To start this period at the right time to achieve the target night time drop in water content.
The night time fall in water content is an important tool in control of the vegetative / generative balance of the crop and root health and development.
Start time
Period 4 will start at the end of Period 3 (4 to 5 hours before sunset).
This time is always difficult to judge as it is dependant on the amount of light received after the last irrigation round and the volume of substrate.
Guide water content drop figures overnight:
0 to 5% - Vegetative
5 to 10% - Generative
10 to 15% - More generative
Figures of over 15% can be used with care but only at the end of the season when the slabs are full of roots as a method of maintaining root health.
See Season Dynamics.
Length of period
Until the start of Period 1 the following morning.
Dose size
It is best not to water during this period.
If very low volumes of substrate are used it may be necessary to put on one additional round during the late evening but only under extreme conditions.
If this is done a very small round is needed just to avoid too large a water content drop.
Time starts
None
Light starts
None
Other factors
Water content control is used widely in tomato crops especially at the beginning and the end of the crop to aid generative steering in the poor light levels.
In peppers it is being used more and more especially at the end of the year when moving into decreasing day lengths with a high fruit load to maintain root health.
With cucumbers the night drop is used less, but can be used when looking to promote flowering.
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