Lime is a soil amendment derived from finely ground limestone rock, containing calcium carbonate and often magnesium carbonate. The purpose of applying this material to a lawn is to correct overly acidic soil pH. By raising the soil’s pH, liming creates a balanced chemical environment that allows turfgrass to thrive and efficiently utilize nutrients.
Determining Soil pH and Lime Necessity
Liming is a targeted corrective measure, not a regular maintenance task, and should never be applied without first knowing the soil’s current pH level. Soil pH is measured on a scale of 0 to 14; values below 7.0 are acidic and values above 7.0 are alkaline. The optimal range for most turfgrass species is slightly acidic to neutral, typically between 6.0 and 7.0.
If the soil becomes too acidic (below a pH of 6.0), “nutrient lock-up” occurs. Even if necessary nutrients like nitrogen, phosphorus, and potassium are present, the grass roots cannot effectively absorb them. This inefficiency results in a thin, weak, and discolored lawn that remains unhealthy despite regular feeding.
The best way to determine the necessity and precise amount of lime required is through a soil test. This can be done using a do-it-yourself kit or, more accurately, by sending a sample to a professional lab. A professional analysis reveals the current pH and provides a specific recommendation for the pounds of lime needed per 1,000 square feet. Guessing the amount or applying lime routinely can push the pH too high, causing micronutrient deficiencies.
Seasonal Timing for Best Results
The timing of lime application is important because the product works slowly, often taking several months to fully dissolve and alter the soil’s chemistry. The optimal time to apply lime is in the fall, typically between late August and November. This timing is ideal because it exposes the lime to winter’s natural freeze-thaw cycles and abundant moisture from rain and snow.
These weather conditions help break down the limestone particles and draw them deep into the soil profile where grass roots can access the newly available nutrients. Applying in the fall means the soil pH will have begun to adjust before the grass enters its peak growth period the following spring. Early spring, as soon as the soil is workable, serves as a secondary window for application, allowing adjustment before the stress of summer heat.
It is important to coordinate liming with other lawn activities, especially aeration and fertilization. If core aeration is planned, the lime should be applied immediately afterward. The newly created holes allow the lime particles to penetrate deeper into the root zone, significantly enhancing the speed and effectiveness of the pH adjustment.
Liming and fertilizing should be separated by a waiting period to ensure maximum benefit from both. Applying lime too close to fertilizer, particularly phosphorus-heavy blends, can cause a temporary chemical interaction that reduces the fertilizer’s effectiveness. A waiting period of at least one week, and ideally one month, between the two applications prevents this nutrient conflict.
Practical Steps for Applying Lime
When selecting a product, homeowners generally choose between powdered and pelletized lime. Pelletized lime is recommended for home lawn application because it is easier to handle, creates less dust, and flows smoothly through a standard spreader. This form is created by binding finely ground limestone into small, easily spreadable granules.
The amount of lime to apply is determined solely by the recommendation on the soil test report, which is typically given in pounds per 1,000 square feet. If a large amount is recommended, never apply more than 50 pounds per 1,000 square feet in a single application. Higher rates should be split into two applications spaced at least six months apart (e.g., one in the fall and one in the following spring).
Lime should be applied using a drop spreader or a rotary spreader to ensure uniform coverage. To avoid missed spots or heavy concentration, apply half of the material walking in one direction (e.g., north to south) and the remaining half walking perpendicular (e.g., east to west). Immediately after application, the lawn must be thoroughly watered. Watering washes lime particles off the grass blades to prevent leaf burn and initiates the breakdown process, allowing the material to move into the soil.