N.F.T SYSTEMS – NUTRIENT FILM TECHNIQUE
- Flat bottom tray promotes most efficient gas exchange by roots
- Eliminates nutrient “pooling” and stagnation
- Use of net pot allows easy transplant of rooted cuttings or seedlings using rockwool cubes
- Roots establish quickly – No transplant shock
The N.F.T. system that’s drawing these rave reviews is simplicity itself: crop roots grow in covered trays, with nutrients slowly flowing along the bottom of the tray. Some of the roots grow down into the food and water solution; while other roots are in the air space above, where they take in oxygen and breath out waste gases. The new N.F.T. systems have been improved over the years from the original concept, and they promise to provide simple, productive gardening for commercial and hobby growers more interested in results than in fighting with complicated, fussy growing systems. The evolution of N.F.T. systems is interesting because it’s a story typical of gardening today: a good idea that became a practical gardening technique through years of testing and refinements.
The original N.F.T. system used sheets of polyethylene film, folded to enclose the roots and stems of the plants. But the loose sheets of plastic caused all sorts of problems – pools of fertilizer formed in wrinkles in the plastic, flooding the root system and causing root disease problems. The sheets of plastic collapsed against the plant stems, keeping fresh air out of the root zone. Growers tried to control this problem by using suspension wires everywhere – holding up the loose plastic, and supporting the stems. And roots formed a shallow, dense mat in the narrow channels, flooding the crops. And the original design allowed only a very thin film of nutrients – about 1/25 of an inch deep – to flow down the rows, since the root systems themselves were so shallow. Any greater depth to the nutrient flow would drown the roots. Controlling the depth of the nutrient flow was crucial -and fussy. But the simplicity of the N.F.T. system inspired changes and improvements: a capillary mat was placed directly under the roots to provide reserves of nutrients and water, in case the pump stopped working. There were still problems with the system, though – the roots continued to grow as a shallow, dense mat along the capillary matting, limiting oxygen uptake and causing a build-up of waste gases and other organic products from the roots.
Now, N.F.T. systems have evolved again, and the new systems have retained the basic qualities of N.F.T.- its simplicity and great crop potential while eliminating some of the design flaws of the “pioneer” systems. The latest N.F.T. systems use net pots, set into covers over a flat-bottomed, ribbed tray made of solid plastic for stability. This creates a much greater depth of roots, eliminating many of the problems of previous systems. Now crop roots can have lots of air as well as nutrients without the fussing of the early systems. The first advantage to the grower is that he can start his seedlings or cuttings in small rockwool blocks, transplanting the rockwool to the mesh pots (lined with hydrocorn) with no root damage or transplant shock. After transplanting, the roots grow quickly out of the rockwool, through the hydrocorn and down into the nutrient solution. Once the root system is well-established, the gardener can simply turn the lid upside-sown to raise the net pot higher in the tray, allowing the roots to grow through an air space and down into the nutrients again. Some of the roots will grow happily into the food and water, while some roots will remain in the moist air, taking up oxygen. The biggest improvement is in the greater depth of the root system, compared with the thick dense mat of roots that grew in the old N.F.T. trays. The extra depth of the root zone helps in supplying lots of oxygen to the plants and allowing waste gases to escape more easily. The depth of the roots also allows more flexibility to the gardener in the depth of the nutrient solution; when roots were forced to grow as a shallow, dense mat in the old systems, the depth of the nutrient flow was limited severely: a millimeter too high and the roots drowned; a millimeter too low and the roots dried out. Because all the roots were squeezed into a thin, dense mat, it was very common to discover ‘fertilizer burn’ problems when nutrient salt crystals formed in the log jam of roots in the bottom of the tray. This added root depth in the new systems will prove to be the breakthrough for N.F.T. hobby systems, allowing gardeners to take advantage of this simple, productive method of gardening.
A key to success in intensive gardening is crop accessibility: you must be able to reach every plant easily. Since achieving high crop yields requires straight ahead, problem-free growth, growers must avoid stress, disease and pest problems and ensure that the best possible growing conditions are in place. If plants are difficult or impossible to reach, pests can multiply and invade the entire garden. Litter from dead leaves also acts as a breeding ground for insects and plant diseases. Uneven growing conditions can also complicate gardening and produce unsatisfactory yields.
Growers can handle both these requirements – plant accessibility and even growing conditions – by placing their NFT systems in open areas rather than in a corner of a room. This allows the gardener to walk complete around the garden and to have easy access to all his plants. Growers can clean the garden, move plants as required, and check throughout the garden for stress, disease or pest problems.
Establishing even-growing conditions in a garden is much easier when the system is set up in an open location. Air flow through the garden is even and uninterrupted, avoiding the problems of air turbulence, heat and humidity buildups, and increased risk of disease and pests found where gardens are shoved into a corner.
One innovation that has helped growers to take advantage of an open location for their gardens is the high-efficiency horizontal reflector. Since these reflectors work so well at directing the light directly down onto the crop, no light is lost to the sides of the crop and reflective walls – and corner placement of the system – are unnecessary.
For proper drainage, it is essential that NFT trays are higher than the reservoir that supplies their nutrients. Gardeners must consider the height of their ceilings and allow for future growth when deciding on the height of their trays. Allow for enough space above the trays for crops to reach maximum size without crowding the lamps. In a room with a standard 8′ ceiling, for example, maximum height from the crop would be only 3 feet, even with the NFT trays placed directly over the reservoir. Gardening in a low-ceilinged room or mounting the NFT trays higher will reduce maximum height more, so plan the set-up of your NFT garden carefully to avoid ‘cooking’ your crops.
Since plant roots grow in a covered NFT tray, and are irrigated by a shallow, slow-flowing nutrient solution, good aeration of the fertilizer mix is essential for fast healthy growth. Using air pumps with air stones in the reservoir and trays will help; irrigating with misters will ensure that plant roots receive well-aerated nutrient solutions for maximum uptake of minerals. Maintaining healthy roots is important, since disease can spread from plant to plant when crops ‘share’ fertilizer solutions.
Although gardeners can use a variety of methods to irrigate their NFT crops, use of the 360° misters is recommended when excellent aeration of the nutrient solution is required. Four or five misters per tray works great! Drill a 5/8″ size hole in the side of one tray, near one end (and near the top of the tray, to avoid leaking!) Put a 1/2″ poly hose through the hole, and plug the end of the hose in the tray with a 1/2″ end plug.
Now punch a series of small holes – with an awl or ice-pick – and insert the 360° misters. Turn the hose so the misters are pointing straight down into the tray, then connect the other end of the hose to your pump. To irrigate several trays from ones” hose, drill two holes in each tray so the 1/2″ hose can go right through all the trays in a straight line. Insert misters, plug the end of the hose, and hook up the pump.
HINT: An in-line flow rate valve allows you to fine-tune the amount of nutrient flow to your trays. Be sure your trays are sloped slightly so nutrients will flow down the tray to the drainage bulkhead. Keep trays level side-to-side so the fertilizer solution flows evenly down the entire width of the tray, not just down one side of the tray.
At the far end of the tray from the irrigation hose, drill a 1″ hole in the bottom of the tray, insert a 3/4″ bulkhead fitting and connect 3/4″ poly hose to the through-hull fitting to return the nutrient mix to the reservoir. To drain several trays, use 3/4″ tees to join the drain lines from the bulkheads into a single drain hose.
- Roots require oxygen to live! Since the nutrient solution is slowly flowing along the tray, aerating the nutrients is very important to good growth and health of N.F.T. crops. Use a good air pump, hose and air stones to bubble your reservoir. Be sure to allow an air space above the flow of nutrients for roots to breath. Some growers will place air stones in the N.F.T. trays to be sure that roots can have adequate supplies of oxygen for gas exchange. Remember that good air in the root zone helps plants take up nutrients faster and easier!
- Use a low flow rate for your nutrients about one to two liters a minute is the maximum recommended flow. I hope your supplier has tiny pumps in stock! Too fast a flow causes poor growth and disease problems.
- Use an open reservoir to allow waste gases to escape from the nutrients. (Be sure to keep your reservoir out of direct light to avoid algae and heat build-up problems.)
Temperature, PH and nutrient strength are very important considerations for your nutrient solution, since the fertilizer will be flowing directly under the bare roots of your crop. HINT: the larger the volume of your reservoir, the more stable the solution, against variations in PH and food strength. The smaller the reservoir, the more rapid the shifts in nutrient quality.
Considering the potential for great crop yields from this system, it’s worthwhile to give N.F.T. a fair test by keeping light levels, temperature and air movement correct.
The tray-cover-net pot system shown here is now available. A ten-foot tray and cover with end caps, 20 net pots and hydro-corn comes complete for approximately $75.00 (pump, reservoir and fittings are not included). Good luck with your new, improved N.F.T. system!