Organic Soil a general term applied to a soil that consists primarily of organic matter such as peat soils and muck soils. Taxonomically organic soil has been classified as Histosols. Because of the presence of appreciable proportions of organic matter, this soil provides favourable physical, chemical and biological conditions for the growing vegetable and shallow rooted crops, and microbial population. A significant proportion of nitrogen, phosphorus and sulphur is generally present in organic combination in the soil. So, organic soils are obviously rich in these plant nutrients. Biochemically organic soils are highly buffered against certain rapid changes in pH due to change in acidity or alkalinity caused by addition of lime and fertilisers.
Organic soil (peat) occurs extensively in the central delta basin areas of Bangladesh. It may occur on the surface or be overlain by clay topsoil. These soils are neutral when wet but become medium to strongly acid if allowed to dry out. Some soils near Khulna could become toxically acid (pH below 4.0) if drained. They occur also in the topsoil of some Noncalcareous Dark Grey Floodplain Soils and acid basin clays, and in buried peat layers occurring in some of these and other floodplain soils. [Rameswar Mondal]