Applying lime to a lawn involves adding calcium or magnesium compounds, usually ground limestone, to the soil. The primary goal is to raise the soil’s pH level, reducing acidity to an optimal range for turfgrass growth. When the pH is correct, the lawn can absorb nutrients efficiently and thrive. The exact amount required is a personalized calculation based on the specific chemistry of your soil.
Determining the Need for Lime
The amount of lime needed is determined by a professional soil test, not guesswork. Over-liming can cause nutrient deficiencies, just as acidic soil can. A laboratory soil test provides an accurate reading of the current soil pH, measuring acidity or alkalinity. For most turfgrass species, the preferred pH range is slightly acidic to neutral, typically between 6.0 and 7.0.
A soil test also measures the soil’s buffering capacity, sometimes called the lime requirement index. This measurement indicates the soil’s resistance to a change in pH. Soils with a high buffering capacity, like clay, require more lime than sandy soils to achieve the same change. When the pH falls below the optimal range, essential nutrients become chemically bound to soil particles. This condition, described as nutrient lockout, prevents the grass from absorbing fertilizer.
Calculating Application Rates
The soil test report provides a specific recommendation for the pounds of lime required per 1,000 square feet. This recommendation is based on the current pH, the target pH (usually 6.5), and the soil’s buffering capacity. For instance, a loamy soil at pH 5.5 may require 75 pounds per 1,000 square feet, while a heavy clay soil might need 100 pounds or more.
The total recommended amount must be managed carefully to avoid damaging the turf and ensure the lime reacts with the soil. Guidelines suggest limiting a single surface application to a maximum of 50 pounds of lime per 1,000 square feet. If the total amount exceeds this limit, you must divide the application into two or more smaller treatments. These split applications should be spaced out by at least six months, or between the fall and spring seasons.
Choosing the Right Liming Product
After calculating the total amount, select the appropriate liming material. The two most common types are calcitic lime and dolomitic lime, both forms of ground limestone. Calcitic lime is primarily calcium carbonate and is the standard choice for raising soil pH. Dolomitic lime contains a blend of calcium carbonate and magnesium carbonate.
The choice depends on your soil test results, which measure magnesium content. If the test indicates a magnesium deficiency, dolomitic lime provides both pH adjustment and the supplemental mineral. If magnesium levels are adequate, calcitic lime is the better choice to prevent an imbalance. Pelletized lime is also available; it is powdered lime bound into granules, making it easier to spread evenly with less dust than agricultural powder.
Proper Application Techniques and Timing
The best time to apply lime is during the cooler seasons, typically fall or early spring. Fall application is advantageous because winter freeze-thaw cycles and precipitation help work the material into the soil profile. Use either a drop spreader or a broadcast spreader, ensuring the equipment is calibrated according to the product instructions.
To achieve uniform coverage and prevent streaking, use a cross-hatch pattern. Apply half of the calculated amount moving the spreader in one direction. Then, apply the remaining half perpendicular to the first pass.
Since powdered lime creates dust, wearing a simple dust mask is a safety precaution. Immediately after spreading, lightly water the lawn. This washes particles off the grass blades and initiates the material dissolving into the soil.