A) About one-third of the area records more than 750 millimetres of annual rainfall
B) The dominant source of irrigation in the country is wells
C) Alluvial soil is the predominant type of soil in the northern plains of the country
D) The mountain areas account for about thirty percent of the surface area of the country
Correct Answer: A
Solution :
[a] The rainfall of India is primarily orographic, associated with tropical depressions originating in the Bay of Bengal and the Arabian Sea. The annual rainfall of India is 120 cm, as slightly more than global mean of 99 cm. The spatial distribution of rainfall in India is uneven. The highest normal annual rainfall (1182 cm) in the world has been recorded in Mawsynram (Meghalaya) while the western part of Jaisalmer district (Rajasthan) is one of the driest parts of the world recording about 9 cm of rainfall in a year. Depending upon the total annual rainfall, the country can be divided into five major discontinuous regions - (i) Region of very low rainfall (less than 30cm a year); (ii) Region of low rainfall (30 to 60 cm a year); (iii) Region of medium rainfall (60 to 100 cm a year); (iv) Region of high rainfall (100 to 200 cm); (v) Region of very high rainfall (above 200cm a year). The main sources of irrigation used in different parts of the country are (i) Canals, (ii) Wells and Tube Wells, (iii) Tanks and (iv)Others (Dongs, Kohls and springs). The dominant source of irrigation in India is wells. Alluvial soils are the largest and most important soil group of India. They cover about 15 lakh sq. km or about 46 percent of the total land area of the country. These soils contribute the largest share of our agricultural wealth and support the bulk of India's population. Most of the alluvial soils are derived from the sediments deposited by rivers as in the Indo-Gangetic plain although some alluvial soils in the coastal areas have been formed by the sea waves. Thus the parent material of these soils is of transported origin. These soils differ in consistency from drift sand to rich loams and from silts to still clays. Their chemical composition makes them one of the most fertile soils in the world. The proportion of N2 is generally low, but potash, phosphoric acid and alkalis are adequate, while iron-oxide and lime vary within wide range. The porosity and texture provides good drainage. These soils are easily replenished by the yearly river floods and support uninterrupted crop growth.
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