Soil acidification and lime quality: sources of soil acidity, its effects on plant nutrients, efficiency of lime and liming requirements

Agriculture sectors support economy of most developing countries. In Sub-Sahara Africa, the agriculture is predominantly based on rain-fed agricultural production of small, semi-subsistence, and increasingly fragmented farms. Thus, the farming is intensive and fields are concentrated on valleys, steep hillsides and mountains. This results in soil acidity, low fertility, accelerated soil erosion and low crop yields. Soil acidity affects crops in many ways and its effects are mostly indirect, through its influence on chemical factors such as aluminium (Al) and manganese (Mn) toxicity, calcium (Ca), phosphorus (P) and magnesium (Mg) deficiencies and biological processes. The application of lime believed to enhance soil health status through improving soil pH, base saturation, Ca and Mg. It reduces Al and Mn toxicity and increases both P uptake in high P fixing soil and plant rooting system. However, the liming effects depend on its source, its characteristics, composition, purity and how finely it is ground. The estimation of lime requirement is constraining its use for smallholder farmers and young soil scientists. This study therefore aimed at highlighting the most causes of soil acidification, lime quality and lime requirement. This review article will serve as a guide for farmers and young soil scientists in addressing soil acidity and properly determining lime requirement.