NCERT Book Class 11 Geography Soils

SOILS

Have you ever thought about the most important factor which supports trees, grasses, crops and numerous lifeforms over the earth’s surface? Can one grow a blade of grass without soil? While some plants and organisms which are aquatic in nature can sustain in water, do they not derive nutrients from soil through water? You will  realise that soil is the most important layer of the earth’s crust. It is a valuable resource. The bulk of our food and much of our clothing is derived from land-based crops that grow in the soil.

The soil on which we depend so much for our day-to-day needs has evolved over thousands of years. The various agents of weathering and gradation have acted upon the parent rock material to produce a thin layer of soil.

Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time. Besides these, human activities also influence it to a large extent. Components of the soil are mineral particles, humus, water and air. The actual amount of each of these depend upon the type of soil. Some soils are deficient in one or more of these, while there are some others that have varied combinations.

Have you ever dug a pit in the field of your school to plant a tree while celebrating Van- Mahotsava? Was the pit of uniform layer of soil or did you notice different colours from the top to the bottom of the pit?

If we dig a pit on land and look at the soil, we find that it consists of three layers which are called horizons. ‘Horizon A’ is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants. ‘Horizon B’ is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered.

‘Horizon C’ is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers. This arrangement of layers  is known as the soil profile. Underneath these three horizons is the rock which is also known as the parent rock or the bedrock. Soil, which is a complex and varied entity has always drawn the attention of the scientists. In order to understand its importance, it is essential to attempt a scientific study of the soil. Classification of the soil is an effort to achieve this objective.

CLASSIFICATION OF SOILS

India has varied relief features, landforms, climatic realms and vegetation types. These have contributed in the development of various types of soils in India.

In ancient times, soils used to be classified into two main groups – Urvara and Usara, which were fertile and sterile, respectively. In the 16th centrury A.D., soils were classified on the basis of their inherent characteristics and external features such as texture, colour, slope of land and moisture content in the soil.

EXERCISES

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

    (ii) ‘Regur Soil’ is another name for the.

             (a) Saline Soil                                (c) Black Soil

             (b) Arid Soil                                   (d) Laterite 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

    (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 fertilisers

2. Answer the following questions in about 30 words.

    (i) What is soil?

    (ii) What are the main factors responsible for the formation of soil?

    (iii) Mention the three horizons of a soil profile.

    (iv) What is soil degradation?

    (v) What is the difference between Khadar and Bhangar?

3. Answer the following questions in not more than 125 words.

    (i) What are black soils? Describe their formation and characteristics.

   (ii) What is soil conservation? Suggest some measures to conserve soil.

   (iii) How do you know that a particular type of soil is fertile or not?

Please refer to attached file for NCERT Class 11 Geography Soils