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GATE 2020 CE (CE2) – Question 46

Irrigation · Irrigation systems and methods, crop water requirements · 2 marks · MTA

Crops grow in soil of field capacity 30% and permanent wilting point 13%. Effective root zone is 80 cm. Irrigation occurs when average soil moisture drops to 20%. Soil and water densities are 1500 and 1000 kg/m³. Daily crop consumptive use is 2 mm. Find irrigation frequency (days).

  1. 7
  2. 10
  3. 11
  4. 13

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Correct answer: MTA

Explanation

Usable moisture depth is $(0.30-0.20)(1500/1000)(800)=120$ mm. At 2 mm/day the interval is 60 days, absent from the choices. The 13% wilting point does not replace the specified 20% trigger. Official grading is **MTA**, preserved.