Compact. Self contained. Inexpensive. Easy to set up. Virtually no growth media required. No need to dial in complex irrigation schedules. Total control over a hyper-oxygenated, thriving root zone. How does this sound so far? If you’re a home grower thinking about giving hydroponics a go, NFT Gro-Tanks sure promise a lot.

Over in Europe, NFT has been the preferred hydroponic method among hobby growers for many years. Now finally, it seems, the word is beginning to spread to hobby growers over on this side of the Atlantic. But what’s the real deal with NFT? Does it truly offer all these promised benefits to hobby growers without any catches or compromises? Is it just suitable for salad crops or can it deliver when applied to heavy, fruit-laden annuals like tomatoes and cucumbers?

Our main man with a high yielding plan, Everest Fernandez, takes a first look at NFT Gro-Tanks and shares some of his hands-on experience.

WORDS: Everest Fernandez

NFT 101

Ok, don’t be shy. Raise your hand if you don’t know what the hell NFT is. No worries! We’ve all been there, and that’s what I’m here for I guess …

NFT stands for Nutrient Film Technique. It refers to a general method of growing plants hydroponically. In NFT nutrients are added to water just like any other hydroponics system and this solution is contained in a tank. Plants sit on a grow tray above the tank and the nutrient solution is pumped up to the tray. The tray is positioned so that it lies on a slight gradient. The nutrient solution flows constantly over the roots feeding them all the nutrients and water they need. Any nutrient solution that is not up taken simply flows back through a hole into the tank where it is re-circulated.

But What Are The Plants Growing In?

The roots of your plants are constantly bathed in an oxygen-rich nutrient solution. It forms a thin ‘film’ about 0.03 to 0.1 inches in depth. A thin layer of capillary matting called “spreader mat” is first placed over the tray. This helps to spread the flow of the nutrient solution evenly over the entire surface of the grow tray. We all know that roots hate light. That’s why they tend to stay under the ground in nature! Fortunately the root zone is protected with a piece of Correx (kind of like a cross between cardboard and plastic). Small holes are cut into the Correx, just big enough for the base of the plants to fit through. This also helps to prevent algae growth in the root zone or nutrient solution.

Cucumbers grown in an NFT system.

The thin nutrient film not only provides your plants with all the water and nutrients they need, it also gives them access to loads of oxygen – essential to maintain key metabolic processes in the root zone that regulate how efficiently your plants can feed. This is a key feature of NFT. There are always some parts of the root zone that have more access to oxygen than others – simply because they are higher up: these parts of the root zone help to supply lower parts with all the oxygen they require. This is just one aspect of plant physiology that NFT growers exploit to their advantage. When plants have access to all this water, nutrient and oxygen simultaneously the growth rates can verge on being scary.

Gro-Tanks vs. Gullies

NFT Gro-Tanks can accommodate a far wider root system than the NFT ‘gullies’ you may have seen on commercial hydroponic farms (commonly used to grow basil and other leafy greens) making them ideal for plants that produce abundant root systems such as tomatoes.

Go With The Flow

NFT Gro-Tanks often come supplied as a complete kit for hobbyists – including the right sized pump. Solution flow is generally unimportant but should normally be between 1 to 3 pints (400 ml and 1500ml) per min. Channels should be sufficiently sloped, normally not less than 1:50 but may be much steeper if set-up allows, so that there is no “pooling” in the channels.

Plant Stability

What about heavy, fruit-bearing plants like tomatoes? Surely without any growth media, the plants are simply going to keel over due to their own weight, right? Amazingly, the plants form such a thick mat of roots underneath the Correx that they are very well supported. That’s not to say that some top heavy varieties won’t benefit from some net supports – but that’s often the case across the board when you grow plants near to their maximum capacity!

Propagation

NFT growers start their seedlings and cuttings off in the regular way, perhaps propagating in rockwool cubes or another inert media (e.g. net pot with clay balls.) Aeroponic cloning machines can also be used. Just as with any other hydroponics system, it’s really important to ensure that your seedlings or cuttings have a sufficiently developed root zone before transplanting them into an NFT grow tank. Don’t just wait for one or two roots to poke out. Aim for a mass of roots first! A great tip is to use an air-pruning tray (see UGM005, page 28) to generate a compact, dense root zone that’s bursting to break free!

Everest’s NFT Grow-Tank Tips

Here are some of my special tips learned the hard way:

1) If you are using rockwool starter cubes, ensure that the ridges at the bottom of the cube are in line with the nutrient flow, not perpendicular to it. Otherwise your nutrient flow will be impeded.

2) No growth media around the root zone means less insulation and less protection from extremes in temperature – so you need to have your garden’s environment dialed in. The temperature of your nutrient solution is also crucial – but this is no different than with other hydroponic applications. Try to keep your nutrient solution at around 65°F for high levels of dissolved oxygen and optimum nutrient uptake.

3) Plants grown indoors under lights will take up water at a greater rate than they take up nutrient. Over time the EC (CF) of the solution will rise. Regularly top up your tanks with water or 50% strength nutrient solution. Keep your top up nutrient solution in a separate barrel rather than using water straight from the tap.

4) Maintain the pH of your nutrient solution at around 5.8 – check regularly as it can rise as the plants feed.

5) As a general rule, drain your nutrient solution and replace with a fresh batch every 7 to 10 days for optimum yields. Obviously bigger tanks can get away with less frequent changes whereas bigger plants prefer more regular fresh nutrients. For more information on nutrient change-outs make sure you read ‘Maximizing The Nutrient Environment’ by Lawrence Brooke (UGM004,005,and 006).

6) Do not let any light leak into the root zone. Ensure the holes in the Correx cover are just big enough for your plants to fit through. Cover the bases of your plants to prevent green algae forming – especially important if using rockwool cubes.

7) Thoroughly clean your tanks in between crops with a soap solution and rinse thoroughly.

Wait until roots are showing out of your starter blocks before inserting them into your NFT system. This is absolutely crucial!

9) Use a half strength nutrient solution to start your plants off, moving to two thirds to full dosage rate (as detailed on the bottle) after the first nutrient solution change (about 7 – 10 days after planting).

10) Take the opportunity to observe your plants’ root growth directly by simply lifting up the Correx cover!

11) Make sure you completely remove plastic wrapping from rockwool cubes or remove pots if using soil or coco. This allows the roots to access more oxygen.

12) NFT is a bare rooted growing technique. All but the smallest of plants will need additional support, i.e. yoyo’s or pea netting.

13) Cut lengths of spreader mat long enough to allow an overhang of a few inches from the channel into the tank. No trickling water sounds!

14) Don’t crowd them! Plants grow incredibly fast in NFT Gro-Tanks – many growers are overwhelmed!

Think NFT – Think Sushi!

NFT constantly provides plants with the opportunity to feed rather than other methods which just provide several opportunities to feed. It’s a bit like sitting in one of those once-trendy sushi conveyor belt restaurants all day, every day. You, like your NFT plants, can take what they want, when they want it, rather than having to wait for their next feed. As a result, you and your plants are going to end up very happy and heavy!

Planting out and Irrigation

First, mark your planting sites with a marker on the Correx sheet. Do not position any plant too close to the pump. Make the holes just big enough. The aim of the game is to allow your cuttings or seedling access to the nutrient film without letting light in through gaps. Lay a single layer of spreader mat over the grow tray. Run your pump 24/7, day and night. There’s no need to work out irrigation cycles and frequencies. Your plants will simply absorb as much or as little nutrient as they require. This is perhaps one of the most appealing aspects of NFT. You should be able to see obvious root activity within 24 hours of planting out. Root axes grow into the nutrient film. Fine root hairs will also grow around the propagation media.

Incredible Root Development

One of the best aspects of NFT growing is the ability to peer at the huge mat of roots that quickly develops underneath the Correx cover. It’s easy to assess the health of your plants – just look for a thick mat of white roots! Watch that the roots don’t get carried away and grow into the pump. (Unlikely, but it does happen.) Clean-up in between harvests is a lot less hassle than with media-based growing methods too, mainly because there is so little media to deal with. This makes NFT Gro-Tanks a great choice for the hobby grower who doesn’t want to endure the regular hassle, expense (and back ache!) of carrying endless bags of soil, coco or clay pebbles.

The Verdict?

Once I tried NFT I immediately saw the benefits, despite grossly overcrowding my Gro-Tanks with waaaay too many plants on my first few attempts. You live and learn. Since then I have come to appreciate that less is, indeed, more!

A greenhouse full of plants grown NFT-style.