Soil Resources

Soil is the thin mixture of small rock particles and rotting organic matter that covers the surface of the earth. The four types of soil are-

1. Alluvial soil
2. Black soil
3. Red soil
4. Laterite soil

Two factors responsible for the formation of soil are —

1. Weathering
2. Erosion

(i) The colour of alluvium soil varies in different areas because its shades depend on the depth of deposition, the texture of the materials and the time taken for maturity.

(ii) Khadar is more fertile than bhangar soil as new layers are deposited year after year during monsoon floods.

(iii) Black soil has a kind of self-ploughing characteristic because during dry season, it shrinks and develops big cracks which help in air circulation. This characteristic causes a kind of self-ploughing.

(i) Soil changes with age - As a soil ages, it gradually starts to look different from its parent material. That is because soil is dynamic. Its components—minerals, water, air, organic matter, and organisms—constantly change.

(ii) One important constituent of soil that adds fertility to the soil is humus.

Alluvial soil is formed by the sediments brought down by rivers. The rivers deposit very fine particles of soil called alluvium in their plains during the course of their long journey. The resultant alluvial soil is known as riverine soil.

Two advantages of alluvial soil are-

1. It is light and porous. So, it is easily tillable.
2. It is suitable for the growth of a large variety of rabi and kharif crops.

(i) Different regions in India have different kinds of soil for agriculture because India is a vast region with varied natural environment. Several physiographic regions and different types of climate lead to the formation of different types of soil in different regions.

(ii) Alluvial soils vary in texture as in the upper reaches of the river valleys, the soil is dry, coarse, porous and sandy. Soil particles are large and non-uniform but as we move further down a river valley, the soil particles become smaller and more uniform. They are more compact and more moist.

(iii) Nearly all types of crops grow well in riverine soils because alluvial soil is a mixture of sand, clay and silt. It is rich in mineral and easily tillable. Its composition makes it suitable for the growth of a variety of crops.

(i) Soil is a valuable resource for India because agriculture is the main occupation in India. Soil supports agriculture and it is the source of nutrients for many forms of life.

(ii) Black soil is considered a productive soil because it has high moisture retention capacity and more clay content which responds well to irrigation. It is suitable for the cultivation of cotton, jowar, wheat, linseed, gram, citrus fruits and vegetables, tobacco and sugarcane.

Black soil is suitable for growing cotton and sugarcane in Maharashtra. Its characteristics are-

1. It is black in colour.
2. It has high quantities of lime, iron, magnesium and generally poor percentage of phosphorus, nitrogen and organic matter.

One soil of volcanic origin commonly found in India is black soil. Cotton is widely grown on this soil.

(i) Deltaic alluvium is more fertile than coastal alluvium as new layers are deposited year after year during monsoonal floods. Also, deltaic alluvium is composed of fine silt and clay whereas coastal alluvium is full of lime nodules.

(ii) Black soil is found in the Deccan trap region because this region is formed due to the deposition of lava produced by the volcanic eruption. When lava rocks breaks down into finer particles due to weathering, it results in the formation of the black soil.

(iii) Black soil is often referred to as Cotton soil or Regur soil because it is black in colour and is suitable for cotton cultivation.

Pawan's farm is likely to have Khadar soil as his farm is located along the Ganges, while Akash's farm is likely to have Bhangar soil as his farm lies 20 km away from Ganges.

Khadar and Bhangar soils are sub-categories of Alluvial soil. Khadar is younger alluvium as flood waters deposit new layers every year.It is formed of fine silt and clay. The bhangar or the older alluvium is composed of lime nodules or kanker and has a clayey composition. Khadar soil is superior to Bhangar as it is more fertile.

Also, Pawan's farm is located close to Ganges so it needs lower input of irrigation than Akash's farm, as being in close proximity to the river naturally replenishes moisture in the area.

(i) Laterite soil is formed as a result of atmospheric weathering of rocks under the conditions of high rainfall and temperature with alternate wet and dry periods. It is the residual soil formed by leaching due to tropical rains.

(ii) One disadvantage of Laterite soil is that it does not retain moisture and hence, is infertile.

The characteristics of Khadar and Bhangar soils are:

Khadar Soil

1. Khadar is younger alluvium as flood waters deposit new layers every year.
2. It is formed of fine silt and clay.
3. Khadar is light in colour.
4. Khadar is very fertile and ideal for intensive cultivation.

Bhangar Soil

1. Bhangar is above the flood levels of rivers and presents a terrace like structure.
2. Bhangar is full of kankars (lime nodules).
3. Bhangar is not very fertile but crops can be grown on it by using manure.

(i) Laterite soils are used as a building material because they become hard like iron when exposed to air. So, they are used as a building material. Laterite soils are red in color due to the presence of iron oxide. These soils are generally coarse in texture and friable and porous in nature.

(ii) Soils of the Western Ghats are affected by wind erosion because a large chunk of Western zone is arid or semi-arid and wind erosion is a result of extreme form of soil degradation due to aridity.

(iii) The foothills of the Himalayas are prone to excessive soil erosion because the vegetation over there is very less. There are not many plant or tree roots to hold the soil in place, which makes the foothills of the Himalayas prone to excessive soil erosion.

(i) Laterite soil is suitable for growing coffee in Karnataka.

(ii) Two main characteristics of this soil are-

1. It is red in colour due to the presence of iron oxide.
2. It is of a coarse texture, soft and friable.

Regur soil is found in Maharashtra and Madhya Pradesh.

(i) Jowar is grown in Maharashtra because of the black regur soil which is rich in lime, potash-magnesium, carbonates, allumina and calcium.

(ii) Bajra is grown in Rajasthan because of the sandy soil found in this region. It is rich in soluble salts.

(iii) Sugarcane is grown in Uttar Pradesh because the climatic conditions and presence of alluvial soil support the cultivation of sugarcane.

(i) Besides cotton, jowar, wheat, linseed, gram, citrus fruits and vegetables, tobacco and sugarcane grow well in Regur soil.

(ii) Regur soil helps agriculture as it is very fertile. In any season, it has moisture stored in its subsoil. This allows dry farming as well. In dry season, it forms big cracks which help in air circulation, and causes a kind of self ploughing.

Two states where red soil is found are Tamil Nadu and Karnataka. Two important crops grown in this soil are rice and tobacco.

I will identify Red soil by its texture. Red soil is porous, loose and aerated.

(i) The soil found in Rishikesh is alluvial soil, which is formed by the deposition of materials carried by rivers. Since Rishikesh lies in the upper course of the river Ganga, the alluvial soil here is dry, coarse, porous, and sandy. This is because, in the upper reaches, the river deposits heavier particles like sand and gravel, while finer materials like clay and silt are carried further downstream.

(ii) Agra is located in the Indo-Gangetic plains. The presence of fine, smooth, and moist particles in the soil near Agra suggests that it is Khadar alluvial soil, formed by deposition of fine silt and clay by the Yamuna River, making it highly fertile and moisture-retentive.

(iii) Scattered patches of red soil are found in Jhansi. Red soil gets its red colour from the presence of high iron oxide content. It is commonly found in the plateau regions of India.

(i) Red soil develops on old crystalline rocks. Under prolonged weathering by rainfall, ancient crystalline and metamorphic rocks of the peninsular plateau break up to form this soil.

(ii) This soil suitable for dry farming as it is formed in areas with poor rainfall.

The removal of the top soil cover by water, wind and human activities is called soil erosion.

(i) Wind erosion affects the dry areas of Rajasthan, Gujarat and Haryana

(ii) Running water erosion affects the badlands of Chambal and Yamuna river, the piedmont zone of western Himalayas, the Chotanagpur plateau, the Tapi-Sabarmati valley and the regur soil area of Maharashtra.

Two agricultural practices used to prevent soil erosion are:

1. Terrace farming — On hilly slopes, terraces act as bunds and prevent the soil from being washed away by running water.
2. Shelter belts — Farmers plant trees in several rows to check soil erosion by wind.

(i) Shelter belts reduce soil erosion in arid areas because planting trees in several rows checks wind erosion.

(ii) Rural development will influence soil conservation as in the programmes of rural development, villagers are provided with the techniques of how to improve vegetative cover and the steps required to be taken for preventing soil erosion. The farmers are briefed about the farming methods (such as strip cropping and shelter belts) to be followed to reduce soil erosion.

(iii) Water harvesting aids in soil conservation as it reduces soil erosion and flood hazards by collecting rainwater and reducing the flow of water which causes the removal of fertile top soil.

(i) Soil conservation means prevention of soil loss from erosion or prevention of reduced fertility of soil caused by over-use, acidification, salinisation or other types of soil contamination.

(ii) Two measures to conserve soil in hilly areas are-

1. Terrace farming- Terraces act as bunds and prevent soil erosion by running water.

2. Contour Ploughing- Ploughing along contours on a slope prevents soil erosion by running water.

The primary cause of erosion in Chambal valley is Gully erosion, which is caused by the continuous action of running water.

Gully Erosion in Chambal Valley

1. Rainwater Runoff: During heavy rains, water flows over the land surface, cutting into the loose soil.
2. Formation of Small Channels: Over time, small streams or rills develop as water continues to erode the surface.
3. Deepening of Gullies: With repeated erosion, these rills expand into deep gullies, removing large amounts of topsoil.
4. Expansion into Ravines: As erosion continues unchecked, the gullies widen and deepen, eventually forming ravines, which are a characteristic feature of the Chambal Valley.

Two methods of controlling erosion of soil caused by running water are construction of dams and plugging gullies.

Two important agents of erosion are water and wind. Water erosion can be controlled by the construction of dams. Wind erosion can be controlled by making shelter belts.

There is an acute need for conservation of soil as a natural resource because of its adverse effects which include the following-

1. Loss of fertile topsoil with its mineral content
2. Lowering of the water table
3. Drying of vegetation and extension of arid lands leading to an increase in the frequency of drought and floods
4. Silting of river and canal beds
5. Recurrence of landslides
6. Adverse effect on economic prosperity and cultural development

(a) Black soil or Regur soil is the soil that becomes sticky when wet and cracks when dry.

Formation of Black Soil — Black soil is formed at the place of its origin over the underlying rocks. It is formed by the denudation of volcanic rocks.

(b) Cotton and Wheat.

(c) The factors that influence distribution of soil types in India are:

1. Changing temperature
2. Running water and rainfall
3. Wind
4. Chemical and organic changes taking place in the soil
5. Parent rock material

Humus

All of the above

Alluvial soil

Red soil

Both A and R are true and R is the correct explanation of A.

Explanation — Transported soils are formed from the movement of soil material by agents such as rivers, glaciers, wind, or human activity, which mix various components together and prevent the development of a distinct profile.

winds

Iron

Both A and R are true and R is the correct explanation of A.

Explanation — The northern plains of India, especially areas like the Indo-Gangetic plains, are made up of Riverine (alluvial) soil deposited by rivers. These riverine soils are formed by deposition of materials like sand, clay and silt.

Both (1) and (2)

Regur

the Peninsular Plateau

It has fifty per cent of clay content

Red soil

Both A and R are true and R is the correct explanation of A.

Explanation — Soluble plant food like potash are leached into the soil due to heavy rainfall, because of which even though Laterite soils are rich in alumina and iron oxide, they are infertile.

All of the above

Soil texture

Red soil is available in this area as this type of soil is formed in areas with poor rainfall.

Though red soil is suitable for cultivating almost all crop types, it is most suitable for growing vegetables, rice, ragi and tobacco. Groundnut and potatoes can be grown on coarse soils at higher levels and sugarcane on heavy clays at lower levels.

My uncle is residing in the highland areas of the Peninsular Plateau.

Laterite soil is available in this area.

Laterite soil is formed as a result of atmospheric weathering of rocks under conditions of high rainfall and temperature with alternate wet and dry periods. It is the residual soil formed by leaching due to tropical rains. Leaching or desilication is the process in which the nutrients get percolated down below the soil due to heavy rainfall; thus leaving the topsoil infertile. Due to heavy rains, lime and silica are leached away and aluminium compounds are left behind. Humus content of the soil is removed by bacteria that survives well in high temperature.

I had gone for an excursion to a mountainous region with my teachers and classmates. I was shocked to see bare mountains with no vegetation or greenery. When I asked the reason for such a condition of the mountain, my teacher told me that the main reason was soil erosion. There are various causes of soil erosion:

1. The loss of vegetation cover leads to Sheet Erosion on hilly slopes because water instead of sinking into the ground washes the soil down.
2. The area also receives heavy monsoon rains which causes Sheet, Rill and Gully erosion.
3. In this area, local population practise shifting cultivation. The heavy rains then wash away the bare soil from the slopes to the valleys below.
4. Another important cause of Sheet, Rill and Gully Erosion is uncontrolled grazing of domestic animals in the upper slopes.

The solutions to rectify the problem of soil erosion are as follows:

1. Terrace Farming — On hilly slopes, terraces act as bunds and prevent the soil from being washed away by running water.
2. Contour Ploughing — Ploughing along contours on a slope prevents soil being washed away by rainwater or by surface run off. Contours act like bunds. Terraces are levelled into step-like small fields with even slope.
3. Plugging Gullies — The gullies made in the soil are plugged with deposition of silt during heavy rains.
4. Planting Trees — The trees are planted along the edges of the fields, the waste land and on steep slopes to prevent soil erosion as well as to enhance the capacity of the soil to retain water.

Sand, silt and gravels brought by rivers Ganga-Brahmaputra together comprise Alluvial soil in Chars. Moreover, since the soil keep changing by the rivers, Khadar alluvial soil is found in Chars which is a very fertile soil. Hence, the main land use in chars is farming and growing short-duration crops like rice, jute, vegetables, etc.