SOIL pH madness, can't get it down...

[kidane]

Hi there I need help once again... I'm struggling with soil pH.

Some of you guys helped me out with a magnesium problem and thanks to you i got that soil pH was too high and caused the deficiency.
Since then, I fed the ladies with ph'd water between 5,5/6 but after 3 weeks run offs are still very high don't seem to go down at all no matter what.
I have 12 plants, 24th day flowering, they've all been fed the same way, same pots, same size, same strain, but 4 of them have a run off around pH 6.7, 4 other around pH 7 and 4 around pH 7.3.

I made sure the pH meter works properly and is calibrated, so that can be ruled out.
I can't figure out why the soil pH doesn't adjust to a more acidic value. And why there is such a difference between all plants run offs.
Even weirder is that when I started giving them pH 5.5 water the magnesium deficiency was under control within a week or so, and run offs were lower, around 6.5 for almost all plants, but now pH is up again.

Might be helpfull to mention that the tapwater has a pH of 7.5 and is hard (300/400ppm) so i'm using quite a lot of pH down (nitric/phosphoric acid) to get to 5.5/6. Could that extra phosphorus has something to do with this? Also having a cold wave around here and temps have dropped a bit in the grow room, around 17°C lights off, 22 °C lights on.

Magnesium deficency didn't strike back yet but something else came up on a few plants, mostly the top and middle leaves, most likely due to incorrect pH, look at the pictures...

Space: L 35 x W 16 x H 43 inches (40*90*110 cm)
Light: 250 W CFL
Soil mix: 80% Plagron Growmix with perlite, 20% Coco
Strain: OG Kush
Pots: 2L (growing Sea of Green)
Organic Nutrients: Green Buzz Grow and Bloom
Water: Tap water pH'd @ 5.5/6
Temps: 17°C-22°C
Extraction: 74 CFM (126 m³/h)

[Chefbjy]

The pH over seven is still high. Have you thought about using different water?

[Chefbjy]

Idk what's in your water that makes it so high but it may lack another nutrient such as copper or zinc. I couldn't tell you but you water company can tell you. Maybe use a different water source.

[kidane]

Yes i thought about using different water, but i can't afford much so i've been mixing 1/2 tap water 1/2 distilled water to reduce hardness but doesn't seem to make any difference, run offs still high, there's 1.5 difference between pH in and out!
And what do you think of the pictures??? What does it look like? I would just like to know so i can identify it next time it happens.

[Deadhead91]

Idk where you live but Wal-Mart sells RO and/or distilled water for 88cents a gallon best water I've found and it comes perfectly balanced which is good for flushes,

[Canuck147]

Looks to me like a bit of nute lock-out. Cannabis plants can only absorb nutrients between 5.5.- 6.5 pH.
First off I would not use distilled water. It has been boiled and cannot be pHed up or down. Other people would differ on my opinion. I would use rain water before I used distilled.
That being said, get yourself lots of Phed water and flush your plants with three times the pot size. Six litres each pot. Test it of course, but test the last two litres. Then let them dry out.

[Deadhead91]

I reccomend getting that Wal-Mart water I mentioned and just give it a good old flush with that and let it dry out then start the feeds again sounds like you just need a reset button which the flush will do

[kidane]

Should i wait for the soil to dry out before flushing? Just watered today ...

[Deadhead91]

I would wait at least till it's dry to the first knuckle test

[Green75]

You say soil..like actual dirt..or coco blends?

Ph for "soil" 6.5-6
Ph for coco 6

Soil with bad ph high or low.. Give with ph 6 always it's a nice even manageable number.. Always give 6.. Never waver.. Ph in needs to be a constant unchanged number..always
If you try to give a higher or lower ph in you will be very hard pressed to get it back in line without changing it the other way again.

Ph coming out is not that huge of deal and I never ever worry about it...why you ask..cause my ph going in never changes..ever...i have learned over all my time that a constant ph in will always allow my nutrients to be consumed by the plant when it's called for and correct itself within the pot and root system.. Just water and feed with plenty of run off so the ph cycle circle can eventually correct itself within a point or two..


If you are really in soil..then pick a number between 6 & 6.5 ph and stick with it every time you pour something into the medium..

[Chefbjy]

He had problems with pH before to get it to a manageable level with his run off really high. He just got it down to 7.3 so watering with 6 will probably get run off in check. With the water being so high I'm sure if he gets the run off corrected he can begin to water with 6 and should be fine from there. But he had run off over 8 before this.

[Sonnyhad]

Right on bro!

[kidane]

The soil is a mix of 80% dirt (Plagron Grow Mix with perlite) and 20% coco coir.
As Chefbjy said, when I first started checking pH, i had been watering with this tap water for 3 weeks of veg, and the run off was the same as the tap water, pH7.8! . So pH in = pH out = 7.8.
Since then i watered 6 times (twice a week) with ph'd tap water and nutrients every other watering. I kept a record of pH in and out.

Watering 1 (+nuts) pH in = 6.2, pH out = 7
Watering 2 - pH in = 5.8, pH out = 6.8
Watering 3 (+nuts) - pH in = 5.5, pH out = 6.6
Watering 4 - pH in = 5.8, pH out = 6.8
Watering 5 (+nuts) - pH in = 5.8, pH out = 8 plants @6.8 / 4 plants @7.2
Watering 6 - pH in = 5.7, pH out = 4 plants @6.7 / 4plants @7 / 4 plants @7.3

Watering 5 and 6 was mixed 50% tap with 50% distilled water.
All plants get each time the same amount of the same water so i don't understand why they have different values and why it's going up again after it went down.
Out of control!
Let's see after flushing.

[Green75]

Does not matter what the different ph levels between the plants are.. The medium inside the pot will always vary from time to time depending on what kind of additives you are giving... Keep the ph in.. a constant always.. When you feed or water... the medium gets soaked.. But before that the medium is dry to damp..more air within the pot the damp medium at bottom or the dry at top will both have different ph levels in the medium.... The ph level of the water or feed will change a few times as it goes through the whole pot and drains out.. keeping a constant ph in is just a simple math must.. Keep your constant..!! It will correct ITSELF.. In time

Always ph anything you give... That's always been number one rule.. in every book... on every bottle

I like to ramble..so take it or leave it

[Canuck147]

Glad to hear I'm not the only one that doesn't check the pH in the runoff. Never have.

[Potted]

Guilty as charged, l find no need! Lol

[Canuck147]

Yeah, it's just going down the sink anyways.

[Trimmings426]

I always check my ph run off, so does it really not matter about the run off? I myself am not sure but if it doesn't matter it's something I will stop checking thanks.

[Chefbjy]

I think it matters too Deadhead. I don't agree that it will always correct itself didn't happen my first grow any way. I was running really low towards the end of flowering and ran into deficiency. That's a good link shows how nutrients are absorbed at different levels some higher some lower. When using liquid nutes it's a good idea. Though I don't check it every single time either.

[DingusKhan]

I think Green and Canuck have gotten to where they don't check their run off because they have gotten their watering process down, and they don't have to check it anymore. Yes, your run off pH matters, but if it's always right, you don't have to check it all the time.

What I think they are suggesting is that if you stabilize your input: meaning adjust the pH your water going in the same way every time, and you water the correct amount, and let her dry off correctly between waterings and feedings, your run off pH will stabilize, and you won't have to chase it around anymore.

[D.A.A.S.69]

Right DingusKhan, having the right stuff in your coco or soil makes it even easier for your ph to adjust.

[MadMike]

I've struggled with low pH in the past - growing in coco. Last crop it plummeted to 4.0! It took a long time to get it back up. Caveat: I am not recommending what I did to try to fix it. Just sharing a newbie experience.

I ended up watering with 8.0 for a couple of weeks, with heavy runoff both water and nutes and it finally started getting into the 5.5-6.0 range. I was stunned by how long it took. I had pretty bad Mg deficiency in one of the plants and less so in others.

So this grow I have been working to catch it before it goes off the rails. I've had it a touch high, and a touch low so I've been fluctuation on my pH of water/nutes to keep it in range: 6.0-6.2 to raise - 5-4.5 to lower. Not optimum and maybe next grow I can dial it in to 6.0 everytime. To dream... I do however champion the others who have said check your runoff. I check it every watering to see how it's moving. It doesn't take long to do and I'm usually waiting to catch the runoff any way. I also treat all my plants the same way (though with different strains) and they all read a little different. I think that's normal.

Also, I use tap that tests at 8.0 that comes straight from an aquifer. So I use a lot of pH down.

Your not alone in having pH problems. You'll get it under control and learn a ton for the next round.

[kidane]

Mornin' everyone and thank you so much for your interest!

As DingusKahn pointed out, I obviously don't have the experience and the knowledge to just pH in and forget. My plants are telling me i've been doing it wrong.
I'm tanking knowledge for my next crop, and I'm really looking forward to put it into practice but I'm also quite worried about this crop.

They still have 5 weeks to go before harvest and I really want to do everything i can to improve the situation.

I'm still waiting for the soil to completely dry out but it's worsening every day and it's spreading downward. I posted a few pictures just for the sake of documenting.

Tomorrow i'll be able to flush them as some of you recommended but i have 2 last questions before flushing them.

• Should i follow Nebula's tutorial about flushing sick plants and flush with 3 times pot volume of 1/4 nutrient mix and a last batch ofregular strength nutrients at the end or just plain water and start feeding again after it dried out?
• Should i remove sickest fan leaves at the top of the plants?

[D.A.A.S.69]

Morning kidane, if you are going to flush, what are you waiting for your soil to dry for ? Are you sure you got to flush? I ain't read your post good ,sorry I'm fixing to.

[D.A.A.S.69]

After reading it, your runoff ain't even out bad, flushing ain't good ,unless you just got to, if she was mine, I would just try feeding at high5s low 6ph, an see if that want straighten your runoff out pretty soon, without flushing.
But if you do think you want to flush, then yes do as Nebula says, quarter strength an then full . Sounds like you know what's going on, she's gonna be ok, you got some time, .

[kidane]

Hi DAAS, i'm not sure about anything right now, so i rely heavily on given advice, which is : it looks like nutes lock out, flush with ph'd water as soon as the soil is dry enough... but i'm still open to new ideas.

[kidane]

And actually i really don't know what's going on... All i know is something's not right.
Maybe i'll flush the sickest plants and do as you said for the less sick ones so i can compare how they react...
I'll sleep on that and see tomorrow

[kidane]

Hi, Nitrogen deficiency would show on bottom leaves first, right? Or can it start from the top too?
Here it's spreading downward, top leaves were affected first and bottom leaves are still fine.
I stopped the grow nutrients last feeding (4th week of flowering, just after stretch was over) was it too early?

[Waltermelon]

You're about right on (maybe a tad early) cutting nitrogen to my schedule. I normally start to step it down each week through the 4th or 5th week of flower.

[Sonnyhad]

If you are watering at 6.0 and getting plenty of run off, say 1 gallon for a 5 gallon planter and have some major ph problems, I would take that sucker to a drain somewhere and water slowly letting it run through all those roots you are imagining right now for about 5 minutes, and I'd be good to go. Now the plant, that's another story. It may look like you killed it ,but in a couple days you'll likely see a huge difference. But that's me. And the when that dries up some feed as usual.

[DingusKhan]

If you flush, it always helps to follow Nebula. It might also help to add some enzyme root cleaner, oxygenate your water, and add beneficial bacteria.

When your done, or to speed up drying before you start flushing, set your smart pots on top of some airstones and blow bubbles up their butts. If not in smart pots, poke the ends of the air tubing up into the drain holes a few inches and pump in air.