NOTES PREPARED BY
ASHAQ HUSSAIN BHAT
TEACHER SCHOOL
EDUCATION DEPARTMENT
JAMMU AND KASHMIR
' SOIL'
Points to Remember
•Soil is a natural resource. Soil provides support and nourishment to plants. Soil is habitat of many organisms. Soil is essential for agriculture.
• Polythene bags and plastics pollute the soil. Chemicals, pesticides, waste products are also responsible for soil pollution.
•Soil is composed of different layers. The upper most layer of soil, rich in rotting dead matter is called humus.
•Weathering is a process by which soil is formed by the breaking down of rocks by the action of winds, water and climate.
• Types of rocks and vegetation are responsible for the nature of soil formed.
•Soil profile is a verticle section through different layers of the soil. Layers of soil differ in texture, colour, depth and chemical. Composition
•Percolation rate (ml/min) = Amount of water (ml)/Percolation time (min)
•Different types of soil are-loamy, clayey, sandy. Soil hold water in it which is known as soil moisture. Clayey soil is used to make pots, toys and statues.
SOME IMPORTANT DEFINITIONS
Humus. The rotting dead matter in the soil is called humus,
Weathering. The process of breaking down of rocks by action of wind, water and climate is called weathering.
Soil profile. A vertical section through different layers of the soil is called soil profile.
Soil. The mixture of rock particles and humus is called soil
Soil moisture. The amount of water present in soil particles is called soil moisture.
Soil erosion. The removal of top layer of soil or land surface by water, wind or ice is called soil erosion.
Soil pollution. The decrease in fertility of soil either by loss of useful components or by addition of foreign particles is called soil pollution.
TEXT BOOK EXERCISES
Tick the most suitable answer in questions 1 to 5.
Q. 1. In addition to the rock particles, the soil
contains
(i) air and water
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants.
Ans. (iii) minerals, organic matter, air and water.
Q. 2. The water holding capacity is the highest in
(i) Sandy soil
(ii) Clayey soil
(iii) Loamy soil
(iv) Mixture of sand and loam.
Ans. (ii) Clayey soil.
Q. 3. The process of soil formation is called
(i) Conservation
(iiiC-Horizon
(ii) Weathering
(iv) Pedogenesis.
Ans:-weathering
Q. 4. Soil profile consists of
(i) Two layers
(ii) Four layers
iii)three layers
iv)Five layers
Ans. (ii) Three layers
Q. 5. Humus is present in
(i) A-Horizon
(iii) C-Horizon
(ii) B-Horizon
(iv) Bed rock.
Ans. (i) A-Horizon
Q. 6. Match the items in column I with those in column II
Column I
(i) A hosoilg
organisms
(i) Upper layer of soil
(iii) Sandy soil
iv)Middle layer of the soil
v)Clayey Soil
Column II
(a) Large particles
(b) All kinds of soil
(c) Dark in colour
d)Small particles And packed tightly
(e) Lesser amount of humus
Answer
Q. 7. Explain how soil is formed ?
Ans. Formation of soil. Many years ago, the earth was hard and stony. With passing times, earthquakes broke down these rocks into small pieces. Volcanoes eruption also helped in breaking rocks into pieces. Water present in rocks also helped in weathering of rocks as its condensation led to cracks which broke the rocks. Rain and river water converted these particles into tiny particles and took them to far off places. Thus the soil was formed.
Q. 8. How is clayey soil useful for crops ?
Ans. Clayey soil is good for retaining water. Clayey soil is rich in humus and is very fertile. So it is good for crops.
Q. 9. List the differences between clayey and sandy soil.
Ans. Differences between Clayey and Sandy Soil.
Clayey Soil
(1) Size of particles is less than 0.005 mm.
(2) Only clay particles are present.
(3) In this soil humus is present.
(4) There are no air spaces present in between the particles.
(5) Water cannot flow through the soil.
(6) It is sticky.
(7) It used for making toys, earthern pots, tiles etc.
Sandy Soil.
(1) Size of particles ranges than 0.005 mm.
(2) It contains only sand particles.
(3) In this soil humus is absent between 0.05 mm to 2 mm.
(4)Lot of space is present in between particles.
(5) Water cannot stay in the soil.
(6) It is non-sticky.
(7) It is not used for making toys, earthen pots and tiles etc.
Q. 10. Sketch the cross section of soil and lable the various layers.
Ans. Soil profile.
Q. 11. Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 minutes for 200 ml of water to percolate through the soil sample. Calculate the rate of percolation.
Ans. Amount of water =200 ml.
Time taken = 40 min.
Rate of Percolation =Amount of water/
Time taken
200/40
= 5 ml/min.
Q. 12. Explain how soil pollution and soil erosion could be prevented.
Ans. Prevention of Soil pollution :
(i) Ban on plastic and polythene bags.
(ii) Treatment of waste before dumping in soil.
Prevention of soil erosion :
(i) Growing trees (cultivation)
(ii) Crop rotation.
(iii) Embankment of rivers.
Q. 13. Solve the following crossword puzzle with the clues given :
Across.
2. Plantation prevent it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down.
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
Ans.
1.......wind
2.......Erosion
3........Wheat
4........Sandy
5........Polythene
6........Black
7.........Earthworm
2......Polythene
3.......Sandy
SHORT ANSWER QUESTIONS
Q. 1. What do you understand from the term Weathering'?
Ans. Weathering. It is breaking down of huge rocks into smaller pieces by some physical, chemical and thologeal and for the formation of soil.
Q. 2. What is Humus ?
Ans. Humus. The upper most layer of soil contains organic matter which increases its fertility. This layer is dark brows in colour and is called humus,
Q. 3. What is top soil ?
Ans. Top soil. The upper most layer of earth crust is top soil. This layer is generally soft, porous and can retain more water.
Q. 4. What is water holding capacity ?
Ans. Water holding capacity. Water holding capacity of soil depends on its porosity, type of soil and its power to pass different materials through it. The power of soil to retain water in it is called water holding capacity.
Q. 5. What is loamy soil ?
Ans. Loamy soil. It is a mixture of sand, silt, clay and humus. It has optimum water holding capacity. It is best soil for growing plants.
Q. 6. How will you observe soil profile?
Ans. Soil profile can be observed on the sides of steep river bank or sides of road on hilly region or the sides of well being dug. Note the colour and thickness of different horizons.
Q. 7. What is nature of desert soil ? Where can be found such type of soil ?
Ans. The particles of this soil are big enough to be seen. It is sandy and porous. It contains many dissolved salt in it. The tiny and light particles of this soil are blown away by wind and carried away to far off places. This type of soil can be found in Gujarat and Rajasthan.
Q. 8. Define soil pollution.
Ans. Soil pollution. It is defined as decrease in fertility of soil either by loss of useful components of soil or by addition of foreign elements which reduces its fertility.
Q. 9. Explain the soil as a medium for growth of plants.
Ans. Plants need soil to grow in as roots of plant take water and minerals from the soil. Soil also holds firmly the roots of plants, thus giving them support.
Q.10. How can you call soil as a natural resource?
Ans. Soil as a natural resource. Soil is one of most important natural land resource. Greenary on earth is only due to soil. Plants need soil to grow, for support and for nutrients. Soil is main vital support to the living world. It provides the basic building material for shelter, bricks and mortar. Soil also provides timber, paper etc. Soil is also source of many elements such as aluminium, potassium etc. It also acts as good habitat for many organisms
LONG ANSWER QUESTIONS
Q. 1. Explain in detail the importance of soil.
Ans. Importance of soil. The uppermost surface of earth's crust is soil. Every living organism directly or indirectly depends upon the soil. The habitat of many organisms is in soil. Plants also grow in soil. Rain water also filters through soil and gets stored underground. In this way, soil is resource of many invaluable things.
Importance of Soil
1. As a medium for growth of plants. Plants absorb water and minerals from soil for its growth. Soil also provides inorganic substances like sodium, calcium etc. to plants. Organic material in the form of humus is present on upper surface of soil.
2. As a habitat for organisms. A variety of organisms live in soil. Algae, fungi are also present in the soil. Many worms and small animals make holes in the soil.
3. As a resource. Many important elements are present in soil. Iron, Aluminium, Sodium, Copper etc. are available here. For building houses, we get timber, bricks, mortar, mud, pots etc. from soil. Besides soil provide food, greenery, paper, rain etc.
Soil is porous. Rain water filters through soil and stores underground. Soil particles have power to retain water. The water present in soil particles is soil water. Plants grow in this soil water only.
Thus, soil is invaluable gift to living organisms.
Q. 2. Name the different layers of soil. What does each layer consist of ?
Ans. Layers of soil. Soil profiles can be grouped into A, B and C-horizons.
A-horizon. This layer is the darkest in colour. It is soft Fig
Soil Profile
and porous. It holds more water. Organomineral complexes are present and thus it provides the essential nutrients. It is earth-worms, etc. are present in this layer. also called the top soil. It is very fertile due to humus. Insects,
B-horizon. It is the next layer and is harder and more compact than the top soil. It is called the subsoil and contains very little organic matter. It is lighter in colour than the upper soil. Roots of tall and huge trees generally reach this level but the remains of plants and animals are not found here.
C-horizon. Next to B-horizon is the last C-horizon of the soil formed of weathered parent rocks, e.g. small bumps of rocks. It has cracks and crevices. To penetrate beyond this horizon, is not possible with simple tools. The roots of the plants usually do not reach up to this layer.
Q. 3. Write a note on the importance of soil.
Ans. Importance of soil. Soil is the topmost layer of the earth's crust. It is formed due to the breaking down of rocks under the action of heat from sun, wind and water.
(i) Soil is one of the most important natural resources.
(ii) Soil supports the growth of plants by holding the roots firmly and supplying water and nutrients.
(iii) Soil is the home for many organisms.
(iv) Soil is essential for agriculture. Agriculture provides food, clothing and shelter for all. Soil is thus an inseparable part of our life.
Q. 4. How will you show the presence of air in soil.
Ans. Collect three or four samples of soil from different places. Put them in different wide mouth glass bottles, filled with water. You will observe the emergence of air bubbles. It shows that soil contains air. You can also compare the number of air bubbles emerging from each soil. As shown in Fig.
Presence of air in the soil
0 Comments