Savannah Valley District

Around the Countryside Does My Garden Need Lime?

Marion Barnes – Senior County Extension Agent

Does my garden need lime? If you live in the southern part of the state, the answer is most likely maybe! This is because our southern flat woods soils are characteristically acidic, low in organic matter, and have low nutrient-holding capacities. Over time our soils become acidic because calcium and magnesium are leached from the ground. The decomposition of plant residues and organic manner and the addition of certain types of nitrogen fertilizers such as ammonium sulfate and animal manures also increase soil acidity. As a general rule, to produce healthy, high-quality plants, most soils require liming every few years.

What is lime? Agricultural lime is a soil amendment made from ground limestone rock that contains calcium and/or magnesium capable of neutralizing soil acidity. Agricultural lime can be either calcitic or dolomitic. Calcitic limestone is a naturally occurring rock comprised primarily of calcium carbonate. Dolomitic limestone is also a naturally occurring rock composed of calcium-magnesium, principally carbonate. Lime comes in several forms, finely ground or pelletized, the two most common types used by homeowners. The finer the grind of limestone, the faster it will react and change the soil’s acidity.

What does lime do? In addition to supplying calcium and/or magnesium, lime makes the soil less acidic. Plants develop healthier root systems because they are exposed to less potentially toxic aluminum in the ground. Plants with aluminum toxicity may also experience calcium or magnesium deficiencies. Nutrient availability is improved, so plants have a better nutrient supply. The optimum soil pH for most garden plants is 5.8 to 6.5. Nodulation of legumes is enhanced, which improves nitrogen fixation.

How long will it take lime to react, and how long will it last? Lime will react completely with the soil in two to three years after it has been applied: although the benefits of the lime may occur within the first few months after application. How long the effects of the lime will last will depend on the type of lime used, total acidity of the soil, amount of organic matter, type and amount of clay in the ground, and type and amount of fertilizers used.

How can I tell if my soil needs lime? The only accurate way to determine if your soil needs lime is to have it tested. Soil test kits can be purchased through garden stores or online, but they are not as accurate as having your soil analyzed at an accredited soil testing laboratory and may not tell you how much lime you need. The Clemson University Ag Service Laboratory will test your soil for a nominal fee and send you the results. Each soil test provides unbiased scientific information on soil pH value current soil levels of phosphorus, potassium, calcium, magnesium, zinc, copper, and boron. Fertilizer and lime recommendations, if needed, are also provided for the plants you are growing.

Should lime be worked into the soil or placed on the surface? Whenever possible, tillage should be used as a tool to incorporate lime into the ground. When lime is worked into the soil, a more significant portion of its surface area is exposed, allowing faster reactivity. Surface-applied lime moves into the earth at a slower rate. Contact your local Clemson Extension Service office for more information on liming your soils.

Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, gender, religion, national origin, disability, political beliefs, sexual orientation, gender identity, marital or family status and is an equal opportunity employer.

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