explai the full ch-soil of 7grade
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Soil - QuestionsPage
Soil
Q39. What are the properties of loamy soil?
Ans. Properties of loamy soil
i. The best topsoil for growing plants is loam. Loamy soil is a mixture of sand, clay and another type of soil particle known as silt.
ii. The loamy soil also has humus in it.
iii. It has the right water holding capacity for the growth of plants.
Q40. What are the properties of clayey soil?
Ans. Properties of clayey soil
i. Clay particles, being much smaller, pack tightly together, leaving little space for air.
ii. Water can be held in the tiny gaps between the particles of clay. So clay soils have little air.
iii. They are heavy as they hold more water than the sandy soils.
Q41. Why is soil regarded as one of the most important natural resources?
Or
Why is soil an inseparable part of our life?
Ans. Soil is one of the most important natural resources. It supports the growth of plants by holding the roots firmly and supplying water and nutrients. It is the home for many organisms. Soil is essential for agriculture. Agriculture provides food, clothing and shelter for all. Soil is thus an inseparable part of our life.
Q42. What are the properties of sandy soil?
Ans. Properties of sandy soil are:
i. Sand particles are quite large.
ii. Sand particle cannot fit closely together, so there are large spaces between them. These spaces are filled with air. So, the sand is well aerated.
iii. Water can drain quickly through the spaces between the sand particles. So, sandy soils tend to be light and dry.
Q43. Sketch the cross section of soil and label the various layers.
Ans.
Image from NCERT
Q44. Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.
Ans. Amount of water = 200 ml
Percolation time = 40 min
Q45. List the differences between clayey soil and sandy soil.
Ans. Differences between clayey soil and sandy soil
Clayey soil
Sandy soil
1. Clay particles are much smaller.
1. Sand particles are quite large.
2. Clayey soils tend to be heavy as they hold more water than the sandy soils.
2. Sandy soils tend to be light as water drain quickly through the spaces between the sand particles.
3. Clay particles pack tightly together, leaving little space for air.
3. They cannot fit closely together, so there are large spaces between them. These spaces are filled with air.
4. Clayey soil is more fertile compared to sandy soil.
4. Sandy soil is less fertile compared to clayey soil.
Q46. Explain how soil pollution and soil erosion could be prevented.
Ans. Steps to prevent soil pollution
i. The polythene bags and plastics should be banned.
ii. Waste products and chemicals should be treated before they are released into the soil.
iii. The use of pesticides should be minimised.
iv. Use of organic manure, fertilizers, and milder pesticides for agricultural activities should be encouraged.
Steps to prevent soil erosion
i. Planting more and more trees.
ii. Terrace farming.
iii. Retaining walls can be built around the area of erosion to prevent water run-off.
iv. Making people aware of pros and cons of deforestation.
Q47. Describe the different layers of soil profile.
Ans. Different layers of soil profile
i. The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the A-horizon. This provides shelter for many living organisms such as worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil.
ii. The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer.
iii. The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices.
iv. Below this layer is the bedrock, which is hard and difficult to dig with a spade.