Maximum Yield Modern Growing | Canadian Edition | May June 2017

nutrient application systems
“CENTRIFUGAL PUMPS will
either pump a small volume of water to
a high delivery head or a large volume
of water to a low head.”
PUMPS
Most NFT hydroponic systems utilize centrifugal pumps,
which can produce a constant flow of nutrient solution
rather than the pulsating flow associated with piston or
diaphragm pumps. Centrifugal pumps will either pump
a small volume of water to a high delivery head or a
large volume of water to a low head. A delivery head is
the highest point that the pump must push water to in a
system. With NFT systems, the delivery head is the height
measured from the surface of the nutrient solution in the
reservoir to the top of the growing channels.
To select the correct size of pump that will deliver the
correct volume of nutrient solution, you need to determine
the system’s delivery head height, flow rate in litres
or gallons per minute, and—for basic NFT systems—the
number of channels. (The standard rate of a basic NFT
system is one litre per minute per channel.)
These specifications can be listed on pump packaging
either as a pump performance curve showing head capacity
at different flow rates, or simply as flow rate at a set head
height. Also, growers should be aware that pump capacity
and flow rates tend to fall over time, and with increasing
nutrient temperature. Allowing for future system expansion
is always a good idea.
DRIP IRRIGATION
As mentioned above, drip irrigated hydroponics is the
most commonly used method of nutrient application.
These may be set up and run as either a batch feed or
inline dosing system.
Smaller indoor gardens often utilize batch feeding,
in which a central tank containing several days’ worth
of working-strength nutrient solution is made up and
manually adjusted for EC and pH. This solution is irrigated
onto the plants using a pump and timer or manually
controlled by the grower as required. Batch feeding is easy
to set up and run; however, time is required to mix up the
working-strength solution every few days.
Inline dosing is a more automated system widely used
in commercial hydroponic operations. Also known as
“fertigation” or “direct dilutor/injector systems”, inline
dosing systems are installed on the main water supply. As
water flows through, nutrient concentrates and pH control
chemicals are directly dosed into the flow at the correct
rate to obtain the EC and pH required for a crop. Inline
injector systems may use several different designs for
Adjustable flow emitter allows nutrient solution volume to be controlled
separately for each plant.
Ebb and flow nutrient application used on a seedling nursery bench system.
NFT flow rates down each channel need to be uniform and at the
correct volume.
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