Lesson: Soil

# Type 1 $–$ Very Short Answer Questions (7 Q.)

### Question: 1

What are soil horizons?

## Solution:

Layers of soil

### Question: 2

Roots of shrubs and other small plants are embedded in the _______ layer of the soil.

## Solution:

Top

### Question: 3

Name the kind of soil which is well aerated, dry and light.

## Solution:

Sandy soil

### Question: 4

Which soil horizon is richest in mineral content?

## Solution:

B- horizon

### Question: 5

_______ soil is the best type of soil suitable for the growth of plants.

## Solution:

Loamy

### Question: 6

Why is terrace farming practised in hilly regions?

## Solution:

To prevent soil erosion

### Question: 7

Name the kind of soil where cotton is grown.

Sandy loam

## Type 2 $–$ Short Answer Questions (7 Q.)

### Question: 1

Which type of soil is best suited for growing lentils and pulses?

## Solution:

Loamy soil is best suited for growing lentils and pulses.

### Question: 2

Why is the top soil dark in colour?

## Solution:

The top soil is dark in colour because it is rich in humus as well as minerals.

### Question: 3

What is deforestation?

## Solution:

Deforestation is cutting down of trees and clearing land occupied by forests to areas for urban use.

### Question: 4

Why is sandy soil not fit for agriculture?

## Solution:

Sandy soil is not fit for agriculture as it cannot retain water which is essential for plant growth.

### Question: 5

What is percolation rate?

## Solution:

Percolation rate is the amount of water that seeps through the soil per unit time.

### Question: 6

Why does clayey soil absorb most amount of water?

## Solution:

Clayey soil absorbs most amount of water because of its high water-retention ability.

### Question: 7

What is weathering?

## Solution:

Weathering is the process of breaking down of rocks by the action of wind, water and climate.

# Type 3 $–$Long Answer Questions (4 Q.)

### Question: 1

Define humus and why is it considered to be an important constituent of the soil?

## Solution:

The decaying dead organic matter, be it dead rotting leaves or animal remains present in the top soil is called humus. Humus makes the soil dark and fertile by providing nutrients to the plants.

Humus keeps the soil moist because it has good water holding ability. Humus encourages the soil life form to multiply and these organisms loosen the soil to make it loosely-bound, light and aerated. Moreover humus, being rich in mineral content, provides nutrition to the plants.

### Question: 2

Define soil and explain how it is formed.

## Solution:

Soil is the uppermost thin layer of the Earth’s crust. It is a loose mixture of rock particles, along with sand and humus. It provides support to the plants by holding their roots and supplying water to the plants too.

Soil is the uppermost layer of the earth’s crust. It is formed by a very long process of weathering of rocks. This includes the breaking down of the parent rocks into small fragments, by the wear and tear action of wind, running water, ice and changing temperature.

### Question: 3

How can soil erosion be checked?

## Solution:

The following are the ways to check soil erosion:

i.            Planting trees in large scale in place of cut down tree

ii.            Adopting better farming techniques, like crop rotation and mixed farming

iii.            Terrace farming in hilly regions

iv.            Prohibiting over-grazing of grasslands

v.            Building embankment at river banks

### Question: 4

Bill collected a beach bucket full of sand from the beach. On reaching home, he conducted an experiment to make a note of the rate of percolation. He observed that it took 15 min for 300 mL of water to percolate through the soil sample. Calculate the rate of percolation.

## Solution:

Quantity of water = 300 mL

Percolation time = 15 min

Percolation rate (mL/min)

Therefore, Percolation rate = 20 mL/min