pH 5.2 vs 6.2?

sativo · Jul 6, 2013

Hello

I have a question that I was hoping one of you more experienced growers might be able to answer for me. The question is: Is it possible to get better yields setting pH to 5.2 as opposed to 6.2? It appears that the plants could benefit from the extra phosphorus that is to be had here, as opposed to 6.2 where phosphorus appears to be a bit locked out of the picture. Thanks in advance everyone :tiphat:

Nevermind, everybody, I got it, thank you. :tiphat:

Hempsmoke · Jul 6, 2013

Actually i think 5.2 is a bit low and would reccomend at least a ph of 5.5.
And one of the great benefits of coco is that you can let the ph swing between 5.5 and 6.2 and if you look at the plants carefully you will recognize which ph they like the most.
A ph of 5.8-5.9 works for me pretty nice, but it depends on the conditions and the genetics i guess.

teemu shalanie · Jul 7, 2013

I rock 5.8 for coco

tS

RedBeardy5 · Jul 7, 2013

a ph of 5.2 will cause the leaves to start curving.

hereigrow · Jul 8, 2013

I think it depends if your drain to waste or recirculating res...in any case 5.2 will cause problems ime. Dtw I alternate 5.5 and 5.8 looosely. 5.5 for cal and 5.8 to access mag. Recerculating I would let the ph swing from 5.5 to 6.0 and reset at 5.5 with every fresh res...

sativo · Jul 8, 2013

Wow, so much I did not know. So, 5.8? Really? I thought this was not a good range, specifically because of the low magnesium levels.

hereigrow · Jul 8, 2013

Your welcome

Xanode · Dec 22, 2016

so according to the very last graph, there's a cal/mag spike right at 5.2, as well as everything else, only thing a little low is manganese

I've been running 5.2 with canna ab, and RO water on a test clone, which comes out at 5.2 without PHing it upon making up the mix. The little plant is doing great, not a single sign of any cal/mag issues

RB56 · Dec 22, 2016

I just came out of a situation where I was accidentally feeding at 5.2 for a month or so. I was doing improvements to the room, trying to keep the veg room going and my pH pen died and I didn't believe what the drops were telling me. . Plants did not like! They're coming back after a few weeks at 5.8-6.1 but growth was seriously stunted and there was lots of leaf necrosis. No way they could go any further at 5.2. I'll always keep a backup pH pen on the shelf going forward.

Douglas.Curtis · Dec 22, 2016

'Proper' pH depends on the type of system your plants are in.

Roots-out systems, where the roots dry out between waterings, have a natural pH drop during the dry out period. 'Proper' pH range will vary with each system but top and bottom pH (edit: of your nutrient solution) will generally be 5.5 to 6.1.

Roots-In systems, where the roots are constantly exposed to the nutrient system, do not have a 'dry out' induced pH swing. Best results are obtained by setting the pH at 5.4 and letting the pH naturally rise as the plants eat nutrients. Res size determines how fast this swing occurs. 5.4 - 5.8 is where you're going to find the best results with these systems.

Just figured I'd clarify.

Offmymeds · Jan 6, 2017

I am new to coco. After reading a scientific sounding post of ph should be at 5.2, I flushed the coco for the last time with a ph of 5.2 with cal-mag. Is it possible to have an issue with that? I have only a few seeds so I'm being super cautious.

Bush Dr · Jan 6, 2017

Why did you do that ^^

gr866 · Jan 6, 2017

Offmymeds said:
I am new to coco. After reading a scientific sounding post of ph should be at 5.2, I flushed the coco for the last time with a ph of 5.2 with cal-mag. Is it possible to have an issue with that? I have only a few seeds so I'm being super cautious.

Note what is available at giving pH. At 5.2 you are blocking many needed nutes.
In a coco grow, It is said that 5.5 to 6.5 in the range, but in coco I use a range of 5.8 to 6.2, try to maintain at around 6.0 - 6.2, and I basically spoon feed the plants, low ppm throughout the grow. This is just what I do, your conditions may require a different pH.

You should note that Ca and Mg are only slightly available between the 6.0 and 6.25 range, that is why you have to add additional Ca/Mg to you mix with certain coco's.

GR

stoned40yrs · Jan 6, 2017

Piss yellow FTW. Fuck ph pens, I'll never buy another instrument like that which is guaranteed to go out of whack on you no matter how on top of it you stay. Not only that but drops are faster than a pen and NEVER wrong. Piss yellow baby! You only use them pens because you think they are high tech and you need to hit a certain number. You don't need to hit a number or vary numbers. PISS YELLOW is what you need from seed/clone to harvest. Free yourself from them fucking pens and numbers- piss yellow man :biggrin:

Daniel_Norway · Nov 10, 2017

hereigrow said:
View Image

I admit I don't grow pot but palm trees, but you guys are very resourceful in investigating optimal plant growing conditions and I am just about to repot my plants into coir, which is not a well documented medium.

The quoted chart is often found on the internet (out of context with no source). But what does it really apply to? This book by A C Bunt from 1988 (page 81) has it, using this journal article from 1981 as source and says it is obtained for a mix of sphagnum peat, vermiculite, perlite, composted bark and sand called "Metro-Mix 300". Bunt also mention that it was Lucas & Davis who in 1961 first drew attention to how optimal pH range for organic soils is 5.0-5.5, 1.0 to 1.5 units lower than for mineral soils.

I just measured EC and pH for the coir I bought and pH is 6.6 after leaching (RO water with water volume = 3x soil volume) so that EC is down at 0.08mS/cm (the meter showed 6.4 before leaching, when EC was 0.98, but pH measurements with such high EC is a bit lower than the true value so the soil should be leached). I used calibrated precision instruments (HM Digital PH-200 with 2 decimals and Hanna HI 98331) and the "saturated medium extract" method, which is easy to do and have been shown to give the most accurate results.

In the pic you quote it even says this chart is valid also for water cultures. Imagine, the same graph for hydroponics and all soilless media? Is this really true? I can't find any data that specifically says it covers coir. If the graph is true then coir should be complete crap (unless you make it more acid somehow, which is unheard of), which I doubt.

Or does anyone have experience of which pH that works when growing in coir? Other posts here seem to say to not have about 6.1 or 6.2 but is that confirmed for coir or just guesswork? Because if this is true then my plants are in for a bumpy ride, repotting is scheduled for tomorrow.. :tumbleweed:

Pot people to the rescue?!

Mikell · Nov 11, 2017

You, you I like.

People who try to answer their own questions first. Novel.

Many of those charts vary. I've always seen them are more general guide.

There aren't many white papers on coir. One, can't recall the name, pops up frequently comparing coir to peat under conditions favourable to peat, and shows little understanding of the particulars of coir.

You'll likely find best result from trialing across a range. One lot at 5.5, one 5.8 and another 6.2.

Cannabis will accept 5.7-6.3. Haven't seen much difference in that spectrum, I am not anal about hitting a certain mark.

Absolem · Nov 11, 2017

Coco coir has a very stable pH between 5.8-6.1. This is why it is recommended to keep the pH of your nutrient solution between 5.5-6.2. Any respectable coir supplier should be able to provide the ec, pH, and moisture content of the coir they are selling.

Here's a study that lists some good info on coir. It can be found on page 2.
https://hortsci.ashspublications.org/content/40/7/2135.full.pdf

The link seems to be messed up.
Google. "Effects of leaching on flower lily"

Daniel_Norway · Nov 12, 2017

Thanks guys. But I am not growing in water culture, but plain old "put the roots in the dirt" (except that I use coir-mix).

And the pH of my coir really is 6.6. I used a 2-digit digital pH meter in accordance to SME method (in 3 spots for 60 secs) and afterwards I checked its readings in both pH 4 and pH 7 solution to verify calibration. This coir is marketed as having pH between 6 and 7.

I repotted 2 plants yesterday. Mixed the coir with 30% seramis, which is said to have pH 5.7. Shall measure pH of the complete mix soon, hopefully lower. (But afraid mix will be high on potassium.)

The plants may have a preference of pH too but for that pH 6-7 is probably fine, what worries me is poor nutrient uptake due to pH > 6, if chart is to be believed.

PS Your link works if you remove the s in https.

RumblefishTwist · Nov 12, 2017

What looks good on paper doesn't always pan out. I find they like 5.8-6.2 so i drift around in that range. Pretty sure if i dropped to 5.2 i would see adverse affects, and can confirm going above 6.2 WILL have adverse affects.

Mikell · Nov 12, 2017

The pH of the medium is less dependent on the medium than the rootzone solution. Coir has a very low CEC, and as we keep it moist with frequent watering, has little deviation from the applied nutrient solution, given that is stable.

Try a slurry test with distilled water on recently fertilized coir. The EC will not jive but the pH should be within 0.2pH.

pH 5.2 vs 6.2?

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