pH - why does it matter and how do I monitor it? Answers!

matto70799

Member
First let me introduce myself. I am new to this forum and fairly new to marijuana cultivation, however, I understand pH, what it means (what are you actually measuring?), why it's critical to plant health, and the many methods for pH monitoring. Qualifications: I have a masters degree in molecular biology, several years of college botany and plant physiology, and I work in biotech for the past 10 years. Ok now that we have established I probably know what Im talking about....First, what is pH and why doea it matter to plant health. pH is literally the measurement of the proton (hydrogen ions with 1 proton, 0 neutrons, and 0 electrons, therefore they carry a +1 charge) content of a solution. Now this matters because the amount of hydrogen ions defines how basic (alkaline) or acidic a solution is and in the case of plants this matters because the nutrients in the soil can only be taken up by the roots within a certain pH range. So even though you bought the high end nutrients, water your plants, love them, encourage them, etc., if the pH is too high or too low they won't be able to use those expensive nutrients and you'll start to see signs of nutrient deficiencies. Marijuana grown in soil likes a pH range similar to that of tomatoes: ~6.0 to 7.5, grown hydroponically (without soil - only water to deliver the nutrients) the correct pH range is slightly more acidic: ~5.5 to 6.5. At these pH ranges the plants can readily dissociate the nutrient ions from the salt form in which they are often supplied (a salt in chemistry is the ionic product of a neutralization reaction of acids and bases. They are composed of a related amount of cations (positively charged ions) and anions (negatively charged ions) such that the resulting compound is electrically neutral (has a net charge of 0). For example: table salt is the salt of chlorine (Cl, anion) and sodium (Na, cation). Chlorine carries a -1 charge and sodium carries a +1 charge. When they come together to make a salt there is 1 of each atom resulting in the neutrally charged salt molecule (NaCl). Nutrients are supplied in their salt form. At the appropriate pH the salt dissociates (aka: dissolves) in water (so in our NaCl example when salt is dissolved in water what really happens is the ionic bond between the Na and the Cl atom breaks. So a solution of table salt contains free Na+ and Cl- atoms). The plant can then (usually through processes involving bacterial colonies in their roots) uptake the nutrients in a form it can use. Ok, so now, how do we measure pH? There are many ways depending on how accurate a reading you need, and your preference between matching up colors or just having a digital number displayed (also how much you want to invest). I personally use a Hach brand portable meter (about $400 retail). I understand I'm nuts, so I wouldn't expect most people to go out and get one of these sophisticated meters. Less expensive options for digital meters are called pH pens. (I put a pic at the bottom). There are many brands but i would try to stay with Hach, Oakton, VWR, or Mettler toledo. They are excellent quality manufacturers. These will cost about $50-$100 and all digital pH meters will require you purchase reference standards to calibrate. You'll want at least a 2 point calibration, and please, if you are most interested in the range of pH from 5-8 then by all means calibrate your meters with pH 4 and pH 10 standards. You want to bracket the pH range you will be testing with your calibration standards. I've seen websites recommend calibrating with pH 4 and pH 7 standards. This is great if your most interested in a range between pH 4 and 7. Anyway, less expensive and still good options include colormetric (a color change reaction) based tests: pH test strips (dip and match color result to chart), or liquid based tests (like for an aquarium). These last two options have the added pros of being cheap, no calibration needed, and they are quick. However you will sacrifice accuracy for price, which may or may not matter to you. Well i hope this quick little blurb helps someone out there. Ask any questions, happy to answer.
 
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Ph don't mean poop in the real world, canna has a such a large range that the potential hydrogen reading is somewhat misleading, true keeping your ph in check does improve yield rates, but for th most part its a nooby catch phrase, that in most cases means you got the wrong water or you are feeding your plant too much, that fact you have a ph tool before you have a plant to measure is some what disturbing ...peace
 
Cut him some slack. Good info. Helps for overall plant knowledge.
I've read to keep ph in a certain range for nutrient absorption, because plants can only uptake ideally at certain ranges

so I helps nutrient uptake and ph swings cause leaf curling , rigidity , and various issues confused some for deficiency when they really caused lock out so treating the wrong issues causes more issues

in organics I don't monitor my ph like I did in soilless I know my RO water is close to 7 and when I use molasses beneficials or tea I don't adjust ph to avoid killing the microcultures in the soil

ph is crucial for soil less , hydro, chemical fed mmj but if your soil and compost and all is your primary source of npk and beneficial cultures then mix and pour works well in my experience

so i don't know the science behind it like a biology book could define it but I know the why of what wrong ph does to plants in my experience

peace and happy growing fellow roll it up medical growers caregivers etc etc etc :)
 
Absolutely grateful growing3. You are totally correct because the natural pH of tea and molasses are low (acidic - tea contains high levels of tannic acid and I believe molasses does to but I'm not sure on that). So when you add them to the other materials you use (compost - high pH, etc).
But it is pretty cool how just by doing what the plants want you are maintaining a proper pH environment - and I bet your plants thank you!

Vostock - FYI I have 21 plants all heathy and happy outdoors and 16 indoors. Peace to you!
 
Absolutely grateful growing3. You are totally correct because the natural pH of tea and molasses are low (acidic - tea contains high levels of tannic acid and I believe molasses does to but I'm not sure on that). So when you add them to the other materials you use (compost - high pH, etc).
But it is pretty cool how just by doing what the plants want you are maintaining a proper pH environment - and I bet your plants thank you!

Vostock - FYI I have 21 plants all heathy and happy outdoors and 16 indoors. Peace to you!
awesome to hear I'm on the right track with some things

hope your 21 plants are amazing and treat you well when the medicine is ready :)
 
I hope so too! My reason for posting on pH is I understand it's not well understood by most people. They think hey ive never monitored pH before and all went well so phooy! Then this happens: they have a grow in progress and all seems great. One day the plants are showing stress and nutrient issues. So they dump in more nutrient. Cool. But next day the plants still look crappy. Ok more nutrient. Eventually they add so much the pH changes and the plants (who had been in lock out because of imporper pH) suddenly absorb tons of nutrients and you have dead burned plants. I thought if I could help I would. So before just willy-nilly adding nutrient, why not take 5 min, check your pH and see if that's your issue? Anyway, happy growing!
 

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Ph don't mean poop in the real world, canna has a such a large range that the potential hydrogen reading is somewhat misleading, true keeping your ph in check does improve yield rates, but for th most part its a nooby catch phrase, that in most cases means you got the wrong water or you are feeding your plant too much, that fact you have a ph tool before you have a plant to measure is some what disturbing ...peace
I would actually agree with you on a lot of what you say. However, it can be a great place to start if you start seeing nutrient related issues. The bacterial colonies in the roots that fix the nitrogen so the plant can use it, as well as most of the other inorganic nutrients (metals, trace elements, etc) require a certain pH range to thrive. This is actually what you are worried about with pH. My point is not you should be hyper worried about it. My point, and I think it's valid, is that before you start treating an issue why not check if that is your issue first? An aquarium test kit costs less than $10 (less than $5 at discount stores) and works great.
To my choice in meter: I admitted I was nuts, but more I have easy access to borrow one from work. Otherwise I'd probably use a pen or the aquarium kit. Lol
 
I hope so too! My reason for posting on pH is I understand it's not well understood by most people. They think hey ive never monitored pH before and all went well so phooy! Then this happens: they have a grow in progress and all seems great. One day the plants are showing stress and nutrient issues. So they dump in more nutrient. Cool. But next day the plants still look crappy. Ok more nutrient. Eventually they add so much the pH changes and the plants (who had been in lock out because of imporper pH) suddenly absorb tons of nutrients and you have dead burned plants. I thought if I could help I would. So before just willy-nilly adding nutrient, why not take 5 min, check your pH and see if that's your issue? Anyway, happy growing!
That would cause issues with salt and dissolved solids buildup not just Ph. It would need flushed
 
Man, I just wish you knew how to use paragraph breaks. No offense, but old farts me like me have a hard time with it and I just struggled to read through nothing new.

I grow soil and despite what anyone says, when I get lazy with ph plants suffer.

I love my blulab pen!
 
So I was going to add to this post about adjusting pH, the types of pH adjusting solutions, pH buffering so it doesn't drift, when to add adjusting solutions and how, etc, but so many people are up in arms about the simple advice to check the pH that it would seem I'm better off just keeping my "mouth" shut. Good luck everyone - hope all your grows finish with spectacular, crystal covered, colas. If not, maybe you should check your pH....lol
:wall:
 
We understand it, you just seem to not understand how it relates to living cannabis plants.

Anyone doing hydro monitors it, people in soil change it if it becomes an issue.

You're trying to make things more complicated than they are. You don't need a research paper to understand this stuff.
 
Absolutely grateful growing3. You are totally correct because the natural pH of tea and molasses are low (acidic - tea contains high levels of tannic acid and I believe molasses does to but I'm not sure on that). So when you add them to the other materials you use (compost - high pH, etc).
But it is pretty cool how just by doing what the plants want you are maintaining a proper pH environment - and I bet your plants thank you!

Vostock - FYI I have 21 plants all heathy and happy outdoors and 16 indoors. Peace to you!
Do you boil the tea first to draw out the acid or just cold steep?
 
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