The US could exhaust its phosphorus reserves in about 40 years, and dependence on imports is already creating risks for agriculture. Europe, Latin America, and Southeast Asian countries are heavily reliant on phosphate supplies from China and Morocco. Scientists warn that without reliable access to phosphorus, it is impossible to maintain current food production volumes.
The work was published in the Proceedings of the National Academy of Sciences.
Phosphorus is classified as one of the three essential elements for plants, along with nitrogen and potassium; this is known as the NPK system. Most of the phosphorus for fertilizer production is obtained from phosphate rock, which is mined, crushed, and processed with chemicals. In 2025, the US included phosphate in its list of vital mineral resources due to concerns about potential supply disruptions.
A new study by specialists from the University of Arkansas and North Carolina State University has shown that a significant portion of the necessary phosphorus is already accumulated in American agricultural lands and various types of waste.
Researchers analyzed data from 3,142 counties in the US, including information dating back to 1866, and made projections up to 2050. They estimate that since 1866, approximately 145 teragrams of phosphorus, or 145 million tons, have been imported into American agricultural lands in the form of fertilizers. As of 2023, about 52 teragrams remained in cropland, and another 47 teragrams in pastures.
At the same time, the problem lies in the extremely low efficiency of phosphorus fertilizer use. Phosphorus quickly binds to soil and becomes unavailable to plant roots. Scientists estimate that about 80% of the phosphorus obtained from fertilizers is not absorbed by cultivated crops. The residues can accumulate in the soil or be discharged into water bodies, contributing to water pollution.
Researchers propose transitioning from the current linear model — mining, fertilizer production, soil application, and significant loss of material — to a circular system where phosphorus is returned to agriculture.
Sources of recycled phosphorus could include manure, agricultural crop residues, animal bones, eggshells, wastewater, and sewage sludge. According to scientists' calculations, the amount of potentially recyclable phosphorus in these sources over the observed period is equivalent to nearly 125% of the volume of phosphorus imported to fields.
However, there is no universal method for phosphorus extraction. For example, cattle manure contains a lot of water, making it economically unfeasible to transport over long distances. Recycling would be more effective in areas where livestock farms are located close to agricultural lands.
Scientists see particularly great opportunities for creating such a system in Arkansas. The northwestern part of the state actively develops poultry and livestock farming, producing large amounts of phosphorus-containing waste. In the east, rice, corn, and soybean cultivation predominates, requiring significant volumes of phosphorus fertilizers.
Researchers believe this creates conditions for the formation of a regional circular phosphorus economy, where waste from livestock and other sectors can become sources of fertilizers for crop production.
