MIGrampaUSA
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I like to see my run-off change no more than .20. For example, if my water/nute solution is 6.5 pH going in, I don't want to see it drop more than .20 down to 6.3pH ... if it drops to 6.2 pH ... I'm ok with it. If it drops more than that my soil is out of range. It never rises so I have yet to worry about that. Here's my theory ... this has not been proven to my knowledge, nor have I spent time researching it ... If my pH swings much more than .20-.30 then something is buffering it down and my theory is it's the peat in my soil driving it down.So upon transplanting a clone from 1/4 gallon to 1 gallon into my soil mix - I fed with a half dose of BioBizz root juice and added citric acid to get to PH 6.8 - the run off came out at 5.8.
What's ideal run off ? I've done a bit of reading and found different theories...
I use Fox Farm Ocean Forest, which is supposed to be buffered to approximately 6.5 pH. It usually starts acidic and over time the buffering kicks in. If my run-off is dropping below 6.0, I give the soil a good flush. After a week or so and sometimes another good flush, the pH begins to rise back up to the range I like it in. If the soil is too acidic, you'll likely see a cal/mag deficiency as those nutrients are not absorbed very well by cannabis in soil that is lower than 6.0 pH.
This works in Fox Farm. I have not attempted it in any other brand of soil. Fox Farm comes already buffered with dolomite lime, although I think I'll be adding some more to the mix next grow. My current grow had a rough patch due to cal/mag deficiency. I fixed it before I flipped to 12/12 but my plants are a bigger due to the delay and I may end up having to move 3 of the plants into my other tent.