Science Class 7 Chapter 9 Full Solutions 2023 | Soil | NCERT | My Eureka Plus

IV. 

1. What does soil contain ?

Ans: Soil contains air, micro-organisms and often some amount of water.

2. Name the three types of soil .

Ans: The three  types of soil are – Clayey soil , Sandy soil  and Loamy soil .

3. What are  the different layers of the soil called ?

Ans: The different layers of the soil are called   Horizons .

4. What lies below horizon C ?

Ans: Hard layer of rocks lie below horizon C .

5. From where do soil organisms obtain air ?

Ans: Soil organisms obtain air from the space between soil particles called Pore spaces .

6. What is meant by water holding capacity of soil ?

Ans: Water holding capacity of soil means the ability of soil to retain water.

V. 

1. What is weathering of rocks ?

Ans: Weathering of rocks means the action of natural factors that lead to breaking of rocks into smaller           and smaller pieces .

2. Differentiate between loamy and sandy soil .

Ans:  LOAMY SOIL  :

i) It contains an equal amount of sand and silt and lesser amount of clay.

ii) It also holds good amount of air and water .

iii) It appears slightly coarse .

iv)  It is suitable for growing crops for its high amount of humus .

SANDY SOIL :

i) It is mainly made up of soil .

ii) Sandy soil does not hold water .

iii) It is very coarse .

iv) It is not suitable for growing crops unless organic matter is added .

3. What do you understand by percolation  rate of soil ?

Ans: Percolation rate of soil is the measure of how fast water flows or percolates through the soil .

4. Excessive use of fertilizers is not beneficial for soil. Why ?

Ans: The disadvantages of excessive use of fertilizers are –

i) It reduces the fertility of the soil .

ii) It makes the soil hard and less porous .

iii) It kills soil organisms which keep the soil fertile .

5. Why do farmers grow cover crops ?

Ans: As cover crops prevent soil from being exposed to wind and flowing water farmers grow cover              crops .

6. What are shelter belts ?

Ans: Rows of plants grown on the boundary of fields to reduce the force of wind and water are known            as shelter belts .

VI.

1. Why do plants grow well in loamy soil ?

Ans: Plants grow well in loamy soil which has good amount of plant nutrients , retains water but does             not gets waterlogged easily . Loamy soil has all these features including rich amount of humus.               Hence,it is an ideal type of soil to grow plants such as vegetables ,onions , garlic etc.

2. What is compost ? Why is it beneficial to soil ?

Ans: Compost is a natural fertilizer made out of plant and animal waste .

It is beneficial to soil due to the following reasons –

i. It improves the quality of soil.

ii. It loosens the soil and helps air and water to move more freely .

iii. It holds moisture and plant nutrients .

iv. It also serves as food for soil micro organisms  which makes the soil fertile .

3.  How is Sandy soil different from Clayey soil ?

Ans:  SANDY SOIL :

i) It is mainly made up of sand .

ii) It doesn’t hold water .

iii) It doesn’t get water logged .

iv) It is not suitable for growing crops .

CLAYEY SOIL :

i) It contains atleast 30% of clay particles .

ii) It holds water .

iii) It gets water logged easily .

iv) It is suitable to grow crops than sandy soil .

4.  Explain the main horizons of soil .

Ans:  The different layers of soil are called   horizons .They are classified into 3 types , namely –

i. HORIZON – A :  (a) It is the uppermost layer of the soil and is called topsoil .

(b) It is rich in humus and is a fertile layer of the soil .

(c) The soil is made up of sand ,silt ,clay and pebbles .

(d) We depend on horizon – A to grow crop and it is full of roots .

(e) Many soil organisms are also present in this layer .

ii. HORIZON – B :  (a) It is found below horizon A and is also  called sub soil .

(b) This soil is made up of sand , silt ,clay and large amount of pebbles .

(c) It contains very little organic material or humus .

(d) It is also store house of minerals .

(e) This layer contains roots of trees and shrubs .

iii. HORIZON – C :  (a) It is the lowermost layer of the soil .

(b) This soil contains large pieces of rocks .

(c) Hardly any roots penetrate this layer.

(d) Below horizon C is the hard layer of rock .

 FAQ’s {Frequently Asked Questions }  : 

         1. Explain how soil is formed .

         Ans: Soil is formed  by the breaking down of rocks by the action of wind ,water and climate and                      the process is called weathering .

          2. How is clayey soil useful for crops ?

         Ans:  Clayey soil are  useful for crops due to following reasons –

                 i. It has excellent water holding capacity . 

                 ii. It is rich in organic matter such as humus . 

                 iii. It has very small sized particles .