Soil Acidification and Lime Quality: Sources of Soil Acidity, 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 aluminum (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 crushed. In addition, the constraints of estimating lime requirement limit its use for smallholder farmers. This review therefore aimed at highlighting the most causes of soil acidification, and provides important formulas to calculate lime requirement and evaluate its effects.