Rock phosphate is a clay material that is surface mined from the hard phosphate rock mines in Egypt. Our rock phosphate contains from 20% - 32% of P205 as well as a percentage of lime and other trace minerals. It is a very fine material, but can be applied with all common fertilizer spreaders. soft rock phosphate is insoluble in water, will not leach away, and therefore is long-lasting Soft rock phosphate used directly under the seed or transplant at planting time is the very best method of application, especially in low acid or high alkaline soils. It is not as critical but still beneficial in slightly acid to neutral soils.