Liming involves adding calcium or magnesium compounds, usually ground limestone, to the soil to reduce acidity. This application raises the soil’s pH level, which directly affects turfgrass health and vigor. Adjusting the soil chemistry ensures the grass can efficiently access necessary nutrients. Understanding the necessity and proper timing of this process is fundamental before seeding a new lawn.
Determining the Need for Liming
Applying lime is a corrective measure dependent on the existing soil pH, not a standard maintenance task. Soil pH is measured on a logarithmic scale from 0 to 14; values below 7.0 are acidic, and values above 7.0 are alkaline. Most common turfgrass varieties thrive in a slightly acidic to neutral range, typically between 6.0 and 7.0.
A professional soil test must confirm the necessity for liming, providing a precise pH reading and a lime requirement recommendation. Guessing the need for lime is counterproductive, as unnecessary application can lead to an overly alkaline state. Highly alkaline soil causes deficiencies in micronutrients like iron, often resulting in yellowing grass.
If the soil becomes too acidic (generally below pH 5.5), it prevents grass from absorbing essential nutrients like phosphorus and nitrogen, even if they are present. This is called nutrient lock-up, where the acidic soil binds these minerals, making them unavailable to the roots. Extreme acidity also increases the solubility of toxic elements such as aluminum and manganese, which inhibits root development and hinders seed germination.
Why Timing is Critical Before Seeding
If a soil test confirms the need, the answer to whether one should lime before seeding is almost always yes. Lime is a slow-acting soil amendment that requires time to break down and react with the soil particles to effectively neutralize acidity. Lime can take several months—often between three and six months—to produce a measurable change in the soil’s pH.
Applying lime just before or at the same time as seeding will not provide the benefit the new grass needs for its initial establishment. The grass seed requires a balanced soil environment from the moment of germination to maximize nutrient uptake and root growth. If the soil is highly acidic, the seedling will struggle for months until the lime begins to take effect.
The best practice is to complete the liming application in the fall if seeding in the spring, or in early spring if seeding in the fall. This allows a minimum of several weeks for the initial chemical reaction to occur. This waiting period ensures that the soil pH is already moving toward the optimal range when the vulnerable new seedlings begin to sprout.
Practical Steps for Lime Application
Once the soil test confirms the need, the application process must be precise to ensure uniform soil correction. The test results specify the exact amount of lime required, often measured in pounds per 1,000 square feet, which must be strictly followed. The type of lime chosen will depend on the soil test, with calcitic lime being standard and dolomitic lime used specifically when a magnesium deficiency is also present.
Lime is most commonly available in a pelletized form, which is easier to handle and spread evenly than fine, dusty powdered lime. Applying lime should be done with a drop or rotary spreader to ensure consistent coverage across the entire area. To avoid uneven distribution, apply half of the calculated amount while walking in one direction and the remaining half while walking perpendicularly in a criss-cross pattern.
Since you are preparing for seeding, this pre-planting stage offers the best opportunity to incorporate the lime directly into the soil. If possible, the lime should be tilled or worked into the top four to six inches of the soil profile. This significantly speeds up the reaction time and maximizes contact with the soil’s acidic particles.