1) Soil is formed by the Parent rock material through a process of break up or wear and tear. The decomposition of plant remains, animal manures and dead animals add to the fertility of the soil.
2) Soil is the thin layer of loose mixture of small rock particles and rotting organic matter that covers much of the world's land surface. It supports all forests, grasslands and crops from which all living creatures on earth derive their food.
3) (i) Black Soil (ii) Alluvial Soil (iii) Red Soil (iii) Laterite Soil
4) The chief region of Alluvial Soils in India is the Indo-Gangetic plain, where Alluvial Soils have been deposited mostly by rivers. The coastal belts are also areas of alluvium. The deltaic alluvium on the eastern coast has also been deposited by rivers. Therefore, Alluvial Soils are rightly called Riverine Soils.
5) The Alluvial Soil of the Ganga plain is formed due to the deposition of alluvium which is brought from the Himalayan region. These are light in colour.
The Alluvial Soil of the Godavari valley is formed due to the deposition of alluvium brought mainly from the Deccan trap region which is volcanic in origin. It is dark in colour.
6) Alluvial soils are formed by the sediments brought by the rivers. The rivers deposit very fine silt called 'alluvium' in their plains during the course of their journey starting from its source in the mountains and ending till its mouth.
This soil is agriculturally very important because it is a mixture of sand, clay and silt (loamy) which makes it very fertile. It is rich in potash and lime. It is light and porous therefore easily tillable. It is suitable for growing large variety of Rabi and Kharif crops.
7) (i) It is Black in colour therefore it is called Black Soil. These Soils are also called Regur Soil. These are formed in situ, i.e., formed where they are found. These Soils have originated from solidification of basic lava spread over large areas of Deccan Plateau during volcanic activity.
(ii) Two characteristics or features of the Black Soil which is most suitable for growing cotton and sugarcane in Maharashtra are:
(a) It is fine grained, rich in iron, lime and calcium.
(b) It retains moisture and becomes exceedingly sticky.
8) Black Soil is formed as a result of denudation of lava-flow rocks. They contain large quantities of lime, potash, aluminium, magnesium. They are deficient in phosphorus, nitrogen and organic matter. Black Soil is highly retentive of moisture, and become sticky when wet.
9) Black Soil is also known as 'Regur Soil' or 'Black Cotton Soil'. Black Soil is found in Gujrat, Maharashtra, parts of Madhya Pradesh, South Uttar Pradesh, North-west Orissa and the western parts of Andhra Pradesh.
10) (i) Black Soil is formed by weathering of volcanic rocks. It is found in Maharashtra and M.P.
(ii) It retains moisture for a long time, is rich in lime, potash and calcium.
11) Red Soil is found in Tamil Nadu, Karnataka, South-eastern Maharashtra, parts of Andhra Pradesh and Orissa. They are also found in the southern districts of Uttar Pradesh, Madhya Pradesh and eastern Rajasthan.
12) The Red Soils are generally poor in nitrogen, phosphoric acid and humus. They become reasonably fertile when fertilizers are added to it.
13) Red Soil is formed by weathering of crystalline and metamorphic rocks. Reasons for low productivity:
(i) Deficient in nitrogen, humus.
(ii) Porous, friable.
14) It is formed by the weathering of Soil or due to intense leaching during the periods of heavy rainfall. All the soluble materials are removed and a hard stony layer remains.
15) It is found in Andhra Pradesh, Tamil Nadu, Karnataka, Assam, Bengal, Orissa and along the Western and Eastern Ghats.
16) Disadvantages of Laterite Soils are:
(i) They are highly acidic.
(ii) It is generally coarse in texture and cannot retain moisture.
17) (i) Laterites are intensively leached Soils of the monsoon climate. They lack in elements of fertility and thus are normally of low value for crop production. Laterite Soil is found in India in hill summits of Eastern and Western Ghats and Assam Hills.
(ii) Laterite Soils are found on the summits of the Eastern Ghats. These are formed in the areas which experience high temperature and heavy rainfall. They are formed by the process of leaching.
18) The washing away or the removal of the Soil is known as Soil erosion. Soil erosion, thus, may be termed as the detachment and transportation of Soil particles by agents of denudation such as weathering, running water and wind, etc.
19) Soil erosion by water can be of the following sub-types:
(i) Sheet erosion
(ii) Rill erosion
(iii) Gully erosion
(iv) Stream Bank erosion.
(v) Sea-shore erosion.
(vi) Slip erosion.
20) The rate of Soil erosion depends upon:
(i) Character of the slope of land.
(ii) The density of vegetation.
(iii) Rainfall Heavy or Light.
21) Leaching Soil is the process by which soluble substances such as organic basic minerals and mineral salts are washed out of the upper layer of a Soil into a lower layer by percolating rain water, e.g., Laterite Soil. Found in Karnataka which is south of Tropic of Cancer.
22) When the vegetation cover of an area is removed, the rain water instead of sinking into the ground, washes the Soil down the slope. Each succeeding rain stream washes away a thin layer of absorbent top Soil. This is known as Sheet Erosion.
23) In rill erosion small finger-like rills begin to appear on the landscape. These rills are usually smoothened out by working of the farm implements. But, slowly the rills increase not only in number but also in their shape and size. They get wider and deeper. This reduces the actual area under crop and results in declining crop yields.
24) The banks of the streams or rivers get eroded every year by the flowing water. In certain areas, the streams and rivers often change their course bit by bit every year and their beds get widened.
25) (i) The tidal waters of sea cause considerable Soil erosion along the coast, particularly during the rainy season when the sea gets rough. The roaring waves rush and dash on the coast, swallowing every time bits of coastal lands.
(ii) Slip erosion is caused by hydraulic pressure exerted by moisture penetrating into the Soil during heavy rains. Sometimes the entire field on hill side may slide down because of slip erosion.
26) When wind blows over barren land, there will be damage to the top Soil. In the areas of scanty rainfall wind erosion is predominant. When deaf forestation due to over-grazing of cultivation makes the top Soil bare, wind erosion occurs.
27) Some measures to check Soil erosion are: Contour method of ploughing, terraced farming, plugging of gullies and ravine method, constructing dams across the streams, check on unrestricted grazing over the pastures, afforestation and legal binding on primitive method of Jhooming cultivation should be exercised.
28) A rich soil in plant food is the chief requirement of a successful agriculture. It is an essential as a support for plants. Soil is a very important natural resource of India because agricultural production is basically dependent on the fertility of Soil. Food products like cereals, pulses, fruits and vegetables are obtained indirectly from the Soil.
(i) Contour ploughing. (ii) Afforestation.
29) Sandy and porous Soils are subjected to least erosion by water action because they absorb a good amount of water at the time of rainfall. Impervious Soils are subjected to gradual erosion by water because they are incapable of absorbing rainwater.
30) (i) Terrace farming.
(ii) Planting shelter belts to check the speed of wind.
31) Soil conservation refers to the methods of protecting the soil from erosion. Roots of the trees protect the soil by holding it in place against wind and water erosion. Re-afforestation means replanting trees which have been cut down. For every tree that is cut, two trees are grown. In this way forest cover is increased.
32) (i) Use of fertilizer.
(ii) Crop rotation: Rotation of crops is a system in which farmers grow pulses or leguminous crops after the harvest of a soil exhausting crop. Through this method the soil retains its fertility or gets back the nitrogen.