In Ethiopia, large areas of highlands with altitude of >1500 m located in almost all regional states of the country are affected by soil acidity. About 43% of the Ethiopian arable land is affected by soil acidity. The main factors giving rise to increased soil acidity in Ethiopia include climatic factors such as high amount of precipitation (that exceeds evapo-transpiration which leaches appreciable amounts of exchangeable bases from the surface soil), temperature, severe soil erosion, morphological and anthropological factors. Soil acidification is the result of a complex set of processes caused both naturally and by human activity. It limits plant growth because of conditions that increase base element deficiencies, Phosphorus-fixation and toxicities of Aluminum, Manganese and Hydrogen ions. Soil acidity is a critical issue requiring urgent attention in most highlands of Ethiopia because of its impact on crop production and productivity. Soil acidity is a combination of soil conditions that limit plant growth, and its management requires manipulation of various soil and plant factors in favor of better plant growth or crop production. These management practices may vary with severity of acidity, type of soil, type of farming practices, and socioeconomic conditions of the farmer. Liming is a major and effective practice to overcome soil acidity constraints and improve crop production on acid soils. Soil acidity and Al3+ toxicity in surface soil can be ameliorated through liming. Changes in soil pH brought about by liming may have profound effects on the availability of many elements absorbed by crops. Liming increases soil pH and thus decreases Al3+ and Mn toxicities which also increase NO3- N, Ca and P availability. Also many researchers reported the combined application of the organic manures and ground lime meliorated acidity problems greatly in tropical soils. It also increases the lime potential and the calcium ion concentration in the soil solution that ultimately results in the displacement of aluminum ions from the soil due to the presence of calcium and magnesium elements in it and its buffer capacity because of forming complexes with Al and Fe in acid soils.

Keywords: Soil acidity; Lime; Aluminum toxicity; Compost and Soil pH