Measuring ppm in soil runoff

When measuring runoff from soil

  1. Should you filter to remove soil particulate?

  2. I measured runoff of one plant and got 1900 after a calmag watering.
    — About 10 minutes later there was more runoff so I measured it and got 900. Obviously this is a heck of a difference. Can anyone help me sort through which measure was correct?
    — if I go by the 1900 number I shouldn’t feed her next time. If I use the 900 number I should.

First I have to say, I love your avatar. :grin:

No need to filter run off.
Channels can form in the soil from watering so what you put in, runs out quickly thru channels. This can cause an inaccurate soil ppm. In my opinion, I’d use the second number.
What nutes do you use?
Do you have a grow journal?

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I just started tracking everything in a spreadsheet I created. Before it was just notes I had. Do you Have a specific question on the journal?

I’m using foxfarm trio and not a huge fan. All their reccomendations are way too hot. I’d really like a 2 part system with a chart for autos and photos. Also prefer organic. Can you recommend a better system?

So you tend to test either the entire runoff or the second half of it, but not the first half.

Thanks for the compliment. I’m a hard core dead fan.

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Oh I surely can! Living no till soil. I think if you look into it, you may like it.
I started out with FF nutes. They grow great pot. Lots of pH swings and salt build up with FF nutes. I eventually learned with my happy frog soil and FF nutes, sledgehammer flushes are required. Salts build up, soil pH drops and poms go thru the roof and lock out occurs if you don’t. I got tired of all that mixing, ph’ ing and flushing. No more of that with organic living soil. I’ll find a good video for you.
Yesterday was the anniversary of Jerry’s death. I just read an interview with Bruce Hornsby talking about his last few shows with Jerry. I toured for a lot of years. I really miss those days. So many good memories and friends I made along the ride. :v::v:
I didn’t take run off reading until I had at least half of the water in. I also water as slowly as possible.


Thank you so much. Living soil sounds right in my wheelhouse. We are an organic (or from the local farm) family. I’d like my cannabis to be chemical free


I did think the sledgehammer wasn’t necessary. Figured it was expensive water. It is necessary you say? That might explain high ppm in runoff yet I have hungry plants with proper ph.

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I’m finding out how much better it tastes. I love it. Check out @AAA journals and also @Budbrother has taught me soooo much on living soil. Check out his grows on here too.
Here’s a few videos to hopefully help

I love this guy’s grows and videos.

Hope it helps.


Yes it’s necessary. It’s saponin derived from the yucca plant. I still use it for watering my living soil, because I want to use it up. With the living soil, it’s not used for removing salt build up, it’s used to help decrease the hydrophobic tendency of my peat moss in the soil.
I was just curious if you had a journal on here so I could check out your grow and girls.

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Oh check out @Big123 and his magnificent outdoor organic girls :heart_eyes:


Like @GreenJewels says, no need filter and the I would use the 2nd reading. I use fabric pots with primarily FF OF and I always get runoff quickly. Even from the first quart when I will be using a gallon or more. It runs down the interior side of the bag or channels. This is what I do. If I am using a gallon per plant, I will use 1/2 and discard the runoff from this first amount. Then, take the readings from the 2/2 gallon. In essence, I am using your second reading.


Thanks @GreenJewels! :nerd_face:
Bookmarked for future experiments!!! :stuck_out_tongue_winking_eye:


Use a sprayer and water slower. Water a lil firstly, then wait five minutes before watering again. The water will absorb rather than to just pour through and out of the dry soil and sides of pots.

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I really pretty much do that. Still seem to get initial run through. I water 1 qt at a time. Then next plant, then next etc. After two rounds (I only have 4 plants in a 3x3 so it isn’t terrible) I discard this run off. Then take my readings from the run off after I finish.


If you haven’t watched that last video yet, don’t bother. It wasn’t the one I thought. And it’s stupid and not worth the watch. The first 2 vids are great :+1: :rofl::v: :green_heart:
Good luck with your grow


@beardless @Budbrother @GreenJewels @Myfriendis410 @kaptain3d

Guys I’m stumped. Every time I feed a plant I’ve never fed the ppm comes out higher.

Ppm in 850 ppm out 1671.

This is a 6 week old auto in ff happy frog. I also have 2 Lowryders that the ppm goes up every time I feed.
Ppm in 1200 ppm out 1800-1900

I use from trio nutes then dilute to 1200 ppm and recheck ph. Ph on all 3 plants has never been above 7 or below 6

What am I missing here? These plants are clearly hungry but when I feed them the ppm goes up not down.

I ordered sledgehammer to flush the plants but it won’t be in for a week. Is this the cause and if so, can someone explain to me?

Have you double-checked calibration on PH meter?

Salts break down in soil and it’s harder to determine cause as it’s adulterated with all kinds of stuff. If you were in a straight media it would be simpler but a flush won’t hurt.

So some of the ppm output could be “spent salt”? Would “Spent salt” show up in the ppm?

I will calibrate it again but it’s typically within .1 of standard solutions.


If it’s been calibrated recently that should be fine.

Yes; plant exchanges salts with media as waste. Possible that there was a PH lockout as well which makes nutrients insoluble to water so they would remain present in media.

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Just ordered some calibration solution. Using a pool tester, test strips and my meter and I’m no longer convinced it’s perfectly calibrated.

I’ll holler at when I have info on whether or not it’s calibrated. If it is calibrated I’ll send you some data. If it isn’t I’ll just slither Back under my idiot rock.

Again, @Myfriendis410 , thanks for the expertise. You’re my marijuana mentor!! I’ll keep asking question till I’m an expert then I’ll share that knowledge with the next noob.

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