Chapter 7 – Soils

Maharashtra Board Textbook Solutions for Standard Seven

Q.1. Complete the Following Table

Factors and Their Role in the Formation of Soil

Factor / ProcessRole in the Formation of Soil
Parent RockDetermines the type of soil through weathering and leaching.
Regional ClimateDetermines the intensity of weathering and leaching of the parent rock.
Organic MaterialMaintains the pH balance of the soil and increases fertility.
MicroorganismsHelp in the decomposition of dead plants and animals, increasing the humus content of the soil.

Q.2. Why Do the Following Occur?

1) To the west of the Sahyadris, laterite soils are formed from basalt rock.

Ans:

  1. The western side of the Sahyadris (Konkan region) receives heavy rainfall.
  2. The climate in this region is hot and humid.
  3. Heavy rainfall causes large-scale leaching of basalt rock, leading to the formation of laterite soil.

2) Humus content in the soil increases.

Ans:

  1. The regular use of organic manure, vermicompost, and compost helps maintain soil fertility.
  2. Microorganisms decompose the dead remains of plants and animals.
  3. The decomposed material forms humus, thereby increasing the humus content in the soil.

3) Soil formation process is faster in the equatorial climate.

Ans:

  1. Weathering of rocks is the first step in soil formation.
  2. The equatorial region has high temperatures (27°C to 30°C) and heavy rainfall (2500 mm to 3000 mm annually).
  3. High temperature and heavy rainfall accelerate the weathering process, resulting in faster soil formation.

4) The salinity of the soil increases.

Ans:

  1. Irrigation is used to increase agricultural production.
  2. Excessive irrigation brings salts from the lower layers of soil to the surface.
  3. This increases soil salinity and reduces fertility.

5) Rice is the staple diet of the people from Konkan.

Ans:

  1. The Konkan region has a hot and humid climate, heavy rainfall, and alluvial soil, which are favourable for rice cultivation.
  2. Since rice is grown on a large scale, it becomes the staple diet of the people in this region.

6) Soil erosion occurs.

Ans:

  1. The top layer of soil is removed by water or wind.
  2. Running water, steep slopes, strong winds, and climatic factors cause soil erosion.

7) Soil degradation occurs.

Ans:

  1. Excessive use of chemical fertilizers and insecticides reduces soil quality.
  2. Over-irrigation increases soil salinity.
  3. Chemicals harm microorganisms and reduce humus content.
  4. These factors lower soil fertility, leading to soil degradation.

Q.3. Give Information on the Following

1) Measures of Soil Conservation

  1. Tree Plantation: Trees reduce wind speed and prevent soil erosion.
  2. Continuous Contour Trenches: Trenches constructed along slopes reduce the speed of running water and control erosion.
  3. Water Development Programme: Construction of embankments, farm bunds, and stream connections help conserve soil and water.

2) Organic Manures

  1. Plant litter, roots, and animal remains decompose due to the action of water and microorganisms.
  2. This decomposition increases the humus content in the soil.
  3. As a result, soil fertility improves.
  4. Therefore, the use of organic manures is essential for soil conservation.

3) Place to Obtain Information About Soil Suitability for Crops

  1. Information about the suitability of soil for a particular crop can be obtained from soil testing laboratories.
  2. These laboratories test soil type, fertility, and humus content.
  3. Based on the results, guidance is provided to farmers.

4) Importance of Soils for Plant Growth

  1. Soil provides support and nutrients necessary for plant growth.
  2. Regions with fertile soil, such as the equatorial region, have abundant vegetation.
  3. In infertile regions like deserts, vegetation is scarce.
  4. In polar regions, where soil is absent, vegetation is not found.

Q.4. Complete the Following Table with Reference to Soil

ActionEffectResult (with reference to fertility)
Construction of embankmentsReduces soil erosion due to heavy rainfallIncrease in fertility
Planting treesWind speed decreasesIncrease in fertility
Farmland kept fallow for some periodSoil fertility is restoredIncrease in fertility
Use of organic manuresHumus content increasesIncrease in fertility
Trenches dug across slopesReduces the speed of running waterIncrease in fertility
Litter burnt in the farmAsh content increasesDecrease in fertility
Excessive irrigationSalt content in soil increasesDecrease in fertility
Excessive use of chemical fertilizersReduces microorganisms and humus contentDecrease in fertility

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