Coco run off ec (again)

[kronic420]

So I’m not new to coco been using it along time with mostly great results but had a few issues last grow, I first thought it was under feeding but now 100% think it was over feeding and I ended up with a toxicity issue. So this grow with the same cuts I thought I’d bring myself up to speed with trying to read the run off ec (something I’d never done before).

The story so far

 

In full veg hand watering once a day I got up to 1.6 ec and run off was coming out 1.5 1.6 ec so thought I was sweet.

 

Plants go into flower tent with automated watering system and within a week need watering twice a day so carry on at 1.6

 

1 week later and I check the run off and we are at 2.0 so I add a 3rd watering and bring feed down to 1.4

 

Another week later and run off ec has dropped but only to 1.7 so I flush with the 1.4 feed until the run off is coming out at 1.4/5 and within a few days we are back up to 1.7

 

So again add another feed but during lights off this time and drop feed to 1.2 (iv never fed this low in flower) and here we are another week later and run off ec is 1.5.

I’m getting at least 30% run off and we are at 4 feeds per day, plants have looked great the whole time iv been messing around with them but what ever ec is going in it always ends up coming out 0.3 higher in the run off, it’s doing my head in now and doesn’t make sense to me as surely the ec should of dropped lower now I’m at 1.2 , everything is clean and I’m checking the ec as the run off is coming out the pots so no chance of a false reading.

 

Any help or thoughts from the coco experts on here would be great. 
 

[Hempire Road]

I think those high dose ec's in early veg you have been administering, are still absorbed at high levels in the medium. I would burn my plants to death if I had 1.5 ec in veg . Try and flush/leech through with a 0.8 ec diluted feed. Have you got any pics of the plants? 

[kronic420]

@Hempire Road 1.6 isn’t crazy high for my water as it’s really hard with crappy ph and when I was up to 1.6 I’m talking fully grown vegged plants with a completely full scroged canopy in a 1 meter tent so not small plants, I worked up from 1.0 to 1.6 in veg as plants got bigger and hungrier ,the run off ec was saying give them more. 

[Lemons&Diesel]

This is perfectly normal OP. Because of the way coco works and its ion exchange capacity, the ec of the rootzone with coco is always higher than whatever strength feed you last put into it. Its all to do with the way coco locks onto calcium, magnesium and potassium ions as the plant takes up water, then releases them again with the next feed as you put more water through. Honestly imho, youre just giving yourself an unnecessary headache when you start worrying about run off ec in coco. Just make sure youre feeding at the correct ec, and the medium never dries out, and if the plants look healthy, and theres no signs of anything starting to go wrong, no need to change anything. I havent tested my run off ec in years and its just been one less thing to worry about.

Edited June 2, 2021 by Lemons&Diesel

[InMyPocket]

Do you add anything else to the coco that could be washing out too such as charge?

[kronic420]

@Lemons&Diesel i appreciate your comment and iv never tested run off before but I’m wanting to up my game and reading the run off is the way to do it IMO.

 

@InMyPocket just straight up canna coco , using Dutch pro A and B and hesi supervit 

 

@GSZZ I’d definitely be interested in what you have to say about this if you have the time.

Edited June 2, 2021 by kronic420

[catweazle1]

Kronic420. Your ec is rising because of evaporation. This is dictated by humidity and temperature. My base water is 0.6ec and I top out at 1.2 - 1.4. The runoff ec tells you the maximum nutes your plants are being fed, so if they are coming out a bit high, lower your ingoing ec 0.2-0.3. If you want 1.6ec, drop the feed ec incrementally until it comes out at that. The idea is to adapt the ingoing ec until the runoff ec is where you want it. Personally, 1.2ec ingoing should be fine. 

Edited June 2, 2021 by catweazle1

[GSZZ]

24 minutes ago, kronic420 said:

@GSZZ I’d definitely be interested in what you have to say about this if you have the time.

 

@catweazle1 has hit the nail on the head. Its not just your plants drinking that effect the rate at which your medium dries up - if the RHis low, temps are high or you've got lots of air flow under the canopy these are all things that will increase the dry back and thus increase EC concentration in the pot.

[Hempire Road]

Just now, GSZZ said:

 

@catweazle1 has hit the nail on the head. Its not just your plants drinking that effect the rate at which your medium dries up - if the RHis low, temps are high or you've got lots of air flow under the canopy these are all things that will increase the dry back and thus increase EC concentration in the pot.

So in other words, an unbalanced transpiration rate causes the ec to spike? From the Nutrients not processing properly? 

[GSZZ]

@Hempire Road Plant nutrients are made from salts, so as the medium dries up (by whatever means) and the salt loses its vessel of water it turns back into a solid. The next time you add water it redissolves the solid and increases the concentration inside of the pot/run off - its also these salt solids etc that actually cause plant burning, as the salt acts like a dessicant and actually pulls water from the plant back into the root zone, so what you're actually seeing is dehydration rather than "burning".

 

Thats why getting the moisture content and EC input correct is so important, cos otherwise you end up with problems like high run off ec and burning. Its not neccesarily that things aren't being "processed" correctly its just that the environment, EC, moisture content or all three are out of whack with each other.

 

IE high EC and low humidity = asking for pain.

 

[Keye]

3 minutes ago, GSZZ said:

as the salt acts like a dessicant and actually pulls water from the plant back into the root zone, so what you're actually seeing is dehydration rather than "burning".

 

 

Really interesting! Bonza.

[Hempire Road]

Higher concentrations of nutrient salts crystallising on the root tips if you let the pot dry out too much or let the moisture exchange turnover get too fast. Thanks @GSZZ. Best to have a low EC and multifeed in coco to have every area covered.

[kronic420]

@catweazle1 @GSZZ great posts thank you both, the science is really interesting.

 

My base water goes between 600-700 it changes a little month to month, so iv read evaporation can cause ec to spike hence why I added the extra irrigation’s as well as dropping the ec at the same time as I thought that’s what might be happening.

 

I actually battle with high humidity most of the time and higher temps as I’m in the loft I also do have a lot of airflow under the canopy and on previous grows have had dried salts on the surface on coco even though it’s never dried out noticeably to the eye .

 

Iv now added a 5th watering during lights on and kept ec the same @ 1.2 if this still doesn’t bring ec down then should I be adding a 6th 7th 8th feed or bring ec down lower (anything lower than 1.2 seems crazy to what I’m used to) adding more feeds is not a problem as it all automated it just takes a while to get the timing of the feeds right.

 

@Keye @Hempire Road it’s really interesting stuff and I love learning about it.

 

Edited June 2, 2021 by kronic420

[GSZZ]

Just now, kronic420 said:

Iv now added a 5th watering during lights on and kept ec the same @ 1.2 if this still doesn’t bring ec down then should I be adding a 6th 7th 8th feed or bring ec down lower (anything lower than 1.2 seems crazy to what I’m used to) adding more feeds is not a problem as it all automated it just takes a while to get the timing of the feeds right.

 

As long as you've got adequate drainage you should be alright, a little higher EC out isn't anything really to worry about. On your next cycle maybe try using a pot a touch larger, it'll hold more water, less dry back swings and less EC swings inside of the pot and all with less irrigation.

[catweazle1]

27 minutes ago, Hempire Road said:

Higher concentrations of nutrient salts crystallising on the root tips if you let the pot dry out too much or let the moisture exchange turnover get too fast. Thanks @GSZZ. Best to have a low EC and multifeed in coco to have every area covered.

Your watering frequency is dictated by how high the runoff ec goes from your target. If the conditions are causing large spikes, then water more often. Unless you nail down the RH and Temp, you will have to adapt your watering frequency to compensate on a regular basis. Consider runoff ec to be what you are actually feeding the plants and not your ingoing ec. Your coco moisture content should be more or less constant i.e wet when fully established. Look at watering as restoring your target runoff ec.