Skip to main content

Class 8, Science, Chapter-1, Lecture-3, 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.

Two systems of irrigation for saving water:

  • Sprinkler system: Perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline. 
    Water can flow through main pipe under pressure, which escapes from the rotating nozzles and gets sprinkled on the crop.
  • Drip irrigation: This system is used to save water as it allows the water to flow drop by drop at the roots of the plants.

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 rainwater and for preventing soil erosion is called water shed management.

WEED: 

Unwanted plants in the cultivated field which compete for food, space and light with the crop plants are called weeds. 
Examples: Xanthium (Gokhroo), Parthenium (Gaja Ghas), Cyperinus Rotundus (Motha)

Measures to protect from pests and weeds:

  1. Use of resistant varieties
  2. Summer Ploughing
  3. Mechanical removal of weeds
  4. Proper seed bed preparation.
  5. Crop Rotation and Multiple Cropping
  6. Timely sowing of crops.
  7. Use of pesticides (herbicides, insecticides and fungicides)

Factors Responsible for loss of stored grains:

  1. Abiotic Factors 
    (i) Moisture content of grains 
    (ii) Humidity of air 
    (iii)Temperature
  2. Biotic Factors 
    (i) Insects, Worms, Bacteria, Fungi, Mites 
    (ii) Rodents, 
    (iii) Birds and Mammals

Effects of improper storage: 

Poor marketability of the produce due to

  1. Degeneration in quality
  2. Loss in weight
  3. Discolouration
  4. Poor germination capacity.
  5. Contamination by the excreta, urine, hair etc of pests.

Measures to minimize storage loss:

  1. Proper cleaning of the storage.
  2. Drying of grains over plastic sheet or cemented floor under the sun.
  3. Cooling of sun-dried grains to room temperature before storage.
  4. Fumigation using pesticides.
  5. Making the storage air tight and free from moisture, rodents and insects.