Agricultural lime is a soil amendment, typically made from pulverized limestone or chalk, primarily consisting of calcium carbonate or calcium magnesium carbonate. Its main function is to neutralize soil acidity, which is measured by pH, making the soil more alkaline. By raising the pH, lime optimizes the soil environment, allowing plants to better absorb essential nutrients like nitrogen, phosphorus, and potassium that may be locked up in acidic conditions.
Pre-Application Checklist: Testing and Selection
Determine the current soil pH and the amount of lime required to reach the target pH. The dosage is determined by a comprehensive soil test, which measures active acidity and the soil’s buffering capacity. While home kits provide a basic pH reading, a professional soil test offers precise recommendations for the quantity of lime needed per area.
This test also provides information on mineral deficiencies, which guides the choice of lime material. Calcitic lime (calcium carbonate) is the choice if only calcium is lacking or if magnesium levels are adequate. Dolomitic lime (calcium and magnesium carbonate) is appropriate if the soil is deficient in magnesium and has low pH. Applying lime without this information risks over-liming, which can lock up other nutrients and harm plant growth.
Preparing the Soil for Application
Preparation of the soil before application is necessary for the lime to work effectively. Since lime moves slowly through the soil profile, preparation ensures the material interacts with the target depth. The soil should be dry or only slightly moist when applying lime to prevent the material from clumping, which would lead to uneven distribution and slow the reaction rate.
Before spreading, remove any heavy debris and mow the area if it is a lawn. For garden beds or bare soil, perform a shallow, light tilling of the top surface layer. Loosening the soil aids in the incorporation process, helping the lime particles reach the necessary depth. The preparation should focus on the root zone, typically the top 4 to 6 inches of soil, where the majority of nutrient exchange occurs.
Methods for Spreading and Incorporation
Spreading and mixing lime corrects soil acidity. Achieving uniform coverage is important to avoid highly alkaline “hot spots” that can damage plants. For large areas, a broadcast spreader is efficient, while a drop spreader provides greater precision, which is useful near garden edges or sidewalks.
For garden beds, mechanical incorporation is the most effective mixing method. After spreading the recommended amount of lime evenly across the surface, use a rototiller or a garden fork to blend the material into the top 4 to 6 inches of soil. Mixing ensures that the lime particles are in direct contact with the acidic soil throughout the root zone, maximizing the neutralization reaction.
For existing lawns, mechanical incorporation is not possible without destroying the turf. For lawns, aerate the soil with a core aerator before spreading the lime. The lime material is then left on the surface, where it will slowly dissolve and move into the soil profile through the aeration holes. For all applications, spreading half the material in one direction and the remaining half perpendicular to the first pass can help ensure coverage is consistent.
Post-Application Waiting Period
Lime is not a fast-acting amendment; it requires time and moisture to dissolve and chemically neutralize the soil acidity. Immediately after the lime has been incorporated, lightly water the area to help settle the particles and initiate the chemical reaction with the soil. This initial watering is particularly important for pelletized forms of lime, which need moisture to break down.
The full effect of the lime application will not be seen for several weeks to a few months, with the reaction continuing for up to a year. If a significant pH adjustment is needed, delay planting sensitive crops until the soil chemistry has had time to stabilize. A follow-up soil pH test should be conducted approximately 6 to 12 months after the initial application to confirm that the desired pH level has been reached.