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Q: The minimum furrow grade to assure surface drainage is-
  • A. 0.02%
  • B. 0.05%
  • C. 0.09%
  • D. 0.07%
Correct Answer: Option B - The slope of the furrow controls the velocity of the flow of water in furrow. A minimum furrow slope of 0.05% is needed to ensure surface drainage. • If the furrow slopes are too less then proper surface drainage may not take place with the result that excessive deep percolation losses may occur. • If the hand slope is steeper than 0.5% then furrows can be set at an angle to the main slope or even along the contour to keep furrow slopes within the recommended limits.
B. The slope of the furrow controls the velocity of the flow of water in furrow. A minimum furrow slope of 0.05% is needed to ensure surface drainage. • If the furrow slopes are too less then proper surface drainage may not take place with the result that excessive deep percolation losses may occur. • If the hand slope is steeper than 0.5% then furrows can be set at an angle to the main slope or even along the contour to keep furrow slopes within the recommended limits.

Explanations:

The slope of the furrow controls the velocity of the flow of water in furrow. A minimum furrow slope of 0.05% is needed to ensure surface drainage. • If the furrow slopes are too less then proper surface drainage may not take place with the result that excessive deep percolation losses may occur. • If the hand slope is steeper than 0.5% then furrows can be set at an angle to the main slope or even along the contour to keep furrow slopes within the recommended limits.