Legacy phosphorus: 4R nutrient stewardship, regional conservation, and collaborative, adaptive management | Science Societies

Legacy phosphorus: 4R nutrient stewardship, regional conservation, and collaborative, adaptive management

August 22, 2025
Illustration courtesy of the USDA Legacy Phosphorus Project.
Illustration courtesy of the USDA Legacy Phosphorus Project.

This collection of articles address the environmental and water quality impacts of legacy phosphorus and how it impacts crop production, soil tests, and long-term sustainability of fertilizer practices across U.S. cropland. Particular emphasis is given to the 4R nutrient stewardship framework as well as regional conservation strategies, hydrological variability, and collaborative, adaptive management.

Table of contents

Managing the legacy of P inputs and outputs is an integral part of 4R Nutrient Stewardship. Illustration courtesy of the USDA Legacy Phosphorus project.
August 18, 2025

Managing legacy phosphorus with 4R nutrient stewardship

Legacy phosphorus is an evolving concept useful in the responsible management of crop nutrition. A cumulative balance of inputs and outputs is part of responsible management of plant nutrition and 4R nutrient stewardship. This cumulative balance can be used to compare fields that have differed in their historical inputs and productivity and identify where current replenishment, deficit, and surplus rates are appropriate. In addition, the legacy concept is also useful for situations in which soil testing is impractical. 

Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz.

Legacy phosphorus can slowly leach off the land, offering a persistent, diffuse supply of phosphorus to nearby waterways. Illustration courtesy of Adobe Stock/VectorMine.
August 22, 2025

The slow drip of legacy phosphorus

Refining conservation practices across the Lake Erie watershed

Phosphorus—especially dissolved and legacy sources stored in soils—continues to drive harmful algal blooms that threaten drinking water, fisheries, and recreation in the Lake Erie watershed. Experts emphasize region-specific management practices, public–private partnerships, and adaptive conservation strategies as essential to reducing phosphorus runoff while balancing farm productivity and environmental health. 

Earn 1 CEU in Soil & Water Management by reading this article and taking the quiz.