My understanding is that acidic soil makes it difficult or impossible for cannabis plants to take up nutrients. So, with the wrong soil mix, you could wind up starving your plants even as you’re “adequately” fertilizing them. The solution is to neutralize any suspect soil or mix up a fresh batch. Since I tend to re-use my home-made soil mix (peat moss/perlite/wormcastings/dolomite lime), it tends to get acidic after a grow, because spagnum peat moss gets acidic as it decomposes.
Mixing powdered lime into a soil mix (or making a soil mix, for that matter from scratch) is a pain in the ass. I solved that by buying a rotating compost bin, which I fill with the soil elements and then spin until they’re thoroughly mixed. With used soil, I put it in the rotator, add powdered dolomite lime (athletic field marking chalk), spin it around for awhile and voila, I have neutralized soil ready for the next grow. Another thing I found that helps is draining water from the bottom spigot on my hot water heater. That’s where the lime from our hard water tends to collect. You can see it cloud up the water. I water my plants with that stuff from time to time, and it seems to help.
As you may have surmised, I’m not much on details like ph meters, etc. which is probably why my grows can be hit or miss, but I prefer to rely on observation, experience and common sense when growing. I fertilize with various bat guanos, some commercial and some scraped off the floor of the shed from back when we had bats.
