Most phosphorus is used to grow food. Phosphorus is an essential plant nutrient, and the U.S. Geological Survey reports that more than 95% of the phosphate rock mined in the United States is turned into phosphoric acid for ammonium phosphate fertilizers and animal feed supplements.
The rest of the mined rock is made into elemental phosphorus, which goes into phosphorus compounds for industrial uses, mainly the herbicide glyphosate. According to the USGS Mineral Commodity Summaries 2026, there is no substitute for phosphorus in agriculture, and world phosphate rock resources exceed 300 billion tons, so no shortage is expected soon.
Source: U.S. Geological Survey, Mineral Commodity Summaries 2026: Phosphate Rock (PDF)
Image: PhosphComby.jpg (white, red, violet, and black phosphorus), derivative work by Materialscientist from images by BXXXD, Tomihahndorf, and Maksim, CC BY-SA 3.0, via Wikimedia Commons.