another quickie reference for run-off testing, and pH estimation...

[The Plant Whisperer]

two types of growers in my opinion.There are proactive and reactive.the novice tends to lean towards reactive and in organic soil where issues can take weeks to show themselves i think more often than not especially with a plant that has almost no veg cycle to many reactions will result in ugly,low yielding plants.
The only thing than effectively change the PH of organic soil would be high alkaline water (higher PH)and normally because of the high amounts of limestone it deposits through to get to reservoirs.But using a regular PH UP and Down in organic soil is completely pointless IMO and wont change the PH of the soil.I wasn't saying that all rain water is 7.0 i was just giving a number cause depending on where it rains it varies.lol
If more growers would be proactive and amend there organic soil and get the PH nailed down before they plant instead of trying to fix it with a live plant in it than there would be no need trying to fix problems that were caused 2 weeks earlier from trying to raise PH of a pot with perfectly fine growing plants in it.

 

[Waira]

...

 

[Ste]

Would love some advice on soil ph and run off just checked my run off and it's 3.4 not sure what to do should I flush them with ph water

 

[Jamie]

Can soil growers please tell me if you ph your water or not? I've been using ph down haven't fed yet and my run off was 1500ppm..my ph from the tap is around 7.3 and when left for 24-48hours it goes up is that right? Biobizz light mix soil. 600hps light 1.2x1.2x2m tent. Growing 6 autos, I no soil is suppose to be a buffer but if my water is say 8.5 surely it won't buffer it to 6.5? Examples of what other people do would be really appreciated!!

 

[Waira]

-- It depends on your water's hardness mate, how much dissolved minerals are in there,... a TDS or EC meter will tell you, but at 7.3 pH it's likely fairly soft,... odd that it goes up though, usually once in open air, more CO2 dissolves into it and lowers pH a bit,... Also, the soil type you have, or soilless may dictate adjusting too,... Generally, soils with a lime source in them buffer acidity better than alkalinity,.... pH'ing your feed solution is wise if using synthetics, not organics though usually,.... here's a chart that show nutrient availability over pH range, and best pH range... I recommend looking for a quality soil pH probe, like the Accurate 8 (Control Wizard),... nothing is better than in-pot measurement, run-off testing is very inaccurate!

 

[IndoorTropics]

-- It depends on your water's hardness mate, how much dissolved minerals are in there,... a TDS or EC meter will tell you, but at 7.3 pH it's likely fairly soft,... odd that it goes up though, usually once in open air, more CO2 dissolves into it and lowers pH a bit,... Also, the soil type you have, or soilless may dictate adjusting too,... Generally, soils with a lime source in them buffer acidity better than alkalinity,.... pH'ing your feed solution is wise if using synthetics, not organics though usually,.... here's a chart that show nutrient availability over pH range, and best pH range... I recommend looking for a quality soil pH probe, like the Accurate 8 (Control Wizard),... nothing is better than in-pot measurement, run-off testing is very inaccurate!

will a soil probe also work in coco? i have access to Hanna and Bluelabs models.

 

[JaPinkman]

.... posted here for fast access and reposting where needed, for those without a quality soil pH probe,....

...The Pour Thru (run-off) Method for Testing Container Media:

* first, test the pH of your usual water source*
1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving... do not use a nutrient solution, it will badly skew the results...
2. after container has drained for one hour, place a saucer under the container -- make sure to use a clean, uncontaminated container- any residuals in dirty one will skew the readings,....
3. pour enough distilled (DI)/RO water on the surface of the container to get about 50 mL (1.5 fluid ounces) or so of leachate to come out of the bottom of the container (Table 1)
4. collect leachate for pH and EC testing;
5. calibrate pH and EC meters, if not done recently
6. measure pH and EC of samples, then do this calculation-->

-- Calculation ->>> If your runoff pH is higher than your starting (water) pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference

--- If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.

For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5

If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5

Thanks !!

 

[JaPinkman]

This actually helped me a lot. I always thought well it's close to what I put in But didn't realize you should add the difference. Makes perfect sense now

Wow, that helped me a lot too. I had one in the infirmary and couldn't figure out why it was so screwed up and the one thing that I felt sure about was the soil ph, haha. So a couple of really good growers politely suggested that I should get a soil meter and confirm the ph and I kept resisting that idea. Anyway, after Waira posted that I went ahead and tested it to find out that I had really screwed my soil up, bad. These master growers are amazing bcz they can look at a picture of your plant, and often with just a limited amount of information lead you to a solution. This forum and this community of growers are a incredible resource.
I'm getting the ph meter.

 

[Olderfart]

.... posted here for fast access and reposting where needed, for those without a quality soil pH probe,....

...The Pour Thru (run-off) Method for Testing Container Media:

* first, test the pH of your usual water source*
1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving... do not use a nutrient solution, it will badly skew the results...
2. after container has drained for one hour, place a saucer under the container -- make sure to use a clean, uncontaminated container- any residuals in dirty one will skew the readings,....
3. pour enough distilled (DI)/RO water on the surface of the container to get about 50 mL (1.5 fluid ounces) or so of leachate to come out of the bottom of the container (Table 1)
4. collect leachate for pH and EC testing;
5. calibrate pH and EC meters, if not done recently
6. measure pH and EC of samples, then do this calculation-->

-- Calculation ->>> If your runoff pH is higher than your starting (water) pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference

--- If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.

For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5

If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5

Nice summary @Waira, thanks for posting it. I am curious if you know of good tests to compare the results of this calculation with pH measurement made by a good soil probe prior to the testing. I remain to be convinced that this process could do much better than ballpark estimate. There are quite a few potentially inaccurate assumptions incorporated in both the process and the arithmetic.

 

[Waira]

:smoking: Cheers OF! The original posting was here before I came I think? Since then, after working Sick Bay for years, I added some extra tricks to it to help get it more accurate and "user friendly"...
I've tried a long while back to do direct comparison, I forget the specifics but I think with the then decent Accurate 8 soil pH probe it was still over 0.5pH off, in real soil-- not soilless! That caveat, particularly with coco is important I think with soilless, and it's less influential mix of components, could be more reliable, if those were run like they should be (frequent weak inputs, lots of run-off)...
But you're right, it's a "lesser evil" option! So much error potential due to the human, technique and equipment factors, magnified by the ham-fisted calculationals....At some point I just told folks to use it as a rough gauge to see how badly off pH things may be, so if it comes out at say 5.2, accurate or not, close enough to say it's too acidic in there and thus needs a corrective flushing at the least...

I loved my first two A8's, I tested those against slurry testing and they were within reasonable error margins (0.2-0.3)... This new one is dogshit right outta the box, just WTF wonky off too! ... It was so handy and easy, but now it seems it's time to cough up the $$$ for a "pro" unit bulb-type, and another bitchy sensitive piece of equip' to nurse along exactly like a pH meter, since they are the same damn thing! That Blue Labs unit is sweet though, made for such in-pot checks unlike a regular meter type... Another reason I've swung to mostly organic grows, "super " soils and supp's. this year I hardly bothered with pH checking after digging up a couple slurry runs, which is fugly shit on the roots in a tight stuffed pot!