Soil in Kerala. The soils of the State are predominantly Lateritic of both sedimentary and residual types. Other soil types have developed in certain areas due to local physiographic and environmental factors. Coastal alluvial soil is originated from recent deposits, predominantly marine, with some fluvial sediments along the coast line. Developed along river valleys, riverine alluvial soil occurs throughout the state. Red loam occurs in isolated patches in foothills and hillocks being associated with laterites. The red colour is due to the presence of iron oxides. Highly porous and friable, it is not fertile. Laterite soil occurs throughout the state. It is acidic and widely cultivated. Greyish onattukara, the grey colour soil occurs in the districts of Alappuzha and Kollam. It is acidic and deficient in major plant nutrients. Acid saline soil is found mainly in the Kuttanad regions. Paddy is successfully grown in this soil with careful management. Brown hydromorphic soil is commonly found in areas of wetlands. Hydromorphic saline soil is observed along the coastal strip. Black cotton soil is found in a small portion of land in Chittur, Palakkad District. It is found suitable for a limited variety of crops. Forest loam found in the forest area is highly enriched with organic matter of decomposed leaves. It is rich in nitrogen. The soil is quite fertile under forest cover and promotes prolific undergrowth.