This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The United States could exhaust its domestic phosphorus supply within 40 years. Europe, Latin America and Southeast Asia already depend on imports from China and Morocco to meet their needs.
Without phosphorus, crops cannot grow—and without a reliable supply of the mineral, the world's food supply is at risk. "You talk to any farmer and they know the 'NPK.' Nitrogen, phosphorus and potassium—NPK—are the three big ones that we typically have to add to make sure we have enough to grow crops," said Becca Muenich, an associate professor of biological and agricultural engineering at the U of A. The chemical symbol for potassium is K.
Most phosphorus used on crops comes from phosphate rock, which is mined and then treated with sulfuric acid. Eventually, the world could run out of phosphorus to mine. The U.S. classified phosphate (the mineral form of phosphorus used in fertilizers) as a critical mineral in 2025 due to concern about potential supply chain disruptions.
In a new paper, Muenich maps where residual phosphorus can be found in U.S. soil, how much the country needs and how it can be recovered from waste. She also holds an appointment in the Arkansas Agricultural Experiment Station, the research arm of the U of A Division of Agriculture. Muenich and her colleagues at North Carolina State University's Science and Technologies for Phosphorus Sustainability Center, or STEPS, examined data going back to the mid-19th century.
The paper, "Opportunities to strengthen US phosphorus supply resilience through circular pathways," is published in Proceedings of the National Academy of Sciences. Phosphorus binds readily with soil, getting stuck in the dirt before it can reach a plant's roots. As a result, roughly 80% of phosphorus fertilizer never reaches the crops in the field.
The low uptake of phosphorus means that farmers must spread a lot of the fertilizer on their fields. "We call it a linear system, because it goes onto the field, some of it gets taken up by the crop, but not a lot, and then the leftovers can wash out into our waterways," Muenich said. While phosphorus is naturally found in most soil from the natural weathering of rocks, intensive farming would exhaust that supply within a few years.
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