Calcitic and dolomitic limestone are the most common materials used to lime soil. Calcitic limestone consists mainly of calcium carbonate. Dolomitic limestone is made from rocks containing both magnesium carbonates and calcium. Adding lime to the garden soil raises the pH of the soil. Most plants prefer a pH between 6.0 and 7.0. According to Clemson University, when soil pH drops below 6.0, the availability of magnesium, calcium, potassium and phosphate decreases, while the availability of metallic micronutrients increases. As a result, plants grown in soil with a low pH may not receive vital nutrients and face the risk of aluminum toxicity.
Contact your local cooperative extension office, or other soil testing facility, and request a soil test kit. Although a home soil-test kit measures the pH of the soil, without an analysis of the soil structure it is difficult to determine how much lime is needed to raise the pH level, according to the Ohio State University Extension Office.
Read the soil summary and analysis sheet carefully to determine the current pH of your soil and the recommended actions for balancing pH and amending soil. Although a bag of lime may provide a recommended application rate to raise the soil pH, the amount and type of lime required depends on the overall structure of the soil. The soil testing service provides you with this information and recommends the proper amount of lime for your soil.
Follow the instructions included with your soil summary for purchasing and determining the application rate of lime. Measure the lime carefully, as too much lime may raise the pH too quickly and too little may leave you with acidic soil.
Apply lime to dry soil, if possible. Washington State University recommends adding lime in the fall so it has time to alter the pH before spring planting. However, the University of Tennessee Extension explains that adding lime before planting does provide benefits and is preferable to not adding lime at all.
Spread the lime evenly over the garden area. Wear protective clothing and avoid contact with bare skin or inhaling the dust particles from lime. Lime is caustic and can burn your skin.
Work the lime into the top 6 inches of the soil with a garden hoe or garden tiller. Lime should not be visible in the soil.