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NFT
Fancy Lettuce Systems |
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| The
most resource/labour efficient
growing system ever invented. |
About
NFT
Critical principles of design
Various details of system design
Important charts and information
pH Chart
CF Values
Diagram of typical nutrient
management system
NFT is an ultra-resource efficient method of
growing plants by providing a highly oxygenated, slowly moving
film (stream) of dissolved minerals to the roots in a flat
bottomed, gently sloped channel (the 
gully).
Plants are placed at intervals along the gully and grown with
their root ends constantly moistened by the nutrient film.
The nutrient film is shallow enough for most of the root mass
to have direct access to oxygen from the surrounding air.
The nutrient solution is recirculated through a reservoir
that is highly aerated and continuously monitored for pH and
nutrient strength. Nutrient strength and pH are adjusted on
demand with the use of automated monitor/dosing computer equipment.
This provides constant balance and optimum conditions for
thriving plant growth. This monitoring equipment is available
from Stockers.
Dr Allen Cooper in England originally developed the NFT growing
method in the late 1970's. It has been
commercially feasible for fancy lettuce in New Zealand since
the late 1970's. Typical NFT lettuce operations achieve 9-12
harvests a year from the system which produces:
- Clean,
mineral rich, pesticide and grit-free lettuce.
- NFT
lettuce requires only a fraction of the labour.
- Boasts
30% more production per acre than the best traditional
soil methods.
- NFT
uses just one tenth the water.
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| Critical
Principals of Design |
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There
are a few critical aspects of NFT system design that cannot
be ignored -
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Water Quality
Source water quality must be a constant, not a variable.
Before even considering hydroponics water must be analyzed
beforehand to determine qualities.
Upon analysis water must be as pure as possible going
in. If too many mineral elements are present, i.e. high
sodium, heavy metals or pathogens, it must be treated
with Reverse Osmosis Membranes and/or Ozone.
If source water mineral, such as sodium, is too high,
reservoir will need to be dumped much more frequently
which is wasteful, costly and unnecessary.
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Gully Features
Gully must be flat bottomed to achieve a broad nutrient
film (stream).
Slope must be a minimum of 1" in 40". No runs
longer than 60' (18 metres).
1 litre a minutes flow rate per gully maximum. ¾
litre per minutes for short runs.
2 feeder tubes per gully, in case one blocks.
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Reservoir Features
Reservoir should be sized so that when the system turns
off the reservoir needs to be able to hold 2000 litres.
Returning nutrient must fall into the reservoir. All reservoirs
must be equipped with venturis for oxygenation. Ethylene,
a by-product waste gas of plant metabolism, can choke
a recirculating system. A venturi that operates off pump
pressure creates a spa like effect in the reservoir, agitating
ethylene out of the solution and introducing fresh air
into the tank are.
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| Various
details of system design |
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| Typical
cross section of a sliding bench
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Typical
seedling nursery
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Miscellaneous
details of a sliding bench system
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Details
of a typical feed and collector manifold
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NFT
recirculating reservoir
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