Clemson web apps calculate soil pH to help growers increase profits, reduce costs

Growers across the southern United States are planting spring crops and many have lime on their minds.

Lime is a very important soil amendment used to grow crops. To help ensure the correct amount is applied where it is needed most, the Clemson University Precision Agriculture Team has developed the Reverse Lime Rate Calculator.

This calculator, or web app, is useful for farmers as well as gardeners. It uses soil pH (acidity level), buffer pH and applied lime rate to provide an estimated soil pH. Kendall Kirk, a precision agriculture engineer who helped develop the calculator, said using this tool may be particularly useful this year in choosing where to place lime as supplies may be limited.

“Farmers expressed concerns this year that they may not be able to get enough lime to satisfy their needs,” Kirk said. “So, we developed this tool to calculate resulting soil pH as a function of the amount of lime applied. With input costs rising in 2022, we recognized the opportunity to also add value to our traditional lime rate calculator by adding lime cost calculations to allow growers to compare costs from different suppliers or across different products. Growers also can gain perspective of cost per acre for comparison to their other input costs.”

The Reverse Lime Rate Calculator evaluates resulting pH when recommended lime rates cannot be satisfied, such as when availability, time or field conditions are limiting. The developers call it a “Reverse” Lime Rate Calculator because it does not provide a lime recommendation; instead, it displays a resulting soil pH from a user-specified lime rate. Growers who need to know a recommended lime rate for a target soil pH can use the Lime Rate Calculator.

User inputs for the Reverse Lime Rate Calculator include soil pH and buffer pH from soil test results, mixing depth, lime rate and relative neutralizing value for lime source. Soil samples can be submitted to the Clemson Agricultural Service Laboratory for testing. Soil test fact sheets are available from the Clemson Home and Garden Information Center.

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