With a 400w hps. how many plant should i try and fit under the area i have to play with? 3x3 pot size??
1 plant in a 7 gallon pot, lst'd, topped, supercropped. veg her for 8 weeks. IMO and scrog. You may get a better yeild than SOG in that tiny area with 400 watts.
SOG vs. scrog should yield about the same per square foot. So to the OP, don't think first in terms of number of plants, think in terms of square footage your light covers. For a 400w HPS figure 4-6 sq ft coverage. Potentially you could fit 20+ plants if the pots are small enough and you go straight to 12/12 for a true SOG.
Toasty again, giving good advice as always. Technically a true SOG isn't done in containers, but rather in beds with 4 plants per SQFT. In containers, this is the same as using 6" pots, preferably square. However, I've seen SOG's done in 3" pots with 16 plants per SQFT successfully. I've never personally gone over 9 plants per SQFT. I've been playing around with different numbers of plants per SQFT lately, currently trying the whole "SOG" idea in 2 gallon grow bags which comes to about 2 plants per SQFT. Not a SOG, but the same techniques are involved - all side branching is trimmed off and focusing only on the main cola - I'm just vegging longer to make 'em a little bigger. Aiming for 24-30" colas @ finish.
^Yeah, 4 per sq ft in 6" containers is typical for a SOG, that's how I figured 20+ plants for that space.