Lime is a soil amendment used in lawn care to correct soil acidity. This involves adding calcium carbonate, and sometimes magnesium carbonate, to the soil to raise the pH level. This adjustment makes essential nutrients, such as nitrogen, phosphorus, and potassium, more accessible to the grass roots. When soil is too acidic (low pH), these nutrients become chemically bound and unavailable for uptake. Maintaining the proper pH balance, typically between 6.0 and 7.0 for most turfgrasses, is necessary for a healthy lawn.
Determining Soil pH
Applying lime without knowing the soil’s current condition can be detrimental, potentially leading to an overly alkaline environment where micronutrients become locked up. Soil testing is required before any lime application. A soil test precisely measures the soil’s pH level and determines if an adjustment is needed. The results also indicate the specific amount of lime required to reach the optimal pH range for your turfgrass.
Professional lab testing, often through a local cooperative extension office, provides the most comprehensive analysis, including nutrient levels and the buffer pH, which determines the required lime quantity. Home soil test kits offer a quick pH reading but lack the detail needed to calculate the exact application rate. To collect a sample, gather soil from 10 to 15 spots across the lawn, digging down about four inches. These samples are then mixed to create a composite sample representing the entire area.
The ideal pH for most turfgrasses falls in the slightly acidic to neutral range of 6.0 to 7.0. If test results show a pH below 6.0, the soil is too acidic, and applying lime is recommended. Conversely, if your soil is already near or above 7.0, adding lime is unnecessary and may cause nutrient deficiencies. Testing should be done every two to three years to monitor the slow changes in the soil’s chemistry.
Optimal Timing for Application
The best time to apply lime is during the late fall or early spring. Fall application is often preferred because winter’s freeze-thaw cycles and consistent moisture help the granular material break down and incorporate into the soil more efficiently. This allows the pH adjustment process to occur gradually over the dormant season before the stress of summer heat.
If a fall application is missed, early spring is the next best window, allowing time to neutralize acidity before the grass enters its peak growth period. Lime is slow-acting, typically taking several months to fully dissolve and significantly alter the pH. Therefore, avoid applying it during periods of extreme heat, drought, or when the grass is dormant, as the lawn will be too stressed.
Lime application should be separated from other lawn care tasks like fertilizing or aerating. Lime should not be applied at the same time as fertilizer, as the pH shift can interfere with the fertilizer’s effectiveness. Allow a waiting period of several weeks between liming and fertilization to ensure both products work as intended. Aerating the lawn before applying lime is beneficial, as the holes allow the particles to penetrate deeper into the soil layer.
Choosing the Right Lime Product
Once a soil test confirms the need for pH correction, select the appropriate type of lime based on the soil analysis. The two main forms used for lawns are calcitic lime and dolomitic lime. Both are derived from ground limestone and contain calcium carbonate, the compound responsible for raising the soil pH.
Calcitic lime is pure calcium carbonate and is used when the soil needs pH adjustment but calcium is the only mineral deficiency. Dolomitic lime contains a significant amount of magnesium carbonate in addition to calcium carbonate. This type is recommended if the soil test reveals the lawn is deficient in magnesium and has an acidic pH. Selecting the correct type ensures both acidity and mineral content are balanced.
Lime is available in both pulverized (powdered) and pelletized forms. Pulverized lime is very fine, reacting quickly with the soil, but it can be dusty and difficult to spread evenly. Pelletized lime consists of fine particles compressed into small, easy-to-handle pellets. This form is much easier to spread using a standard lawn spreader and is the preferred choice for most homeowners.
Application Techniques and Safety
Applying lime correctly ensures even coverage across the entire lawn. Accurately calibrate your spreader based on the product’s instructions and the rate recommended by your soil test results. Using a broadcast or drop spreader is the most effective method for uniform distribution of the material. To avoid applying too much in one area, divide the total recommended amount of lime in half.
Apply the first half of the material by walking in one direction across the lawn (e.g., north to south). Apply the second half by walking perpendicular to the first pass (e.g., east to west). This crisscross pattern ensures comprehensive coverage and prevents streaking or uneven pH correction. Never apply more than 50 pounds of lime per 1,000 square feet in a single application; if more is needed, split the total amount into two applications several months apart.
Safety precautions are necessary when handling lime, particularly the dusty, pulverized forms. Wear gloves, protective eyewear, and a dust mask to prevent irritation to the skin, eyes, and respiratory system. Immediately after spreading, the lawn should be lightly watered. Watering helps wash the lime off the grass blades to prevent burning and encourages the material to dissolve into the soil surface.