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Frequency of irrigation from soil moisture

Short answer

Frequency of irrigation is the interval (days) between successive irrigations. It is calculated by available moisture depth = (FC – PWP)/100 × dry density/water density × root depth, then readily available moisture = p × available moisture, and frequency = readily available moisture / daily consumptive use (ETc).

Define the frequency of irrigation and how do you calculate the frequency of irrigation on the basis of soil moisture?

Frequency of irrigation is the number of days between two successive irrigations of a crop during its growing season (also called irrigation interval).

Calculation on the basis of soil moisture

  1. Find the available moisture: AM=FC−PWP100×γdγw×DrAM = \dfrac{FC-PWP}{100}\times\dfrac{\gamma_d}{\gamma_w}\times D_r (mm).
  2. Find the readily available moisture (allowable depletion): RAM=p×AMRAM = p\times AM, with pp = 0.5-0.75.
  3. Divide by the daily consumptive use ETcET_c:
f=RAMETc (days)f = \frac{RAM}{ET_c}\ \text{(days)}

Alternatively, f=(FC−θmin)100γdγwDrETcf=\dfrac{(FC-\theta_{min})}{100}\dfrac{\gamma_d}{\gamma_w}\dfrac{D_r}{ET_c} if a minimum allowed moisture θmin\theta_{min} is given.

✓ Answer checked by Claude Opus 5.5 (high effort)

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