Grass Care With Lime

Soil pH and Grass

• The pH of soil refers to its acidity or alkalinity. A pH of around 7.0 is considered neutral, while anything lower is acidic and anything higher is alkaline. All plants, including turf grasses, have specific pH ranges in which they thrive. Most of the grasses commonly grown on home lawns prefer a pH between 6.5 and 7.0, or neutral to slightly acidic.

Uses of Lime

• Many areas across the United States naturally have acidic soils -- in many cases too acidic for grass to grow to its highest potential. In such cases, liming is the most common way to improve the soil. Common liming materials like crushed limestone and dolomite are composed mostly of calcium carbonate, an alkaline substance that raises pH by neutralizing acid. Alternative lime sources include wood ash, crushed eggshells and oyster shells. Lime also benefits grass by adding nutrients to the soil and encouraging beneficial bacterial activity.

Timing and Rate of Application

• The best time to apply lime to your soil is while it is being prepared, before grass is ever planted. Lime can be worked into the soil as well as left on the surface to ensure that both the topsoil and subsoil are affected. If you have an established lawn that is in need of lime, you can apply it at any time of year, though fall is generally the best time, followed by winter and spring. Lime should be spread evenly over the necessary area. Application rates depend on the starting pH of your soil, which can be determined through testing.

Soil Testing

• A mistake that many homeowners make is assuming that lime is a cure-all solution to lawn problems. This is not the case, and overusing lime, or applying it when you don't need it, can be more harmful than not using lime at all. A soil test from your local university extension office will tell you the pH of your soil. The results will also include recommendations for soil amendments, including lime, and the necessary rate of application.