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A hydroponic garden can be as simple as a plant in a pot filled with rock or some other type of inert growing media, that is watered by hand. The water must contain the elements required for plant growth that the plant doesn't get from the air. Water mixed with these elements is called the "nutrient solution".
The
elements required for a nutrient solution are Nitrogen, Phosphorus, Potassium,
Calcium, Magnesium, Sulfur, Iron, Manganese, Copper, Zinc, Molybdenum, Boron,
and Chlorine. Off the shelf soil fertilizers don't contain all the elements, in
the right proportions, to make a hydroponic nutrient solution. Only quality
hydroponic nutrient formulas contain all the elements required.
A nutrient formula can be made from scratch with a little knowledge of chemistry and what chemical form the elements should be in. But that is beyond the scope of this discussion. We will be adding a link to a book on this topic in the future.
Watering a hydroponic garden by hand may be impractical with more than a couple of plants or with a growing medium like rock that will dry out in a few hours. Most hydroponic gardens have a "hydroponic system" that is automated with pumps and timers to do the work for you.
Most hobby growers like to experiment with different types of hydroponic systems, often building them from parts. Here is a few of the most common systems with a brief description.
Flood/Drain system
A
plastic tray filled with plants (usually in pots), on top of a reservoir filled
with nutrient solution. A pump in the reservoir is connected to the bottom of
the tray. When the pump turns on, the tray fills with water. When the pump turns
off, the water runs back down through the pump into the reservoir. The tray must
be above the top of the reservoir so gravity pulls the water back down. An
overflow fitting must be added in the tray to regulate the depth of the flood.
When the water level reaches the top of the overflow, it runs back into the
reservoir. The pump can be turned on with a timer. A system like this usually
waters 3-4 times a day.
Drip system
Drip
systems can use a number of different types of containers but the operation is
usually very similar. The nutrient solution is stored in a reservoir. A pump in
the reservoir has tube connected to it that runs up to the base of the plant.
The tube may branch off to smaller tubes feeding many plants. It works just like
a drip irrigation system in your yard. In fact, you can use most of the parts
available for drip irrigation systems like drippers, stakes, tubing and
fittings. If the nutrient solution is going to be recovered, the containers
should be above the reservoir so gravity can do the return work for you. If not,
the system becomes more complex with another pump to return the water. Of course
you don't need to recover the nutrient solution at all, it could just run off.
This may not be the best setup if it's in your extra bedroom. Some drip systems
run continuously, others are on a timer.
Nutrient Film Technique (NFT) system
The
NFT system starts like a drip system, it has a reservoir with a pump. The pump
has a tube that branches off to smaller tubes to feed the plants. But, the
plants are watered at the roots. The plants are setup in troughs like rain
gutters. The trough has a cover with round or square holes cut out for each
plant. The holes are spaced correctly for the crop. The plants are growing in
small plastic baskets about 2 inches across, filled with rock or rockwool. The
baskets are placed in the holes in the cover of the trough. Some systems don't
use baskets just a cube of rockwool or similar growing material. The water comes
in the trough at one end and drains out the other. Most of the roots will fill
the bottom of the trough. The goal with this system is to get just enough water
flowing all the time to keep the roots wet and also keep them exposed to the air
to get the extra Oxygen. It works quite well when setup and maintained
correctly.
Aeroponic system
An
aeroponic system looks like an NFT system but works a bit different. The plants
are growing in small plastic baskets that are placed in holes cutout along the
top of a tube. The roots grow down into the tube. The tube is filled with water
by a much smaller tube running along the inside of the large tube. The small
tube has holes cut every 6 inches or so to let the water come out. At the end of
the large tube is an overflow just like the Flood/drain system that regulates
the depth of the water. The large tube remains half-filled with water. The trick
with this system is to have a high-pressure pump so the water coming out of the
small tube sprays, oxygenating the water in the large tube. The pump should run
all the time.
We could go on and on with different types of systems but the basic idea is to keep the roots moist AND exposed to the air.
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