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Class 9, Science, Chapter-12, Lecture-4, Irrigation (Notes)

IRRIGATION:

The process of supplying water to crop plants through human efforts by means of canals, wells, tube wells etc is known as irrigation.

Agriculture in India is rain-fed.

Justification:
The success of crops in most part of India depends on water from rainfall during the growing season of the crop plants.
Poor monsoon can cause crop failure. So, in India, agriculture is rain-fed.

Need for Irrigation System in India:

The success of crops in most part of India depends on water from rainfall during the growing season of the crop plants.
Poor monsoon can cause crop failure.
To ensure that crops get water at the right stages during their growth, irrigation system is needed.

IRRIGATION SYSTEMS:

  1. Well
    (i) Dug Well - used to draw water from upper layers of water table.
    (ii) Tube Well - used to draw water through pumps from deeper layers of water table.
    Advantage: makes underground water available for irrigation.
  2. Canal System - used to collect water from rivers, lakes, dams, barrages and to direct it to the fields through distributaries.
    Advantage: takes the surplus water from one region to the water deficient regions.
  3. River Lift System - used to draw water directly from river to the fields near the river.
    Advantage: makes water available to the regions where canal or wells are not functional.
  4. Tank System - used to store the runoff of smaller catchment areas.
    Advantage: increase the period of water availability by storing the runoff of smaller catchment areas.

Methods of Increasing Water Availability for Irrigation:

  1. Rainwater Harvesting:
    The recharging of ground water by collecting rain water and pouring into wells or deep drain pipes is called rain water harvesting.
  2. Watershed Management:
    Construction of small check dams for increasing the percolation of water into ground, for reducing wastage of rain water and for preventing soil erosion is called water shed management.

Cropping Patterns:

  1. Multiple Cropping - (i) Mixed Cropping (ii) Inter Cropping
  2. Crop Rotation

Mixed Cropping:

The technique of growing two or more different crops simultaneously without any definite pattern in the same field is called mixed cropping.

Criteria for selection of crops:

  1. Contrasting root pattern.
  2. Different water requirement.
  3. Different nutrient demand.
  4. Different maturation period.
  5. Different growth habits.

Pair of Crops selected for mixed cropping:

  • Groundnut + Sunflower
  • Groundnut + Gram
  • Ragi + Gram
  • Wheat + Gram
  • Wheat + Mustard
  • Cotton + Groundnut
  • Maize + Urad bean

Inter Cropping:

The technique of growing two or more different crops simultaneously in a definite pattern in the same field is called inter cropping.

Advantages of Multiple Cropping:

  1. Insurance against crop failure.
  2. Increased yield.
  3. Variety in produce.
  4. Improved soil fertility.
  5. Optimum utilisation of soil and nutrients.
  6. Reduced pest infestation.
  7. Reduced irrigation requirement.

Disadvantages of Mixed Cropping:

  1. Difficulty in applying fertilizers for individual crop.
  2. Difficulty in applying pesticides for individual crop.
  3. Difficulty in harvesting and threshing of crops separately.

Advantages of Inter Cropping over Mixed Cropping:

  1. Specific fertilizer for individual crop can be applied.
  2. Specific pesticides for individual crop can be applied.
  3. Individual crops can be harvested and threshed separately.

DIFFERENCES BETWEEN:

Mixed croppingIntercropping
1. Seeds of different crops are mixed before sowing.1. Seeds of different crops are sown separately.
2. There is no pattern of sowing.2. The different crops are sown in separate rows or strips.
3. Only a common type of fertilizer can be added.3. Specific fertilizers can be provided to each crop.
4. Crop specific pesticides cannot be sprayed.4. Crop specific pesticides can be sprayed.
5. Harvesting of early maturing crop provides a lot of difficulty.5. Harvesting individual crops is possible.
6. There is some mixing of the produce of different crops.6. There is no mixing of produce of different crops.
7. Lesser inputs of irrigation and nutrients are required.7. Requirement of inputs is comparatively more.

Crop Rotation:

The technique of growing different crops on the same piece of land in a pre-planned succession is called crop rotation.

Crop rotation replenishes the soil and increases crop production.

Justification:
Non-leguminous plants consume nitrogen compounds and make the soil nitrogen deficient.
Leguminous plants, cultivated after the non-leguminous plants, bear nodules in their roots.
The root nodules contain nitrogen fixing bacteria. The bacteria fix atmospheric nitrogen into nitrates and enrich the soil with nitrates.
Thus, crop rotation replenishes the soil with nitrogen compounds and increases production of non-leguminous crops.