Period 1

Objective

• To replace the water lost overnight and to achieve drain by the end of the period.
• To re-fill all of the slabs to the target water content to keep the variation in water content around the glasshouse to a minimum.
   

Start time

• All start and finish times for irrigation should be related to sunrise and sunset.
• The start time of period 1 depends on how you want to steer the crop.
• Sunrise + 1 hour = Vegetative
• Sunrise + 2 hours = Normal
• Sunrise + 3 hours = Generative
   

Length of period

• 1.5 to 2 hours
   

Dose size

• A dose size factor 25 down to 20 if you want to increase the target water content during this period.
   

Time starts

• Irrigation during this period works well using mainly time starts evenly spaced for the length of the period.
• If you achieve drain too early in the period you are putting on too much.
• If you do not achieve drain during this period then you are not putting on enough.
   

Light starts

• It is wise to also include a light induced start to increase the amount of water applied in this period on brighter morning to cope with the additional demand and to achieve the objective by the end of the period.
• A light figure of 2.5 ml/joule/m2 would be an average figure for most crops (see Dose Size Calculator)
• Click here for more information on light influenced starts.
   

Delta EC

• Delta EC is the difference between the EC applied through the drip and the EC in the slab.
• Care must be taken during this period that this is not too large (no more that 1.5 ms) as a sudden decrease in EC will stimulate water uptake and may cause fruit quality issues such as splitting in tomatoes.
   

Other factors

• Period 1 is a very important period for irrigation as it is the best time to “even up” the slabs around the glasshouse and reduce the standard deviation of water content and EC.
• It is also the best time to increase the water content when moving it up for the summer. Once the plant is fully active it is much more difficult to influence the slab.
   

A good Period 1 will make the rest of the day much easier to manage.

The good water distribution achieved during this period will give better water management and EC control for the rest of the day.