The health and appearance of a lawn are fundamentally influenced by the chemical balance of its soil. Soil pH, measured on a scale of 0 to 14, dictates how effectively grass can absorb necessary nutrients. When soil becomes too acidic, essential elements like nitrogen, phosphorus, and potassium become chemically locked up and inaccessible to grass roots, regardless of fertilizer application. Lime, a soil amendment made from ground limestone rock, is used to counteract this acidity and raise the soil’s pH toward a more neutral state. Correcting an overly acidic lawn unlocks the full potential of the soil and subsequent fertilization.
Determining When and Why Your Lawn Needs Lime
The decision to apply lime should never be based on guesswork, as unnecessary application can harm the lawn. An accurate soil test is the only reliable way to determine the current pH level and the precise amount of lime required. While at-home testing kits exist, professional soil testing labs, often through a university extension office, provide the most detailed analysis, including nutrient levels.
To obtain a representative sample, small soil cores should be collected from multiple spots across the lawn and mixed to create a composite sample. The ideal pH range for most common turfgrass varieties is between 6.0 and 7.0, considered slightly acidic to neutral. If test results show a pH below this range, a liming recommendation will be provided.
Soil that is too acidic can lead to a toxic accumulation of elements like aluminum, inhibiting root growth and nutrient uptake. Lawns struggling with excessive moss growth, poor fertilizer response, or increased weeds often indicate low soil pH. The required amount of lime depends on both the current pH and the soil type; clay soil, for instance, requires a much higher application rate than sandy soil for the same adjustment.
Comparing the Types of Lime Available for Lawns
The best lime depends on the specific chemical needs of the soil, as revealed by the soil test results. The two primary types of limestone used for lawns are calcitic and dolomitic lime. Both contain calcium carbonate, the active compound that neutralizes soil acidity, but their secondary components differ significantly.
Calcitic Lime
Calcitic lime is composed predominantly of calcium carbonate and is the preferred choice when the soil already has sufficient magnesium. Calcium is an essential nutrient supporting cell wall development and plant structure. Using calcitic lime prevents the unnecessary accumulation of magnesium that can occur with repeated application of dolomitic lime.
Dolomitic Lime
Dolomitic lime contains both calcium carbonate and a significant amount of magnesium carbonate. This type is specifically recommended when the soil test indicates a magnesium deficiency. Magnesium is a structural component of the chlorophyll molecule. Choosing dolomitic lime addresses two issues simultaneously: it raises the pH and supplies the necessary magnesium for healthy, green leaf tissue.
Pelletized Lime
Pelletized or granular lime is not a separate chemical type but a physical form factor of either calcitic or dolomitic limestone. Finely ground limestone is bound to create easy-to-spread pellets, making it the most popular choice for homeowners. This form is less dusty than pulverized lime and dissolves quickly upon contact with moisture, making it easier to apply with a standard spreader. Highly caustic forms, such as hydrated or burnt lime, should be avoided for general lawn use due to their fast-acting nature and potential to damage the grass.
Proper Timing and Application Techniques
The most effective time to apply lime is during the fall or early spring. This allows the material several months to break down and react with the soil before summer heat. Fall application is often preferred because winter’s freeze-thaw cycles and moisture help work the amendment deeper into the soil profile. Avoid application when the lawn is dormant or stressed by extreme heat or drought.
Before application, it is beneficial to aerate the lawn, as this creates holes allowing the lime to penetrate the soil more easily. Load the recommended dosage from the soil test into a rotary or drop spreader set to the appropriate rate. To ensure uniform coverage, apply the material in a criss-cross pattern. Spread half the amount walking in one direction, and the remaining half perpendicular to the first pass.
For large applications requiring more than 50 pounds of lime per 1,000 square feet, split the total amount into two separate treatments spaced at least six months apart. After spreading, water the lawn immediately to wash the product off the grass blades and start the dissolution process. Wearing protective gear, such as gloves and a dust mask, is recommended, especially when handling non-pelletized forms.