I use smart pots(and like types of fabric pots..in coco). Normally I use 3 gallon. My question is..what are the positives, and negatives of going with 2 gallon pots vs 3 gallon pots. I am hearing different things from different people. My quality is very good to excellent, but my yield is horrible(>.35gr. per/watt..more like.25-.30gr per watt)...I grow under 1000watt lamps. With 9-12 plants under each reflector(magxxxl). If I go with 2 gallon SPs I can bring that up to 16 per reflector, but will it make a noticeable difference? or make it worse. I know that this is not my main problem, but it is one of the few areas I am still uncertain of. In truth I guess its the old question of "more small plants" or "less bigger plants". will 2 vs 3 gallon make a difference? wow just realized this is my first post after 18months(approx) on this site...Seems like I am on here weekly looking stuff up, and following threads..
I like the 2 gallon variety myself. What I find works best is having the right volume of root mass for the coco. In my grow room, more coco means more veg time, and 2 gallons seems to be about the right amount of media for me. There are a lot of variables, and really one isn't "better" than another. It is just a growers preference thing. To each their own. There could be a lot of factors messing with your yield outside of the planter size. If you'd like some help figuring out where your bottleneck is the. Toss out some info. Coco brand, is it amended, nutrient program, EC and pH levels, temperature and humidity highs and lows, veg time, strain, age and brand of the HPS bulb, ventilation setup, and watering process including frequency and runoff volumes. I find that big, healthy, root systems make for the best harvests. During flowering the plant dedicates very little energy into building new roots. Take advantage of the smartpots fabric liner by allowing the roots to fill the container before flowering. You do not need to fear circling or root binding in these planters and by allowing the tips to hit the edges they will air-prune and increase lateral root growth from the main root. Flipping to flower before this point and it really wouldn't matter if you were in a plastic bucket because the roots won't have the energy to continue to grow for the edges and branch off laterally. Coco and fabric planters are great but you should definitely take advantage of what makes that combination so great. Coco being a hydro media can be watered regularly, so using extra coco to retain moisture and prolong watering frequency is unnecessary. Fabric planters need to air prune the roots for them to offer their benefits so don't transplant right before flipping to flowering. Give your plants a few weeks to fill out the media with root mass before focusing her on flower growth.
If you're using hydro method, which in my mind is the best way to use coco, you can go with the smaller containers. I think containers over 2 gal are more oriented toward the organic grower who has to contain enough nutrient in the soil to last the entire cycle. And that takes a lot of soil for a big plant. In coco hydro, you only need enough media to support the plant and that holds enough solution so that you're not watering multiple times a day. I use 7" square pots that hold 1.65 gallons, and that allows me to feed them once a day the entire cycle with plenty of support even for my big lanky Eldorado sativas. I can't speak to your low yield, since I never actually measure mine as a ratio of watts and it wouldn't be good anyhow seeing as how I only grow/smoke sativas. They are the best smoking weed by far in my mind, but don't produce particularly attractive buds or a lot of weight per plant. Also they take around 12 weeks to mature. Purely connoisseur stuff, not commercially viable, won't win any gram/watt contests against an indica. I'm a big fan of several small plants, with rapid cycle times. So I grow 12/12 from seed. Pretty much have to if you want to grow indoor sativas without knocking a hole in the ceiling, and it works out really well. I can manage five to six plants which go from seed-in-ground to harvest in around thirteen weeks or so. Then I just immediately plant ten more, from which I get another five or six females. All I can say is that I get more than I know what to do with, and the occassional buddy I gift some of my overflow to is always very, very happy. I've taken to walking through groups of obvious beach stoners, and "accidentally" dropping a cigarette box with an eighth in it among them. My good deed for the day.