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Irrigation interval: FC 27%, PWP 14%

Short answer

Available moisture = (27–14)/100 × 1.5 × 750 = 146.25 mm. Irrigation interval = 146.25 / 12 = 12.19 days. Water should be supplied every 12 days.

After how many days will you supply water to a field in order to ensure sufficient irrigation of a given crop, if the field capacity of the soil is 27%, the permanent wilting point is 14%, the density of soil is 1.5 gm/cm³, the effective depth of root zone is 75 cm, and daily consumptive use of water for the given crop is 12 mm.

Given: FC = 27%, PWP = 14%, γd=1.5\gamma_d = 1.5 g/cm3^3, Dr=75D_r = 75 cm = 750 mm, ETc=12ET_c = 12 mm/day. The full available moisture is taken as usable (no RAM fraction is given).

AM=27−14100×1.5×750=146.25 mmI=AMETc=146.2512=12.19 days\begin{aligned} AM &= \frac{27-14}{100}\times 1.5\times 750 = 146.25\ \text{mm}\\ I &= \frac{AM}{ET_c} = \frac{146.25}{12} = 12.19\ \text{days} \end{aligned}

Answer: water should be supplied after about 12.2 days, i.e. every 12 days. (Round down for safety.)

✓ Answer checked by Claude Opus 5.5 (high effort)

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