Digital Lime Calculator to Boost Crop Yields in Acidic Soils

By Gift Briton

With soil acidity being a major problem facing tea farming mainly in central parts of Kenya, the issue of how much lime to apply in order to raise the soil pH to the required levels has been a big challenge to most farmers.

According to Prof. Njue Muigai, an Associate Professor of Soil Science and Plant Nutrition of the Department of Horticulture and Food Security, Jomo Kenyatta University of Agriculture and Technology (JKUAT), raising the soil pH above 6.7(over liming) and applying less lime (under liming), may lead to low crop yields.

Furthermore, for a soil to realize its full potential in terms of yields, a soil PH of 5.5 is deal, he noted.

Through his digital lime calculator (, farmers can now calculate the required amount of lime to apply on their farms by just keying in the soil pH in the calculator.

After carrying out field experiments on acid soils in central Kenya, Prof Muigai developed a digital lime calculator that uses a regression equation to determine the amount of lime required to raise soil pH to the recommended levels.

Farmers only need to get their soil pH determined by an extension worker then key in the soil pH value in the digital lime calculator and it estimates the liming amount automatically.

Prof. Muigai further notes that there are three main problems associated with soil salinity(acidity); aluminum toxicity, deficiency of calcium, magnesium and phosphorous.

Prof muigai speaking during the interview at JKUAT

However, many methods of improving this condition are not relevant to Kenyan soils, noting that other methods also require laboratory work, a process which is beyond farmers and extension workers.

“This lime calculator is a very timely innovation that will be very helpful to students who are doing their projects on soil acidity, farmers and researchers,” he said.

According to him, liming (anything that when applied to soils raises its pH) precipitates the toxic aluminum which is the major cause of low yields in acid soils. Aluminum toxicity reduces the root growth of crops leading to stunting of the crops.

Even though there are many types of limes used to raise the soil pH, Prof Muigai warns that the use of calcium carbonate lime is not recommended because if you use it to raise the pH to around 5.5 the yields declines due to lack of magnesium.

Therefore, the recommended lime to apply is a lime that contains both calcium and magnesium like the Dolomite lime.

According to him, factors leading to soil acidity includes weathering of soil, application of inorganic fertilizers especially the ammonium nitrogen fertilizers which tend to increase the soil acidity by removing the humus which was buffering the toxic aluminum and the cultivation type which depletes organic matter also tends to increase soil acidity.

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