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NIR and FIR and frequency of Irrigation

Following particulars were recorded from agriculture Land growing where:-

  • FC = 20%
  • PWP = 8%
  • Permissible Depletion of available moisture = 50%
  • Root Zone Depth = 2m
  • Dry unit weight of soil =1400 kg/m^3
  • Effective Rain fall = 20mm.
  • Cu = 5.6mm/d
  • Find NIR and FIR if application losses are 10%. Also,Find the Frequency of Irrigation.
1 Answer
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$$As, N I R=C I R+\underbrace{L R+P S R}_{0} $$ Assuming leaching Requirement and Pre-sowing Requirement to be Zero, $$ \text { NIR }=C I R=C u-\text { Peff } $$

  • Depth Required to the raised to satisfy consumptive use $=1.4 \times 2 \mathrm{~m}× 0.06 $ $=0.168 \mathrm{~m}$
  • [Out of total Required of $.168 \mathrm{~m}$ for the crop, $20 \mathrm{~mm}$ is contributed by Rainfall]

$\therefore$ NIR $=168-20=148 \mathrm{~mm}$

  • $\quad F I R=\frac{N I R}{N a}=\frac{148}{0.9}=164.44 \mathrm{~mm}$

  • $f=\frac{\text { Total Depth ofwater a vailablefiom }}{\text { various sources }}$

$$f=\frac{168 d}{5.6}=30 \text { Days } $$

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