I never used lime before. Does it really make a difference?
Yes, but only if it's powdered. The coarser the texture, the less effective it is within the timeframe of a MJ plant. Pelletized dolomite might be good for a houseplant where the soil's in use for 2-3 years. Or, outdoor gardens. But, for a 3-4 month grow, it needs to be the texture of beach sand or finer. The finer the better. You can mash coarse dolomite into powder.
Use 1-2 Tbsp per gallon of soil. I've done a test (without a plant) and 8 Tbsp per gallon only raised the soil's ph another .02 compared to 2 Tbsp/gal. I'm not sure how a plant would like 8 Tbsp/gal, but you don't need to worry about using too much in the 2 Tbsp range.
It's also a source of magnesium and calcium.
FWIW: I disagree with
@Yodaweed about measuring runoff ph. I agree that it's not very reliable and you're only seeing the wet ph, not the ph as it rises (as it dries). But, if your soil turns acidic (perhaps feeding too much and accumulating salts), you'll see that as a trend of the runoff becoming lower. It's either that or waiting for nutrient lockout to appear in the leaves. Watching runoff can give you a sense of where it's at if you see lockout. (Even better is the meter I mentioned.). The trick with measuring runoff is being consistent with how long you let the water saturate the soil before being displaced into runoff. The longer it sits the more it reaches equilibrium with the soil. You'll get a feel for how to interpret the runoff if you keep track of (or try to be consistent with) that saturation time. The official runoff process can be found by googling for "NCSU Pour-Thru Method."
