Balancing agriculture and environment: Andrew Sharpley's nutrient, soil, and water management legacy

Managing agricultural phosphorus (P) to balance food security and water quality priorities is a massive challenge fraught with uncertainty and competing interests. Throughout his career, Andrew Sharpley addressed this challenge by building our understanding of the fundamental principles and processes that control P behavior in agricultural land, developing tools to assess P losses, and then evaluating and refining nutrient, soil, and water beneficial management practices (BMPs). Together with an exceptionally large and diverse group of collaborators, Sharpley developed, tested, refined, calibrated, and validated management practices and risk assessment tools to develop site-specific recommendations for the right practices, in the right places, and at the right times. This approach has resonated globally, with the strategic use of BMPs in "critical source areas" widely implemented in an effort to improve the effectiveness of BMPs while reducing implementation costs. Additional contributions to nutrient management include determining environmental thresholds for soil test P and measuring the risk of P loss from different sources of P (e.g., various manures and commercial fertilizers). Sharpley's work was also distinctly realistic, ensuring that strategies for mitigating P loss were critically evaluated so that not only were the benefits highlighted, but also that trade-offs were measured. Nowhere is this better illustrated than with trade-offs in particulate P loss and dissolved P loss with conservation tillage. This review summarizes Sharpley's enormous contributions to our knowledge of agricultural P stewardship as well as his model of collaborative, multi-disciplinary leadership, helping the world to maintain agricultural productivity and protect water quality. Andrew Sharpley built a source-transport framework to describe factors that control phosphorus (P) loss from land to water. Sharpley applied that framework to improving beneficial management practices (BMPs) for nutrients, soil, and water. Sharpley also used the framework to identify critical source areas for making the most efficient use of BMPs. Sharpley shared this knowledge widely with scientists, practitioners, and the public for the benefit of the world. Managing agricultural phosphorus (P) to balance food security and water quality priorities is a complex and difficult challenge. Throughout his career, Dr. Andrew Sharpley (recently retired University of Arkansas and U.S. Dept. of Agriculture research scientist) addressed this challenge by building our understanding of the fundamental principles and processes that control P behavior in agricultural land, developing tools to measure or estimate P losses, and then evaluating and refining nutrient, soil, and water beneficial management practices (BMPs) to minimize those losses. This brief overview summarizes the broad themes and a few highlights of Sharpley's contributions to those nutrient, soil, and water BMPs.