Agriculture Reference
In-Depth Information
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Background
Whereas the commercialization of hobby or “popular” hydroponics
became very active in the past 25 to 30 years, simple, self-designed sys-
tems were in use since the 1940s and 1950s. At that time the most common
methods were gravel culture and water culture.
The bucket system of gravel culture was the most common, in which
a small bed or bucket of gravel had a bucket attached to a hose joining
them (Figure 1.1). A bucket was filled with nutrient solution and then
supported above the growing bed to allow the nutrient solution to flow
into the bed flooding it from the bottom upward. This was a subirriga-
tion gravel culture system. Within a period of 5 minutes when the bucket
completely drains into the substrate void spaces of the bed, it is lowered
below the level of the bed and the nutrient solution drains back to the
bucket. This is repeated by hand a number of times a day depending upon
the water demand of the plants, which is determined by the temperature,
light, and stage of plant growth. Although the system is very simple and
works well, it requires that the hobbyist spend time during the day caring
for the plants' irrigation needs.
A water culture system termed a “litter tray” system used a reservoir
of nutrient solution in a rectangular tank with a tray of substrate located
above the nutrient solution (Figure 1.2). The most common medium was
excelsior wood fibers, wood shavings, sawdust, dry straw, rice hulls, or
peanut hulls. The tray was 2 to 4 inches thick, constructed of wood with a
wire mesh on the bottom to hold the substrate. Galvanized chicken wire of
1-inch diameter was coated with asphalt paint to prevent the release of zinc
from its galvanized coating. The nutrient tank had a depth of 4 to 6 inches.
The substrate would be watered when transplanting by hand for several
days until the roots began growing into the nutrient solution below. Once
the roots of the plant became established into the nutrient solution below,
the solution level would be lowered gradually from 1 inch to 2 to 3 inches
between the top of the solution and the base of the litter tray. This helped
oxygenate the plant roots.
With the introduction of plastics, small pumps, timers, and drip irriga-
tion supplies, these similar designs could be modified to operate automati-
cally. For example, using the principle of the litter tray, construct the tray
of plastic sitting on top of a rigid plastic or fiberglass nutrient reservoir.
The growing tray contains 2 to 4 inches of a substrate such as lightweight
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