Lime is a soil amendment derived from ground limestone, typically containing calcium carbonate or a blend of calcium and magnesium carbonate. Its primary function in lawn care is to neutralize soil acidity, which is measured on the pH scale. When soil becomes too acidic, the availability of essential plant nutrients, such as nitrogen, phosphorus, and potassium, becomes restricted. Applying lime raises the soil’s pH level toward the ideal range of 6.0 to 7.0 for most turfgrasses, allowing grass roots to absorb nutrients effectively. This creates a more favorable environment for strong, healthy lawn growth.
The Necessity of Soil Testing
Determining the correct amount of lime to apply per 1,000 square feet requires a professional soil test. This test measures the soil’s current pH and, more importantly, the buffer pH, which indicates the soil’s resistance to a change in acidity (buffering capacity).
A professional lab uses the buffer pH to calculate the precise amount of lime needed to reach the target pH for your specific grass type. This approach prevents the mistake of blindly applying lime, which can be detrimental. The soil test recommendation is the only reliable way to know if lime is needed and the exact quantity, provided in pounds per 1,000 square feet.
Factors Influencing Lime Application Rates
The exact pounds of lime needed per 1,000 square feet are highly variable and determined by several factors beyond the soil test recommendation. Soil texture is a major consideration because it dictates the soil’s buffering capacity. Clay soils have a higher buffering capacity and require significantly more lime to change the pH than loamy or sandy soils.
For example, a moderately acidic sandy soil might require 25 to 30 pounds per 1,000 square feet, while a clay soil with the same pH might need 70 to 80 pounds. The type of lime product also influences the required application rate. Calcitic lime contains mostly calcium carbonate, whereas dolomitic lime supplies both calcium and magnesium carbonate.
The neutralizing value of the product, often listed on the bag, affects the amount needed. Homeowners typically prefer pelletized lime because it is easier to spread and creates less dust than pulverized lime. As a general guideline for moderately acidic soil, application rates often fall between 25 to 50 pounds per 1,000 square feet, but relying on this without a soil test is discouraged.
Step-by-Step Guide to Spreading Lime
Once the required rate is known, the application process can begin. The best time to apply lime is typically in the fall or early spring, allowing the material time to react with the soil before the peak growing season. Preparing the lawn by mowing the grass low and considering aeration or dethatching helps the lime reach the soil surface quickly.
Lime should be spread using a drop or rotary spreader, similar to applying fertilizer. To ensure even distribution, set the spreader to release half of the total required amount. Apply the first half in one direction (e.g., north to south) and the second half in a perpendicular direction (e.g., east to west), creating a criss-cross pattern. Lightly watering the lawn afterward helps wash the lime into the soil, initiating the chemical reaction.
Common Mistakes and Signs of Too Much Lime
The most common error is applying lime without a soil test or applying too much at once, which is as damaging as having acidic soil. Over-liming pushes the soil pH too high (above 7.0 or 7.5), leading to a condition known as nutrient lockup. In this alkaline environment, essential micronutrients like iron and manganese become chemically unavailable to the grass roots.
This lack of nutrient uptake causes chlorosis, which presents as yellowing of the grass blades, especially in new growth. To avoid this, do not apply more than 50 pounds of standard agricultural lime per 1,000 square feet in a single application. If the soil test calls for a higher rate, the application should be split into two smaller doses, applied six months to a year apart, to prevent shocking the soil.