Plants need food (nutrients) for healthy growth; Nitrogen, Phosphorous, and Potash (N, P, and K for short) play a vital role in plant growth just as vitamins, minerals, carbohydrates, and protein do in our health. This kit allows 10 tests for each: pH, N, P, and K in your soil. Soil should be tested periodically throughout your plant’s cycle to be sure the nutrient levels are at a good range. A great test for preparing your soil before use.