You're in peat based soil I bet.
Keep the soil pH at 6.5-6.8 and if that means watering with a slightly higher nute solution, so be it.
Now, when you take the water pH, are you doing it before or after you mix the nute solution? 'Pure' RO water with a high pH is indicative of an aging filter. The pH you are concerned with is that of the solution including all nutes and additives you are using.
I'd try to adjust your nute solution to no higher than 7.2, and still keep checking runoff.
stinkyattic Reviewed by stinkyattic on . Another queation for Stinky or other experts Is it the soils pH that needs to be around 6.5 to up take nutes or is it the solution of the nutes that needs to be 6.5 to take up the nutes? I am growing in soil. The pH of my RO water is 7.4. When I run that through my soil (in 1 gal containers) my runoff reads 6.5 which is what I want. If I adjust the ro water to 6.5, the runoff reads 6.2 which is too low. So heres my question. When I add nutes to the RO water, I then adjust it to 7.4 so that my runoff is 6.5. Is this correct? Can my Rating: 5