Passive hydroponics, semi-hydroponics or passive sub irrigation is a method of growing plants without soil, peat moss, or bark. Instead an inert-porous medium, transports water and fertilizer to the roots by capillary action.
Water and fertilizer are held in a reservoir and conducted to the roots as necessary, reducing labor and providing a constant supply of water to the roots.
In the simplest method, the pot sits in a shallow solution of fertilizer and water, or on a capillary mat saturated with nutrient solution. Since routine maintenance is much simplified, passive sub irrigation can reduce the labor required to maintain a large collection of plants.
The various hydroponic media available contain more air space than more traditional potting mixes, delivering increased oxygen to the roots. Allowing air to reach the roots is particularly important in preventing root rot in epiphytic plants such as orchids and bromeliads, whose roots are exposed to the air in nature.
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Passive sub irrigationmay also add additional ambient humidity through evaporation. It is important in passive subirrigation to wash out the system from time to time to remove salt accumulation. Plants that require drying between waterings, or a dry dormant period, may fail to thrive under the constant moisture ofpassive sub irrigation.
Many media are available forpassive sub irrigation, but the most common are expanded clay pellets, coconut husk chips, perlite, vermiculite, diatomite, charcoal, and rockwool. These are frequently used in combination. Go here to read more on each individual media.
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