UT Extension News: “Don’t Guess, Soil Test” – Part I

January 14, 2020

by Chris Hicks, County Director – UT Extension Smith County

Soil testing is one of the most basic, yet most important steps in growing plants in Tennessee. Testing the soil is an inexpensive method of determining the exact amount of nutrients that are needed. When growers guess about the need for lime or fertilizers, too little or too much is likely to be applied.

By using a soil test report, the grower does not need to guess. The report will tell exactly how much of each nutrient needs to be applied, as well as how much lime the soil needs.

A soil test run through The University of Tennessee Soil, Plant, and Pest Center will cost you $15. So why spend the money on getting your soil tested when you could just buy a complete fertilizer that has nitrogen, potassium, and phosphorus and apply that?

The most obvious reason is that soil testing will promote plant growth by providing the best lime and fertilizer recommendations. Using a complete fertilizer year after year will likely lead to a build up of phosphorus in the soil. Testing your soil can also save you some money since it will prevent you from spending money on lime and fertilizer that isn’t needed.

A soil test will also tell you the appropriate amount of lime to apply. When the soil pH drops below 6.0, a number of nutrients necessary for proper growth become less available for use by the plant.

Applications of enough lime to raise the soil pH above 6.0 can increase the availability of these nutrients, making the plants healthier and more resistant to stress. Although we are commonly concerned with a lack of lime which causes a low pH, a high pH caused by applying too much lime can be just as damaging as it can also lead to nutrients being less available.

Having your soil tested is the only way to ensure that you are applying the correct amount of lime and fertilizer. If you would like to pick up some soil sample boxes, or would like more information about soil testing, stop by the UT Extension office at 125 Gordonsville Hwy in Carthage or call us at 615-735-2900.