Liming is the process of adding materials containing calcium or magnesium carbonate to soil to raise the pH and neutralize acidity. Soil acidity limits plant nutrient availability and overall growth, making liming necessary for soil health. This process works by replacing hydrogen ions with calcium and magnesium, creating a more balanced environment for plants. Proper application ensures the material is used effectively to achieve better soil conditions.
Determining Soil pH and Lime Needs
Lime application should only follow a thorough soil analysis. While DIY kits estimate current pH, professional laboratory testing offers the accuracy needed for determining precise lime requirements. A professional test provides two critical values: the current soil pH and the buffer pH. The soil pH measures the active acidity in the soil solution, indicating whether lime is needed.
The buffer pH measures the reserve acidity and the soil’s resistance to pH change, known as the buffering capacity. Soils high in clay or organic matter resist pH change and require a greater amount of lime to reach the target pH. Laboratories use the buffer pH, along with the target pH for the crop, to calculate the exact quantity of liming material required.
The lime recommendation is typically provided as a specific weight, based on a target pH range, often between 6.0 and 6.8 for most crops. Guessing the amount is discouraged; applying too little is ineffective, while over-liming can make certain micronutrients unavailable. If the recommendation exceeds 50 pounds per 1,000 square feet, the application should be split into two separate treatments over a six-month period.
Selecting the Right Liming Material
Once the required amount is determined, selecting the correct type of liming material is the next step. The two primary forms are Calcitic Limestone and Dolomitic Limestone. Calcitic limestone is mainly calcium carbonate and is the preferred choice for soils that already contain adequate levels of magnesium.
Dolomitic limestone is a combination of calcium carbonate and magnesium carbonate, making it suitable for soils deficient in magnesium. The choice between them should be based on the nutrient levels reported in the soil test, as both types are equally effective at neutralizing soil acidity. Applying dolomitic lime repeatedly to soils already sufficient in magnesium could lead to an imbalance.
Liming materials are also available in different physical forms: pulverized, pelletized, and liquid. Pulverized lime, a finely ground powder, reacts quickly but is dusty and difficult to spread evenly. Pelletized lime is finely ground lime formed into small, easy-to-handle granules using a binder. Pelletized lime is much easier to apply uniformly with a standard spreader and is less prone to drift, making it a popular choice for homeowners.
Step-by-Step Application Techniques
Effective lime application requires the right equipment and a precise pattern to ensure uniform coverage. The most common tools are drop spreaders and broadcast (rotary) spreaders. Drop spreaders are precise and best suited for smaller areas or near walkways where overspray must be avoided.
Broadcast spreaders are faster and more efficient for large lawns, distributing the material in a wide arc. Wear protective gear, including gloves and a mask, especially when dealing with dusty pulverized lime. To ensure even distribution, divide the total recommended amount of lime into two equal portions.
Apply the first half by walking the area in one direction, such as north to south. Apply the second half by walking perpendicular to the first pass, such as east to west. This criss-cross pattern minimizes gaps and overlaps, resulting in the most uniform coverage possible. For garden beds or tilled areas, mix the lime into the top four to six inches of soil immediately after spreading. For established lawns, the lime is left on the surface, relying on moisture for incorporation.
Post-Application Care and Monitoring
After the lime has been uniformly applied, initiate the reaction process. If the application is not followed by rain within a day or two, the area should be lightly watered. Moisture is necessary to dissolve the liming material, which begins neutralizing soil acidity. Pelletized forms rely on water to break down the pellets and release the fine lime particles.
The full effect of a lime application is not immediate, as it is a slow-acting soil amendment. It takes several months for the pH change to become noticeable, with maximum adjustment occurring six months to a full year later. Agricultural lime may take up to two or three years to fully react.
Because the effect is slow, wait before re-applying any additional material. Retest the soil approximately one to two years after the initial application. Retesting confirms whether the desired target pH was achieved and determines the necessary maintenance schedule. Routine re-testing every few years ensures the soil pH remains in the optimal range.