Sub irrigation involves water soaking up into the bottom of plant pots or trays.
Such capillary watering supplies a constant supply of water to plants without needing to wet the foliage.
The number of times water needs to be applied is reduced to however often the supply below the plants needs to be replenished.
There are several ways in which water is supplied to pots through capillary irrigation.
Ebb and flow
This system of irrigation is becoming a popular method, particularly in nurseries that produce flowering pot plants.
Production rates are very high with thousands of pots all the one size and containing the same species and therefore water requirements can be reduced.
The plants are set in shallow trays or basins that are periodically filled with a few centimetres of water for a set period of time.
Capillary mats are used by large scale wholesale production nurseries.
The mats are set into metal trays or beds that are irrigated by drip lines. Tensiometers are placed directly on the mats to monitor humidity.
Outdoor sand beds
Outdoor sand bed irrigation is a simple, manual, non-electric, system that was developed in the UK.
Bed widths need to be narrow so that they can be reached from either side to prevent compaction caused by walking on wet beds.
Water well pots
Water well pots are an extremely simple watering method that can be used for individual plants or for very small quantities.
A reservoir of water is attached to the bottom of a pot. As the plant uses water and the potting mix dries, it is replenished by water soaking up through the bottom of the pot.
A wick bed is similar to a water well pot. It is a garden bed filled with a growing medium (eg. potting soil) sitting on top of a reservoir of water.