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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 types of drip systems.
The pipe work and drip lines also need regular replacement to combat clogging
and salt build-up.
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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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