Can someone school me on EC/TDS

Howdy Y’all!
Not sure if I posted this in the proper place, please move if not but I need some edjumakatin’
A couple weeks ago on my SSSC G&S post
it was mentioned that my EC levels were way too high
Up until that point I had only one “guide” to use, which was this one from Fox Farms

It was at that time that I was given this EC chart by @SuperSativaSeedClub-David.

As you can see there is a significant difference in the EC levels !
I started out playing with the EC levels because I decided to try my first DWC bucket grow a couple months ago.
It’s been going very well, so much so that I will most likely switch over to all DWC this fall.
When I was having leaf yellowing issues in soil, (Mendel Below) a friend recommended flushing with RO water and measuring runoff, which I did. With that said I don’t have a clue what the readings mean or how to use them in real life to diagnose issues or keep my grows where they need to be , in both Hydro and Soil.

I’m hoping that by learning what these readings mean I can become a better grower and if any major issues arise I can sorta nip them in the bud. Hopefully this post will help others who may need it as well.

Here’s 2 examples I have and would like to know how it all breaks down, if possible.
In both examples the catch pans and measuring tools were cleaned and sanitized in hopes of not skewing the readings.
Example #1-
Is a healthy plant, with no known issues, that was at day #38 from sprout. This is one of my SSSC AK47 x Karels Haze x Low Ryder G&S.

Ingoing mix Foop/RO water :
PH 6.4
EC 1.0
PPM5 480
PPM7 680
Watered very slowly with 1.25qt(40oz)
Runoff Specs:
Amount in 1.25qt (40oz) , amount out 12oz
Specs
PH 6.1
EC 1.4
PPM5 710
PPM7 1000
Example #2-
This is a Brother Mendel- Dark Jedi on Day#63 which had a lot of yellowing leaves and why I used straight RO water as a baseline. It is also a Foop plant.
It is now doing much better but not sure why the flush maybe ? It had much higher output than what I was putting in, so I’m guessing that it was over fed ?

Ingoing mix:
Used 4 qts of RO water PH’d to 6.3 -EC/TDS 0.0/0000 500 and 700 scale.
Measured run off
Specs:
PH 5.4
EC 1.1
PPM5 530
PPM7 750
Amount captured right around 22oz

I use a blue lab TDS pen and have EC, PPM5, PPM7 and temperature readings available with this pen. I use an Apera PH20, I’ve been calibrating the Apera once a month
I get confused by the two ppm measurements 5 and 7 . I record them both anyways LOL

Thanks in advance for any help or reference material you can provide when using runoff as a diagnostic tool.

 

[Simplicio]

The second chart above is almost identical to what I use in hydro.
Right now a couple of 9 week flowering autos are at about EC=1.3
There is a delicate interplay between food and light, and the more light given the more food eaten.

Your hydro plant looks good, but that soil plant is getting too much light for the food given.
I'd cut back on light for a few days and see what happens, and then it will probably need more food.

Growing opinions can vary greatly, and mine is just an opinion.

 

[Lil Dab]

I get confused by the two ppm measurements 5 and 7

they are the same thing. TDS is a conversion of EC. I use hanna 500. my EC meter has TDS factor set to .5

 

[Pigskin Fanboy]

The second chart above is almost identical to what I use in hydro.
Right now a couple of 9 week flowering autos are at about EC=1.3
There is a delicate interplay between food and light, and the more light given the more food eaten.

Your hydro plant looks good, but that soil plant is getting too much light for the food given.
I'd cut back on light for a few days and see what happens, and then it will probably need more food.

Growing opinions can vary greatly, and mine is just an opinion.

Both of those are in soil but the SSSC is under a MH FC-E3000 and the Mendel is under a MH FC-E4800. I’m the same 4x8 tent.
When I took the photo it was just sitting on top of a 5 gallon bucket so I could get it at eye level while taking the photo and watering. I try to garden from a chair as much as possible :smoking:
I started using that second chart also, as soon as it was shared, even for my DWC. Seems to be working though. That thing has been a beast from day 1.
Another question that just came to mind…. Let’s say you make your mixture and your EC reading is low and you are using a multi-part nutrient line like FF, how do you decide which component to use to try and bring the EC up ?
If I’m over I have been using RO water to bring it down and rechecking PH but not sure on raising it, other than adding more nutrients and trying to choose one to use to do that with.

 

[JP1]

Tds is ppm. And it's basically x2 and stick a decimal point in there. 500 scale is the usual for cannabis. So 500ppm is 1.0 ec, 600ppm is 1.2ec, 700ppm is 1.4ec, 1000ppm is 2.0ec ect...

 

[Pigskin Fanboy]

they are the same thing. TDS is a conversion of EC. I use hanna 500. my EC meter has TDS factor set to .5

I think what confuses me was when using the FF schedule above, I’d see 1750-2100ppm in week 4 but is that using the 500 scale or 700 ?

 

[Pigskin Fanboy]

Tds is ppm. And it's basically x2 and stick a decimal point in there. 500 scale is the usual for cannabis. So 500ppm is 1.0 ec, 600ppm is 1.2ec, 700ppm is 1.4ec, 1000ppm is 2.0ec ect...

Ok that did answer one question then. Thank you. I kept thinking which one are they wanting me to use LOL

 

[JP1]

Both of those are in soil but the SSSC is under a MH FC-E3000 and the Mendel is under a MH FC-E4800. I’m the same 4x8 tent.
When I took the photo it was just sitting on top of a 5 gallon bucket so I could get it at eye level while taking the photo and watering. I try to garden from a chair as much as possible :smoking:
I started using that second chart also, as soon as it was shared, even for my DWC. Seems to be working though. That thing has been a beast from day 1.
Another question that just came to mind…. Let’s say you make your mixture and your EC reading is low and you are using a multi-part nutrient line like FF, how do you decide which component to use to try and bring the EC up ?
If I’m over I have been using RO water to bring it down and rechecking PH but not sure on raising it, other than adding more nutrients and trying to choose one to use to do that with.

Make a gallon that's double strength and mix it in, in smaller amounts and recheck just like you water down

 

[Pigskin Fanboy]

Make a gallon that's double strength and mix it in, in smaller amounts and recheck just like you water down

Good deal then, that makes sense. Since it will be equally mixed in the proper ratios. Thank you ! I’m probably over-complicating it but my mind has a way of going off on a tangent at times Way off LOL

 

[JP1]

I think what confuses me was when using the FF schedule above, I’d see 1750-2100ppm in week 4 but is that using the 500 scale or 700 ?

That's 700 scale. Take the ec x 700 and that'll give you 700 scale.