...And we're running out.

This is pretty alarming.

Our addiction to cheap P (as it's known in the periodic table) is risky for two reasons. The first, better-known one is that not all the phosphorus that farmers put on their land is absorbed by crops. A lot leaches into water, ending up in lakes and rivers, where it causes algal blooms—which, as they decompose and suck up oxygen, create dead zones.
But the scarier reason is that, like any mined material, phosphate rock is a finite resource, and there's fierce debate about just how long our supply can last. "Peak phosphorus" doesn't get a lot of buzz, but it should. In a recent essay in Nature, Grantham, who also runs an environmental foundation, put the case bluntly: Our P use "must be drastically reduced in the next 20-40 years or we will begin to starve."
You Need Phosphorous to Live—and We're Running Out | Mother Jones