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The
Dutch who grow everything using this system, have mastered this technique.
Nor do they just grow everything, they grow on an unprecedented scale
compared to any other nation. The plants are propagated in a rockwool
cube then grown on in a rockwool slab. The plants are individually fed
using drippers. These drip emitters are designed to deliver at a set rate
at a pre-set volume of water per hour.
Each dripper is wired to an infrastructure of tubes and delivery pipes,
which are fed by one master pump. Most commercial systems are what are
known as high-pressure drip systems and most domestic systems are known
as a low-pressure drip system. These commercial high pressure drip systems
are typically run to waste systems. This is when the nutrient is bled
off and after dripping through the rockwool slab then simply allowed to
run down the drain i.e. to waste. This ensures these plants get the exact
maximum nutritional value from the nutrient solution and also cuts back
on the possibility of bacteria or fungal problems like pythium. Most low-pressure
drip systems are recycling or re-circulating systems where the nutrient
returns to the tank then gets pumped back to the plants, then to the tank,
so on and so forth.
These systems are relatively cheap compared to others and easily built
once you get your head round the spaghetti of pipes, tubes and fittings.
Drip systems are also very versatile and can be made in many shapes and
formats allowing you a more modular design for your grow rooms.
The running costs of these systems are not cheap as after each crop you
basically dispose of the rockwool slab and replace it with a new one.
A 1 metre slab normally holds approximately 3 plants which can run up
quite a bill if you have many plants. Also if you are running to waste
then the cost of nutrient is very expensive indeed.
The main draw back with these systems is that the dripper can clog. Similar
to the NFT system, if a dripper stops your plants will suffer. If you
fail to notice that a dripper has stopped, the plants run the risk of
dying or at least losing their potential to give good yields. These systems
need constant maintenance and upkeep and are not recommended for the beginner.
All drip irrigation systems are a little tricky to maintain, as you need
to take constant pH and CF readings from your tank, from you run off and
from your rockwool medium. This process is achieved by using a syringe
to suck up a sample from inside the rockwool where the plants are growing.
As the medium itself will hold a different pH and CF value to the tank
and indeed even the run off. Then armed with this info you need to re
adjust the system again and do all those tests once more until you are
happy that you have the right levels that you require. This process can
easily need doing once a day. It is also advisable when growing in rockwool
slab culture to flush the salt out every 2 weeks with pH adjusted plain
water. This needs to be done as rockwool tends to absorb unused salts
which can build up, therefore need flushing every 2 weeks or so. It is
also advisable to do this flushing out process to flush out any salt build-up
that can concentrate in the drippers. Regular flushing can alleviate some
of the maintenance problems of these systems. However, getting blocked
drippers is part and parcel of this system so it is always advisable to
clean them regularly and also to have ample spare drippers to swap when
old drippers need cleaning.
The above to one side, this is a very productive
hydroponics technique and has served the Dutch very well. The rockwool
slab does offer a lot more support that you would achieve if you were
using NFT systems. It is also less prone to pump failure and as the slabs
absorb a lot of water you do have some breathing space if the pump or
drippers fail. It is very detachable and modular allowing easy expansion
or removal of the system. Low pressure drip systems are more prone to
dripper failure compared to high pressure drip systems, however, for Percy
Throwers, the high pressure option is too expensive and industrial for
a small indoor garden. Overall high levels of maintenance are required
for both
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types of drip systems.
The pipe work and drip lines also need regular replacement to combat clogging
and salt build-up.
Ventura Action Drip System.
Another entirely different drip irrigation system is that which uses Ventura
Action to deliver the dripping effect. These are individual grow tubs
or pots specially designed for the smaller gardener. The system consists
of a large outer pot which acts as a smaller water tank. Inside this large
pot is a shorter inner pot which holds the grow medium which is typically
clay pebbles. This smaller pot sits inside the bigger pot but does not
actually hit the water level of the bigger pot, which is the holder of
the nutrient solution. In English, it is a pot within a pot; the smaller
inner pot is where the plants grow, the bigger outer pot acts as the tank.
A Ventura pipe is then placed through the upper grow pot and submerged
under the water level of the outer pot. Air is pumped down the Ventura
pipe which causes the water to be pushed up above the level of the top
of the grow pot. This is then piped into a delivery tube with large holes
punched into it. The tube runs completely round completing a circle joining
back up to the Ventura pipe. Water pressurised via the air pump is then
delivered through this drip ring which slowly but perpetually drips onto
the clay pebble medium. The nutrient solutions then drips entirely through
the clay pebbles back to the outer tank, which in turn is then pumped
back via the Ventura pipe to the top and delivered to the clay pebbles.
If you like, it is a cross between a NFT system and a drip irrigation
system but uses clay pebbles as the medium for the plants to grow into.
Due to the fact that an air pump is used to deliver the water through
the Ventura pipe, the nutrient solution delivered is highly aerated. Also,
the constant dripping effect pulls air down through the clay pebbles medium.
This system is typically only used for 1 to 3 plants or mothers. The reason
for this is that to grow more would require more pots. Each has its own
individual tank. This tank due to the small nature in size needs regular
upkeep. To maintain lots of plants, you would need to maintain lots of
tanks. This would be a too big a time consuming enterprise to undertake.
Also, to adjust the inner tank you have to lift out the smaller inner
pot which the plants are growing in. This again can be a costly exercise
and it is very easy to damage the plants when lifting out and placing
back this smaller inner pot. In recent years, a controller has been invented
so you can link multiple individual systems together. But as the individual
pots still have individual tanks passively connected to the controller,
the controller fails to do its job in terms of pH and CF management, i.e.
you get different pH and CF levels in the different individual pots, but
also in the controller as well, making it very hard to maintain precise
control of your lovely crops. Also, due to the small size of the outer
tank, the system will need daily maintenance to keep the tank topped up
and the pH and CF at the right level.
Algae is also very prone to develop in this system
as the medium is fed from the top down ensuring that the top of the medium
is continually wet. The constantly wet medium being exposed to long periods
of light will always result in algae breakouts. As each system is packaged
with its own individual air pump, the pumps after prolonged use can stop
having the same problems but not as frequently as the NFT system resulting
in a failed crop. On this note, the drip ring can also become blocked
up with salt build-up and calcium deposits so this too needs regular cleaning.
All of the above to one side, this is an ideal
first system and is an inexpensive valuable teaching aid to the hydroponicist.
The system provides good aeration to the rootball and excellent support
to your bigger yielding plants. It is good for mothers but it is necessary
to be very careful when removing the inner pots to top up and adjust the
CF and pH of the outer tank.
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