Soils are formed by the weathering and denudation of parent rocks. Constituents of soil: Humus Clay Silica Sand Soil Fertility: The strength of the soil to support soil life. It depends on the following characteristics: The amount of moisture in the soil. The depth of the soil column. The presence of nutrients like phosphorous, nitrogen and potassium. The humus content of the soil. Soil fertility can be improved by the addition of fertilisers to make up for the absence of certain minerals. Classification of soil: Residual soil- formed at the original place only, less fertile 'cause less variety. Transported soil- More fertile, as more variety.
Alluvial Soil Formed by sediments brought down by the river. Also called riverine soil- Mainly found in river basins. Alluvium- a mixture of sand, clay and silt called loam. Entire northern plain made by alluvium soil. On the basis of its age, alluvium soil can be: Bhangar- Old alluvium soil(literally meaning waste), is composed of lime nodules and has a clayey composition. Khadar- Newer soil composed of newer deposits. More fertile as new layers are deposited year after year during monsoon floods. Classification based on distribution: Inland alluvium: Mainly on the Ganga plain. Deltaic alluvium: Mainly found in the deltaic regions of Ganga and Brahmaputra. Characteristics: Light and porous, so easily tillable. Rich in minerals like potash and lime. Compact, coarse, and very moist. Soils in the drier regions are more alkaline. Suitable crops: Cash crops- Sugarcane, cotton, tobacco, and jute. Food crops- Rice, wheat, gram, and oilseeds.
Black Soil Also called regur soil Also called black cotton soil- cotton grows well on this soil. Also called lava soil because formed by the denudation of basaltic volcanic rock. Distribution Mainly found in Maharashtra, Gujrat, MP, UP. Characteristics Fine textured Clayey- up to 50% clay content. High quantities of phosphorous, nitrogen and organic matter. Black colour- formed from basaltic lava rock. Has moisture stored in subsoil in any season- so ideal for dry farming. Crops Cash crops- Cotton, Tobacco, Sugarcane. Food crops- cereals, oilseeds, citrus foods and vegetables.