Nutrient Film Technique (NFT)
Many growers use the NFT system to achieve bumper yields. This is possible because the roots
have a constant supply of oxygen. The system is also easy to set up and maintain. It’s these
benefits that make NFT system one of the most popular systems on the market.
Read on to see how you can join the many growers achieving great results with NFT system.
How does NFT work?
With the aid of a pump, a thin film of nutrient solution from the grow tank continually flows through
plastic channels and past the roots of the plants. The nutrient solution then drains back into the tank and is recirculated to the plants. As a result, a root mat develops partially in and above the
recirculating solution.
Growing in an NFT system
Before transplanting your plants
Only transplant your plants into the NFT system channels if they’re strong and healthy. There should be lots of white roots showing outside the propagation block. Never be tempted to transplant your plants before they reach this stage. If you do, the propagation block will absorb a large amount of the nutrient solution, causing your plants to die of oxygen starvation.
A few days before you transplant fill your collection tank with clean water (no nutrient).
This enables the temperature of the water to rise to room temperature and the chlorine to escape
from tap water. If the temperature is below 15 oC you’ll need to raise it to 20 – 24oC. A water heater will help.
You should also check that your system is leak-proof and that your pump is in good working order.
Ironing out any problems at the beginning will make your soilless gardening ventures much more
enjoyable. Tip- note the volume of water your grow tank holds. You’ll need this information to work out how much nutrient to use.
Placing the spreader mat
You should place the spreader mat into the channel. Make sure that the mat overhangs at each endof the channel. This’ll prevent any leaks from where the water drops into the collection tank.
The solution flow
The solution flow should be between 400ml to 1.2 litres per minute and slopped to a gradient of
1:50. This’ll help to prevent pooling.
When you’re happy with the reliability of your system, water temperature and air space
environment, you can transplant your plants into the channels. Remember, your system should only contain water.
Planting out
It’s important that planting out distances are appropriate for your plant type. For example, lettuce
can be positioned closer than tomatoes. Plants grown in an NFT system also seem to prefer their
roots to run together. Tall plants can, therefore, be set out reasonably close together. This’ll also
train the stems of your plants to make full use of the air space available.
The first few days
If the transplant has been successful, the roots will quickly shoot through the propagation block and
into the water flow. In the right conditions root growth will be rapid – several inches per day! Signs
of successful growth will be noticeable within 48 hours.
At this stage, you’ll need to drain and refill the water, and add the hydroponic solution (half
strength). You’ll also probably have to add some hot or warm water in order to bring the water
temperature back to an acceptable level.
Additionally, you’ll almost certainly have to adjust the pH of the nutrient solution. Remember, the pH
level of the nutrient solution should range between 5.5 and 6.5. The best way to adjust the pH level
will depend on whether you’re using soft or hard water.
Using soft water
1. Using an approved testing kit, measure the pH level of the nutrient/water mix in your collection
tank.
2. Add Phosphoric acid (pH down) if the nutrient solution is above the correct range.
3. Add Potassium hydroxide (pH up) if the pH level of the nutrient solution is below the correct
range.
Using hard water
1. Measure the pH level of the water (before adding any nutrient).
2. The pH of hard water is always higher than 6.5. You’ll, therefore, need to add Phosphoric
acid.
3. Add hydroponic nutrients to the water and begin circulation.
4. After an hour check the ph level and, if necessary, add more Phosphoric acid.
Maintaining the system
When growing with NFT SYSTEM, it’s important to avoid any large changes in the pH level and nutrient strength. Large changes can cause salt build-up, which prevents the ability of all plants to absorb nutrients. Overtime, this can lead to poor plant growth or even death. It’s, therefore, essential to check the ph level on a daily basis, and adjust as necessary. In soft water areas, very little, if any, will be needed. But in hard water areas, especially if you’re using Grodan rockwool, the pH level will rise gradually. Don’t be alarmed by this; simply, adjust the pH level back down to the ideal level.
Also, never let the level of the solution in your tank drop significantly. Nutrients can concentrate in
small levels of water, causing a salt build-up. If you have a large system, an automatic top up will
prevent this from happening.
When using a conductivity meter to monitor the solution, to get a more accurate reading, top up the
tank with water approximately an hour before testing. Also, if you do use the ‘top up’ method of
nutrient (dose rates will be given on the pack of your nutrient), make up a large container of the
nutrient solution. You’ll then be able to withdraw a sufficient amount of nutrient to top up the grow
tank on a regular basis.
Observe root growth regularly
If you want to be successful with your growing, it’s important that the roots of your plants are
healthy. Remember, there should be a full healthy root system showing outside the propagation
block. Below, we discuss what you should be looking for.
1. Primary roots
The primary roots are large in diameter and the first to emerge from the propagation block. Primary
roots also grow rapidly.
2. Secondary steps
The secondary roots, which emerge from the primary, are small in diameter. Their large surface
area allows them to absorb minerals and water from the nutrient solution.
3. Root hairs
The role of the root hairs is to take up atmospheric oxygen, which all plants require for healthy
growth. It’s, therefore, important that the root hairs of your plants are always above the nutrient
solution.
Also, for the same reason as above, you should never let the nutrient solution ‘pool’. To avoid this,
simply have the channel on a slope and ensure the inlet flow is appropriate. As a general guide,
and as highlighted above, the flow of the solution should be 400ml to 1.2 litres per minute with a
gradient of 1:50.
Other useful tips
Phosphoric acid/Potassium hydroxide and water don’t mix well together. To improve mixing:
1. Add Phosphoric acid or Potassium hydroxide to a glass of warm water.
2. Stir vigorously before adding to the nutrient solution.
3. Add to the nutrient solution
4. Stir Vigorously again
5. Test the pH level.
It’s also important to highlight that it’s very easy to overdose with either chemical. Overdosing will
prevent your plants from absorbing nutrients, which can lead to death. You should, therefore, only
use Phosphoric acid and Potassium hydroxide very sparingly. As it’s not critical for the pH level to
be within the ideal range, only adjust this every few days.
We recommend that you take note of the amount of Phosphoric acid Potassium hydroxide you use
to adjust your first tank of nutrient solution. This’ll make it much easier to make changes to the
solution in future.
Safety – Phosphoric acid is strongly acidic, while Potassium hydroxide is strongly alkaline. Always
follow the safety instructions on the container. NEVER mix both together.
GVI systems is providing NFT systems in different models. It all depends on your crop and we will find the right system for you.
See our site at http://www.gvi.dk/Growing_Troughs.asp to see more of the types.
I hope with this little introduction that we hear from you in the future.
Team GVI
Giv us a mail on
Danvan@danvan.dk and we will find a solution for you.
