PH drift has to do with many variables. I find that it is best to mix my solution at least 24 hours before i need it and let it sit, after 24 hours i adjust my ph to desired level (5.6 for rockwool 5.9 -6.0 for dwc systems 6.3 for
promix) i use a small pump to circulate the solution for an additional 60-90 min. and check ph once more. I find it remains stable for longer periods if done this way.
There are a few ph adjusters on the market for lowering ph; sulphuric, phosphoric, nitric and citric acids are the most common. Sulphuric works well but at high levels can lock out other micro nutrients, phosphoric is the most common used when plants are in bloom but doesnt seem to hold the ph as well, Nitric is typically used during the vegetative phase but can be used in bloom as well with good results. Then there is the more organic adjuster citric acid. Citric typically comes in a powder or "crystalized" form and at first appears to work well the problem with this acid is its ability to maintain a ph for any amount of time as it breaks down rapidly.
The use of benificial fungi and bacteria have become wide spread these days and something that has been overlooked by many using these living organisms is just that, THERE ALIVE! and being alive means they interact with there surroundings (your medium)
feeding and defecating, releasing a multitude of ph altering substances. (there is a lot more going on as well but ph is the issue here)
PH is also constantly rising and falling due to natural processes of the plant itself, and this is a good thing. A natural fluctuation of ph means the plant is getting all the macro and micro nutrients it requires for healthy lush growth.
PH is one of the most important factors often overlooked, maintaining a healthy ph while allowing a slight drift to occur is the key (slight drift meaning from 5.5-6.3 in most systems) constantly adding adjusters to your solution in an effort to maintain a locked ph will likely do more harm than good.
There are other causes for ph drift as well that i have not gone into. Like the temp of your room as well as your nutrient solution, the amount of D.O. present in the rhizosphere and the reservoir, whether you use aerators or not as well as many other factors.
In closing i would like to wish you all a bountiful year with lots of big smelly sticky flowers to enjoy!
Happy growing,
Farmer Jon
