Lime is applied to soil to increase the soil pH, which is a measure of the soil's acidity or alkalinity. A pH below 7.0 is said to be acidic; above 7.0, it is alkaline. For most garden plants, a soil pH between 6.0 and 7.0 (slightly acidic) is ideal. To determine whether your soil needs lime and how much, you need to answer these basic questions: What is the current pH of your soil? What do you want the pH to be (based on the plants you want to grow)? What is your soil type? To get this information, you'll need to have your soil tested. Contact your county extension service or a commercial soil-testing laboratory to order a soil test kit. The results will indicate whether your soil needs lime and how much to add. Keep in mind, however, that the kind of lime you use makes a difference; refer to the package directions for general guidelines.