Validation of a quantitative phosphorus loss assessment tool

Area of Science:

• Agricultural Science
• Environmental Science
• Water Resource Management

Background:

• Phosphorus (P) loss from agricultural fields is a significant environmental concern.
• Nutrient management and conservation planners require accurate tools to assess P loss.
• Existing models may be complex, necessitating user-friendly alternatives.

Purpose of the Study:

• To evaluate the accuracy of the Pasture Phosphorus Management Plus (PPM Plus) tool.
• To validate PPM Plus using extensive field data from various agricultural land uses and conditions.
• To compare the performance of PPM Plus against an empirical model for P loss prediction.

Main Methods:

• Utilized 286 field-years of runoff, sediment, and P validation data from studies in Oklahoma, Texas, Arkansas, and Georgia.
• Applied the PPM Plus tool, a simplified Soil and Water Assessment Tool (SWAT) model, to diverse land uses (pasture, small grains, row crops).
• Compared PPM Plus predictions with an empirical model based on soil test P, applied P, slope, and precipitation.

Main Results:

• PPM Plus explained 68% of the variability in total phosphorus loss.
• The tool accurately predicted runoff (56% variability) and sediment yield (73% variability).
• An empirical model accounted for only 15% of total P loss variability, highlighting the need for process-based models.

Conclusions:

• PPM Plus is an accurate and user-friendly tool for predicting phosphorus loss from agricultural fields.
• Process-based modeling is essential for capturing the complexity of P loss across diverse conditions.
• PPM Plus has potential for regional and national application in conservation planning with further modifications.