Overcoming Soil Acidity Constraints Through Liming and Other Soil Amendments in Kenya. A Review

Abstract

Food production in Kenya is constrained by low and declining soil health resulting from low soil fertility and increasing widespread soil acidity, coupled with emerging climate change effects leading to recurrent food and nutrition insecurity. The major food production areas with high crop yield potential in the country are greatly affected by soil acidity due to continuous cropping, loss of organic carbon, nutrient leaching and inappropriate use of fertilizers. While use of organic and inorganic fertilizers, improved seed varieties and crop protection have received much research attention, liming as one way of improving soil health and crop production has not received similar attention. Consequently, potential yield of hybrid crops remains constrained. Soil acidity is mainly ameliorated by applying lime or other acid‐neutralizing materials, which neutralize the acidity, raises soil pH, increases the availability of plants’ nutrients and adds calcium and magnesium to the soil. It also improves the environment for beneficial soil microorganisms thus enhancing rapid breakdown of organic materials in the soil and releasing nutrients for growing plants. Soil buffer capacity determines the amount of lime per unit of soil volume needed to alter soil pH. Soils with low Cation Exchange Capacity (CEC) respond rapidly to liming than soils with high CEC. But the low-CEC soils have a high capacity for rapid leaching of the added bases, thus a quicker return to original acidity unless additional liming is done. Over-liming is recommended for soils which have low CEC, such as sand which is deficient in buffering agents such as organic matter and clay. There is therefore need for appropriate attention to to ameliorate soil acidity in order to maintain good soil health for food and nutrition security. A meta-analysis of a desk study supported by field experiment was carried out in areas viewed as most affected by soil acidity. The aim of the study was to evaluate amendments that can be used for alleviating soil acidity in acidic soils. The results showed that extensive work has been done in Western and Rift valley regions of Kenya targeting soil acidity alleviation and few studies in the coastal and eastern regions due to perception that these areas do not have acidic soils. Among the soil acidity amendments, use of lime and organic sources showed positive crop response and increased yields when applied in acidic soils.