Agriculture Reference
In-Depth Information
7
Soilless Culture
SUBSTRATES (MEDIA)
The most popular substrates for small hydroponic units are expanded clay
pebbles, rockwool, and perlite. All substrates must be inert, provide ade-
quate oxygenation, and yet have good water retention as described earlier
(Chapter 2). On a small scale we do not sterilize the medium and reuse it,
as that is somewhat difficult and the amount of medium required per crop-
ping period is generally fairly small and inexpensive. Many of the small
commercially available hydroponic units that use mesh (net) pots are most
suited to expanded clay pebbles, other small rocks, or perlite. Rockwool
slabs to grow mature plants will have to fit into narrow, long trays as each
slab is 6 to 8 inches wide by 3 to 4 inches thick by 36 inches long.
SOILLESS SYSTEMS-EXPANDED CLAY
Most combination water and soilless culture systems use expanded clay
pebbles as has already been described. Various systems of soilless cul-
tures have been designed by a number of manufacturers. Starting with
the smaller one-pot systems of General Hydroponics, it has a WaterFarm
(Figure 7.1 and Figure 7.2), a PowerGrower (Figure 7.3), and an EcoGrower
(Figure 7.4). They differ mainly in size of growing pots and reservoirs. The
WaterFarm uses a 2-gallon grow pot and a 4-gallon reservoir, whereas the
PowerGrower has a 3-gallon grow pot and 5.7-gallon nutrient tank. The
EcoGrower has a 17-gallon reservoir and with a drip system to each of six
6-inch mesh pots for growing larger plants. The growing pot(s) filled with
expanded clay pebbles (Grorox) sit on top of the reservoir container. The
nutrient solution from the reservoir moves up by an air pump positioned
outside and attached to a tube that enters a small piece of PVC pipe and is
connected to a circular perforated drip ring or spider drip assembly in the
case of the EcoGrower. This system is best suited to herbs or a single plant
like a dwarf patio tomato plant. They are priced from about $50 to almost
$200 for the EcoGrower.
The PowerGrower may be connected in a series of pots (Figure 7.5).
This 8-Pak Kit is a top feed, drip system with seven 3-gallon growing
chambers. The nutrient reservoirs are termed a “Standard Controller,”
which is a 13-gallon master reservoir positioned on top of a float-activated
97
