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Chapter-6 Soil 1. Choose the right answer from the four alternatives given below. (i) Which one of the following is the most widespread and most productive category of soil? (a) Alluvial Soil (c) Black Soil (b) Laterite Soil (d) Forest Soil Ans: (a) Alluvial Soil (ii) ‘Regur Soil’ is another name for the. (a) Saline Soil (c) Black Soil (b) Arid Soil (d) Laterite Soil Ans: (c) Black Soil (iii) Which one of the following is the main reason for the loss of the top soil in India? (a) Wind erosion (c) Excessive leaching (b) Water erosion (d) None of these Ans: (a) Wind erosion (iv) Arable land in the irrigated zones of India is turning saline due to which of the following reasons? (a) Addition of gypsum (c) Over irrigation (b) Over grazing (d) Use of fertilizers Ans: (c) Over irrigation 2. Answer the following questions in about 30 words. (i) What is soil? Ans: Soil is a layer of unconsolidated material at the surface of the earth which has been derived from rocks and organic matter through agencies of decay and disintegration. (ii) What are the main factors responsible for the formation of soil? Ans: The main factors in the formation of the soils are parent rock material, relief, climate and vegetation of the area. (iii) Mention the three horizons of a soil profile. Ans: ‘Horizon A’ is the topmost zone. ‘Horizon B’ is a transition zone. ‘Horizon C’ is composed of the loose parent material. (iv) What is soil degradation? Ans: Defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. (v) What is the difference between Khadar and Bhangar? Ans: 1. 2. 3. 4. Khadar Found in the lower level in the plains near the rivers. Loamy, porous soil. More fertile compared to Bhanger. New layers are developed after monsoon floods. Bhanger Found at the higher level in the plains at the river terraces away from rivers Clayey and non-porous soil. Less fertile compared to Khadar due to old deposite. 3. Answer the following questions in not more than 125 words. (i) What are black soils? Describe their formation and characteristics. Ans: These soils are also known as the ‘Regur soil’ or ‘Black cotton soil’ as these soils are best for cotton growing. They are developed on basaltic rocks of the Deccan plateau which falls under the semi-arid climatic regime. The black soils are generally clayey, deep and impermeable. They swell and become sticky when wet and shrink when dried. So, during the dry season, these soil develop wide cracks. The colour of the soil ranges from deep black to grey. Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash, but they lack in phosphorous, nitrogen and organic matter. (ii) What is soil conservation? Suggest some measures to conserve soil. Ans: It is a methodology to maintain soil fertility, prevent soil erosion and exhaustion and improve the degraded condition of the soil. Important methods to reduce the erosion of soil: controlled grazing terraced farming ban on shifting cultivation contour bunding Regulated forestry cover cropping mixed forming crop rotation (iii) How do you know that a particular type of soil is fertile or not? Differentiate between naturally determined fertility and culturally induced fertility. Ans: To determine the fertility of soil, we have to know the inherit characteristics and external features of the soil such as texture, colour, slope of land and humus in the soil. Naturally determined fertility: the fertility which is seemed naturally in the soil is called naturally determined fertility. It includes the texture, colour and moisture in the soil. Culturally induced fertility: When the soil is made fertile by adding other chemical contents such as fertilizers and other manures.