Itís vital to know the existing pH, Nitrogen, Phosphorus and Potash levels in garden soil. The soilís pH controls the availability of these three nutrients essential to plant health. Test results allow the gardener to amend and fertilize appropriately, ensuring the best possible growing results. Kit comes with 10 color coded tests: 4 for pH, 2 each for nitrogen, phosphorus and potash. Easy to use with full instructions!