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Class 8, Science, Chapter-1, Lecture-2, Soil Enrichment (Notes)

Methods of Soil Enrichment: 

  1. By using Manure 
  2. By using Fertilizers

MANURE: 

A partially decomposed organic matter derived from plant and animal wastes which is added to the soil to increase its fertility is called manure.

Types of Manures: 

  1. Compost: 
    A mixture of organic matter derived from plant and animal wastes which is decomposed in a pit is called compost.
  2. Vermi-compost: 
    A mixture of organic matter derived from plant and animal wastes which is decomposed in a pit along with earthworms is called vermi-compost. 
  3. Green Manure: 
    Manure formed from the green plants grown and ploughed back into the soil prior to sowing is called green manure.

Composting: 

The process in which plant and animal wastes are decomposed in a pit to obtain a mixture of organic matter to increase soil fertility is called composting.

Advantages of Manure: 

  1. Increases soil fertility by providing nutrients to the crops. 
  2. Increases water holding capacity of sandy soils by adding bulk of organic matter. 
  3. Prevents from water logging in clayey soils by adding bulk of organic matter. 
  4. Protects environment from harmful effects of chemical fertilizers by reducing their use. 
  5. Saves energy by the recycling of plants and animal wastes.

FERTILIZER: 

Commercially produced chemical which provide specific nutrients to crop plants for increasing yield is called fertilizer.

Types of Fertilizers: 

  1. Nitrogenous fertilizers- contain nitrogen as the primary nutrient. 
  2. Phosphate fertilizers- contain phosphorus as the primary nutrient. 
  3. Potassium fertilizers- contain potassium as the primary nutrient. 
  4. Complex fertilizers- contain two or more critical nutrients.

Advantages of Fertilizers: 

  1. are nutrient specific. 
  2. are easy to store and transport, since these are compact. 
  3. are readily absorbed by water. 
  4. are available throughout the year at all places. 
  5. increase the yield. 

Disadvantages of Fertilizers: 

  1. Cause water pollution. 
  2. Changes the soil chemistry. 
  3. Are costly. 
  4. Harms soil microorganisms. 
  5. Prolonged use reduces fertility of the land. 

DIFFERENCES BETWEEN:

Manure

Fertilizer

1. Manure is semi decomposed organic matter.

1. Fertilizer is a chemical formulation.

2. It is prepared from natural materials.

2. It is synthesised from chemical salts.

3. It contains only a small quantity of mineral salts.

3. It contains large quantity of mineral salts.

4. It is not nutrient specific.

4. It is nutrient specific.

5. It adds organic matter to the soil.

5. It does not add organic matter to the soil.

6. It is required in large quantity.

6. It is required in small quantity.

7. Nutrients are slowly absorbed by plants.

7. Nutrients are readily absorbed by plants.

8. It is bulky and difficult to transport.

8. It is compact and easy to transport.

9. Manure cannot be stored for long.

9. Fertilizers can be stored for long duration.

10. It helps in maintaining soil texture, its hydration and aeration.

10. It can harm soil texture and other soil characters.

11. Excess manure is not much harmful.

11. Excess fertilizer is harmful to plants and environment.

Methods of fertilizer application: 

  1. Directly to the soil before sowing. 
  2. By dissolving in the water during irrigation. 
  3. Spraying dilute solution over the standing crops.

Fertilizer should not be applied directly to the soil after sowing. 

Reason: 
Mixing of fertilizer with the soil causes high osmotic pressure around the seed or the roots. 
Water from the seed or root moves to the soil and the seed or the plant withers.

Excess of fertilizers cause water pollution: 

Justification: 
Plants absorb very small quantity of fertilizers. Fertilizers are readily soluble in water. 
So, the excess of fertilizer moves along with water to the water bodies (lakes, ponds, rivers) or seep into the ground water. Thus excess of fertilizers cause water pollution.

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