Soil PH too low can anyone help?

I’m growing AK-47 for my first grow, everything was ok till about two weeks ago when the bottom leaves started turning yellow. I purchased a soil ph tester (aqua lab) and found the ph to be too low. It measured at 5.2 ph. I usually water at 5.9-6.0 ph. She’s planted in foxfarm coco loco, according to Foxfarm coco loco should be treated like regular soil. It’s emended with bat guano and all that good stuff btw. At the time I tested the soil ph she was in a 3 gallon fabric pot, so I decided to plant her in a 5 gallon fabric pot with new coco loco soil. She still growing but her leaves keep turning yellow. I started watering at 7ph 0 ppm no nutrients. Btw I checked the soil PH again and it’s now at 5.4 ph. What’s the best way that I can quickly bring the ph up? image image


How about taking a runoff TDS? Your soil could be low in salts as well. You have all kinds of defs going on other than N.

Clear signs you need to be adding cal mag too.

If you want to bring up the PH of the media, a top dressing of dolomite lime would help.


The other day I was reading the fact sheet on Blue Cow Organics Activated Compost. A product I use to amend my FF OF soil . It is supposed to have a ph of 7.7

I did this morning, 5.6 ph. I always add calmag but not the last two times I watered… thanks for the reply guys

Not PH but TDS

My tds meter doesn’t even read it cause there’s so much. But it was the same reading when I first germinated. I would check it just to check it.

Look up how to do a ‘slurry test’. Then look up doing a runoff test.

So I YouTubed and googled slurry test. I took two ounces of dirt (two inch deep) and two ounces of water (RO/DI). Mixed both and I let it sit for 10 minutes. Here are my results…

image image

My PH is definitely too low but I’m not too sure about the TDS.

The slurry test tells you it’s time to supplement and your PH is actually not bad. I would let it ride and work on developing a solid feeding plan.

I like GH for it’s economy and it’s ease of use. Regardless; don’t mix above around 800 ppm and keep PH at 6.0 nominal and alternate between feeding and watering. When you water; use a max dose of cal mag: don’t add to nutrient solution as it will take the TDS up too high and risk burning plant.

I would dose with cal mag first, next day feed, and continue feed until runoff TDS approaches or exceeds input TDS. Maintain feeding for 7 days, daily, before doing water w/cal mag. Just measure PH and TDS of runoff water: try to get 10% or so runoff and measure only the last 100 ml or so. This would be the correct way to feed soilless. Which is where you are at now based on slurry test.

Once salt level is where it should be you can start a feed/water/feed/water cycle which is beneficial for coco to help exhaust waste salts.

If you need help with the supplements, tag me.

Hey man thank you so much for your help! But just to clarify this is the medium that I’m using.

1 Like

Yeah I know: that is now depleted and you are essentially running coco: so soilless. Treat it as soilless and use grow schedule for coco.

Also in coco you need to feed or water daily.

Ok just making sure lol, it make sense now!
These are the nutes I initially purchased for my grow.

1 Like

Those will work. Like I said: find the schedule on the FF website and follow that. Except! Do not use their TDS numbers. They are, first of all on the 700 scale and still too high IMO. (backed by many many other growers) Run in veg around 750 ppm and after salt levels come up in the runoff you can start on a f/w/f/w schedule.

Awesome! Sounds like a plan. Thank you again!

1 Like

She bounced back pretty fast! I’m just a bit concerned about mold…

The plants bounced back but now the leaves are starting to curl up. I have been feeding at 650-700 ppm and have done a slurry test and it resulted at 80 ppm at a 5.8 ph. I’m at my wits end with coco and am considering replanting with regular cannabis soil. Is it too late? I thought this particular coco was like regular soil but obviously I’m wrong.

What are the temps? That looks like heat stress.

You could pot up into fresh soil but will have to supplement regardless.

Right now that’s not the biggest concern. You will have to figure out how to get it below 45% in flower though.