Need help with EC management

Hi everyone!

I’ve recently been left with 5 mid-late veg, feminized AK47’s as my housemate moved out rather abruptly last week. He was managing the grow, I invested the money for the setup, we were splitting the harvest (we had just harvested our first autoflower crop of GSC’s 2 weeks ago).

While I was watching from the sidelines and reading up quite a bit on basic growing guides, my friend was doing all the work and I wasn’t actively managing anything. For example, I’d read a bunch about managing EC and how this was an important factor in producing healthy plants.

His feed schedule and approach to measuring EC had always seemed a bit off to me - he was only watering in coco once every 2-3 days - and the plants all appeared to have some form of nutrient problems. One I nicknamed The Leopard because it had a bunch of pale yellow leaves with dark spots, and another was pale green.

Anyway, I took them over 5 days ago and after the first feed the EC was way too high - up in the 5s, 6s and 7s in some cases, indicating nutrient lockout. I double checked EC meter was calibrated correctly and it is, and it’s a Bluelab EC meter so it’s good quality, so no problems there. I flushed the plants, increased fertigation frequency, and dialed in my EC inflow, and while every 2-3 feeds it reads within the +300 range, it continues to blow out daily, up into the high 2s/low 3s.

I’m so confused, and although the plants appear to be pretty healthy, I’m worried they are going to take a turn for the worse.

I’ve read so many guides on how to manage EC, but I really need an expert to tell me the exact formula for managing EC inflow. Most guides, and my feed chart, says it needs to be between 1.1 - 2 depending on the stage, but then I’ve read guides saying things like

"EC of drained water – original EC = excess EC

Original EC – excess EC = EC value for the next watering"

Should I be mixing up a nutrient solution with EC between 1.1 - 2 every time, or should it be lowered/increased based on the reading of the run-off from the previous feed?

Thank you so much!

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Welcome to the forum @Hey_Hey_Smoke_Weed_Everyday , you will find lots of help here.
What are you using for nutrients?
What are your pH levels?

Most conversations here speak in terms of PPMs (parts per million) and not the actual EC reading. There are some who can speak in those terms but a lot of us just use the ppm readings.


I can’t help, I don’t know the answer but going to stick around for the answer. By the way welcome and thanks for posting your question.

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Thanks! I have been reading here for a while, it’s already been helpful.

I’m using Greenplanet GP3 nutes and my PH levels have been consistently between 6-6.3. Not sure if you’re familar with GP3, but if it helps, I have dropped back the ratios to:

  • Grow 0.75ml/litre
  • Micro 0.75/litre
  • Bloom 0.5/litre
  • CalMag - 0.75/litre

EC is consistently around 1.1-1.3 on the inflow. Not sure if any of that helps.

Your original post said you are in coco, so your pH needs to be 5.5 to 5.8
You can water every day and water til you get 10 to 20 % runoff. Test the run off for ec and pH.
Coco will naturally raise the pH so the runoff will be higher than 5.8. Just watch your plants new growth for issues. Coco is actually my preferred media now.
Those EC levels seem fine.

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Thanks for the help. My runoff readings are sometimes the very high end of that chart, around 3.2/1600 ppm. Is that too high, as it’s +1.8/900ppm over my inflow reading?

I think I may be overreacting a little because the new growth all appears to be healthy. Just don’t want my crop going down the toilet.

The plant itself is the best indicator. Nutrient burn will show up on the leaf tips. They will turn yellow then brown quickly if you overfeed. Get the pH down to 5.8 and maybe next watering flush them out by watering till you get the ec down some. Its always going to be higher than the incoming water. Just dont want it too high.

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