Hi guys and girls, I've got an autopot grow currently on, I've also got 5 amnesia dutch passion photos sprouted about 4 inches tall, has anyone ever bottom fed plants in a tray with fabric pots? Like I'll buy a tray 1mx1m stick it in my tent upstairs and 5050 soil perlite mix and just fill the tray with feed and let them soak it up? Any advice would be great. Cheers
Bottom feeding in fabric pots can work well. If you are doing it manually, keep in mind why the autopot system works - it allows the water to be fully used up before flooding again, and it only floods about an inch deep, not deeper. You can duplicate this manually, but doing it would be difficult due to the need to constantly monitor water/nute uptake, especially when the plants get bigger and start drinking lots. If I were you, I would try your tray idea, only install one autovalve to supply the whole tray. Get the extra cover designed to protect the valve and hold it in place in a tray. You can set a valve up without it, but the cover is cheap, and works great. I am currently using one autovalve to feed three 10 gallon fabric pots with soil mix, and it works fine. You can do the job manually until you get your valve. You need to top water for a week or two anyway, so odds are you can have a valve by the time you need it.
One extra issue with the large tray setup is that you need to keep debris away from the autovalve. Start with a clean tray, and do everything you can to keep it that way. I learned a new valve screwup this grow - perlite floats and if a piece just the right size finds its way beneath the autovalve cover, it can lodge between the inner float valve and the cover, keeping the valve open, and cause flooding. Luckily, I noticed the valve malfunction (unexplained flooding to a couple inches deep, but still contained) and checked it out early. Luckily also, the grow is outside so the problem would not have caused damage. Had it been in a grow tent in the house, and had I not noticed things early, it could have been a bit of a screwup. So, keep that valve clean. I will consider containing the valve in a piece of panty hose in my next big tray grow. With the valve cover sold for tray operation, you could contain the entire cover and valve assembly without affecting operation of the valve.
Also, it seems that nute concentrations for bottom feeding need to be lower than for top feeding, other things being equal, in order to compensate for no runoff, i.e. no mini-flush with each watering. Most of the issues that seem to crop up later in grows with autopots seem related to salt buildup and/or nute imbalance due to this issue. Even experienced autopot growers seem to run into this with the odd plant when using salt nutes.
And finally, if you are going organic, keep the organic nutes out of your reservoir or you risk plugging of lines or valves, with flooding or starving plants as possible outcomes.
Good luck with it.
