Coco coir pH issue

During my last grow, I noticed a few signs of nutrient lock out on my BC blueberry plants. After measuring the run off pH which was 4.9 after watering at 6.0, I came to the conclusion that the coco coir was becoming acidic. After harvest, I decided to treat the 10 gal of coco coir that I had with 10 tbsp of fine dolomite lime. Now, after about 2 weeks of transplanting them into the 5 gal pots with dolomite lime treated coco coir, I'm starting to see more lock out symptoms. I water at 6.0 and run off comes out as 7.3. I should have used less lime I suppose, but it's too late now.
Has anyone ever been in this situation before? Is there anything I can do for the high pH in my coco coir asides from watering at 5.5?

What type of coco are you using?i use the ph drops and have never had a problem...also you have to use coco specific nutrients(h&g) as it is designed for special properties coco possess...

I use Canna with Canna coco A+B nutes and botanicare cal-mag. Last grow, my pH meter was off for a while and realized I was actually was feeding in the 5.0 range instead of 5.8 when I tested with pH drops color test. It turned red instead of yellow. I know run off is not the true pH of the coir but if I get a 5.5 reading in the run off after flushing with 6.5 water, the coir is still too acidic. So I put dolomite lime, probably put too much and now I'm looking for a way to fix this but there is no info out there on what if anything, can counteract the dolomite.

I use AN coco ph perfect. I dont care if its noob nutrient or if lots of people hate it because I threw away my ph meter 3 years ago. I think I over thought ph anyway and often got stuck in an overcorrecting loop, so I was usually the problem or I was blaming other stuff on the ph. Ive never used canna, but they have a good reputation, so Im going to go out on a limb here and say your problem probably isnt (or initially wasnt) ph, but its showing in a manner that looks like ph. Go down the list, check for bugs, root zone temp, feeding strength, mg coco treated, overwater, underwater, room temp, look your water source, then come back to looking at ph of the coco. If you are still suspicious then buy new coco from a new place and try again.

So I take it that you are recycling your coco?

Yes, this is like the 4th grow with the same stuff...the problem isn`t that bad. The plants are healthy otherwise and are coming along well.

Smootherpete said:

View attachment 3330949
Yes, this is like the 4th grow with the same stuff...the problem isn`t that bad. The plants are healthy otherwise and are coming along well.

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I don't ever check run-off ph anymore.
When I WAS re-using coco, I found that the 3rd run would have problems/deficiencies, and not worth it. Second run was always really good.
I don't re-use at all anymore though.

It seems like some may have missed the part that you treated your coco with dolomite lime. That's exactly where your ph issue is coming from as you seem to already know.

If it were me and the plants were in veg, I would rip that part of the root ball out. Obviously you've got nugs on your plants, so too late for that.

Are you multi feeding or once a day feeding? Multi feeding might help you out with your issue. I don't think you can really do anything to 'wash' the lime out of your mix but the multi feed should help keep ph in check. I would stop giving them the Botanicare CalMag also.

You are keeping your coco moist/wet right? Never drying out?


Your girls look happy from here, good work otherwise. How long till chop?

Why no calmag? I water every 48 hours, they don't have time to dry out. Another 5 weeks until harvest, I hope they will make it there ok, here are some more picutres...

Eventually coco's affinity for calcium is filled and it is readily available for the plant, also coco specific nutes already have extra calcium in them then you add cal-mag on top of limed coco and you have to much carbonates in your medium which buffers it to the high side. On your 4th run I would say it's filled to capacity plus.