Managing the reduction of soil phosphorus can prolong global reserves of fertilizer phosphorus and improve water quality

Authors: MCDOWELL, RICHARD - Lincoln University - New Zealand; Simpson, Zachary; DOSCHER, CRILE - Lincoln University - New Zealand; STEINFURTH, KRISTEN - University Of Rostock; Mott, Joshua; MARGENOT, ANDREW - University Of Illinois Urbana-Champaign; APPELHANS, STEFANIA - Instituto Nacional De Tecnologia Agropecuaria; ELLEDGE, AMANDA - Department Of The Environment, Tourism, Science And Innovation; THORNTON, CRAIG - Department Of The Environment, Tourism, Science And Innovation; Moore Jr, Philip

Submitted to: One Earth
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2025
Publication Date: 12/19/2025
Citation: Mcdowell, R.W., Simpson, Z.P., Doscher, C., Steinfurth, K., Mott, J.D., Margenot, A.J., Appelhans, S.C., Elledge, A.E., Thornton, C.M., Moore Jr, P.A. 2025. Managing the reduction of soil phosphorus can prolong global reserves of fertilizer phosphorus and improve water quality. One Earth. 8(12):101448. https://doi.org/10.1016/j.oneear.2025.101448.
DOI: https://doi.org/10.1016/j.oneear.2025.101448

Interpretive Summary: Globally, excessive phosphorus fertilization has led to phosphorus levels in soils that are well above what is needed to grow major food crops. In addition to being an agronomic inefficiency, this surplus of phosphorus in soils can pollute aquatic ecosystems. The practice of stopping phosphorous fertilization while continuing crop harvests, termed ‘drawdown’, can be a simple and cost-effective way of decreasing soil phosphorous to sufficient levels. In this study we gathered data from over 200 trials conducted globally that investigated how quickly soil phosphorous levels depleted. We developed a model predicting soil phosphorus drawdown rates and times, accounting for factors such as soil composition, climate, and crop type. Drawdown times to reach sufficient phosphorus levels in soils varied across regions, with the fastest times in Oceania and Asia (9 years) and slowest in Europe (14 years). By practicing drawdown, farmers globally could save an estimated ~ 200 Mton of phosphorous fertilizer. These insights support more efficient phosphorus use and can guide policy aimed at minimizing both environmental impacts and agronomic costs. This research supports the USDA goals of Promoting Soil Health to Regenerate Long-Term Productivity of Land.

Technical Abstract: Long-term nutrient use has led to 27% of global soils exceeding threshold soil test phosphorus concentrations needed for crop yields, contributing to phosphorus-rich water in runoff that threatens water quality for three billion people. The cessation of phosphorus fertiliser applications can lead to drawdown of soil phosphorus and can be a simple and cost-effective way of decreasing excessive soil phosphorus to threshold concentrations needed for optimum crop growth. We tested this by analysing ~12,700 observations from 225 trials across 21 countries, and developed a model that aimed to predict soil phosphorus drawdown rates and times, accounting for agroecosystem factors such as soil types and properties, climate, and crop type. We modelled the time required to deplete excess soil test (Olsen) phosphorus under drawdown to a minimum optimal agronomic threshold (i.e., 15 mg kg-1 of Olsen phosphorus) for globally major crops (barley, maize, rice, rye, soybeans, and wheat) and improved grassland. Drawdown times varied across regions, with the fastest times in Oceania and Asia (9 years) and slowest in Europe (14 years). Our findings suggest the potential for substantial phosphorus fertiliser savings (~190,430 kt varying from 159,880 to 233,183 kt, about 10-fold the largest annual global consumption of 20,500 kt recorded in 2020) and environmental benefits through drawdown of soil phosphorus, while maintaining yields. These insights support more efficient phosphorus use globally, minimising both adverse environmental impacts and costs.