is essential in building a biological soil, it is a major building block in all living plants and crucial for plants to develop healthy root systems, set fruit and assimilate nutrients for good plant growth.
Hard rock phosphate should not be confused with soft rock phosphate, which is a by product of mining the phosphate rock. While both these products supply the much needed phosphate required by plants their use in agriculture and gardening are different.
Unlike soft phosphate rock phosphate from hard rock is not immediately plant available, the end product of the crushed phosphate rock releases its nutrient fairly slowly making it good to build the long-term supply of phosphorous in your soils but of little help with soils that require immediate phosphate.
Phosphate mined from rock mineral deposits is usually granulated for ease of application, it contains 20 percent phosphorous and 48 percent calcium, this can raise soil pH so use needs to be avoided if your soil is already alkaline. Crusted and washed phosphate rock is a total natural substance and is approved for use in organic agriculture and food production.
Phosphate fertilizer for traditional agriculture is often further treated with sulfuric acid to produce Triple phosphate or Super phosphate, by changing the composition of the phosphate it is rendered unsuitable for use in organic agriculture and gardening.
Phosphate Rock is not a complete fertilizer and is best used in combination with other nutrient sources to provide what your soil need. Application rates depend on a variety of factors but a rough guide is 3-8 lbs per 100 square feet.