UT Extension News: Let’s Talk about pH

October 14, 2020

By Chris Hicks, County Director – UT Extension Smith County

I can vividly remember sitting in Mrs. Hackett’s high school science class at Smith County High School and thinking, “why do I have to learn about pH? no one cares, and I’ll never need to use this.” Well here we are 20 years later and Mrs. Hackett is still teaching kids why science is important, and I am all in on the significance of pH.

Soil pH refers to the acidity or alkalinity of the soil, and affects how available the mineral nutrients are to plants. If the pH level is too high or too low, nutrients can be “tied up” and are unavailable for plants to use. This means that while you may be fertilizing properly and have all the necessary nutrients in the soil for good crop growth, they aren’t actually being used.

In Smith County, our soil are naturally acidic meaning the pH is below 7.0. The optimum pH depends on the crop you are growing. For example most garden vegetables prefer a soil pH between 6.0 – 6.5, while blueberries thrive best when the soil pH is around 5.0.

The level of pH is managed by following soil test recommendations for adding lime (to increase) or sulfur (to decrease) pH. Keep in mind that it takes several months to see the benefit of these materials in adjusting your pH. That makes the fall a great time to soil test and start addressing your pH issues.

When taking a soil sample, make a zigzag pattern across the field and collect 10-15 subsamples at a depth of 6 inches. Get rid of surface debris and plant material and mix the samples in a clean (non-galvanized) bucket or container. This will ensure you have a good composite sample of the field.

The UT Extension office will provide a sampling box and paperwork to send to the University of Tennessee Soil, Plant, & Pest Center. After sending your soil to the lab, you will receive a report with fertilizer recommendations based on your specific crop. This will include a recommendation for lime or sulfur if your pH needs adjusting.

The pH of your soil affects the availability of nutrients, can alter the activity of microorganisms, and even influences the effectiveness of herbicides. To make sure your levels are where they need to be, “don’t guess, soil test.” For assistance, call the UT Extension office at 615-735-2900 or stop by and see us at 125 Gordonsville Hwy in Carthage.