The national phosphorus project: Interfacing agricultural and environmental phosphorus management in the USA

The Unites States National Phosphorus (P) Project was initiated to address the needs of farmers, regulators, and policymakers by identifying environmental thresholds of soil P, constructing tools to define critical source areas of P export from watersheds, and developing integrated nutrient management strategies for water quality protection. A consortium of federal and state government agencies and universities are participating in the project. Initial project results point to a nonlinear relationship between runoff P and soil P for most soils, suggesting the existence of natural thresholds in soil P, above which there is a higher risk of P loss in runoff. Other findings indicate that P release to runoff from noncalcareous soils is greater than that from calcareous soils. Over the next five years, the National P Project is expected to contribute to the development of cost-effective nutrient management strategies that target remedial activities on landscapes susceptible to P loss.