Kit includes: 4 color comparators, 40 test capsules, 10 each for pH, N, P and K, complete instructions for adjusting soil pH, fertilization guidelines and pH preferences list for over 450 plants for the home, yard and garden. Plants need food (nutrients) for healthy growth. Nitrogen, phosphorus and potash (N, P and K for short) play a vital role in plant growth. This kit enables you to test all four levels of pH, nitrogen, phosphorus and potash.