What Does Limestone Do for Grass?
- Turfgrass prefers a slightly alkaline soil. Limestone is a safe and efficient method to reduce acidity. Soil tests are available at nurseries and home centers or can be obtained from your county agricultural extension. If the test results show a soil pH below 6.5, your soil is acidic and would benefit from lime. Too much water -- in the form of heavy rainfall or excess irrigation -- can cause an increase in soil pH. Overuse of nitrogen fertilizers can reduce pH as well.
- Limestone supplies calcium and magnesium to grass plants and its ability to lower soil pH helps turf take in other vital nutrients. The Ohio State University Extension warns that when soil is too acidic, the turf cannot efficiently absorb and process nitrogen, phosphorus, potassium, sulfur, calcium, magnesium and molybdenum. Without these nutrients, grass becomes more vulnerable to drought, foot traffic and high temperatures. Stressed, nutrient-starved turf yellows and thins, allowing weeds to invade.
- Lime helps control thatch, improve drainage and suppress weeds. The beneficial soil microorganisms needed to break down grass clippings do not thrive in an acidic environment. This allows thatch -- a layer of dead organic material -- to build up. Thatch prevents water, nutrients and air to reach the plant roots. Adding lime to lawns encourages the decomposition of clippings. This natural composting action makes soil more porous. Liming lawns also inhibits the growth of moss, an acid-loving lawn weed.
- The best time to apply lime is when the soil is being prepared for seeding. On an established lawn, apply lime any time during the growing season, though West Virginia University Extension suggests that fall is the optimum time. It should not be applied when the grass is frost covered. Too much lime can make soil overly alkaline so do not make yearly lime applications without confirming the need with a soil test.