Centipede grass is a popular warm-season turf common in the southeastern United States, valued for its light green color and low-maintenance requirements. Homeowners often encounter recommendations to apply lime, a soil amendment used to neutralize soil acidity by raising the soil’s pH level. The question of whether this common practice benefits centipede grass is a frequent concern for those seeking to maintain a healthy lawn.
The Unique Soil Needs of Centipede Grass
Centipede grass (Eremochloa ophiuroides) is uniquely adapted to thrive in highly acidic and naturally infertile environments. Its optimal growing range is typically between a pH of 5.0 and 6.0, with a target pH of around 5.5 for the best health and color.
The grass is poorly suited for soils with high fertility, especially those rich in phosphorus. Applying high-phosphorus fertilizers or maintaining soil that is not sufficiently acidic can cause significant problems. Centipede grass relies on these acidic conditions to properly absorb necessary micronutrients for growth.
The Detrimental Effects of Increasing Soil pH
Applying lime will inevitably raise the soil’s pH toward a more neutral or alkaline state. When the soil pH rises above 6.0 or 6.5, it triggers a condition known as nutrient lockout. This means the grass roots can no longer absorb nutrients effectively, even if the nutrients are present in the soil.
The most common consequence of this pH increase is a deficiency in iron and sometimes manganese. The elevated pH renders the element chemically unavailable for plant uptake, even if the soil contains adequate iron. This unavailability leads to chlorosis, characterized by a noticeable yellowing of the leaf blades while the leaf veins remain green.
This yellowing is often most severe in the spring when the grass is emerging from dormancy and nutrient demand is high. Applying lime to an already healthy centipede lawn can be counterproductive, severely inhibiting the grass’s ability to maintain its characteristic apple-green hue.
Determining the Need for Soil Amendments
Amending the soil pH for centipede grass should not be a guessing game or a routine annual application. The only way to accurately determine the need for any amendment is by obtaining a professional soil test. A soil test provides precise measurements of the current pH level and the concentrations of macro and micronutrients.
If a soil test indicates the pH is below 5.0, which is considered too acidic even for centipede grass, a minimal application of lime may be recommended to raise the pH slightly. Conversely, if the test shows a pH above 6.0, elemental sulfur can be used to safely lower the pH back into the preferred acidic range.
If the lawn is already showing signs of chlorosis due to a high pH, a temporary solution is the foliar application of chelated iron or ferrous sulfate. These iron supplements bypass the nutrient lockout by being absorbed directly through the leaves, providing a rapid green-up without permanently altering the soil pH.