Phosphorus, the “P” in the N-P-K, and always the second number.
Another essential element, phosphorus, or sometime called phosphate is the piece of the plant growth puzzle that is essential in promoting a healthy root development in your lawn. Usually a lower number than the N, phosphorus occurs naturally in the soil, but is usually in a form that is not readily available to the plants feeding system, thus the need to apply an additional amount each year.
Did you know that phosphorus is mined from the soil, and is usually the result of mother nature and time converting bird droppings into a “phosphate rock” that we mine. The rock in its natural form will not release to the soil, any tangible amount of the P plants need, however when reacted chemically, it converts to a form more readily available to plants.
Central Florida has huge deposits of phosphate rock, the result of bird droppings on an ocean floor many thousands of years ago. Indeed there is an Island in the Pacific, Nauru, that is almost entirely formed from “guano’ or bird droppings. Nauru has almost disappeared as the entire island has been mined in our quest for phosphorus.
Remember the balance
Due to the fact that phosphorus is naturally occurring in the soil, and relatively slow to be taken up by plants, many areas have become quite saturated with P, and there is a concern of a possibility of run off entering our streams and waterways, thus being quite threatening to water life. Indeed, many municipalities are legislating a ban on phosphorus use, or at least requiring a mandatory soil test to determine the correct application levels.
However, as the second number, phosphorus is usually the lower one, and most manufacturers will sell a blend that is in the correct proportion to the other elements, and there is little concern if it’s used correctly.