Class 8 science chapter 1 33-36

34. Question
Explain how, the irrigation requirements depend on the nature of the
crop.
Answer
Proper watering of crop at right time is called irrigation. Each crop
needs a speciϐic amount of water during its various stages of its growth.
The irrigation requirements depend on the nature of crop. Some crops
like paddy crop (rice crop) need more water whereas other crops like
wheat, gram require less water.
35. Question
Explain how, the irrigation requirements of a crop depend on the nature
of soil in which the crop is grown.
Answer
The irrigation requirements of a crop depend on the nature of soil in
which the crop is grown. There are two types of soil- sandy soil and
clayey soil. Sandy soil is highly porous having highly permeability. So,
the water quickly percolates down to the soil and crop plants standing
in the sandy soil, are not able to get adequate amount of water. Thus,
crop cultivated in sandy soil need more frequent irrigation of water. On
the other hand, the clayey soil is much less permeable than sandy soil
due to which it can retain water for a much longer time. Thus, crop
cultivated in clayey soil can absorb adequate amount of water. Hence,
the crop grown in a clayey soil need irrigation less frequently.
36. Question
Describe the sprinkler system of irrigation. State its advantages.
Answer
 In the sprinkler system of irrigation, a main pipeline is laid in the ϐield.
The perpendicular pipes, having rotating nozzles on top, are joined to
the main pipeline at regular intervals. When water is allowed to ϐlow
through the main pipe under pressure with the help of a pump, it
escapes from the rotating nozzles. It gets sprinkled on the crop as if it is
raining.
Advantages of sprinkler system of irrigation:
(i) This system is more useful on the uneven land where sufϐicient water
is not available.
(ii) This system is also very useful for sandy soil   . 

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