DAV Class 7 Science Chapter 10 Soil Question Answer Notes
DAV Class 7 Science Chapter 10 Soil Question Answer Notes Solution by Expert Science Teacher. DAV Class 7 Science 10th Chapter Soil for Students of DAV Schools.
Lesson No 10
Soil
A.) Fill in the blanks.
Answer: (1) soil horizons (2) silt (3) Cohesion (4) breathing (5) Insecticides, fertilisers
B.) Match the following:
1.) Potter’s soil |
a.) No percolation |
2.) Organic material |
b.) Clay |
3.) Vermicompost |
c.) Well aerated |
4.) Sandy soil |
d.) Humus |
5.) Concrete floor |
e.) earthworms |
Answer: 1. (b), 2. (d), 3. (e), 4. (c), 5. (a)
C.) Tick the correct option.
Answer:
1.) organic acids
2.) bed rock
3.) earthworm
4.) clayey soil
5.) sandy loam
D.) Answer the following questions in brief.
Q.) 1.) State the meaning of the term ‘soil.
The mixture of organic material and minerals that makes up soil, which naturally occurs on the earth’s surface and serves to support plant life, is called soil. Life on Earth is supported by a complex mix of minerals, organic material, gases, liquids, including various organisms.
Q.) 2.) List the four main agents of physical weathering.
Answer: Temperature, water, wind, and plants are the primary agents that cause physical weathering.
Q.) 3.) Write one difference between sand, clay and silt.
Each of them have a different texture and water retention capacity. Sand has the largest and coarsest particle size and cannot retain much water whereas silt and clay have smaller particle size and are fine . Due to better water retention capabilities they are more fertile.
Q.) 4.) Name the types of soil classified on the basis of soil texture.
According to soil texture, there are many different types of soil, including silt, sandy, clayey, and loamy soils. Sandal soil has weak nutrient concentration but is characterised by large particles and effective drainage. Despite having extremely small particles, bad drainage, and minimal aeration, clayey soil has a high source of nutrients. Loamy soil has a mix of smaller and larger particles, adequate drainage, adequate circulation, as well as a high nutrient concentration. Silt soil is rich in nutrients, has incredibly small particles, and is both well-drained and aerated.
Q.) 5.) Give the meaning of the term ‘Cohesion.
The term cohesion is used to express how much a collection of individuals feel a sense of belonging to one another. It is frequently used in the framework of a group or organisation to express how linked and cooperative the members are. Shared objectives, trust, and effective communication are just a few of the many variables that might influence cohesion.
Q.) 6.) List any three causes of soil pollution.
- Pesticide and Fertilizer Use
- Industrial Waste
- Mining
E. Answer the following questions.
Q.) 1.) Classify, and explain, the categories of soil on the basis of ‘texture of the soil.
The textures of three different types of soil—sandy, loamy, and clayey—are used to separate them. Sandal soil is made up of large particles and has a poor ability to retain nutrients and water. It is also known as “light dirt.” Loamy soil, which is considered as the greatest soil type for farming, contains sand, silt, and clay. In addition to the nutrients plants require to flourish, it provides appropriate drainage and aeration. Clayey soil is made up of tiny particles and has a great ability to retain water and nutrients. This type of soil is harder to work with because it is more likely to compact.
Q.) 2.) Differentiate between infilteration rate and percolation rate.
Answer: Water can penetrate the soil at a certain rate, known as the infiltration rate. It gauges the soil’s capacity to take in and hold water. The speed at which water can percolate through soil is known as the percolation rate. It gauges how well the earth can transfer water. The percolation rate determines how fast water may move forward through soil, whereas the infiltration rate determines how much water the soil can hold.
Q.) 3.) Write a short note on ‘composition of soil.
Soil is made up of elements, gases, liquids, and living creatures, all of which support life. Organic matter, which is the byproduct of decaying plant and animal substances, provides food for soil-dwelling organisms. Minerals, which include clay, sand, and silt particles, give the soil its composition. For soil to breathe, gases like carbon dioxide and oxygen are essential. For keeping soil moist, it’s essential to have access to liquids like water. Soil organisms such as worms, fungi, and bacteria that help support the nutrition cycle break down organic waste.
Q.) 4.) “The type of crop that may be grown in a particular field depends on the type of soil: Give three examples in support of this statement.
Root vegetables like turnips, potatoes, as well as carrots grow best on clay soils because of their capacity to pierce the compact soil. Cucumbers, peppers, and tomatoes all do better in sandy soils because plants can absorb more nutrients and move through the soil more easily. Loam soils are ideal for growing a variety of crops, including both grains and vegetables, since they have a suitable balance of sand, clay, and silt that encourages good aeration and drainage.
Q.) 5.) What is soil erosion? How can it be avoided?
Soil erosion is the process through which topsoil, which contains essential nutrients, is transported away from a particular location by either water or wind. It might lead to lower crop yields, less fertile soil, and ultimately desertification. Crop rotation is one approach that can be used to prevent it.
Q.) 6.) Why is it said that ‘plasticity’ and ‘cohesion, play an important role in the workability of a soil?
Plasticity as well as cohesiveness are key factors in determining a soil’s workability because they both affect how readily a soil may be worked. While cohesion refers to the force that holds soil particles together, plasticity refers to how easily a soil can be twisted and moulded. In order to be easily compressed, moulded, as well as shaped, a soil must have both of these qualities in order to be helpful for construction purposes.
More Extra Questions for Preparation
Q.1.) Fill in the blanks.
1.) The arrangement of the horizons in a soil is known as soil profile.
2.) Bigger coarse soil particle are termed as sand.
3.) Percolation is the rate at which water moves through a soil.
4.) Lumbricus rubellus species used for vermicomposting.
5.) Soil air is important for the respiration of roots.
Q.2.) Multiple choice questions.
1.) The tendency of similar particles to stick to one another is known as
a.) Adhesion
b.) Cohesion
c.) Percolation
d.) None of these
Answer – b.) Cohesion
2.) Spaces between the soil particles contain
a.) Water
b.) Organisms
c.) Both a and b
d.) Air
Answer – d. Air
3.) Cemented and concrete floors cannot absorb
a.) Water
b.) Air
c.) Heat
d.) None of these
Answer – a. Water
4.) is a mixture of sand, silt and clay particles.
a.) Clayey soil
b.) Sandy soil
c.) Loamy soil
d.) Both a and b
Answer – c. Loamy soil
5.) C horizon is the layer beneath the
a.) B horizon and above the horizon
b.) R horizon and above the B horizon
c.) Below the O horizon
d.) A horizon and above the C horizon
Answer – a. B horizon and above the horizon
Q.3.) Define the following.
1.) Soil
Answer – Soil can be defined as naturally occurring loose covering of broken rock particles and decaying organic matter on the surface of earth.
2.) Plasticity
Answer – Plasticity is the property that enables moist soil to change its shape on application of force and retain this shape even when the force is withdrawn.
3.) Infiltration
Answer – Infiltration is the rate at which water enters a soil.
4.) Earth sheltering
Answer – Earth sheltering is architectural practice of using soil as external thermal mass against building walls.
5.) Soil erosion
Answer – Soil erosion implies the removal of the top soil by agents such as wind and water.
4.) Short answer questions.
1.) Living organisms present in soil.
Answer – Microorganisms like bacteria, fungi and algae.
2.) Any two causes of physical weathering.
Answer – Temperature and Water
3.) A bacteria grows in soil when condition are warm.
Answer – Actinomyctes
Q.5.) Long answer question.
1.) Write types of crops grown in types of soil.
Answer –
a.) Cereal crops like wheat and legumes like gram are grown in loamy and or clayey soil.
b.) Paddy grows in clayey soil.
c.) Pulses grow in loamy soil.
d.) Coconut trees grow in sandy soil.
2.) Sandy soil may be structure less and clayey soil stick together. Give reason.
Answer – Sandy soil may be structure less because sand grains behave independently of each other, clayey soil have tendency to stick together because there is very little space between the soil particles.
3.) Classification of soil.
Answer – Soil is classified into three categories –
A.) Sandy soil – They have bigger soil particles, there are large spaces between them are filled with air.
B.) Clayey soil – They have higher proportion of fine and smooth soil particles. There is very little space between the soil particles.
C.) Loamy soil – It is a mixture of sand and clay particles. It can hold both air and water.
4.) Write about soil pollution.
Answer – Soil pollution is caused by factors like use of chemical pesticides, excessive use of fertilizers, percolation of contaminated surface water to the layers below the surface, oil and fuel dumping, leaching of wastes from landfills.
5.) How can we prevent soil erosion?
Answer – a.) Soil erosion can be prevented by extensive afforestation particles.
b.) This involves planting of trees on bare lands and nearby fields.
c.) Avoiding overgrazing, and overuse of land also help in preventing soil erosion.
6.) What is soil composed of?
Answer – Soil is composed of-
a.) Inorganic substances
b.) Organic material like dead and decaying parts of plants and animals.
c.) Soil water
d.) Soil air
e.) Living organisms like bacteria, fungi and algae.
7.) Explain soil horizon diagram.