Rapitest Soil Test Kit uses a patented color comparator test system. Performs forty (40) tests, ten (10) each for soil pH, Nitrogen, Phosphorus and Potash. Test results allow the gardener to amend and fertilize appropriately, ensuring the best possible garden results. Extensive, yet simple, instructions are included along with recommendations for over 400 plants. Test results allow the gardener the amend and fertilize appropriately, ensuring the best possible results.