In Aquaponics 101 – NFT I introduced the concept of NFT, or Nutrient Flow Technique and demonstrated how to build a simple Aquaponic NFT cylinder out of 110mm PVC pipe. This posting is a report back on this system (after about 2 weeks) as well as about some things that I have learnt about NFT since then.
First the report back. To test the concept I planted the following;
- Lettuce seeds directly onto the wick in the yogurt cup.
- Lettuce seedlings that had been germinated in seed trays.
- A fully grown mustard lettuce plant with some roots through the bottom of the cup.
- Two small strawberry plants.
The lettuce seeds germinated immediately and have grown faster that seeds planted at the same time in seed trays. I find this quiet amazing because they are only getting their moisture (and nutrients) from what is sucked up by the wick from the water flowing in the pipe. Here is what the little seedlings look like now.
The lettuce planted from seedlings has also done well but to varying degrees. I think the two plants that didn’t make it were probably planted away from the wick and just dried out. But anyway this is what 3 of the survivors look like.
The reason I planted one fully grown mustard lettuce plant was to see how the roots handled being mostly submerged in water 24/7. Remember that I am also applying aeration by means of a slinky airstone to the NFT. As you can see the roots have grown like crazy and shows no sign of root rot. (that dark colour is solids build up)
Something I have learnt, and you can see from the photograph, is that some sort of pre-filtering is necessary because of the solids build-up on the root mat. Once all the roots are established like this plant, I believe that the NFT tube will clog up altogether and in fact overflow from the build up of solids. Using pre-filtered water will also result in much cleaner roots. If I was going to incorporate NFT into an existing gravel-based flood and drain system, I would place it AFTER the gravel to reduce solids build up.
Secondly, the aeration is great and will give you extra insurance against root rot. Using a blower and airstones may be a slight overkill but any extra bubbling will help.
Thirdly, the secret is to get half the root mat developing out of the water and the rest in the water. The flow of water in my NFT tube is too deep and is flowing too fast. I have now taken the endcap off of the outlet, elevated the tube more (ie. it now slopes more) and I am also going to slow the flow, probably by introducing a bypass.
Lastly, another thing that has become apparent is that a tube-based system may be too expensive to make NFT in Aquaponics commercially viable. This is because the capital cost per plant bay is very high. To prove the concept is great, but there are surely cheaper ways of achieving the same goal. I was recently invited to view a pilot site that incorporates NFT and found them using a brilliant idea of plastic roof sheet as water throughs and corex sheets over the top with lettuce planted through little holes. Here is what it looks like. I’ll be making one of these real soon.
Anyway, enough for now.