Luster Leaf 1605 Digital Soil Test Kit for pH, N, P and K, 25 Electronic version of Luster Leaf?s popular 1601 Soil Test Kit. The rapitest Digital Soil Tester utilizes advanced LED digital technology and patent-pending optical calibration system to read test colors. The system is calibrated to read small color variations that can be difficult to distinguish with the human eye. The tester is easy to use. Just follow the easy instructions for each soil pH, nitrogen, phosphorus or potash tests; slide the test tube in optical chamber and push the appropriate button to get the test results. Once you have your soil test results, the tester booklet tells you how to adjust soil pH and provides recommendations for fertilizers. The booklet?s pH preference list allows you to select plants for your soil?s pH or know how much to adjust the soil pH for your current plants. Features Reads test colors utilizing advanced LED digital technology Just push test button to get results in a few seconds Includes pH preferences for over 450 plants and how to adjust soil pH Booklet has fertilizer guidelines based on nitrogen, phosphorus and potash test results. Performs 25 tests: 10 for pH and 5 each for Nitrogen, Phosphorus and Potash USA SHIPPING estimates delivery times and we work to get your item to you as quickly as possible and within those times, but please know it may take slightly longer than the estimate.