While I was away in Tampa last week for EV Expo (http://evexpo.org), the NFT system began to overflow. The reason appears to be the 3" PVC pipe became clogged with roots like these. I removed the large Kasumi cabbage (I ended up doing a stir fry experience with it; tasted pretty good actually). the roots were huge. What I am wondering is are other similar NFT systems experiencing the same problem? Also shouldn't the roots be whiter than this? All the plants seem quite health; actually appear to be doing better than in the flood & drain bed.
the roots look fine. actually, that is a very healthy root mass.
i had similar growth and consequent blockage/overflow with kale in my 4" pipes. moral of the story is to harvest your plants when they're ready and to avoid planting long-term crops in NFT.
Yes, even 4" pipe can easily be overflowed by big root masses. I have to do some radical root pruning on the basil in the NFT in summer since the root masses will get big enough to block flow regularly.
The roots don't look super pretty but they also don't look nasty and if the plants are doing well then it is probably ok. They may have just started collecting a bit of the brown stuff because there is so much root mass that the fine gunk started collecting. NFT pipes are definitely most appropriate to the shorter term crops where they don't spend enough time to cause the clogging and require root pruning.