Has anybody else here had success with zero/minimal runoff coco grows? What approaches do you use?
I started out by hand-watering coco to 20% runoff every time, because the Coco for Cannabis site insisted it was required to prevent salt buildup. That quickly got old, so I set up automated irrigation (again, with runoff every time). That worked really well, but managing the runoff was a problem when I was away from my grow for several days, and it seemed generally wasteful. When I checked the runoff with my EC meter, it said salts weren't actually building up, so I timed my irrigation to stop just before producing runoff, and then I hand-watered extra & checked the runoff a couple times a week. Further EC testing showed that I could just water to runoff once or twice a week, at most, without significant salt buildup. That was already a massive improvement over watering to runoff every single time, but made me wonder if I could do better.
I did a bunch of research, including reading about bottom-feeding and wicking. In particular, I found an old ICMag post about a kind of modified hempy bucket where wicking rope went out the drain hole and into a surrounding bucket. (Apparently we aren't supposed to link to other forums...) This meant the bucket could be used as an extra reservoir, to supplement the area at the bottom of the hempy bucket, and the plant could also be bottom-fed by watering the outer bucket directly and then letting the plant wick it up (though in that case, multiple holes and pieces of rope may be necessary).
My previous grow was an experiment with three different kinds of wicking-based passive hydro. (The posts are on the autoflowers subreddit.) I had six different strains, all in 1-liter containers -- two with 1L airpots in small buckets, two with wicking hempy-style 1L cans in small buckets, and two with 1L plastic bottles inverted over 1 qt. runoff jars, with wicking ropes going through the bottle neck and down into the runoff jars. I did a mix of hand-watering from the top and bottom-feeding. All three containers worked out pretty well, and I was able to leave the grow twice for 5-6 days with only minor issues -- mostly because some started flowering later than others, so some wanted more nitrogen, some less. I also found that six different 1L containers wasn't too crowded for a 2x2'/60x60 cm tent, with training (LST), so I've continued with that for variety. I got about an ounce from each, except the one I accidentally topped late in veg, and found some new favorite strains.
The 1L airpots were my favorite container, so my current grow has five in 1L airpots and one in a plastic 2L wicking hempy (I ran out of airpots). They're in 23" windowboxes, three each. The windowboxes fit perfectly in my tent. I need to top-water the hempy, but can otherwise just dump nutrient water into the trays and let the plants wick it up. I'm intentionally following what autopots do -- only give the plants as much nutrient water as they're able to wick up within a couple hours, so there isn't water standing for days and getting stagnant. I usually water once per day, though I can see how quickly the trays dry out, and sometimes water again later in the day. The plants love it. I hand-watered from the top for the first 10 days or so, until their roots reached the bottom of the containers, and I have a small piece of rope looped through the airpot base to wick water past the small air gap. (The roots eventually grow past it.) I still hand-water from the top once every week or two, to wash out any salt buildup, but so far I've just diluted the runoff with more bottom-feeding and let them wick it up later. No issues yet. While that might not work indefinitely, autos will probably be harvested long before it matters, and the concentrated salts from one liter of drying coco shouldn't add up to all that much anyway.
Oh, and in case the specific nutrients matter -- I'm using Dyna-Gro's Foliage-Pro in veg, Bloom in flower, and their Pro-Tekt silicon supplement the whole time.
..not to be done...locked out all other nutes until I flushed...
