Question

Which one of the following soils is formed by capillary action?
A) Regur-black cotton soil
B) Gray and brown soil
C) Red and Black soil
D) Saline and alkaline

Answer 1

Hint: These refer to clay soils having a poor soil structure as well as a low infiltration capacity. In both of the soils, the availability of plants nutrients is considerably low. Also, both of the soils do not favour plant growth.

Complete answer:
Saline and alkaline soils which are also known as Usara soils having local names for saline soils are Reh, Kallar, and Chopan, Rakar, Thur, Karl etc. These soils have developed in regions having dry climatic conditions (in areas having a little more rainfall than the areas of desert soils)are accompanied by lack of proper drainage. In a situation like this, salts of sodium, calcium and magnesium are deposited on the upper layer of the soil by the means of capillary action.

These are basically Clay soils having 25-40% clay. These soils have a great quality of transporting water by capillary action from the deepest of deep layers but somehow the rate is slow, so plant water requirements are thus not met through capillary water. These kinds of soils are darker in colour and soil aggregation is also more distinct.

In the Rann of Kachchh, the Southwest Monsoon brings salt particles as well as deposits there in the form of crust. Such soils are also formed at the time when the saline water spreads on the land during the high tide in coastal areas. Plus, seawater intrusions in the deltas also promote the occurrence of saline soils.

Salinization also takes place due to over-irrigation (canal irrigation/groundwater use) as well as in areas of high water table (as in the coastal areas of states like Maharashtra and Tamil Nadu). Salinity from irrigation can occur over the time wherever irrigation takes place. This happens because almost all water (even natural rainfall) contain some sort of dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually they begin to accumulate. Also, excessive amounts of irrigation along with dry climatic conditions play an active part in promoting capillary action,resulting in the deposition of salt on the top layer of the soil.

Thus, the correct answer is option ‘D’.

Note: They generally occur in the arid and semi-arid regions, and in waterlogged or swampy areas. These are more widespread in western Gujarat,or in deltas of the eastern coast and in Sunderban areas of West Bengal.The texture of these soils varies from sandy to loamy.