The focus of much of the research on mitigating agriculture’s impact on the environment is on soil, specifically in the storage and cycling of nutrient elements such as carbon, nitrogen, and phosphorus. Biogeochemists such as Andrew Margenot, an Associate Professor of Soil Science at the University of Illinois Urbana-Champaign, are leading efforts to accurately measure the accumulation of phosphorus in the soil, which is essential for understanding phosphorus cycling in the Anthropocene, the new geological era created by human activities. Margenot, along with other phosphorus experts from around the world, recently published a position paper in Global Change Biology outlining a roadmap to tackle this challenge.
The goal of the position paper is to provide a comprehensive overview of measuring legacy phosphorus and identify priorities for future research. It emphasizes the importance of understanding the uncertainty surrounding legacy phosphorus, which can have long-lasting impacts on water quality. Legacy phosphorus can take up to a century to fully disseminate into waterways, highlighting the urgency in identifying where residual phosphorus is located. By measuring the balance of phosphorus added to the soil versus what is exported, researchers can estimate the quantity of residual phosphorus, guiding future recommendations for phosphorus use.
The paper includes case studies from two of the oldest continuous agriculture test plots in the world, the Rothamsted Experiment in England and the Morrow Plots in Illinois. Key findings include the accumulation of phosphorus in the top 12 inches of the soil and the transformation of added phosphate into forms associated with organic matter, iron, and calcium. Recommendations from the consortium include validation of estimates, collaboration between researchers and the private sector, uniform measurement methods, and the identification of hotspots of legacy phosphorus to prioritize resources for reducing water quality impacts.
One of the challenges identified in the paper is convincing researchers and funders to allocate resources to provide data that will make a difference in understanding legacy phosphorus. Margenot emphasizes the need for policymakers to view the data on legacy phosphorus as a living document due to the estimates involved in measuring it. Despite the focus on nitrogen as a major environmental concern, phosphorus has been significantly impacted by human activities, with quadrupled amounts in circulation compared to nitrogen. Margenot stresses the importance of addressing legacy phosphorus to mitigate its long-term impacts on water quality and agricultural sustainability.
In conclusion, the efforts of researchers like Margenot and his colleagues are crucial in advancing our understanding of legacy phosphorus and its implications for agriculture and the environment. By addressing the uncertainties and challenges surrounding legacy phosphorus measurement, researchers can provide valuable insights for policymakers and stakeholders to develop effective strategies for sustainable phosphorus use. The collaboration between experts from around the world and the recommendations outlined in the position paper offer a roadmap for future research and action to mitigate the impact of phosphorus cycling on the environment in the Anthropocene.