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Improvements in Food Resources

Tutormate > CBSE Syllabus-Class 9th Biology > Improvements in Food Resources

05 Irrigation


  • Organisms that enrich the soil with nutrients are called bio fertilizers.
  • Two biofertilizers, called Rhizobium cultures and blue green algae (such as Anabaena and Nostoc) have gained popularity amongst farmers cultivating pulses, legumes, oil seeds and wet-land rice.


Mycorrhiza is a symbiotic (mutualistic) association of certain fungi with roots of higher plants. Mycorrhiza increase water and nutrient uptake by plants.


  • The process of supplying water to crop plants by various means like canals, wells, reservoirs, tube-wells, etc., is known as irrigation.
  • Water management is arranging and supplying required water to crops without affecting soil aeration, change of water table or causing water-logging and soil salinity.


  • It is essential for the growth and elongation of the roots of the crop plants.
  • It is also essential for the absorption of nutrient elements by the crop plants from the soil.


  • The supply of water by irrigation is regular and reliable unlike rainfall which is often seasonal or unpredictable.
  • Irrigation water supplied by rivers in flood often carries silt. This adds to soil of the fields, and enhances fertility and yield of crops.
  • With irrigation, cultivation can be done throughout the year and not only during the rainy season.
  • In desert areas, the constant flow of irrigation water through the soil helps in reducing the salinity of the soil. However, if the water is allowed to evaporate in the fields, it will increase the salt content of soil.
  • Modern multipurpose dams not only provides water for irrigation but also helps to control floods, generate hydroelectric power and improve the navigability of the rivers.


  • The irrigation of crop plants depends on the following two factors:
    • Crop Based Irrigation: Irrigation dependent on the nature of the crop plants
    • Soil Based Irrigation: Irrigation dependent on the nature of soil of the crop fields (i.e., soil-based irrigation).
  • Crop-based irrigation.
    • Crop- based irrigation depends on the nature of the crop.
    • Water requirements of different crops are different during the various stages of their growth and maturation.
    • For example, paddy crop (rice crop) is transplanted in standing water (wet lands) and requires continuous water supply, whereas, other crops such as wheat cotton and gran requires less water.
  • Soil based irrigation.
    • Irrigation also depends on the nature of the soil in which the crop is grown.
    • For example, the frequency of irrigation for crops cultivated in the sandy soil is comparatively less than the crops grown in clayey soil. This is because of the poor water retaining capacity of the sandy soil.
    • Sandy soil is highly porous, and has high permeability and thus when the crop plants standing in a sandy soil are irrigated, water quickly percolates down the soil and the crop plants are not able to absorb adequate amount of water.


  • Canal system: In this system, the human-made canals receive water from one or two reservoirs or from rivers. This is usually an elaborate and extensive irrigation system. And so, the main canal is distributed into branch canals, which further has distributaries or field channels.
  • Tanks: In this irrigation system, small storage reservoirs are built, which catch and store the runoff water from the smaller catchment areas.
  • Wells: Wells are constructed in the regions where enough ground water is available. They are further classified into following 2 types:
    • Dug wells: In the dug wells, water is collected from water bearing strata.
    • Tube wells: A tube well can tap water from the deeper strata. From these wells, water is lifted either by diesel or by electricity run pumps.
  • River lift system: The river lift system is more useful in the areas where the canal flow is not sufficient or regular due to inadequate release of water. In this system, water is directly drawn from the rivers for the supplement irrigation.
  • River valley system: Certain parts of the country like Kerala and Karnataka which lie along the Western Ghats, use water that is discharged into the steep and narrow riverine valleys, during the raining season.
  • Drip and sprinkler system: In this irrigation system, overhead pipes for spraying water. This saves a lot of water and is more natural.


  • Rain water harvesting: Rain water is collected and used for recharging the ground water by sinking deep drain pipes. This allows rain water to not go waste.
  • Water shed management: In order to reduce the flow of rain water and prevent soil erosion, small check dams are built up in water shed areas. This increases percolation of water into ground.


Manure Fertilizer
Manure is a natural substance which is obtained by decomposing animal waste such as dung (gobar) of cattle and buffaloes and plant residues. Fertilizer is a human made substance which is an inorganic salt or an organic compound.
It contains small amounts of essential plant nutrients such as nitrogen, phosphorus and potassium.

It is very rich in plant nutrients such as nitrogen, phosphorus and potassium.

It adds a great amount of organic matter in the form of humus in the soil.  It does not add any humus to the soil.
As manure is not soluble in water, nutrients present in the manure are absorbed slowly by the crop plants. Nutrients exist locked inside the organic compounds of humus. Being soluble in water, a fertilizer is readily absorbed by the crop plants.
Manure is not nutrient specific and it tends to remove the general deficiency from the soil. A fertilizer is nutrient specific and can specifically provide nutrients such as nitrogen, phosphorus and potassium to the soil according to the need.
Manure is voluminous and bulky. And so it is inconvenient to store, transport, handle and apply it to the crop. A fertilizer is compact and concentrated and so it is easy to store, transport and apply to the crop.
Manure is cheap and is prepared in rural homes or fields. A fertilizer is costly and is prepared in factories.

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