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Peat Soil

Peat Soil organic soils containing more than 20% organic matter in various degrees and states of decomposition. Deposits that are decayed slightly or not at all are termed peat, while those that are markedly decomposed are called muck. In peat deposits, the kind of plants that were deposited, particularly in the upper layer can be differentiated. By contrast, muck is generally decomposed to the point where the original plant parts cannot be identified. Peat may be quite coarse or fine-structured, depending on the nature of the deposited plant residues. On the other hand, well-decomposed mucks are often quite fine.

In Bangladesh, peat soils occupy about 0.13 million ha and occur in the low-lying areas of the Gopalganj-Khulna region and also more locally in some haors of the eastern Surma-Kushiyara floodplain and the adjoining northern and eastern Piedmont plains. These are sedimentary peats. In general, organic materials occupy more than half of the upper 80 cm of the profile and sometimes in different layers within the same soil. Dark brown muck is the most common constituent of the soil. It has been mapped in a number of basin areas along the boundary between the Ganges river floodplains and the Ganges tidal floodplain. It occupies the Agroecological Zone-14, ie Gopalganj-Khulna Beels. The area remains wet in the dry season, and is mainly deeply flooded in the rainy season. The Agroecological Zone-14 occupies a number of separate basin areas in Madaripur, Gopalganj, Narail, Jessore, Bagerhat and Khulna districts. Soils with peat or muck at the surface generally remain under reeds that are cut annually for thatching material. Poor peat soils have a low bearing capacity when wet. If allowed to dry out, they shrink and eventually are lost by oxidation. Muck layers harden irreversibly into coal-like lumps that are eventually used as fuel. These soils are potentially strongly acidic and are low in essential nutrients. Boro rice could be grown more widely where there is clay topsoil. Reclamation by controlled drainage and/or burial by alluvium are expensive. The soils are limited due to unavailability of potassium (K), sulphur (S), zinc (Zn) and copper (Cu). Peat layers are thought to be instrumental in the arsenic release to the groundwater of Bangladesh. [SM Imamul Huq]