PH drift

[Killian]

Hopefully someone can help me figure out this ph drift i keep hearing about. I'm using Fox farms ocean forest soil that is buffered 6.3 to 6.8 when I ph,d going in it was 6.4 when I checked the runoff which I filtered through a coffee filter it checks 5.7. Does this mean my ph is drifting down and I need to ph closer to 6.8 going in? I can't wrap my head around this oh drift thing. Your help would be greatly appreciated. Thank you.

 

[vyserage]

I wont pretend i know a whole lot, but as far as i do know that is what people usually do. What you could also do is run a bunch of water through the soil, say like twice as much as the pot size then let it dry for an hour and water in your nutes and see what the out ph is. I've had success doing this. From that point on check the runoff ph the next few waterings to observe which way the drift is going. With new soil i find the drift to not be accurate until you've watered the soil completely a few times. I've only done 2 grows with soil and it was just with lowes or home depot cheap soil that gets the job done lol. No experience with FFOF

 

[Emilya Green]

Here is an example of where runoff pH can confuse the entire thing. Runoff pH tends to go lower after organics in the soil, mainly peat, start to break down. Peat is very acidic, and a little bit of this debris breaking loose and flowing into the runoff can really dive that reading down, when it has nothing to do with the actual base pH of the soil.

Then there is the compulsion of folks to try to adjust up to compensate... Here is why that doesnt work:

If you water at 6.8, then the pH of that entire container, for the duration of the time that water is in there, is 6.8. When you fill up the soil with water, most of the weight there is water... pH adjusted water. The soil has no choice but to assume the pH that you set to. If you set to 6.8... none of your nutes that are active on the low end will even be seen.
Always always always... adjust your pH to 6.3 or near the lower end of the range. Let the soil drift. At least when you water, you know it is correct. The only way to figure out that base pH is to do a slurry test.

 

[vyserage]

Runoff pH tends to go lower after organics in the soil

Perfect example of experience im lacking, i've never grown organic

 

[Killian]

I wont pretend i know a whole lot, but as far as i do know that is what people usually do. What you could also do is run a bunch of water through the soil, say like twice as much as the pot size then let it dry for an hour and water in your nutes and see what the out ph is. I've had success doing this. From that point on check the runoff ph the next few waterings to observe which way the drift is going. With new soil i find the drift to not be accurate until you've watered the soil completely a few times. I've only done 2 grows with soil and it was just with lowes or home depot cheap soil that gets the job done lol. No experience with FFOF

Thank you for your input. Emilya explained in my journal. She is going to copy and paste it here for others to see.