Doubt there is a definitive answer. Somewhere when I was admiring your system I posted that this was a drawback you would meet, especially because it is not really an NFT system although it looks a lot like one. Can't find the post though.

There is probably no correct answer as usual. If you cut roots you will stimulate the production of more root growth, and then have open wounds that are subject to disease everywhere where you least want it in the oxygen poor bottom.

If you absolutely must cut the roots then, just bite the bullet and try some maybe in different ways and if it works ok do what works best and introduce that into your cultural practices.

But if you can change the order of the plants and harvest (remove) some, slip some a little younger new plants to help the flow, that sounds like a more comprehensive strategy to me. I would also look into increasing the angle of my zigzags if my design allowd this modification on the fly.

The problem with flow rates below 1-2 L per minute is less oxygenation anyway, as well as less nutrient delivery at the end of the line the latter may or maybe not be important and maybe by careful species order down there can be fine. It stems from the natural stagnation that is happening as the dense roots back up and create a very different unhealthy environment where the water stagnates.

Good Luck and Happy New Year.

Found the original post in case you missed it, it was the 9th reply to you in a thread about and really belongs in this new thread and not hidden hereoxygenation of water:

Posted by PupillaCharites FL 9a (My Page) on
Mon, Dec 9, 13 at 16:29

I don't remember how long your plant path was, but it was probably around 32 feet. In the beginning that is no problem, nor is it a problem if the plants are small rooted. As a matter of fact some people go 100 feet on straight nft channels. Therein is the devil in the detail.
You don't have an NFT setup strictly speaking. It is a hybrid NFT/RDWC. This is because the pipe bottoms are rounded, so there is no nutrient film thin layer for that technique strictly - and that is how the oxygenation stay high for so long.

Yours on the other hand varies from NFT in that as soon as your roots get massive, the structure of your channel is to leave oxygen deprived roots at the pipe low point. You may have a liter or two per minute returning, but it says nothing as to how much water is retained by all kinds of damming from root matting and balling. Inside that zone is where the O2 depletion occurs with this design, so it is what I'm thinking about.

... (omitted info about return head design)...

...won't solve the over all drawback, just saying that every little bit helps.

O2 depletion = root rot, even if the plant gets sufficient O2 from the upper root zone. Hope this helps.

This post was edited by PupillaCharites on Tue, Dec 31, 13 at 14:21

Some plants are more suited to a soil garden bed , especially if you have mixed plantings of other varieties. I also know that Kang Kong (Asian plant) have huge roots and will block most systems no matter what the system is.
I try to grow compatable plants that will not hog the system and cause problems. Having said that, my heirloom Brandy wine tomatos is such a thirsty devil it really takes up a huge ammount of nutrient, luckily I have a 200 litre reservoir of nutrien.

Robert's right. Kang Kong in particular is a vicious invasive in some parts here, Hawaii and Puerto Rico. We call Swamp Morning Glory (Even though it's an acuatic plant, is a vine like others in the morning glory genus which grow weedy in these parts) or more commonly Water Spinach.

It can block any natural water system. It is naturally an aquatic plant, not soil plant so either way it requires special consideration.

I believe neither Mycle nor I could grow it anyway unless we apply for a special permit from our respective states which both especially regulate growing it, since it also can block and stagnate our inland waterways. Even by throwing a leaf from a sandwich into the waterway it can take. The Cambodians in Houston call it Trakuon where it was cultivated for over 25 years under the federal radar though lobbied successfully recently to be made legal to possess in quantities for personal consumption.

Wikipedia lists the high nutritional value of the plant but I believe whoever made the wikipedia page might have it somewhat confused with skunk/swamp cabbage which is a different plant. In any case most leafy greens are quite high in iron anyway.

This post was edited by PupillaCharites on Wed, Jan 1, 14 at 8:36