Liming is a common lawn care practice that involves applying calcium carbonate, an alkaline material, to the soil surface. This process is undertaken to raise the soil’s pH level, which counteracts acidity that naturally develops over time. When soil becomes too acidic, it can cause a condition known as nutrient lockout, preventing grass roots from absorbing essential elements like nitrogen, phosphorus, and potassium. By adjusting the soil pH, liming ensures that fertilizer and naturally occurring soil nutrients are available to the turfgrass, promoting healthier growth and a denser lawn.
Understanding Soil pH and the Need for Liming
Soil pH is a measure of acidity or alkalinity, recorded on a scale from 0 to 14, where 7.0 is considered neutral. Values below 7.0 indicate acidity, while those above indicate alkalinity. Most turfgrass species thrive in a slightly acidic to neutral range, typically between 6.0 and 7.0. When the pH drops below this ideal range, the chemical balance in the soil shifts, leading to the reduced availability of necessary plant nutrients.
Determining the exact acidity level requires a soil test. While do-it-yourself kits and pH meters are available, they often provide only a general pH reading. A more accurate analysis is obtained by sending a soil sample to a professional laboratory, such as a university extension office.
Professional lab tests provide precise pH data and, critically, a lime requirement recommendation. This recommendation details the exact amount of lime needed to raise the pH to the desired level. The application rate depends entirely on these test results, as applying lime without knowing the soil’s current condition risks making the soil too alkaline.
Choosing the Correct Liming Material
Once the need for liming is confirmed by a soil test, selecting the right material is based primarily on its chemical makeup and its physical form. The two main types of limestone used are calcitic and dolomitic lime. Calcitic limestone consists primarily of calcium carbonate and is the preferred choice if the soil test shows that calcium levels are low but magnesium levels are adequate.
Dolomitic limestone, conversely, contains both calcium carbonate and magnesium carbonate, making it the appropriate choice when the soil is deficient in magnesium. Choosing between the two should be guided strictly by the nutrient profile provided in your soil test report. Applying dolomitic lime to soil that already has sufficient magnesium may lead to an imbalance in the calcium-to-magnesium ratio.
Physical Forms of Lime
Liming materials are also sold in different physical forms, typically pulverized (powdered) or pelletized (granular). Pulverized lime is very finely ground and reacts quickly in the soil, but it is challenging to spread evenly and creates a lot of dust. Pelletized lime is finely ground lime compressed into small, uniform pellets using a water-soluble binder, making it easier to handle and spread with standard equipment. While pelletized lime is generally more expensive, the ease of application and reduced mess often make it the preferred option for homeowners.
Step-by-Step Application Process
The first practical step is to precisely calculate the total material required based on the professional soil test recommendation. If the recommended rate exceeds 50 pounds per 1,000 square feet, the application must be split into multiple doses spaced several months apart to prevent turf damage. Before application, mow the lawn to a low height and lightly moisten the soil to help the lime stick to the surface and begin dissolving.
Next, it is necessary to calibrate the spreader to ensure the correct amount of lime is dispersed. Both drop spreaders, which provide precise coverage, and rotary (broadcast) spreaders, which cover ground faster, can be used. Proper calibration is achieved by loading a known quantity of lime into the hopper and adjusting the spreader setting until the calculated amount is evenly distributed over a measured area.
To achieve the most uniform coverage and avoid streaking, plan on making two passes over the entire area. Set the spreader to half the calculated application rate and spread the first half of the material in one direction, such as north to south. Then, apply the second half by walking perpendicular to the first pass, moving east to west. This cross-hatch pattern significantly minimizes gaps and overlaps, ensuring an even distribution. When handling dusty pulverized lime, wearing goggles and a dust mask is advisable to prevent inhalation and eye irritation.
Post-Application Management and Timing
Immediately following the application, the lawn must be watered lightly to wash the lime pellets or powder off the grass blades and down to the soil surface. This initial watering is important for preventing potential leaf burn and for activating the water-soluble binder in pelletized products. The lime needs to dissolve and travel into the soil profile to begin neutralizing the acidity, a process that relies heavily on moisture.
Liming is a slow-acting soil amendment, not an instant solution. The chemical reaction to effectively adjust the soil pH takes time, often requiring several months before a measurable change is observed. Depending on the material used and the soil type, it can take six months to a full year for the pH level to stabilize.
For this reason, liming is often best done in the fall, allowing the winter’s freeze-thaw cycles and consistent moisture to aid in breaking down the material. Once the initial application has had sufficient time to react, typically after 12 months, the soil should be re-tested to determine the new pH level. Most lawns only require liming treatments every one to three years to maintain the desired pH range.