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Irrigation interval for clay loam soil

Short answer

Available moisture = (25–13)/100 × 1.5 × 750 = 135 mm. Interval = 135 / 10 = 13.5 days. Irrigate every 13 days.

After how many days will you supply water to soil (clay loam of 1.5 g/cc dry density, Field capacity = 25% and PWP = 13%) in order to ensure efficient irrigation of the crop for which daily consumption use of water is 10 mm. Take 75 cm of root zone depth.

Given: FC = 25%, PWP = 13%, γd=1.5\gamma_d = 1.5 g/cc, root zone depth Dr=75D_r = 75 cm =750= 750 mm, ETc=10ET_c = 10 mm/day.

Step 1: Available moisture depth

d=FC−PWP100×γdγw×Dr=25−13100×1.5×750=135.00 mm\begin{aligned} d &= \frac{FC-PWP}{100}\times\frac{\gamma_d}{\gamma_w}\times D_r\\ &= \frac{25-13}{100}\times 1.5\times 750 = 135.00\ \text{mm} \end{aligned}

Step 2: Irrigation interval

I=dETc=135.0010=13.50 daysI = \frac{d}{ET_c} = \frac{135.00}{10} = 13.50\ \text{days}

Answer: irrigate after about 13.5 days, i.e. every 13 days (rounded down so the crop does not suffer stress).

✓ Answer checked by Claude Opus 5.5 (high effort)

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