Peaty soils originate in the humid regions due to the accumulation of large amount of organic matter in the soils. These are generally submerged under water during the rainy season and are utilised for paddy cultivation afterwards.

The soils are black and heavy and highly acidic. They are highly saline, rich in organic matter but deficient in phosphate and potash. Sometimes these soils are highly toxic to plant life as they contain ferrous and aluminium sulphates in considerable amounts. These soils mainly occur in the western parts of Kottayam district and some parts of Alappuzha district (Kerala).

Marshy soils are found in the coastal regions of Orissa, West Bengal and Tamil Nadu; central portion of north Bihar and in Almora district of Uttaranchal. They are the result of water-logging anaerobic conditions of the soils, and the presence of iron and varying amount of organic matter.