Soil pH and its Effect on Nutrient Availability and Plant Health (1-30-12)

I have mentioned on numerous occasions the importance of soil testing and maintaining an optimal soil pH for your lawn. What is pH (acronym for potential hydrogen) and what affects it?

In the simplest terms, it is a measure of relative acidity or alkalinity on a scale of 0 to 14 with 7 being neutral. When the soil pH becomes too low (acidic) or too high (alkaline) some nutrients become insoluble, therefore limiting their availability to plant roots.

The pH scale is a logarithmic scale, so a change of 1 unit represents a 10-fold difference in acidity or alkalinity. This means a soil with a pH of 5.0 is 10 times more acid than one with a pH of 6.0 and 100 times more acid than a soil with a pH of 7.0.

Soil pH is affected by applications of fertilizers, rainfall, organic matter, soil texture, and soil microorganisms, so it is important to periodically take a soil sample to determine if the pH is still within a desirable range for nutrient availability, microbial activity, and good plant growth.

Healthy Southern lawns of bermudagrass, zoysia, or St. Augustinegrass respond best with slightly acid soils in a pH range of 5.9-6.2 while centipede and carpetgrass lawns enjoy a soil pH range of 5.0-6.0.

Published January 30, 2012

Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. wwells@ext.msstate.edu