Luster Leaf Rapitest Soil Test Kit 1601 is an inexpensive and innovative way of testing several soil conditions. Uses a unique and easy color comparator capsule system, 40 tests come with this kit and allow you to perform 10 tests each to measure the levels of pH, potassium, nitrogen and phosphorus. Easy to follow instructions require no experience to perform these 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.