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The moisture content of soil in the root zone of an agricultural crop at certain stage is found to be 0.05. The field capacity of the soil is 0.15. The root zone depth is 1.1m. The consumptive use of crop at this stage is 2.5 mm/day and there is no precipitation during this peirod. Irrigation efficiency is 65%. It is intended to raise the moisture contant to the field capacity in 8 days through irrigation. The necessary depth of irrigation is
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- 115 mm
- 169 mm
- 200 mm
- 285 mm
Correct Option: D
Depth of water required for root zone
dω = S.d [Fc – ω]
Assume mass specific gravity, S = 1.40
dω = 1.4 × 1.1 [0.15 – 0.05]
= 0.154 m = 154 mm
Total consumptive use of water for 8 days
= 8 × Cu = 8 × 2.5 = 20 mm
Total depth of water to be stored in root zone = 154 + 20 = 174 mm
η = 65%
| Total depth of water to be supplied = | ||
| η |
| = | = 267.7 mm ≈ 285 mm | |
| 0.6 |
