Ph drifting, soil.

[EarLobe]

Afternoon all, wouldn't normally ask about this but wondered if anyone has had this problem before. 

Got 2 plants, 1st one is a Double Black by G13 and second is Blue Cindy by the same.

Both are in the exact same soil, been watered the same and have been roughly the same distance from the light throughout the grow but the soil didn't get the f*cking message...

Both have been growing fine and I've been checking the run off on both since I started feeding the bottle and the blue Cindy is just not having any of it.

 

Ph in has been 6.5 and around 800-1000 ppm depending on the run off.

Double black ph out is 6.5 but the Blue Cindy has crept up to 7.2 in the past week or so and it doesn't want to come back down at all. A few of the bottom leaves and middle leaves are starting to show signs of this now and I just wonder what the best solution to bring the ph down and stop it creeping back up?

 

Double Black.

 

Blue Cindy

[Slippy One]

Soil is a ph buffer, you’re probably over/under watering or your tap water has the cap/mag ratio out of whack. If you’re checking the ph this much you might as well use coco coir as it will eliminate and overwatering issues. 

[MindSoup]

Yeah the only thing I could think of is if the soil hasn't been buffered properly, but it must be if two plants are growing from the same bag. So as Slippy says it's probably something else. Winters approaching, could you have cold roots? Cold roots don't drink as much, so then the soil gets too wet, which makes the roots drinking even less and thus the viscous cycle begins. Keep the soil too wet and cold for too long and you'll have lockouts etc. maybe the one that's struggling is by the intake so is colder than the rest, seem that quite a few times. I guess it might also cause the run off PH to rise but I don't have a deep enough understanding to confirm that. 

Edited Thursday at 17:13 by MindSoup

[EarLobe]

@Slippy One this is why it's doing my head in. I do have relatively hard water. Ca is 84 and Mg is 4. I use Mono Mg and do allow run off and to make sure nothing builds up. It's 240ppm from the tap. Pretty sure I need to supplement Mg at this rate... I do the same with both plants. The other one is fine, I don't think I have it in me to start filtering water for a plant 

 

@MindSoup The roots have cooled down but nothing below 23 at the minute. They're taking an easy 3L of water a day at the minute and in fabric pots and nothing is sat in water. Humidity around 50 and daytime temps about 26. I have lowered this recently.

 

E2A: it probably needs more feed. If it's using up all the nutrients it's surely only going to have the 7.4 tap water left until next feed? Sound logical lol?

Edited Thursday at 17:34 by EarLobe
Stoner moment.

[FlowerChild420]

I highly doubt your issue is ph growing in compost. I've never heard of anyone checking pH and run off ec in compost, not sure if the readings you get are anywhere near accurate.

[EarLobe]

@FlowerChild420 if I'm feeding liquid nutrients in water I check run off and ph and ec at every feed. I have too much go wrong in the past not to keep a close eye on everything.

[Shumroom]

47 minutes ago, Slippy One said:

If you’re checking the ph this much you might as well use coco coir as it will eliminate and overwatering issues. 

This ^^^^^^^^^^^^

[EarLobe]

That's the plan for the next grow. Just trying to fix this one for now.

Edited Thursday at 17:53 by EarLobe

[Shumroom]

First things first,

whenever you see an issue you need to start with the basics,

what's the environment like?

 

 

I'm sure you're aware that different plants will have slightly different feed and water requirements.

 

With that in mind,

do you just routinely water them at the same time,

or do you wait until each has dried back somewhat and water separately?

 

 

As hinted at by others,

doing this testing when using compost(active) could actually be misleading.

 

Plus,

repeatedly watering compost to run off is not a good idea,

as it retains more water and less oxygen than is ideal for plant roots and soil life.

 

What nutrients are you using?

 

How much are you feeding them?

 

Atb

 

 

 

[EarLobe]

Thanks @Shumroom

 

Environment is good. Was 28c and 55% but I've let it drop down to 26/27 but I noticed a little spotting before this.

 

I usually only check the ppm of the run off to make sure I'm not getting salt build up but since the spotting on this started I've been checking the ph as well.

 

After 24 hours they're both light, not bone dry but light enough to take a full watering can each. There's little to no difference in the water intake at the minute.

I've also got the blue lab soil ph pen, the vampire killing stake, giving me the same reading. 6.5 in one, 7.2 in the other.

 

Plant magic soil supreme, plant magic grow and now bloom and at most 3ml/l. Around 900ppm most feeds. Haven't started the pk booster until I sort the ph out in this freaking soil.

[Slippy One]

Spotting is often an air flow exchange issue, or lack thereof, and 28° causes some issues for my strains. 25-26°C gives me better results. My temp probe is under the canopy so your mileage may vary

Edited 23 hours ago by Slippy One

[ControlLED]

top dressing your soil could help if you have more space in your pots as you may have run out of buffers? i would try a flush with a lower ph to "dilute" the ph down back to where you want it to be  

[EarLobe]

Thanks @ControlLED. I've top dressed the soil with the same plant magic, about 2 inches of extra soil and, all being well, that has near immediately brought the PH down to 6.6 and I think I will keep the ph slightly lower in the feed to the end to hopefully stop the drift again.

 

Thanks for the input all. The headache continues

 

[Slippy One]

Don't forget a nice big bag of coco for the next run!  

 

[EarLobe]

Will the hard water be a problem with coco? I've been pricing up an ro filter to chuck in the groom incase I might need it.

Absolutely love to over complicate everything.