Plants need food (nutrients) for healthy growth. Nitrogen, Phosphorus, and Potash (N, P and K) play a vital role in plant growth just as vitamins, minerals, carbohydrates and protein do in our health. pH needs varies depending on what you are planting, so it is crucial to provide each individual plant with the right pH level and other important nutrients.Kit Includes: * 4 Color Comparators* 40 Test Capsules (10 pH, 10 N, 10 P and 10 K)* Complete instructions for adjusting soil pH* Fertilization and pH preference list for over 450 plants for the home,yard and gardens * A chart of pH and NPK levels on over 100 plants.