Do we need to pH adjust our nutrient solutions?

[farside05]

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.

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It may help in clearing some things up.

Yours is a simpler read than mine.

 

[Conradino23]

I suppose that’s why it’s called ‘buffering’, not ‘stabilising’

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.

That’s what you’re supposed to do. Prepare your soil and buffer it with the right amount of base. When you get a saturation base of around 70-80% and you have the right Ca:Mg ratio you don’t have to take care of ph anymore. The plant will do the rest for you.

 

[Momma's Kitchen]

According to this we don't need to struggle to control our nute pH, just struggle to control our medium pH!

Or it isn't after all.

I know right? I kept asking different ways until he finally gave me a straight answer. I told him that was going to throw a lot of folks for a loop!

that is crazy! I had no idea

 

[syenite]

Boy, I wish I'd found/digested this thread a couple of days earlier.

I just had my own struggles with a peat-based mix registering at 4 - 4.5 pH (both in my current grow containers and out of the bag), according to my soil pen and slurry tests. In the troubleshooting phase, I managed to speak to a Canna grower support rep (I'm transitioning to their potting mix) about pH in general.

Apparently there are very few controls on some of the peat-based products made where I live. Hence how I was sold such a poorly buffered mix. Yes, it even said it was properly buffered and amended with dolomite lime on the bag.

He highlighted the substrate's pH and pH buffering as being critical to the grow, and irreducible to the nute solution. He also confirmed that nutes can and do cause drift in the substrate pH over longer periods of time.

So my finding this thread has been timely in allowing me to process some of this!

Lastly, I asked him about dealing with low pH by adding dolomite lime. He said that this isn't generally advisable unless one has had the mix's levels tested, as without knowing how much calcium and magnesium is already in it, adding lime can "fix" the pH but throw lots of other things out of balance. Lime also takes some time to cook properly. Ideally, you would also want to know how the lime behaves in your mix over time, with nutes, etc. etc.

So I would caution against adding lime to a mix while one has a plant already in it. And against adding lime to a mix in general unless one has the time and resources to test and calibrate the mix to some degree!

IMO it would have saved me money and time to have simply committed to a better, more reliable mix from a reputable/trusted brand, and to have re-potted the plant in it, as soon as I aggregated the substrate pH results. I personally will not bother to fight a badly buffered mix in the future! Not unless I wanted to make a project of it.

 

[MrSauga]

He highlighted the substrate's pH and pH buffering as being critical to the grow

Hence the reason for not having to pH your nutes in a well buffered media.

He also confirmed that nutes can and do cause drift in the substrate pH over longer periods of time.

That's dependant on the acidity or akalinity of the ferts. Ammoniacal nitrogen is about three times stronger an acid than nitrate nitrogen is a base. For example, a fertilizer such as 17-4-17 has about 25 percent ammoniacal nitrogen and 75 percent nitrate nitrogen (1 NH4-N:3 NO3-N ratio), and the reaction produced by the 17-4-17 fertilizer tends to be neutral. If you have a mix that contains 40 percent of the nitrogen in the ammoniacal form and 60 percent in the nitrate form, 20-10-20 has an acidic overall effect (2 NH4-N:3 NO3-N ratio). In comparison, 15-0-15 contains only 13 percent of its nitrogen in the ammoniacal form and 87 percent in the nitrate form (0.5 NH4-N:3 NO3-N ratio). The reaction produced by 15-0-15 tends to be basic.

The other factor is the akalinity of the base water. The higher the akalinity the faster the pH will rise in the substrate over time.

 

[syenite]

Hence the reason for not having to pH your nutes in a well buffered media.

That's dependant on the acidity or akalinity of the ferts. Ammoniacal nitrogen is about three times stronger an acid than nitrate nitrogen is a base. For example, a fertilizer such as 17-4-17 has about 25 percent ammoniacal nitrogen and 75 percent nitrate nitrogen (1 NH4-N:3 NO3-N ratio), and the reaction produced by the 17-4-17 fertilizer tends to be neutral. If you have a mix that contains 40 percent of the nitrogen in the ammoniacal form and 60 percent in the nitrate form, 20-10-20 has an acidic overall effect (2 NH4-N:3 NO3-N ratio). In comparison, 15-0-15 contains only 13 percent of its nitrogen in the ammoniacal form and 87 percent in the nitrate form (0.5 NH4-N:3 NO3-N ratio). The reaction produced by 15-0-15 tends to be basic.

The other factor is the akalinity of the base water. The higher the akalinity the faster the pH will rise in the substrate over time.

Crystal clear, thank you! Curious. Now I wonder what other decisions are behind having those various combinations of different N compounds. For example, why product A has more ammoniacal N than nitrate N while with product B it's the other way around?

 

[Ganjagrandaddy]

Hence the reason for not having to pH your nutes in a well buffered media.

That's dependant on the acidity or akalinity of the ferts. Ammoniacal nitrogen is about three times stronger an acid than nitrate nitrogen is a base. For example, a fertilizer such as 17-4-17 has about 25 percent ammoniacal nitrogen and 75 percent nitrate nitrogen (1 NH4-N:3 NO3-N ratio), and the reaction produced by the 17-4-17 fertilizer tends to be neutral. If you have a mix that contains 40 percent of the nitrogen in the ammoniacal form and 60 percent in the nitrate form, 20-10-20 has an acidic overall effect (2 NH4-N:3 NO3-N ratio). In comparison, 15-0-15 contains only 13 percent of its nitrogen in the ammoniacal form and 87 percent in the nitrate form (0.5 NH4-N:3 NO3-N ratio). The reaction produced by 15-0-15 tends to be basic.

The other factor is the akalinity of the base water. The higher the akalinity the faster the pH will rise in the substrate over time.

You are a true bod when it comes to this stuff Mr Sauga. Total respect for your intelligence and knowledge buddy. Not often we find someone of your calibre that has an actual personality and you certainly rank up there as one of the major personalities on here. Peace and love buddy

 

[Ganjagrandaddy]

I got away with no ph checks throughout the grow with Mc. No signs of any negatives in the cured bud or during the grow that ibcould see. I did occasionally add a little ph down as the silica and my 7.2 out the tap ph did seem a little like pushing it to be left completely. Was a pleasant surprise and I don't feel luck could have held for the whole
grow.

 

[MrSauga]

Now I wonder what other decisions are behind having those various combinations of different N compounds.

I'm not sure if I understood the question correctly but the acidity or basicity value on the fertilizer bag is only a relative measurement of how the fertilizer formulation will affect media pH. In otherwords why is 20-10-20 more acidic than 15-0-15? Because 20-10-20 has more ammonium than 15-0-15.

You are a true bod when it comes to this stuff Mr Sauga. Total respect for your intelligence and knowledge buddy. Not often we find someone of your calibre that has an actual personality and you certainly rank up there as one of the major personalities on here. Peace and love buddy

Thanks GG! I learned from many others here and I thank for that.

 

[Mr. Magoo]

Crystal clear, thank you! Curious. Now I wonder what other decisions are behind having those various combinations of different N compounds. For example, why product A has more ammoniacal N than nitrate N while with product B it's the other way around?

The Nitrate form of Nitrogen carries a negative ionic charge. This helps the plant produce leaves and stems and helps to bulk up buds. The ammoniacal N carries positive ions and these help grow calyxes and pistols. Timing each application correctly should provide the soil energy needed to grow healthy happy plants.

 

[InTheShed]

Thanks MrS and Magoo!

I personally will not bother to fight a badly buffered mix in the future! Not unless I wanted to make a project of it.

An excellent choice! The quality brands have already done all the work for us so we can focus on the growing and not the medium, unless that's part of the project.

 

[Elvin]

Thanks MrS and Magoo!


An excellent choice! The quality brands have already done all the work for us so we can focus on the growing and not the medium, unless that's part of the project.

I'm trying Iowa topsoil and perlite this grow.
I had to dig a hole to empty a burn barrel (and bury a full barrel that's burned out) so I figured what the heck? Heck of a lot more weight than FFOF (no filler or cut to use cocaine parlance) and the fan leaves are already bigger than the last grow in the purchased medium.
Since soil self buffers I may be doing this from now on and save some serious dinero.
Hopefully, the dog will like the piles after this grow like he does the dumped bags of FFOF in my back yard. One must not screw up his beds.

 

[BigD13]

The Nitrate form of Nitrogen carries a negative ionic charge. This helps the plant produce leaves and stems and helps to bulk up buds. The ammoniacal N carries positive ions and these help grow calyxes and pistols. Timing each application correctly should provide the soil energy needed to grow healthy happy plants.

I use Mega Crop. It has an NPK of 10-7-18. On their website they state that it is 95% Nitrate Nitrogen & 5% Ammonium Nitrate, a 19 to 1 ratio. Since it is a 1 part dry mix, how would one “time each application correctly”? I’m just trying to understand how what you say would be applicable with MC, or how MC works according to what you posted. I’m just trying to get a better understanding of how things work.

 

[InTheShed]

If you're using premixed nutes like MC, you just feed the plant and let it ride! I think Magoo's advice would only apply if you have separate sources of nitrogen handy.

 

[Mr. Magoo]

I use Mega Crop. It has an NPK of 10-7-18. On their website they state that it is 95% Nitrate Nitrogen & 5% Ammonium Nitrate, a 19 to 1 ratio. Since it is a 1 part dry mix, how would one “time each application correctly”? I’m just trying to understand how what you say would be applicable with MC, or how MC works according to what you posted. I’m just trying to get a better understanding of how things work.

If you're using premixed nutes like MC, you just feed the plant and let it ride! I think Magoo's advice would only apply if you have separate sources of nitrogen handy.

If you have a 2 part (or more) fertilization system then you can try to dial in cycling through the feedings in a way that helps maximize that growth. This works great in living soils. Helps supercharge the microbes. But regardless of what you use the main thing is to keep the conductivity from going flat or on the other end getting over fertilized and burning the plants. I think a lot of fertilizers just provide a buffet of everything the plant will need so that it doesn’t ever lack anything it needs. That works well with salt based systems or sterile growing methods. I don’t really know anything about Megacrop personally though. Except a lot of people around here use it and like the results they get. Lol

 

[Elvin]

I use Kelp4Less's line but I must say that the free sample of Mega Crop I got on a whim sure is making my tomatoes look nice
Even smells similar to the other stuff.
Everyone loves MC here so it does sound like a no muss no fuss way of going about it with good results.

 

[syenite]

I'm not sure if I understood the question correctly but the acidity or basicity value on the fertilizer bag is only a relative measurement of how the fertilizer formulation will affect media pH. In otherwords why is 20-10-20 more acidic than 15-0-15? Because 20-10-20 has more ammonium than 15-0-15.

To rephrase, I'm asking, "what are the pros and cons of these different forms and combinations of N, beyond how they affect the substrate pH?"

The Nitrate form of Nitrogen carries a negative ionic charge. This helps the plant produce leaves and stems and helps to bulk up buds. The ammoniacal N carries positive ions and these help grow calyxes and pistols. Timing each application correctly should provide the soil energy needed to grow healthy happy plants.

And this seems to be the answer! TY

 

[Momma's Kitchen]

You are a true bod when it comes to this stuff Mr Sauga. Total respect for your intelligence and knowledge buddy. Not often we find someone of your calibre that has an actual personality and you certainly rank up there as one of the major personalities on here. Peace and love buddy

Intelligence is sexy!

 

[Ganjagrandaddy]

Intelligence is sexy!

Just don't look at his feet !!!. Lol

 

[Buds Buddy]

The content of the water determines how the roots respond. This is what he's saying in 2 a-d.

This part confuses me. If the content of the water determines root response & you add nutes to your water then the nutes are part of the water content at this point.
If after time it raises your soil pH (which is what I thought we were taught from day 1) , I would think adjusting your nute / water content pH would help keep the soil pH in the correct range longer. All this is just way over my head.
I guess I'll pH 1 plant & not the other & see what happens to get a better understanding. I have 2 Blueberry's less then a week old in FFOF & haven't fed any nutes yet. Haven't pH'd water yet either; but was planning to once it gets 2 sets of leaves. So I'll pH one to 6.4 every time & I wont pH the other to see what happens. Going to start a journal on that later today. I'm interested in seeing if there's a difference or not.