U.S. Dairy Forage Research Center in Madison, Wis., 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.
The team showed that APLE could reliably quantify phosphorus losses in runoff for many different situations and could produce more reliable estimates than some existing phosphorus indexes. Vadas also has been adapting APLE to simulate phosphorus loss from pastures grazed by beef and dairy cattle, as well as from barnyards and exercise lots on cattle farms.
With these improvements, APLE can be used to develop whole-farm estimates of phosphorus losses and the most effective strategies for reducing phosphorus losses from cattle farms. These practices could include barnyard improvements for capturing discharge, soil conservation practices that reduce erosion or manure application practices that reduce exposure to runoff water.
APLE is free to download at www.ars.usda.gov/Services/docs.htm?docid=21763, including supporting technical documentation and a user's manual.