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Readily available moisture, PWP, interval

Short answer

Readily available moisture is the portion of available water (50–75%) easily extracted without stress. Permanent wilting point is the 15‑atm moisture content at which plants wilt permanently. Irrigation interval (days) = depth of RAM / daily ETc.

Describe briefly the readily available moisture, permanent wilting point and irrigation interval.

  • Readily available moisture (RAM): the part of the available moisture (FC - PWP) which the crop can extract easily without stress, usually 50-75% of the available moisture (the upper part of the available range).
  • Permanent wilting point (PWP): the soil moisture content (as % of dry weight) at which plants wilt and cannot recover even if kept in a humid atmosphere; soil moisture tension is about 15 atm (1500 kPa).
  • Irrigation interval (frequency): the number of days between two successive irrigations during the growing period. It is found as
I=RAM depth (mm)ETc (mm/day)I = \frac{\text{RAM depth (mm)}}{ET_c\ (\text{mm/day})}

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