What is PROPER way to test run-off ph?

[Max Frost]

Hey folks,

Can someone please give me a short course on the best, most accurate way to test the ph of the run-off water from your soil? I've heard conflicting methods recently, and I've even heard that testing run-off ph is so inaccurate, it's not even really a useful diagnostic tool. Is this true? Is this the best way to test the soil's ph?

Thanks in advance,

Max :wacky:

 

[sixstring]

in my experience the runoff is always really close to soil ph itself.i do mine once in a while on plants that might look a bit off in color and its usually low like around 5.5-5.6 in coco/promix so for my 2 gal pots ill run a gallon through and check it right when it starts coming out and again at about half gal and one more time when im done pouring water in.if its low at first i would have already adjusted up to say 6.8-7.0 and finished the jug.by the time im done with that first gallon it is coming out within my range of 5.8-6.2.but if its high thats ok imo because it will probably come down again as the plant eats.but i would have checked ppm/ec before even grabbing the ph meter.usually if you ph your nutes going in and the plant is eating well the soil ph just takes care of itself.but i always look at that first reading as the true soil ph ,as the water first starts to drain out the bottom.sorry thats not so short an answer lol.

 

[Seamaiden]

My experience is different, so I do a slurry test. Very simple and really only takes about 10mins or so. I take my samples of media from the root zone, then mix them into a water sample I've already tested for pH and EC. I let that slurry sit for about 7mins, then test. I've found this is a much more accurate method, and better for *me* with regard to solving problems.

What's most important, however, is to make certain that whatever you're using to test parameters is itself accurate.

 

[Max Frost]

My experience is different, so I do a slurry test. Very simple and really only takes about 10mins or so. I take my samples of media from the root zone, then mix them into a water sample I've already tested for pH and EC. I let that slurry sit for about 7mins, then test. I've found this is a much more accurate method, and better for *me* with regard to solving problems.

What's most important, however, is to make certain that whatever you're using to test parameters is itself accurate.

So how are you testing the slurry once you've prepared it? I've always done pretty much the same as sixstring, but I always had to wonder if I wasn't just reading the ph of the water I just put through, and not really getting a true measurement of the ph of the root zone environment.

Thanks guys!

Max :wacky:

 

[Capulator]

My experience is different, so I do a slurry test. Very simple and really only takes about 10mins or so. I take my samples of media from the root zone, then mix them into a water sample I've already tested for pH and EC. I let that slurry sit for about 7mins, then test. I've found this is a much more accurate method, and better for *me* with regard to solving problems.

What's most important, however, is to make certain that whatever you're using to test parameters is itself accurate.

This is the most accurate way.

 

[sixstring]

but how? i mean where do you set you water ph and ec before mixing in the slurry and then how much slurry do you add to the water?she left out alot of variables.it sounds like a good way if you have a standard to go off but im confused on how to get there.

 

[Bannacis]

u don't set your water ph, you just get a ph reading of your water. then when you add your soil to the water and mix it up, you take another ph reading and by the difference from your water ph you can tell which way your ph is swinging.

 

[Seamaiden]

So how are you testing the slurry once you've prepared it? I've always done pretty much the same as sixstring, but I always had to wonder if I wasn't just reading the ph of the water I just put through, and not really getting a true measurement of the ph of the root zone environment.

Thanks guys!

Max :wacky:

I always take parameter readings before I make the slurry. Otherwise, you have no idea where you started from.

but how? i mean where do you set you water ph and ec before mixing in the slurry and then how much slurry do you add to the water?she left out alot of variables.it sounds like a good way if you have a standard to go off but im confused on how to get there.

I'm happy to outline my method, which I didn't do before.

Start with cleanest water, I use RO/DI, but in this instance distilled could be a very good way to go. Measure EC and pH.
Add enough of your media samples to make a slurry.
You obviously don't want it too thick, or it's going to be difficult to get a reading. I want it to be like... like crepe batter, I suppose, you want a very loose consistency.
Stir well, and then allow to sit for 7-10mins. I usually end up testing at 7mins, because I've done comparisons between 5mins, 7mins, 10mins, 15, 20, and 30. After 10mins I observe no shift in values.
Now, you can either strain it to test, or just dunk your meter in there and take your readings. What you're after is whether or not anything has shifted. Obviously, EC will likely be the biggest parameter to change, but, for example, when growing in coir, I want to see that pH shift from around 6.5+ (where it lands in my storage tub) to the high 5's. If I don't see that shift, I know the root zone pH is out of whack.

When I've tried to just test run-off, I get pretty crazy readings and have ended up chasing my tail. HOWEVER! I know that many people are better able to resolve their issues by using run-off pH, so I don't tell folks they *must* do the slurry test, just what I prefer and why. :)

I hope that answers your questions.

 

[altitudefarmer]

Seamaidn for the win once again. Great detailed post!

 

[waayne]

To get an accurate reading,I always do a slurry method much like Seamaidens
For consistency and accuracy I was instructed to always use Distilled H20

The only thing I do different is that I soak my samples for 24 hours before straining off the solids and testing the solution

A Botany Professor taught me this method,and I've never strayed from his methodology........

 

[sixstring]

sounds easy enough,ill give it a try next time i need to check something.thanks for all the "gooey details" seamaiden:)

 

[Max Frost]

Super info Seamaiden! Thanks so much! I appreciate ya'll taking the time to detail that out. I'll pick up some DI h2o over the weekend and give it a try. Quick question tho...why do you also take your EC reading? if you're just trying to find out ph, it's not necessary is it? (I'm afraid I don't have a meter). So when I do the slurry, I should just dip the ph pen right into the "mud"? I shouldn't try to strain it first as Waayne brought up?"

Thanks again!

Max :wacky:

 

[waayne]

Max you're gonna get the same reading whether it's strained or not...

The purpose of straining the slurry is to remove the heavier solids to avoid gunking up the test equipment's probe
or the PH pens conductivity electrode

 

[Max Frost]

Max you're gonna get the same reading whether it's strained or not...

The purpose of straining the slurry is to remove the heavier solids to avoid gunking up the test equipment's probe
or the PH pens conductivity electrode

Yeah...I was a little worried about that!

Thanks!

Max :wacky:

 

[DieselDuds]

Great advice right here, should not be avoided and thank you Seamaiden for the valuable info

 

[Seamaiden]

Super info Seamaiden! Thanks so much! I appreciate ya'll taking the time to detail that out. I'll pick up some DI h2o over the weekend and give it a try. Quick question tho...why do you also take your EC reading? if you're just trying to find out ph, it's not necessary is it? (I'm afraid I don't have a meter). So when I do the slurry, I should just dip the ph pen right into the "mud"? I shouldn't try to strain it first as Waayne brought up?"

Thanks again!

Max :wacky:

Because I'm using RO/DI water, not distilled, and I want to know the starting point. I strained at first, then tried it without straining, did a side-by-side and found that it made no difference at all, so I stopped bothering with it. You can certainly strain, of course.

 

[DieselDuds]

what kind of ph testers do the pros use? digital or 3 drop system?

 

[Max Frost]

what kind of ph testers do the pros use? digital or 3 drop system?

Well...the 3-drop kits (IMO) are frustrating. After you add nutes, it's hard to read...if not impossible at times. The color and cloudiness can throw you off badly. For the sake of accuracy (foremost) and convenience, go with a digi pen. You don't have to spend allot, although you do tend to get what you pay for. I'd get the best one I could afford. It'll save countless hours of frustration!

Best,

Max :wacky:

 

[Max Frost]

Because I'm using RO/DI water, not distilled, and I want to know the starting point. I strained at first, then tried it without straining, did a side-by-side and found that it made no difference at all, so I stopped bothering with it. You can certainly strain, of course.

Thanks seamaiden! That explains it!

 

[Seamaiden]

Most welcome. :)

what kind of ph testers do the pros use? digital or 3 drop system?

I have used colorimetric/titration kits, but as Max says, it's difficult to take a reading if nutrients have changed the color of the water much. I now have a Hanna meter.

I do also test plant sap pH, with a goal of achieving 6.4, and for that I use litmus that comes on a roll. I'll have to search for it, I got it on Amazon.