Soil is natural occurring substance forming the thin upper most layer of the earth’s surface made by accumulation of the weathered materials on which plants and animals live.
Acidic soil can be defined as those having PH less than 5.5 in 1:1 water extract.
The following are factors which may cause the soil to become acidic:
- Parent materials. Rocks like granite and rhyolite are acidic rocks and on disintegration and decomposition of these rocks results in the accumulation of acid soil materials.
- Organic matters. The carboxylic, enolic, and phenolic materials present in organic matter debris, dissociate releasing hydrogen ions thus contributing towards soil acidity.
- Climate. In heavy rainfall areas, the continuous leaching process removes most of the calcium carbonate and gypsum from soil giving rise to increased soil acidity.
- Roots biomass and soil organisms. Respiration by plant roots and soil microorganisms are major contributing factors to soil acidity. Carbon dioxide liberated during respiration reacts with water to produce carbolic acid which in turn break down to produce hydrogen ions. On another hand when plants exchange cations with the external medium they give an equivalent number of hydrogen ions and thus contributing to soil acidity.