- 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.
- 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.
- 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.
- 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.