Potassium deficiency? Or heat stress? Or soil pH too high?

[BigD13]

It’s not the pH of your water that’s important, it’s the alkalinity. Here’s what the guys at Pro-Mix have to say about it:

“The higher the alkalinity of the water, the more lime it contains and therefore, the more rapidly the water can cause the growing medium pH to rise. On the other hand, the pH of the water does not have any influence on the pH of the growing medium.”

Water Alkalinity vs pH in your Growing Medium - What's the Difference? | PRO-MIX Greenhouse Growing

Water pH measures the amount of hydrogen (acid ions) in the water, whereas water alkalinity is a measure of the carbonate and bicarbonate levels in water.

www.pthorticulture.com

Also, the type of fertilizer can have an effect on soil pH. Again from Pro-Mix:

“Ammonium and urea are acidic forms of nitrogen which cause growing medium pH to drop and nitrate is basic which causes growing medium pH to rise.“

How to Maintain the Proper pH of a Growing Medium | PRO-MIX Greenhouse Growing

When asked “How do you maintain the proper pH of a growing medium?”, often the answer is to adjust the water pH to achieve a growing medium pH in the ideal range of 5.6-6.2. This is simply not true.

www.pthorticulture.com

If you haven’t seen it, here’s a good thread on whether you need to adjust nute pH.

Do we need to pH adjust our nutrient solutions?

Greetings all! I recently had a running email conversation with the "Grower Services & Product Development Director" at ProMix (aka Premier Tech). I began the conversation by posting a question on their website, asking if I should be treating ProMix HP as soil or soil-less when mixing...

www.420magazine.com

 

[Emeraldo]

I personally have never had to ph my soil up or down, it’s a waste of time because soil naturally buffers ph which leads to you always chasing some magical number. I would concentrate on nute levels, environmental conditions, and any pest issues since you are outside.

Ghost Farmer: I agree that pest issues and offering the plants a good growing environment are most important. But I don't know if you are referring to organic plant foods or bottled "nutes". Do you grow organically in super soil? I just mix the soil in preparation for the grow, and the plants take what they need. There really isn't much chance of a toxicity, unless I really went overboard with Nitrogen in giving too much, say, bat guano. Another reason to think my current issue was caused not by anything related to soil but rather by the heat stress.

 

[Emeraldo]

It’s not the pH of your water that’s important, it’s the alkalinity. Here’s what the guys at Pro-Mix have to say about it:

“The higher the alkalinity of the water, the more lime it contains and therefore, the more rapidly the water can cause the growing medium pH to rise. On the other hand, the pH of the water does not have any influence on the pH of the growing medium.”

Water Alkalinity vs pH in your Growing Medium - What's the Difference? | PRO-MIX Greenhouse Growing

Water pH measures the amount of hydrogen (acid ions) in the water, whereas water alkalinity is a measure of the carbonate and bicarbonate levels in water.

www.pthorticulture.com

Also, the type of fertilizer can have an effect on soil pH. Again from Pro-Mix:

“Ammonium and urea are acidic forms of nitrogen which cause growing medium pH to drop and nitrate is basic which causes growing medium pH to rise.“

How to Maintain the Proper pH of a Growing Medium | PRO-MIX Greenhouse Growing

When asked “How do you maintain the proper pH of a growing medium?”, often the answer is to adjust the water pH to achieve a growing medium pH in the ideal range of 5.6-6.2. This is simply not true.

www.pthorticulture.com

If you haven’t seen it, here’s a good thread on whether you need to adjust nute pH.

Do we need to pH adjust our nutrient solutions?

Greetings all! I recently had a running email conversation with the "Grower Services & Product Development Director" at ProMix (aka Premier Tech). I began the conversation by posting a question on their website, asking if I should be treating ProMix HP as soil or soil-less when mixing...

www.420magazine.com

Thanks BigD13!

The ProMix folks must know what they're talking about.

So, my question to you: If I use ProMix (which I do) and I amend it with lime and have a soil pH of 7.0, does it do nothing for my plants to pH the irrigation water to 6.0?

 

[BigD13]

Thanks BigD13!

The ProMix folks must know what they're talking about.

So, my question to you: If I use ProMix (which I do) and I amend it with lime and have a soil pH of 7.0, does it do nothing for my plants to pH the irrigation water to 6.0?

It won’t hurt them, but my understanding is that it is not necessary. The alkalinity of you water is what matters. Also, below is a quote from one of the links above on whether you need to adjust pH. It’s from the very first posting in that thread by @InTheShed.

And at the bottom of that summary I added one last direct question:
"If I’m growing in ProMix HP and I mix up the nutrient solution and it reads 7.4 pH, it is not necessary for me to adjust that number down using phosphoric acid or the like. I can pour it into the pot at 7.4 and my plants will be able to uptake those nutrients?"

His response was a direct "Yes."

Do we need to pH adjust our nutrient solutions?

Greetings all! I recently had a running email conversation with the "Grower Services & Product Development Director" at ProMix (aka Premier Tech). I began the conversation by posting a question on their website, asking if I should be treating ProMix HP as soil or soil-less when mixing...

www.420magazine.com

I grow in soil. My well water has a pH of 7.4. My alkalinity is somewhere around 120-140 ppm. I never check the pH of my water/nute solution. In fact the other day I went and took the batteries out of my pH pen because I didn’t want them leaking from lack of use and ruin the pH pen.

 

[Emeraldo]

Ok, now I am a bit confused. The word "alkaline" is defined to mean having a pH greater than 7.0.

al ka line

1. having the properties of an alkali, or containing alkali; having a pH greater than 7.
   "an alkaline soil"

You seem to be saying "it's the alkalinity of the water, not it's pH level, that matters", which to me is a non-sequitur. Sorry, but please explain again.

If you said "it's the EC, not the pH", that matters, it would make sense to me. Am I wrong to think you are using "alkaline" in the sense of electrical conductivity, the density of the nutrient molecules in the liquid?

The discussion you referenced it a ProMix page stating that a water with pH of 9 but low "alkalinity" needs less acid to reduce the pH to 5 than water with a pH of 8 but much higher "alkalinity". This I know from experience to be true. If you take a liter of distilled water (which has an EC of 0), just a few drops of vinegar will drop the pH substantially, while a liter of water with high EC (because "nutes" are mixed in) will hardly respond to the same amount of acid at all.

This information is valuable for growers who use "nutes" and need to find a balance between EC and pH.

I don't use "nutes". I mix in various amendments into the soil before growing, including sufficient lime, but I almost never feed the plants with liquid nutes mixed into the water. I use plain water. So I don't and can't pH my nutrients at all, they are in the soil mix. I am not sure we are on the same page here...

 

[FelipeBlu]

I understand your confusion, brother. There’s alkaline (pH) and Alkalinity (bicarbonate load). Alkalinity is basically equivalent to how much limestone is in the water, soil mix, etc. Alkaline refers to the amount of H+ that is present.

 

[BigD13]

Go back and read my posts. I never used the word “alkaline“.

Yes I’m saying “alkalinity“ and so are the Pro-Mix guys. Here’s a quote from their article I linked to:

“Contrary to popular belief, the pH of the water does not influence the pH of the growing medium. Actually, it is the bicarbonate and carbonate levels in the water, known collectively as alkalinity, the potential acidity or basicity of the fertilizer and the plant itself:

Water Alkalinity
As stated above, water alkalinity is a measurement of carbonates and/or bicarbonates in the water, or another way to put it, is the amount of limestone dissolved in the irrigation water.“

It doesn’t matter if you add “nutes” or if you amend your soil. What is your water alkalinity in ppm? What is the ratio/percent of Ammonium/Urea to Nitrite fertilizer in your amendments? That is what will affect the pH of your growing media.

Also, please go and read the whole thread I posted below about whether we need to pH adjust your nutes. I think it will answer a lot of your questions.

Do we need to pH adjust our nutrient solutions?

Greetings all! I recently had a running email conversation with the "Grower Services & Product Development Director" at ProMix (aka Premier Tech). I began the conversation by posting a question on their website, asking if I should be treating ProMix HP as soil or soil-less when mixing...

www.420magazine.com

 

[Emeraldo]

Thanks, I will go back and re-read.

 

[Emeraldo]

Ok, BigD, I read the thread. Wow. Game changer. This information throws years of growing practice, i.e., pH-ing the water or nutrient solution, out the window. Fortunately, no harm done because all that work pH-ing the water was totally unnecessary and irrelevant, lol, spending all that time getting the water pH'd to the sweet spot that existed only in our minds and in the advice given in online forums.

I just wonder why this information was not commonly understood. Did experienced weed growers, who spend a lot more time obsessing about their plants like I do, not have this insight, while university agricultural projects about it were published? It's just basic (no pun intended) soil science!

One thing probably hasn't changed, though: Watch your plants to see if they are happily growing. If they are, that may be all you need to know.


Thanks!

 

[syenite]

Hi Emeraldo! I was just in this mess a few weeks ago. Took a while to climb out of it! There's a part of me that's still processing it all, haha.

 

[BigD13]

Ok, BigD, I read the thread. Wow. Game changer. This information throws years of growing practice, i.e., pH-ing the water or nutrient solution, out the window. Fortunately, no harm done because all that work pH-ing the water was totally unnecessary and irrelevant, lol, spending all that time getting the water pH'd to the sweet spot that existed only in our minds and in the advice given in online forums.

I just wonder why this information was not commonly understood. Did experienced weed growers, who spend a lot more time obsessing about their plants like I do, not have this insight, while university agricultural projects about it were published? It's just basic (no pun intended) soil science!

One thing probably hasn't changed, though: Watch your plants to see if they are happily growing. If they are, that may be all you need to know.


Thanks!

Hey, glad you enjoyed it! Yeah, I’m no soil scientist, nor did I stay at a Holiday Inn last night. I do try and listen to the real soil scientists because that’s what they do for a living. I figure the good folks over at Pro-Mix want people to have a successful grow using their products, so they put out information that will help you achieve those results.

I don’t think it’s commonly understood because people are too lazy to do the research. I look at the “Frequently asked questions“ almost on a daily basis. After a while you realize it’s a lot of the same questions over and over. Seems like a lot of people can’t be bothered to do a simple search to find the answer. I researched just about daily for around 3-4 months before I started buying stuff for my first grow. I’m glad I did because I really didn’t have any major problems and when something came up I either knew how to fix it or where to go to find the answer. I have a ton of stuff bookmarked for reference.

I agree with watching your plants to see if they’re happy. If they look good, they probably don’t need fix in’.

 

[Emeraldo]

I continue to maintain that a soil pH below 6 is not typically recommended, according to these graphics

That would be a good question to put to Arjan Rascom at GHS. I am fully on board with the recent discussion you pointed me to -- about soil PH not being raised by pH-ing the water. So does GHS really grow these wonderful plants in soil with a pH of 5.5? That would be close to pure peat moss.

 

[adudecalledjay]

That would be a good question to put to Arjan Rascom at GHS. I am fully on board with the recent discussion you pointed me to -- about soil PH not being raised by pH-ing the water. So does GHS really grow these wonderful plants in soil with a pH of 5.5? That would be close to pure peat moss.

I know in hydro I'd usually start pH pretty low 5.5-5.8 for VEG and work my way up to 6.5-6.8 for flower. I wonder if they are expecting that the soil will slowly raise pH over time?

 

[Emeraldo]

I know in hydro I'd usually start pH pretty low 5.5-5.8 for VEG and work my way up to 6.5-6.8 for flower. I wonder if they are expecting that the soil will slowly raise pH over time?

They don't really say. GHS said that in reference to Arjan's Strawberry Haze. Given that they said 5.5 hydro, and 5.7 in soil (raising to 6.5 at end of flowering), they must be raising the water pH by all that I know.

Anyway, I received my soil pH meter today. Not sure it was worth the extra $$ over a cheaper one, but I tested the soil the Super Lemon Haze is in, and it showed pH 6.6 consistently. That being so, am happy the pH is not too high (by normal standards).

I also tested the ppm or hardness of my water going in. It's at about 98 ppm. Felipe, what does that tell you? That the alkalinity is low and that there is insufficient lime to raise it? The plant looks ok, so I'm good with it.

Thanks for your help, all!



Emeraldo

 

[Emeraldo]

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Is a pH of 6.0 as low as you'd go? In my current grow, three new plants are in veg still, about ten weeks along now. I've tested the soil today and it is exactly 6.0. It occurred to me that I could raise the pH gradually by top-dressing dolomite lime into the soil and watering it down. Maybe that is what Arjan Rascom is suggesting with Strawberry Haze. He's "clearly ambiguous" about it, saying 5.7 for soil, then gradually raising it to 6.5 by the end of flowering, he's not talking about hydro there at all because he mentions the hydro values separately. All I am wondering is how would he do that? How would he raise the soil pH gradually? Maybe topdressing lime is the answer? I may need to try that out if I run into some deficiency, maybe a magnesium, calcium, or phosphorus deficiency.

 

[FelipeBlu]

If your water has a high alkalinity (high carbonate/bicarbonate level), the pH will rise in your medium over time. If you use a fertilizer with mostly the nitrate form of nitrogen, the pH will rise in your medium over time. If you use up your buffer (lime) with a lot of low pH water reacting with it, the pH in your medium will go down over time.

 

[Emeraldo]

Your answer is absolutely correct. Thank you

 

[NorCAKnowYourGrow]

@Emeraldo good thread. Thanks for directing me to it.

We must live near-ish as your weather matched mine. Massive heat wave in mid-to-late June. And tons of wind this summer. Girls looked just like yours. Same issues. I moved them from 12+ hours direct sun to 7 and that helped. And this compost tea I learned about from a gardener in my area has been amazing. Every time I use that the next day I can tell the girls are thanking me for the brew.

Still processing all this from this thread and the other. Alkalinity vs alkaline. Clearly, I missed something in science class 33 years ago.

 

[Emeraldo]

@NorCAKnowYourGrow good thing you could move yours into the shade a bit. Mine were trapped in that beast of a wind with sun blazing at 105 F temps. Did you get the yellowing around the edge of the leaves?

The heat in the Central Valley around Sacramento pushed up with such power the Delta Breeze became a windstorm. I guess there' always been that potentially, but it was strange to say the least. My plants had windburn from the high wind whipping them, and the leaf serrations turning upward. Not the whole leaf cupping, just the serrated edges. Then came the splotches of yellowing, then crispy brown edges.

My original thought was maybe the soil pH was too high for Super Lemon Haze, which was most affected. GHS says soil at 5.5. Well, mine is not that low, but now I know it is at 6.5. I eventually concluded the problem was the heat & wind, but the whole soil science discussion around alkalinity was educative, us old dogs can learn new tricks after all Lol.

It's a lot to process with the "alkalinity" (a term I thought referred the degree of alkaline but isn't). Actually, not having to pH all the water is ok with me... I did get a soil pH meter, and will go with extra lime if the soil pH is too low. My 4 big plants are in soil at 6.5 and the three younger ones are in soil at 6.0, so have been slowly adding a few tbsp of lime in top dressing them to raise that a bit.

 

[NorCAKnowYourGrow]

@NorCAKnowYourGrow good thing you could move yours into the shade a bit. Mine were trapped in that beast of a wind with sun blazing at 105 F temps. Did you get the yellowing around the edge of the leaves?

The heat in the Central Valley around Sacramento pushed up with such power the Delta Breeze became a windstorm. I guess there' always been that potentially, but it was strange to say the least. My plants had windburn from the high wind whipping them, and the leaf serrations turning upward. Not the whole leaf cupping, just the serrated edges. Then came the splotches of yellowing, then crispy brown edges.

Yellowing at the edges, yup. And crispy tips. And cupping or quickly being wilty. I’ve had to water SO much.

Yep....we are relatively close. I’m just a bit further west in the east bay. Been a weird summer. What else? Weird year. Weird world. but that’s a whole other topic.