Exercises: Soil | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

Objective type Questions

Soil erosion is fastest in hot and moist climates.
This is because in such climates, heavy rainfall and high temperatures promote rapid growth of vegetation which in turn causes the soil to lose its protective cover, leading to increased soil erosion.

Q.2. _____ (Subsoil/Bedrock) is rich in minerals that seep down along with water and contains compactly packed fine particles of soil.

Subsoil is rich in minerals that seep down along with water and contains compactly packed fine particles of soil.
It is located just beneath the topsoil and plays a vital role in plant growth by providing essential nutrients and water to the roots.

Q.3. Soil particles have empty spaces between them that are called ______ (spores/pore spaces).

Soil particles have empty spaces between them that are called pore spaces.
These spaces are important for allowing air and water to flow through the soil and for providing room for plant roots to grow.

Q.4. The rate at which water exits the soil is called soil _____(percolation/fertility)

The rate at which water exits the soil is called soil percolation. 

It is influenced by various factors such as soil type, structure, compaction, and porosity. Good soil percolation is essential for healthy plant growth as it ensures that the roots receive adequate water and nutrients.

Q.5. A soil suitable for growing crops has to be ____ (fertile/ dark in colour).

A soil suitable for growing crops has to be fertile.
Fertility refers to the soil's ability to provide essential nutrients to plants for growth and development. Dark color soil is not necessarily an indicator of soil fertility as soil color can vary based on factors such as organic matter content, soil type, and mineral content.

Q.6. _____ (Terrace/Limited) farming should be adopted in hilly areas.

Terrace farming should be adopted in hilly areas.
This is because terracing involves building steps or ridges on the slope of the land which helps to prevent soil erosion and allows for easier cultivation of crops on steep slopes. Limited farming is not a specific type of farming and is not related to hilly areas.

B. Write T for the True and F for the False statements. Correct the false statements. 
Q.1. All soils are tight and compact.

False
All soils are not tight and compact. Some soils like sandy soils are loose and have low compaction.

Q.2. The physical features of a place play a very important role in soil conservation.

True
The physical features of a place play a very important role in soil conservation. The type of vegetation, slope, and terrain affect soil erosion and degradation.

Q.3. The topsoil contains partly weathered pieces of rock.

True
The topsoil contains partly weathered pieces of rock. This layer is rich in organic matter and nutrients and supports the growth of plants.

Q.4. Larger the soil particles, lesser will be the pore space.

False

Larger the soil particles, greater will be the pore space. Soil texture affects pore space and water holding capacity. Coarser soils have larger pores and better drainage while finer soils have smaller pores and retain more water.

Q.5. Loamy soil is good for cultivation of crops and gardening.

True
Loamy soil is good for cultivation of crops and gardening. It has a balanced mix of sand, silt, and clay particles and provides good drainage and water retention.

Q.6. Acid rain and acid water from factories and industries help in conserving the soil.

False
Acid rain and acid water from factories and industries do not help in conserving the soil. They increase soil acidity, which can be harmful to plants and soil organisms.

C. Choose the correct option.

Very short answer type questions

Weathering

Q.2. Dead and decayed plant and animal remains that increase fertility and porosity of soil 

Humus

Q.3. A vertical section of soil that shows the different layers of soil or horizons 

Soil profile

Q.4. The capacity of soil to provide nutrients in the right quantity for growth of plants 

Soil fertility

Q.5. The removal of soil by running water and wind  

Soil erosion

Q.6. Reduction or prevention of soil erosion

Soil conservation

Short answer type questions 

Soil is the uppermost layer of the Earth's crust, formed by the weathering of rocks and the decomposition of plant and animal matter. The five main things that make up soil are minerals, organic matter, air, water, and living organisms.

Q.2. What is porosity of soil? What does it depend on? 

Porosity of soil is the amount of space between soil particles. It is the ratio of the volume of spaces to the total volume of the soil. Porosity depends on the size of soil particles, their arrangement, and the amount of compaction.

Q.3. Define percolation rate of soil. 

Percolation rate of soil is the rate at which water moves through soil. It is influenced by the soil's texture, structure, and porosity.

Q.4. What is soil fertility? 

Soil fertility refers to the ability of soil to support plant growth. It depends on the presence of nutrients, organic matter, and microorganisms in the soil.

Q.5. Define soil conservation. 

Soil conservation refers to the practice of protecting and managing soil resources to prevent soil erosion, improve soil fertility, and maintain soil health. It involves the use of various techniques like crop rotation, contour plowing, and terracing to conserve soil resources.

Long answer type questions

Weathering refers to the process of breaking down of rocks, minerals, and other substances under the influence of weather conditions such as wind, water, temperature changes, and living organisms. The different ways in which rocks undergo weathering are:

(i) Physical weathering: It is the breakdown of rocks into smaller pieces without altering their chemical composition. Physical weathering can be caused by temperature changes, wind, water, and ice.

(ii) Chemical weathering: It involves the breakdown of rocks through chemical reactions. Chemical weathering can be caused by water, acids, and living organisms.

(iii) Biological weathering: It is the breakdown of rocks due to the activities of living organisms such as plants and animals. The roots of plants can grow into cracks in rocks, causing them to break apart.

The weathering process leads to the formation of soil. Soil is formed when the broken-down rock particles and other organic matter mix together and are acted upon by weathering agents. Over time, soil develops layers or horizons, each with its own characteristics such as texture, color, and composition. The top layer of soil is called the A-horizon, which is rich in organic matter and nutrients. The B-horizon is the subsoil layer, which contains less organic matter but more minerals. The C-horizon is the deepest layer, which is composed of partially weathered rocks.

Q.2. Discuss the different kinds of soils.

Soils can be classified based on their properties, texture, and composition. The different kinds of soils are:

(i) Sandy soil: It is composed of large particles and has a gritty texture. Sandy soil drains quickly and does not hold water or nutrients well. It is ideal for plants that require good drainage.

(ii) Clay soil: It is composed of small particles and has a sticky texture. Clay soil retains water and nutrients well, but it drains slowly. It is ideal for plants that require a lot of water and nutrients.

(iii) Loamy soil: It is a mixture of sand, clay, and silt particles and has a balanced texture. Loamy soil retains water and nutrients well, and it is ideal for most plants.

(iv) Peaty soil: It is composed of organic matter and has a dark color. Peaty soil is rich in nutrients, but it does not drain well. It is ideal for plants that require a lot of moisture.

(v) Chalky soil: It is composed of calcium carbonate and has a white color. Chalky soil is alkaline and is ideal for plants that prefer alkaline soil conditions.

Q.3. Describe the three special properties of soil that determine its types.

The three special properties of soil that determine its types are:

(i) Texture: It refers to the size of the soil particles. Soil particles can be classified as sand, silt, or clay. The texture of the soil affects its water-holding capacity, drainage, and aeration.

(ii) Structure: It refers to the arrangement of soil particles. Soil can be structured as granular, blocky, or platy. The structure of the soil affects its ability to hold water and air.

(iii) Composition: It refers to the amount of organic matter, minerals, and nutrients present in the soil. The composition of the soil affects its fertility and nutrient content.

Q.4. Explain the causes and prevention of soil erosion.

Soil erosion is the loss of soil due to the actions of wind, water, or other agents. The causes of soil erosion are:

(i) Deforestation: Trees and plants hold the soil in place with their roots. Deforestation leads to soil erosion.

(ii) Overgrazing: Livestock feed on vegetation, making the soil vulnerable to erosion.

(iii) Poor farming practices: Tilling and plowing can expose the soil to erosion.

(iv) Construction activities: Construction activities can lead to soil erosion by removing vegetation and altering the natural landscape.

Soil erosion can be prevented by:

(i) Planting trees and vegetation to hold the soil in place.

(ii) Using conservation tillage practices that reduce soil disturbance.

(iii) Building terraces and retaining walls to prevent soil from washing away.

(iv) Controlling water runoff by using contour plowing and installing drainage systems.

Q.5. What is soil pollution? Describe the various measures that will help control soil pollution.

Soil pollution refers to the contamination of soil with harmful substances such as chemicals, heavy metals, and pesticides. Soil pollution can have severe consequences on human health and the environment. The various measures that can help control soil pollution are:

(i) Proper disposal of hazardous waste: Hazardous waste should be disposed of properly to prevent soil contamination.

(ii) Use of organic farming practices: Organic farming practices use natural methods to control pests and diseases, reducing the need for chemical pesticides.

(iii) Soil remediation: Soil remediation involves the removal of pollutants from soil using physical, chemical, or biological methods.

(iv) Recycling and reuse of waste: Recycling and reuse of waste can reduce the amount of waste that ends up in landfills and prevents soil contamination.

(v) Monitoring and regulation: Regular monitoring and regulation of industrial activities can help prevent soil pollution by identifying potential sources of contamination.