Phosphorous mines

Phosphorous is a macronutrient.

Phosphorous is indispensable for plants.

Phosphorous is often a limiting factor in environments because plants need phosphorous to maintain their cellular biology. If there is insufficient phosphorous, plants will be stunted or not grow at all. If there is too much phosphorous, plants also have a difficult time or won't grow. Phosphorous uptake is not something that plants can control with certainty, and phosphorous could be a limiting nutrient in a given area under study. Use the link to the Wikipedia article on phosphorous and see what is posted on phosphorous and biology.

Also phosphorous is the ion (PO3)3-.