Which numbers are the most reliable - of course we are talking ph and ppm

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Here we go again. I am sampling a new soil mix to obtain its base ph and ppm for my next grow.
Here is the soil mix


The ph is fairly consistent but the ppm readings are all over the place

1 & 1a I used a 6" nursery pot and ran dehumidified water through it.
2 & 2a I filled a 5 gallon fabric pot with the soil and essentially did a run off test
3 is a traditional soil slurry
4 is same as 1 except using distilled water and only sat 30 minutes
I am comfortable in saying the ph is mid-6ish range.
But the ppm’s cover a wide range from 1300 to over 5000.
I think I will let the nursery pot and fabric pot sit overnight and retest to see if they have settled in a bit.
When I check ppm of the dehumidified water it is zero.
Thoughts?
Any thing jump out at you?
Other than, good grief, get a life…
@BeeKeeper2 @Zee @Bobbydigital @Covertgrower @AutoMattik

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Wonder if it’s your organic material breaking down giving the ppm spikes.

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Not sure if distilled would have similar properties or not, but based on your measurements, looks like it does.

Spikes in the soil ppm is definitely from organic material breaking down. Worm castings have a lot potential for ppm spikes.

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I use Mother Earth Coco Peat, and I stopped paying attention to the crazy run off PPM numbers quite a while ago now. I saw readings of 6500, lol. I had a talk with the owner of my local grow store, and as @Bobbydigital said above, the organic matter in the soil will wreak havoc on PPM readings. I really trust the owner of my grow shop, so I did as he said, and I monitor what goes in very carefully. I’m not interested in what comes out unless I see something on the plants that concerns me.
As far as pH, I also stopped checking the runoff for similar reasons. The Coco Peat I’m using always gave me heart stopping pH readings, very high, sometimes over 8.5, and I’m usually going in at between 5.7 and 6.2. At first it terrified me, but the plants were doing great. Aside from my local store owner, some very experienced growers here also suggested I be more concerned with what goes in, and only worry about what comes out if there’s a problem.
Bottom line is that when I used to test my runoff it would lead me to do things that were clearly giving my plants problems. I was trying to correct issues that didn’t really exist, and I had all kinds of lock out and deficiency problems. Since I stopped checking runoff (except for when I’m flushing), I feed based on a schedule and how they look. I have not had a single issue through my last few grows.

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I could not honestly answer that. I don’t make soil anymore. I just don’t have the time. I loves Roots Organics soil. I kinda am like capt ron. I don’t check my runoff. I don’t even check my PH when mixing nutes. I just trust AN. I used to check constantly and would get the same PH constant with AN nutes.

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I am almost there. I do pay more attention to ph but was surprised by the variation between the different readings. I looked up Mother Earth Coco Peat. Coco is listed first in the ingredients but I didn’t see anything about amount or ratio compared to peat. Otherwise, it is probably similar to my soil. Mine is around 25% coco

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I’ve been using the coco peat for about a year now, and it’s working really well for me. I honestly don’t understand how my runoff pH is so high, but like I said, no issues with the plants at all, so I’m sticking with it. Also, I’ve been using Advanced Nutrients for a while now. It’s easier for me to use, and my plants love it!

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PH perfect line? Actually I am switching this next grow to AN’s OIM line of Iguana, big bud, bud candy, sensi, mother earth tea, and nirvana. This current grow was cruising along ppm out 2000 - 2400, then it jumps to over 4000 without a change in ph. Ok that’s strange, move on she is doing great.

Yeah, the pH perfect technology was a dream come true for me, lol. I still check it before I feed just to be on the safe side, but I never have to adjust it up or down, it’s always perfect. It was Hellraiser who suggested I try it, and I went with the Connoisseur line with all of the additives because that’s what he was using. It’s worked out great, my plants have never been happier.

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@beardless @Cap_Ron @ @Zee @anybody? lol I am buying AN nutes. I think I have all I need for decent grow. This is first grow and I use FF trio. Ive been feeding them 1/2 nutes and less. I have been lucky so far I think. I have a couple of questions. On the Fox Farm soil feeding schedule the ppm(700scale) What scale is that? I bought a fairly decent tds meter. It reads 3 different modes in tds (KCI…442…NaCL) What would I use? What does everyone use? I have been doing searches and reading, it’s confusing to me. Also another question on FF schedule ppm ranges go up as plant gets older. Are these ppm readings from nutes going in or run off? Another Question for instance… my last feed RO at four weeks flower as far as I can tell was 1570, What does that tell me and what would I do on the next water/feed. I know bunch questions, maybe everyone can chime in.

The ppm 700 scale is based on measuring the KCl or potassium chloride content of a solution. The ppm 500 is based on measuring the NaCl or sodium chloride content of a solution. The ppm 500 scale is also referred to as TDS - total dissolved solids .
Your meter must be geared toward chemists. As a retired accountant I like number scales

If your meter was set KCI (700 scale) you would be a little lite on max ppm per FF of 2100-2310.
However, if your meter was set ti NaCI (500 scale) you would be right in the middle of the recommended ppm for that week.
The conversion of FF 700 ppm readings is straight forward.
Eg. Week 8 ppm range is 2100-2310. To convert to 500 divide FF number by 7 and then multiply by 5.
(2100/7) X5 = 1500
(2310/7)X5= 1650
Hence, you 1570 reading is right in the middle using 500 scale
Here is a conversion table for the EC & US/CM nerds


You can see on the table under 700 scale the 2100 and to its right under 500 scale 1500. Universally, EC ( electrical conductivity) is 3.0
Play with the unit readout. I suspect the 442 is either EC or UC/Cm

Yes - ppm going IN
Each life stage of cannabis has a target ppm range. You are right the demands of a seedling or young plant in veg is much less than one in full flower. Therefore the ppm of nutrients (as measured by the type of salt is uses to measure ppm) it can utilize increases.

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Can you calibrate your TDS pen. I ask because if you are administering 1/2 doses, I would expect the ppm to be more like 750±. Or, if you are like me when I started I used tablespoon amounts rather than teaspoons.

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Get the connoisseur line if you can find it.

Thank you so much for all this info! I have to go back and read a few times. The 1570 came from the meter on the left. I calibrated it with the 1000 solution which is NaCl.

I got the new meter on right in mail yesterday after I used the other. I fed two plants yesterday (AKs) 1 is a little better then the other. The weaker of the two started getting brownish pistils mid way up a cola on side branch almost as i watched. I made sure wasnt seeing things I really saw it spreading and pHed a gallon water and threw that in. It stopped it, dont know how damaged. 1570 was after the gallon water. First run off was 1961. the others was 1569. These readings were all after the noticed burn pistils. I have been getting habit of saving the RO samples untill all is cleaned up and I can record them.

Now I can say my meter will be calibrated with NaCI it will be 500 scale correct? Use the the chart you gave me for the conversion. I read people saying they fed 1.2 and three and four digit numbers. how do we all know what scale other is using? Is this a dumb question?

I already got the sensi Matti. Ive seen some of your grow dude, very nice!! :smiley:

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Awesome. I believe there stuff is the Bomb.

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Same here using Connie line in soil as per @Hellraiser got 4 in flower and 5 in veg tent plants couldn’t be happier And so am I :+1:

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Yeah, it’s been a tremendous improvement in my plants for sure, and I love the pH perfect technology. Also, I don’t flush at all during the grows anymore, just at the end.

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Your white meter has the same face and buttons as my old meter. It was labeled HoneForest. I recently switched to a bluelab conductivity pen. If a number is used without any reference, you actually don’t know what scale is being used. I believe TDS always refers to 500. However ppm can mean either. That is why EC is often used and is easy to convert to either scale.
The safest thing to do is ask which scale is used in stating ppm. Any article worth reading about recommended ppm for a growth stage should tell what scale is used

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