SOIL

The land between two tributaries of a river means DOAB'. The place where two small streams join seether and form a big river is called a DOAB. The small streams might be the tributaries of a river also.

The Terai region in Northern Plains of India consists of wet, swampy and marshy land. Geologically, we find great physical variations on carth re-emerge and create a wet, swampy and marshy region knows as the Terai. Terai region lies berween Yamuna and Brahmaputra rivers.

Alluvial soil is classified into two groups hased on its age, the bhangar and the khadar. The Khalar (new alluvial) is light in colour and is composed of newer deposits. The bharugur (old alluvial) is made of kanker or lime nodules, and its composition is clayey.

Laterite is a deep red soil found in tropical regions and often formed on mafic igneous bedrock. The fertility of this soil is low. This soil is rich in iron oxide and aluminium oxide but lacks nitrogen, phosphoric acid, potash, lime and organic elements.

The government of India established the All India Soil Survey Organisation in 1956 with Headquarters at the Indian Agricultural Research Institute, New Delhi, and five Regional Soil Correlation Centres at Bangalore, Delhi, Kolkata, Jorhat and Udaipur. Later in 1958, this scheme was integrated with the Land Use Planning Scheme of the Central Soil Conservation Board primarily to carry out detailed soil surveys in the catchment areas of major River Valley projects, with the setting up of the organisation "All India Soil and Land Use Survey".

Dry soils are the sandy soils that form in arid regions of Rajasthan and Gujarat. These soils are entirely od of any organic matter. They also have a very high saline content, making them largely mfertile. Only desert vegetation (cacti, bushes etc.) can grow in this type of sod

Fertile riverine alluvial soil is best sated for paddy (rice) cultivation. Such soils in the river deltas are called deltaic alluvium (coastal alluvam). Alluvial soil is rich in Potassium.

Karewas are lacustrine deposits (deposits in the lake) in the Valley of Kashmir and the Bhaderwah Valley of the Jammu Division. These are flat-topped mounds that surround the Kashmir Valley on all sides. They are characterised by fossils of mammals and at places by peat. Karewas are thick deposits of glacial clay and other material embedded with moraine. It is found only in the Kashmit region and is suitable for saffron cultivation.

Horizon A part of the soil possesses organic materials mixed with the minerals, nutrients and water. The layers of the soil are called horizons. The uppermost horizon is called the topsoil. The topsoil is a mixture of sand, silt, clay and decomposed organic matter called humus. Humus is a rich, highly decomposed organic matter made from dead plants, crunched-up leaves, insects and twigs.

Peat soils are also called marshy soils. They result from waterlogging and anaerobic conditions (which lead to partial decomposition of organic matter). They are found in areas receiving heavy rainfall and with high humidity where there is a luxuriant growth of vegetation.