Tube Tomatoes and Root Pruning
I mentioned on an earlier thread that I had to cull my lettuce plants much earlier than normal this year due to the extreme heat. So now I've got some free space in my 4" tubes. I've been considering filling the vacancies with a mixture of tomatoes and peppers - perhaps doing a little experiment on pruning (root pruning in particular) and plant spacing.
A couple questions:
(1) Does anyone have any experience growing large plants (e.g. tomatoes or peppers) in 4" tubes? NFT or FAD?
(2) I did a search of the forum for the terms "root pruning" but didn't come up with a thread, only an occasional mention. Does anyone root prune their plants?
I grew 6 foot tall pea plants in the 4 inch ADS irrigation tubing. I forgot to take into account getting the root mass out when I first built it. So I had to cut the tube in half to get it out. I attached a picture of the root mass that came out of one half of the tube. I don't know how you plan to construct the system, but good luck getting to the root system. You would need to be able to pull the whole plant out of the tube to prune the roots. If not you will be leaving dead/decaying roots to feed pathogens, bacteria, and fungi.
It will be just a mater of weeks before the roots begin to entangle with the other plants. That will make it impossible to pull the whole root system out to prune. After a month or so, you wont be able to pull the baskets up from the tube at all, and wont even be able to get to the roots. I had to take a stake knife and sliced the roots from the baskets as I slowly pulled them out. Once the baskets were out, I just grabbed the whole root mass and slid it out from the open end. Also fintuckyfarms has grown tomato's in 4 inch PVC tubing, and had a problem with their root mass clogging the water flow through it.
If you want to do a root pruning experiment, I would recommend using a water culture or aeroponic system, designed for easy access to the roots, and being able to easily take out the cut/pruned roots.
I don't remember anyone doing any root pruning experiments in the past few years I've been on this forum. I cant say I really remember reading any research on it either. But what I do know is there's a fine line between pruning and causing the plant stress. I prefer to let the plants roots grow as big as they want. Just taking into consideration how big the root mass will get before I design the hydro system I put the plants in. What do you mean by "FAD"?
I'm considering doing an experiment growing corn in a NFT or Flood & Drain type system. It wont be in the near future. But a friends wife told me about a variety of sweet corn that only grows 3-4 feet tall, grows 3-4 ears per plant, and matures fairly quickly. I would need to grow some in order to see how big the root mass will get. But I can see having rows of tubes with corn growing in them. Staggering the age of the plants so I have a continual supply of maturing corn plants, and thus fresh corn. The problem is I have many more ideas than money or space to do them. I have another plan to grow year round raspberries commercially on the list as well (even here in the desert).
Home Hydroponic Systems
Nice root pic GPS. I've attached a pic of the roots I got on one cycle in my recirculating deep water culture prototype system. By the way, when I type "FAD," I'm using short hand for "flood and drain" - who doesn't love an acronym.
There is actually a pretty large body of academic literature on three topics relevant to this thread: root restriction (e.g. container), root-shoot proportional growth, and root pruning experiments. Regarding the latter, I believe the typical finding is that roots recover quickly from trimming.
For a more popular hydro story on root pruning experiments, you can read J. Benton Jones Jr.'s article The Root Whisperer (Maximum Yield, August 2011) where he states:
For most plants it has been demonstrated that just one actively functioning root is capable of supplying most, if not all, of its essential nutrient elements...In general, there is no consistent positive correlation between root mass and plant growth and product yield. In fact, a large root mass may actually be detrimental to plant growth and product yield due to the amount of carbohydrates and oxygen necessary to sustain the function of such large roots.
I'd say that most of my previous pruning experiments agree with Dr. Jones' statements. I've just never tried to grow larger plants in tubes because smaller plants can clog tubes pretty easily - lettuce roots ain't no slouch so to speak - and, taking my cue from large commercial growers, I usually grow larger plants in drip systems. But you never know unless you try, and try I shall.