Soil - Types, Profile and Conservation - NCERT Solution Class 7 Science

Soil – Types, Profile and Conservation – NCERT Solution for Class 7 Science, Chapter 9 Soil – NCERT Solution for Class 7 Science Chapter 9 (Soil – Types, Profile and Conservation)

What is soil?

Technically, the soil is a mixture of minerals, organic matter, and organisms. But broadly speaking, clay can indicate any loose residue. In addition, several types of soils are distributed worldwide and are generally classified as follows: 

Clay

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Sandy soil

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Loamy soil

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Silt soil

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Soils typically contain 45% minerals, 50% free space or vacuum, and 5% organic matter. In addition, it performs several functions: 

Provides growth medium for plants



Provides habitat for organisms

Soil is the backbone of agriculture. Therefore, it is crucial to understand the consistency and the type of soil used before cultivating. There are different types of soil – some are loamy and fertile, some are sandy and fertile. Not all soil types are suitable for all crops. Crops growing in fertile soils do not have to yield because the soil needs preparation for better quality.

What is a soil profile?

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A soil profile is the result of physical, chemical and biological processes under certain environmental conditions. It contains microorganisms, insects, minerals, decomposing organic matter, humus, water and air that make the soil fertile and a source of nutrients.

As discussed earlier, there are four main types of soil: loamy, sandy, clay silt soil.

Of these, loamy soil is the most suitable for cultivation. Such soil has the following characteristics: 

Good water holding capacity

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Proper ventilation

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Good stability (texture)

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Balanced acid and alkaline content

What is soil preparation?

No soil is suitable initially since it is very loose, so it needs preparation before and after cultivation. It can also lose fertility due to continuous cultivation.

In agriculture, cultivation, levelling and composting are the three stages of soil preparation.

Step 1: Ploughing

Ploughing is the process of loosening and digging the soil with a plough. It helps provide proper ventilation to the soil.

Before sowing the seeds, the soil in the field needs to be loosened and compacted. It helps decompose soil to the size of a grain.

During ploughing, the soil shakes and the nutrients in the deep soil rise. In addition, it increases soil aeration, which provides the plant/seeds air to breathe, and lets the roots easily penetrate the soil. Ploughing further helps to compost, weed, and remove infectious diseases and pests. A wooden or iron plough gets used for such purposes.

After ploughing, the soil is evenly distributed and levelled during the levelling process. After this, the soil gets fertilized.

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Step 2: LEVELLING

Levelling helps in the even distribution of soil after it gets ploughed. For this, a wooden or iron board gets used. Levelling also helps in supplying water during irrigation without cutting down the tree.

Levelling is a crucial step for soil preparation as it ensures that the depth of the field and the discharge variability of soil is relatively uniform. It also enables water supply to the bottom of the soil where plant roots exist.

This field activity becomes crucial throughout the harvest time, especially during significant post-harvest surface area disturbance.

Preparing the field surface for transport and distribution of irrigated water is as beneficial as any other management system used by the farmer for efficient surface irrigation. However, there can be two ways in which levelling gets achieved – 1. Provide suitable slope for water supply 2. Level the soil to its optimum position with minimal soil movement, then adjust the water supply to suit field conditions.

This second approach is generally the most economical, as land levelling is expensive, and large earthquakes can leave significant land without fertile soil.

Step 3: MANURING

Manure is a fertilizer consisting of decomposed plants and animals applied to the soil to increase productivity. It is a natural fertilizer and is inexpensive. Human and animal wastes also get used as manure.

Manure contains a lot of organic matter and humus, thus improving soil fertility.

These are excellent in the long run and do not cause pollution.

After ploughing, the manure gets applied in the later stages of cultivation. It fills the soil with nutrients and thus helps in the proper growth of the crop.

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How does manuring help?

1. They are a good source of macronutrients.

2. It improves soil fertility.

3. Manure is inexpensive, so it becomes cost-effective.

4. It reduces erosion and leaching.

5. The physical properties of soil get improved significantly with manure.

6. It increases water supply to the soil and improves its nutrient retention capacity.

7. It’s easy to carry.

8. Methane gas gets developed as a by-product of fertilizers. This gas gets used for cooking and heating.

9. Crops grown in fertilized soils give healthy crops.

In addition, for better yields, farmers use organic and chemical fertilizers to improve soil nutrients.

MANURING

What is soil erosion?

Erosion is the removal of topsoil. There can be several causes of erosion like deforestation, overgrazing, excessive use of fertilizers or pesticides, rainwater runoff, landslides and floods.

What are the methods of soil conservation?

1. Mulching – Soil covering helps to retain moisture in the soil. Mulching is the process of covering vacant land with organic matter, like straw.

2. Contour Barrier – Contour barriers help to prevent erosion caused by rain. The contour barrier gets made of stone, grass or soil attached to the contour. A trench has been constructed in front of the dam to store water.

3. Rock Dam: Dams can reduce the flow of water. As such, rocks get arranged to form a dam. Such dams reduce water flow. Thus, it prevents the loss of dirt and soil.

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4. Terrace Cultivation: Terrace cultivation gets practised in hilly areas to reduce the erosion caused by water flow. The plots are constructed in terrace shapes to ensure a flat surface for growing crops.

5. Intercropping: Different crops are cultivated alternately in this manner. Crops grow at different times. It helps to prevent erosion caused by rain.

6. Contour ploughing: This method of ploughing is done parallel to the outline of the hill slope. It helps create a natural barrier and prevent water from flowing down a slope.

7. Shelterbelt: This method gets used in coastal and arid areas. Trees get planted at the boundary of the field. It helps to prevent soil erosion.

Soil Conservation Class 7 Science

Frequently Asked Questions (FAQ)

1. What are the different types of fertilizers?

Answer. Different types of compost include: 1. Green manure 2. Farmyard manure 3. Compost manure

1. Explain how fertilizers differ from manure.

Answer.

1. Manures are organic matter, while fertilizers are chemical.

2. Fertilizer is prepared in factories while manure gets made on farms.

3. Manure contains all the nutrients, but chemical fertilizers contain some nutrients.

1. Explain how continuous planting in the field affects the soil.

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Answer. Continuous sowing in a field can lead to nutrient depletion in the soil.

That can lead to barren farms. Continuous ploughing does not give the soil time to replenish its nutrients. Thus the soil is not able to maintain healthy and good crops.

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