Soil pH and Liming

Soil pH is a measure of the acidity or alkalinity of the soil. The pH of 7.0 is neutral, less than that is acid and greater than that is alkaline. Lime is used to raise the pH of an acid soil whereas sulfur is used to lower the pH of an alkaline one. The pH is important because it affects the availability of nutrients. Optimum turf grass growth usually occurs at pH’s of 6.0 to 7.0. Because of the difficulties associated with changing the soil pH under established turf grass, no adjustment is recommended if the pH is between 5.5 and 7.5. The soils in our area fall into this range naturally. Therefore, the common practice of applying lime every spring is not recommended.

One condition associated with improper pH is iron chlorosis. This common problem occurs in alkaline soils with a pH greater than 7.5. At this level, plants are not allowed to absorb iron from the soil causing them to turn light yellow-green. Turf grasses vary in their susceptibility to iron chlorosis, with Bluegrass and Zoysia grass being very susceptible and Tall Fescue being the least. Buffalo grass, Bermuda grass, and Perennial ryegrass fall somewhere in between. Do not apply sulfur until a soil test indicates that it is needed.

Adjusting soil pH is a slow, pain-staking process. It is best to incorporate lime or sulfur materials into the soil before establishment and only if they are needed. To determine your soils needs, collect and submit a sample to your local county extension office for testing. And remember, never apply lime or sulfur unless a soil test indicates that one or the other is actually needed.

Lynn Loughary, LLoughar@oznet.ksu.edu
County Extension Agent, Horticulture
Wyandotte County, Kansas
Kansas State University Research and Extension