Greenhouse Production Systems
Substrate Culture Systems
Capillary Mat System
In a capillary mat system, the containers are set on a porous fabric mat from 3/16 to ½ inch (5 to 13 mm) thick that is in contact with the bottom of the container (See Figure 14.6). Their principal use was to provide uniform watering on greenhouses benches. Water is inserted inside the mat through multiple pressure compensating drip tubes running the length of the mat. This allows water to move vertically from the mat into pots through the drainage holes once plants are placed on the mat and capillary action is established. The operation of the capillary mat system is based on the fact that water rises to a certain height in tubes with very narrow diameters through a process known as capillarity. In potted plants, the continuous pore spaces in the growing medium act as capillary tubes and lift the water from the mat to the roots inside the pot. Keep in mind that this water column must not be broken, as it is difficult to reestablish the column. It is usual to top water to help start this capillary action.
Advantages and Disadvantages
One advantage of capillary mats is that plants of different size and water requirement can be placed on the same mat without under- or over-watering individual containers. Empty areas of the mat would not be subject to evaporative loss and can be restocked when practical. Using capillary mats should result in using much less water, and this watering method can increase crop uniformity and reduce risks of foliar disease. Bottom watering has been known to create stronger root systems and to prevent foliage damage. Additionally, the total containment can help to decrease pest problems as there should be less standing water around plants and greenhouse films can stay drier.
Containers
With a capillary mat system, pots with flat bottoms are set onto a capillary mat. Containers must be saturated before being placed on capillary mat systems to ensure effective water uptake. The capillary mats must stay continuously saturated and in good contact with the bottoms of pots so that capillary action will draw water from the mats into the potting media. If the containers are disturbed in some way and the capillary action is destroyed the pots must be re-watered from the top to reestablish the capillary action.
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