What is it?
Rock phosphate is a mined rock that contains limestone and clay as well as a high concentration of phosphorus (P). The actual composition varies depending on it’s source but it usually contains 16 to 20% P.
How to use it?
To use soft rock phosphate, incorporate it into your soil prior to planting, or apply in the planting hole for transplants and when planting trees.
For established landscaping, lawns, and trees, top dress the CalPhos and rake it into the soil, or apply after aerating. The better you can incorporate it into the root zone, the better your results will be.
Use 5 pounds per 100 square feet in phosphorus-deficient soil, and less for soil with adequate phosphorus.
For trees and transplanting, use 1 to 10 pounds per planting hole, depending on the size of the plant.