Lesson: Soil

The microorganisms present in the soil require moisture (water) and nutrients for growth and survival. Choose from the options below the habitat (place) where the soil has plenty of water and nutrients.

(a) Desert

(b) Forest

(c) Open field

(d) Cricket ground

b

Availability of water and minerals in the soil for maximum absorption by roots is in the $–$

(a) B-horizon

(b) C-horizon

(c) A-horizon

(d) Surface of soil

c

Soil conservation measures are mainly aimed at protecting which of the following?

(a) Plants

(b) Top soil

(c) Sub soil

(d) Soil organisms

b

Read the following statements with reference to soil.

(i) Weathering is a very fast process of soil formation.

(ii) Percolation of water is faster in sandy soils.

(iii) Loamy soil contains only sand and clay.

(iv) Top soil contains the maximum amount of humus.

Choose the correct statements from the above.

(a) (ii) and (iv) (b) (i) and (iii)

(c) (ii) and (iii) (d) (i) and (ii)

a

Soil has particles of different sizes. Arrange the words given below in increasing order of their particle size.

Rock, Clay, Sand, Gravel, Silt

Clay, Silt, Sand, Gravel, Rock

The components of loamy soil are ______, ______ and ______.

The components of loamy soil are clay, silt and sand.

Read the following statements and give the appropriate terms for each of them.

(a) The process of breakdown of rocks by the action of wind, water, sunlight.

(b) Removal of top soil during heavy rains or strong winds.

(c) Accumulation of wastes in the soil generated by human activity which alter the features of soil.

(d) The process of movement of water into deeper layers ofsoil.

(a) Weathering

(b) Erosion

(c) Pollution

(d) Percolation

Unscramble the following jumbled words related to soil.

HUMUS

SOILPROFILE

HORIZON

LOAM

WEATHERING

PERCOLATION

Which of the following situations $–$ ‘A’ or ‘B’ $–$ is advantageous for absorption of water and minerals? Why?

Situation ‘A’: Growth and branching of roots in the C-horizon.

Situation ‘B’: Growth and branching of roots in A and B- horizons.

Situation ‘B’ is advantageous for absorption of water and minerals.

This is because the uppermost horizons, especially the A-horizon, are generally rich in humus and minerals. The humus makes the soil fertile and provides required nutrients to the growing plants through the roots. This layer is generally soft, porous and can retain more water, and thereby allows proper growth and branching of the roots.

How can a farmer convert acidic soil to neutral soil?

An acid and a base react to form a neutral product. A farmer can convert acidic soil to neutral soil by adding basic substances to the soil, such as a solution of quick lime or slaked lime, in small quantity.

Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give reason to support your answer.

Grass covers the soil surface and small plants bind soil firmly with their roots, so that soil cannot be eroded. In the absence of plants, the soil becomes loose and thus it can be moved away by wind and flowing water. So, in order to check soil erosion, the removal of grass and small plants cannot be considered to be a good practice.

A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.

The soil profile gets hard to harder from the A-horizon downwards towards the bedrock. That is why the man digging the pit found that he could initially dig the soil with ease because the soil structure towards the top were more loosely bound whereas it became more difficult as he went deeper. But digging beyond the depth of 5 feet became impossible for him because that region of the soil had lot of hard pieces of gravel which made the digging procedure difficult.

Locate the following zones given in the figure below which shows a diagram of soil profile.

Top soil, Subsoil, C-horizon, Bedrock

Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several streams and rivulets of rain water during the journey but to his surprise he did not see streams of water in the desert region even during rains. Help Boojho find a suitable explanation for this.

Rajasthan, being a desert state, has sandy soil. Sandy soil has the characteristic of high rate of percolation which means sandy soil permits water to seep down to the lower layers, without forming water stagnation on the surface of the land. This explains why the streams and rivulets of rainwater, formed due to rainfall, disappear into the soil.

Match the animals in Column I with their natural place of dwelling (habitat) in Column II.

Continuously water-logged soils are disadvantageous for plant growth. Why?

Continuously water-logged soils are harmful for plant growth because water-logging leads to lack of oxygen (in the form of air) in the soil. Lack of oxygen supply to the plant roots result in the rotting of roots because the roots fail to breathe. So ultimately the plants die.

Why is soil erosion relatively less in dense forests as compared to barren, open fields?

Dense forest consists of lot of trees and plants. Roots of trees, small plants and grasses together bind the soil firmly, so that soil erosion does not take place in large amount here. In the absence of plants, as in barren lands and open fields, the soil becomes loose and so it can be easily moved by wind and flowing water.

Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons.

Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently so as to allow air and water to reach the roots of the plants. This aids in plant growth. In this way plants can breathe in oxygen through their roots too for a healthy growth. This process also helps in the removal of weeds.

In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages.

Give suitable reasons.

Population is much denser in cities and towns than in villages. So, rate of water consumption is much more in cities and towns than in villages. This accounts for more usage of water in the former case than in the latter case. As a result, the level of underground water falls. So bore wells have to be dug to much deeper levels to reach the level of ground water.

Several terms related to soil are hidden in the squares given below. Spot them and make a list. Two examples are given for you.