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Q: The amount of water content remaining in a unit volume of soil after downward gravity drainage has ceased is called :
  • A. field capacity
  • B. permanent wilting point
  • C. readily available moisture
  • D. seepage water
Correct Answer: Option A - Field capacity– After a rain or application of irrigation water, when all the gravity water has drained down to the water table, a certain amount of water is retained on the surface of soil grains by molecular attractions and by loose chemical bond. This water cannot be easily drained under the action of gravity and is called the field capacity. Permanent wilting point– It is that water content at which plant can no longer extract sufficient water for its growth & wilts up. Readily available moisture– It is that portion of the available moisture which is most easily extracted by the plants and is approximately 75 to 80% of available moisture.
A. Field capacity– After a rain or application of irrigation water, when all the gravity water has drained down to the water table, a certain amount of water is retained on the surface of soil grains by molecular attractions and by loose chemical bond. This water cannot be easily drained under the action of gravity and is called the field capacity. Permanent wilting point– It is that water content at which plant can no longer extract sufficient water for its growth & wilts up. Readily available moisture– It is that portion of the available moisture which is most easily extracted by the plants and is approximately 75 to 80% of available moisture.

Explanations:

Field capacity– After a rain or application of irrigation water, when all the gravity water has drained down to the water table, a certain amount of water is retained on the surface of soil grains by molecular attractions and by loose chemical bond. This water cannot be easily drained under the action of gravity and is called the field capacity. Permanent wilting point– It is that water content at which plant can no longer extract sufficient water for its growth & wilts up. Readily available moisture– It is that portion of the available moisture which is most easily extracted by the plants and is approximately 75 to 80% of available moisture.