Growers across the southern U.S. are planting spring crops and many have lime on their minds. To help ensure the correct amount is applied where needed most, the Clemson University Precision Agriculture Team has developed the Reverse Lime Rate Calculator.

This online calculator 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, says 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 says. “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.

The Reverse Lime Rate and Soil Acidification calculators, as well as other calculators and web apps developed by the Clemson Precision Agriculture Team can be found at https://bit.ly/CU_CalculatorsAndWebApps.

Shannon Alford, Clemson Agricultural Service Laboratory director, says applying the correct amount of lime is imperative to achieving target soil pH and making nutrients available to plants.

“Both of our Lime Rate Calculators allow farmers to consider the types of liming products and current costs to make the best selection for their needs,” Alford says. “These factors are important to consider in times when the supply chain is interrupted and costs are not stable.”

Michael Plumblee, Clemson Cooperative Extension Service corn and soybean specialist, says using the Reverse Lime Rate Calculator will save growers time and money.

“This app takes out the manual calculation part of determining liming rates,” Plumblee says. “It also allows for the ability to compare several rates rather fast compared to doing the math by hand. This app will help farmers save money by making sure that the appropriate rates of lime are being applied based on soil sample results. Putting a closer eye on all of our inputs and the rates we apply these inputs ultimately will help increase profits and reduce costs where applicable.”

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