I have received so much good advice in this forum – I feel it is my turn to contribute my thoughts on something I have learned from the school of hard knocks.
I have been experimenting with hydroponic and now aquaponic strawberries – on a relatively large scale – right now about 500 plants. I have tried NFT first because I originally wanted my channels to be as light as possible. I had a pythium problem, and then decided a better way would to be to level the channels and flood them to about an inch deep for 15 minutes or so at a time, then drain them. This method would purge any anaerobic areas and also allow the roots to breath between floods, and it was better, but my plants in gravel media were still always doing much better. After a while I realized that plants that don’t like their “feet wet” such as strawberries have a certain requirement that I think NFT will never provide. In an NFT type system – the roots always bunch together and lay on the floor of the channel. I believe the culprit lies in the surface tension of the nutrient solution. Even when the channel is drained, there is a fair amount of bridging of the solution between roots and to the channel floor that simply will not drain away. This water being held in surface tension does not allow the roots to breath as they need to, and eventually will cause the roots to rot. With a gravel media – the roots can all progress in separate directions so they do not bunch together, and never lay on the channel floor. Plus the porosity of the gravel media draws the water away from each root, and eliminates any water being held in surface tension. I am certain that roots of plants such as strawberries cannot be allowed to lay together, or on a channel floor. The water surface tension around the roots is the enemy. A porous matt on the floor would help this matter – but I think the roots laying together will still never allow the roots to breath as they need. All my strawberries are now in aquaponic gravel media beds and doing fantastic. I look forward to any of your thoughts on this. Dan
I've found that most of my plants seem to do better in media in general, but I think you may be onto something about the tendency of the roots to all stick together in an NFT set up.
I think the media also has an upper hand at allowing the plants access to nutrients that are being mineralized in the media beds that are not as easily available in solution to the plants in NFT or raft beds. My big system tends to be nutrient compromised by elevated pH and an over abundance of calcium giving me issues with Iron lock out, potassium availability and probably some other issues. I've noticed that even with all those handy caps, the plants growing in the media beds do far better than the ones in the NFT or rafts.