Soil texture is one input, not the whole schedule

Texture helps describe water retention and movement, but rooting depth, compaction, organic matter, slope and current wetness also matter. Identify the soil in each relevant bed rather than assuming the whole property is uniform. Use observation or appropriate testing. A soil label alone cannot justify an exact interval for every plant and weather condition.

Distinguish storage from infiltration

Storage describes how much plant-available water the root zone can hold. Infiltration describes how rapidly applied water enters the surface. A soil can have useful storage yet accept a sprinkler’s application too slowly. Surface pooling therefore does not prove the full root zone is adequately watered; it may show a rate mismatch or a compacted surface.

THE EXAMPLE AT A GLANCERoot depth turns capacity into stored water
Available root-zone water36 mm
Chosen depletion threshold14.4 mm

At 3 mm/day loss the example threshold is reached after 4.8 days without effective rain.

120 mm/m × 0.3 m roots; illustrative 40% depletion threshold, not a soil calendar.

A root-zone storage illustration

Assume a measured available-water capacity of 120 mm per metre and an effective rooting depth of 0.3 metres. Total available water is 120 × 0.3 = 36 mm. If a locally justified management rule permits depletion of 40 percent, the planning amount is 14.4 mm. At a scenario loss of 3 mm per day, that amount is reached in 4.8 days without effective rain.

Do not turn that illustration into a rule

The 120 mm capacity, 0.3 metre roots and 40 percent threshold are selected examples, not defaults assigned to all sandy or clay soils. A shallower root zone reduces available storage, and different plants tolerate different depletion. FAO’s root-zone water balance provides a framework, but appropriate parameters and stress criteria require local agronomic judgement.

Adapt application using observations

Check several depths and locations after watering rather than only the surface. When runoff begins before the required volume is delivered, investigate application rate and consider justified shorter cycles with infiltration breaks. On freely draining soils, avoid adding more than the root zone can retain. Recheck after cultivation or soil amendments because site behaviour may change.

Soil-watering checklist

  • Identify texture and compaction.
  • Estimate effective root depth.
  • Distinguish storage from entry rate.
  • Obtain suitable depletion parameters.
  • Account for effective rain.
  • Observe wetting at depth.
  • Prevent runoff.
  • Revise timing with weather and plant stage.
  • Avoid universal soil-only watering calendars.