Do we need to pH adjust our nutrient solutions?

Thanks DC! But please, I don't advise that anyone feed their plants 10g/gallon of MegaCrop :).
 
He can do what he likes! It ain't my recommendation :cheesygrinsmiley:
 
10 gr/gallon whooooey! :thedoubletake:

I’m a living life on the edge kinda guy, but damn! My spinter just tightened up there!
 
I have been on both ends of this discussion. In this thread I do believe.

I grew for a handful of grows without PH'ing my water. However during that time my act, top dressing, etc was outta hand. But I saw discolouration and issues. Eventually things worked out. I also suspect my crappy understanding of watering had a factor. I under watered those crops I think.

Then I grew with PH'ing my water. No real other changes to the process. I had good results. Still had occasional issues. But at this time I chilled the F out with acts, over feeding, under watering. Made other adjustments.

Then I have essentially stopped. However. Because my water is around 8 out of the tap. I do bring it down to a reasonable range for the soil and soil food web to do the rest. I am not really using a chelated nutrient program. Although small supplements of calcium/magnesium.

So for me I see it both ways. The PH of water or nutrient solutions of chelated amino acids can be unnecessary for many. However in other individuals organic soil grows the PH of the water is important.

edit. I was equally half-assed in both watering techniques for this alternative science based peer reviewed post. My post was also written while genuinely super high. So its really not very helpful after all.
 
zeroday said:
One would think it would be possible to test the theory by just growing a couple of clones from the same mother, in the same soil, same tent, except PH one and not the other? Some people are bored, and have no life, and might be up for doing such an experiment. Just saying.

:lot-o-toke:
Click to expand...

Hey Zeroday. I did that earlier in the thread.

Here

Though definitely not induced by any boredom or lifelessness over here, I’m happy to report. :passitleft:

So anyway.... to finish the report on that test- both the clones, the one grown in low PH around 3, and the other one in high PH between 10 and 11. were pretty much exactly the same, health-wise, by harvest time. Like some other plants in the room both had a little calcium deficiency, but that’s an unrelated nutrient issue I’ve been struggling with a bit. Otherwise they were totally healthy.


Weaselcracker said:
I’ll contact Shiv Reddy at Sungro Horticulture
Click to expand...

I finally got around to emailing the ph guy at Sungro Horticulture. I ran a few questions by him, told him about my recent high/low ph grow results. I also explained some of my past experiences wherein I have been totally 300% convinced I had serious ph related issues in Sunshine Mix and assumed it was from feeding/watering at the wrong ph.

The conversation pretty much echoed Shed’s with the Promix guy in post #1 of this thread, including the difficulty in getting straight answers. But then it’s a complicated subject for us stoners I guess ...


Anyway.... after a bunch of back and forth I’ll sift it down to this. His writing is in blue.



Can you answer definitively whether or not we need to adjust our pH of our nutrient solutions when using Sunshine Mix and similar soilless mixes containing lime?


You don’t need to adjust the pH of the nutrient solutions. But you have to maintain ‘pH of the soil mix’.

Even if you adjust pH of the solution going to the soil mix, pH of the soil mix itself (so the PH that plants see/experience) can change because of what is in the soil mix. Lime in the soil mix is a decent buffer.

Thus pH of the soil mixes in your experiment with pH 3 solution & pH 10 solution would have been similar.

Remember ‘pH of the soil mix’ is important & needs to be monitored. How you maintain/change pH of the soil mix depends on a few things. Probably in your case, your pH adjustment of the nutrient solution was maintaining pH of the soil mix. If it is working, let it be.


Given that I fed the two test plants with such extreme ph levels- it seems from that experiment that the lime does a very good job.

In the past though I’m sure I’ve had ph related issues. Perhaps there are situations where the lime wouldn’t be enough to keep the ph of the medium at a good level?


Correct, but pH not being at a good level is not so much due to lime content, but due to the type of fertilizer used, water used, how fast/slow plant is growing, etc., all of which affects pH of the substrate.

Is it safe to say that in Sunshine Mix we do not need to worry about adjusting the ph of our nutrient solutions for a regular 4-6 month seed- flower grow cycle?

= yes about not worrying about pH of the nutrient solution, but still worry or monitor pH of the substrate

InTheShed said:
I'm curious to what pH the Sunshine Mix is buffered to.
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What ph is Sunshine mix buffered to? I couldn’t find that info online or on the bag.


Sunshine mixes pH generally hovers around 6 plus or minus 0.3-0.5 units.


It makes sense that there are a lot of variables and different interactions and the PH of the substrate itself is the obvious place to monitor.

However- amost all cannabis growers I know of that are growing in soilless do not test the ph of the substrate. They measure the ph of the added nutrients and water and assume that this will keep the ph at happy levels in the container.

Is this true ? Would you consider that adjusting the ph level,( as I have been doing to a level of 5.6-6) is generally a good thing, and beneficial in maintaining the substrate at a good level?


I know cannabis growers measure & adjust pH of nutrient solutions. Part of it is due to lack of knowledge.

I doubt adjusting pH of the nutrient solutions would be beneficial to substrate pH maintenance. We need more info to say for sure.*



*Note that this answer completely contradicts what he said earlier:

“Probably in your case, your pH adjustment of the nutrient solution was maintaining pH of the soil mix. “

Which is a bit confusing...
But I’m trying to get simple answers to a complicated subject.

Call it a ‘maybe’ I guess. But more likely a ‘probably not’.:hmmmm:
 
I should also mention that in the slurry tests I’ve done, the Sunshine Mix balances out the ph quite quickly.


My tests were prompted by a conversation with Emilya here RO water & pH adjustment
where we had different ideas about the ability of the medium to quickly buffer against the ph of rainwater. I’d say we were both wrong on some points. But one main thing I wanted to test was her statement that the substrate takes quite a long time to buffer against the ph of a solution dumped into it.

For the most part, in the slurry tests I did, PH would swing to within an acceptable range within the first ten minutes or so.

I did various tests but for example, in a slurry test with Sunshine Mix and a nutrient solution which was 1100 TDS and PH 9.8-

Within one minute after I mixed the slurry the PH was at 7.2.
Twenty minutes later it was 6.2.
 
“But you have to maintain ‘pH of the soil mix’.”

Ok I didn’t want to wear out my welcome with the PH guy, but the next logical question is- how?

Has this already been covered? I haven’t read 95% of the thread.

Otherwise- what would be a good, hopefully easy and sane strategy or schedule for;

- testing the PH of the medium, and
-doing anything about it, if the ph isn’t ‘good’.

Thanks
 
Great test, man.

Now I have a 64k question to everybody? What is PH and why does it change over time? :)
 
Excellent posts @Weaselcracker!! Thank you for taking the time to do these experiments that provide us with unbiased factual results. I know I for one feel more confident in this line of non PHing solutions since reading this.
 
conradino23 said:
Great test, man.

Now I have a 64k question to everybody? What is PH and why does it change over time? :)
Click to expand...

I believe your answer is here.

Understanding pH management and plant nutrition
Part 3: Fertilizers
Bill Argo, Ph.D.
Blackmore Company,

Solution pH and the effect that fertilizer has on substrate-pH two different aspects of water-soluble fertilizers
There is a great deal of confusion when it comes to understanding the difference between the pH of the fertilizer solution and the effect that fertilizer has on substrate pH, and why they are important to the health of your plants.

Just like with water pH, the pH of the fertilizer solution is a direct measurement of the balance between acidic hydrogen ions (H+) and basic hydroxide ions (OH-), and can be measured with a pH meter. The pH of a solution can range between 0 (very acidic) and 14 (very basic). At a pH of 7.0, the concentrations of H+ and OH- are equal, and the solution is said to be neutral. When the pH is above 7.0, the concentration of OH- is higher than H+, and the solution is said to be basic or alkaline (not to be confused with alkalinity). When the solution is below 7.0, the concentration of H+ is higher than OH-, and the solution is said to be acidic.

The effect that a water-soluble fertilizer has on substrate pH is dependent on the reactions that take place once the fertilizer has been applied to the crop and are based on the type of nitrogen contained in the fertilizer. There are three types of nitrogen used in water-soluble fertilizers: ammoniacal nitrogen (NH4-N), nitrate nitrogen (NO3-N) and urea (Figure 1). Uptake of ammoniacal nitrogen causes the substrate-pH to decrease because H+ (acidic protons) are secreted from roots in order to balance the charges of ions inside the plant with the solution surrounding the outside of the roots. Urea is easily converted into ammoniacal nitrogen in the substrate and therefore can be thought of
as another source of ammoniacal nitrogen. In contrast, uptake of nitrate nitrogen increases substrate-pH
because OH-or HCO3- (bases) are secreted by plant roots in order to balance nitrate uptake.

Another important fertilizer reaction is a process called nitrification. Several types of bacteria in container substrates (including inert substrates like coir, bark, peat, rockwool, and scoria) convert ammoniacal nitrogen to nitrate nitrogen. Nitrification releases H+ (acidic protons), causing the substrate-pH to decrease.

Consider the difference in the amount of acidity supplied by a solution with a pH of 5.0 verses the amount of acidity supplied by 100 ppm of ammoniacal nitrogen. A solution with a pH of 5.0 would supply about 0.01 mEq/liter of acidic hydrogen ions to the substrate. If all the 100 ppm ammoniacal nitrogen were converted into nitrate nitrogen through nitrification, the maximum amount of acidity produced would be 14.2 mEq/liter of acidic hydrogen, or about 1,400 times more acidity than would be supplied by a solution with a pH of 5.0. Put another way, applying 100 ppm of ammoniacal nitrogen has the potential to supply the same amount of acidity as a solution with a pH of 1.8. The acidity produced by a solution with a pH of 5.0 would be equivalent to the nitrification of 0.14 ppm ammoniacal nitrogen (almost undetectable).

While the effect that different nitrogen forms have on the substrate pH is more complicated than this simple example, it does give you an idea why the nitrogen form of the fertilizer has a much greater effect on the substrate-pH than does the solution pH.

The main problem with predicting how the nitrogen form affects substrate pH is that the key reactions are not consistent. For example, the application nitrate nitrogen (NO3-N) can cause the substrate-pH to increase, but only if it is taken up by the plant. If plants are small, or are stressed and not growing, nitrate has little influence on substrate-pH.
The application of ammoniacal nitrogen (NH4-N) can cause the substrate-pH to decrease even if the plant is
small or is not growing, because in addition to plant uptake, nitrification will occur independently of the plant. However, nitrification is inhibited by low substrate-pH (starting at around 5.5), low substrate temperature (less than 60oF or 15o
C), and lack of oxygen through water-logging.

Finally, you never apply either all nitrate nitrogen or all ammoniacal nitrogen to your plants. Most fertilizer is a mixture of salts containing different forms of nitrogen and so the overall reaction produced by the fertilizer will depend on the ratio of the different nitrogen forms. There are also other factors that either magnify or buffer the reaction of the fertilizer including the substrate (cation exchange capacity, residual lime, decomposition – to be covered in a later article) and the irrigation water.
 
Yep that’s it. In other words stabilising ph in soil systems is near to impossible cause hydrogen is highly reactive. Yes you can ph your solutions all the time, but plant takes an active role here and she decides what range is good for her. It fluctuates so much, that the only way to keep it stable is to go hydro :laugh:
 
I suppose that’s why it’s called ‘buffering’, not ‘stabilising’ :)
Weaselcracker said:
how
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My understanding is by enhancing the buffering capacity of the soil, pre grow, with lime/limestone powder and that this might need replenishing over time, depending on what frets are added and what is grown in it. That’s why the dude said to you that one grow cycle would not interfere with the soil buffering capability.
 
Weaselcracker said:
“But you have to maintain ‘pH of the soil mix’.”
Ok I didn’t want to wear out my welcome with the PH guy, but the next logical question is- how?
Has this already been covered? I haven’t read 95% of the thread.
Click to expand...
I'm not sure it's been answered here because it's not the intent of the thread, but there are ways of modifying the pH of an existing peat/soil based substrate that involve soaking it in a solution of something that will raise/lower it. Since I start with new ProMix HP almost every time I haven't had to deal with it, but I know that @Virgin ground needed to raise hers on her last grow, so perhaps she can speak to that.
Biffo74 said:
7 is neutral so 7.4 is not high.
Correct?
Click to expand...
7.4 is high if you are slurry testing your medium. It's not high if you're watering a buffered medium.
 
To raise use fast acting lime or do a potassium bicarbonate dip. To lower use sulfur or aluminum sulfate.
 
:thanks:
 
Below is info readily available at the Promix website for anyone to view.

What Changes Growing Medium pH?
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. The higher the alkalinity, the faster the pH of the growing medium climbs regardless of the water pH . If water is passed through a reverse osmosis unit, then alkalinity is very low, so the water does not cause the pH of the growing to rise quickly. Reverse osmosis units are not necessary for most water sources if the fertilizer is properly matched to the water profile and the crop grown.

Fertilizer
Quality water soluble fertilizers typically have the potential acidity or potential basicity posted on their labels to predict their influence on the pH of soilless growing medium. For example, the higher the potential acidity of the fertilizer, the more acid it is. This is often determined by the ratio of nitrogen forms. 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. Therefore, if your water has high alkalinity, a fertilizer that has a higher ratio of ammonium to nitrate can be used to minimize pH climb in a growing medium. Also, as a rule, most calcium-based fertilizers are alkaline and cause the pH of the growing medium to increase even if the water goes through a reverse osmosis unit.

Crop
When plants take up fertilizer elements through their roots, these elements all have either a negative charge or positive charge. The plant has to maintain its internal electrical balance, so in order to obtain a positively charged element, such as ammonium, potassium, calcium, magnesium, etc. the plant will release hydrogen into the growing medium, which causes a slight drop in pH near the plant root. Likewise, when a plant root takes up a negatively charged element such as nitrate, phosphorus, sulfate and most micronutrients, it will release hydroxide ions, which will cause a slight pH rise. Depending on the plant’s requirement for these individual elements, some use a higher ratio of positively charged fertilizer elements, so they are more efficient at acidifying the growing medium. Other plants use a higher ratio of negatively charged fertilizer elements, thus are more efficient at increasing the pH of the growing medium.

To review, the pH of the water does not influence or predict the pH of any growing medium. Adjusting the water pH to the ideal growing medium pH of 5.6-6.2 does not mean the pH of a growing medium will remain in this range. Often growers experience nutritional problems because the pH changes independently of the pH of the irrigation water.

END:::

It may help in clearing some things up.
 
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