Luster Leaf Rapitest Soil Test Kit 1601 provides simples methods of testing several soil conditions. 40 tests come with this kit allowing you to perform 10 tests each to measure the levels of pH, potassium, nitrogen and phosphorus. Easy to follow instructions. Simple, accurate, tests with fast results. The included chart contains levels for NPK and pH for over 100 plants and has instructions included on adjusting fertilization and soil conditions.