Notes to broadcasters on soil liming

    | September 26, 2011

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    The research on the impact of applying lime as reported in this story was conducted by the Kenya Agricultural Research Institute (KARI) in Kakamega and Moi University in Eldoret, supported by a grant from AGRA’s Soil Health Program. Farmers like Mr. Owanyi who received free lime will need to buy and reapply it in three years’ time.

    Lime is normally used to balance soil pH in overly acidic soils. Testing for soil pH is simple and affordable. Many agricultural extension workers can access soil pH testing kits. Farmers should get their soils tested for pH before considering a lime treatment. In the soil, agricultural lime also replenishes magnesium and calcium.

    David Mbakaya, a soil scientist at KARI, notes that the soils they sampled in western Kenya have pH levels of 4.3 to 5.5 (pH 7 is neutral, below 7 is acidic, above 7 is alkaline). Subsistence staple crops, such as maize and beans, thrive at a pH of 5.5 to 6. While lime is a relatively simple way to correct acidic soils, it must be used carefully and only in correct dosages. KARI supervises farmers who apply lime to ensure they don’t use too much and make the soil too alkaline. After one full application of lime, KARI advises farmers to reapply the lime again after three years. David Mbakaya cautions, “Over-applying lime leads to toxicity.” When applying lime on their soils, Mr. Mbakaya advises farmers to use gloves and face masks as lime can irritate the skin and throat.

    These links provide some basic facts on agricultural lime: (Scroll down the page to section on “Liming”)

    For those interested in reading the scientific research paper with full results, you can visit:

    If soils are too acidic or too alkaline, yields will be affected. Because testing pH is relatively simple, you could broadcast a program on the topic, in collaboration with a farmer and someone from an organization who has access to a soil test kit – perhaps an NGO or the local extension service. Talk to farmers to find out how much they know about the pH levels of their soils. You could organize a test of a farmer’s soil, complemented by a discussion to raise awareness and inform listeners about the effects of soil pH and options for correcting it.