Period 3

Period 3


  • To maintain the target water content and achieve drain on every round of 25 to 30% or to achieve the target slab EC.
  • Especially during periods of high temperature and high VPD or low humidity the plant tends to use more water and less salts during this period.
  • The EC build up is therefore higher so more drain is required to hold the EC level.

Start time

  • Period 3 will start at the end of Period 2 (midday).
  • If the start time and stop time during the day are related to sunrise and sunset, period 2 and 3 will increase naturally in length as the day length increases.

Length of period

  • As this is the last true watering period of the day the stop time will be depend on the target night time water content drop and the volume of the substrate.
  • As a guide figure 4 to 5 hours before sunset (or later in hot climates).

Dose size

  • A dose size factor 25 as a base figure with perhaps up to dose size factor 30 in high light intensities or if trying to reduce EC.

Time starts

  • Time induced starts also are necessary to avoid a build up of EC in dull weather.
  • The time between time starts is dependant on slab volume etc.
  • Guide 15 to 60 minutes.

Light starts

  • To achieve a higher drain percentage during this period the irrigation needs to be more frequent so a higher mls/joule figure will be needed (or a larger dose size).
  • These have to related to crop and conditions but in general for most crops in Northern Europe 2.5 to 3.2 mls/joule/m2 (see Dose Size Calculator). In extreme climates this may be a higher figure.
  • Click here for more information on light influenced starts.

Other factors

  • EC levels in the slab can build up very quickly during this period so it is very important to achieve the target drain especially in low volumes of substrate.
  • The end time of this period also needs to be looked at in association with any pre-night on temperature being used. Watering during the pre-night temperature period will increase root pressure.