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Is the calcium in tap water available to plants?

Dr.Mantis

Active member
The question is, why should a person think that something dissolved in water is unavailable? (calcium in aqueous solution obviously being ionized Ca++)
Fair point, especially if your soil pH is good and has decent buffering capacity. If you run in lower ec substrates like coco or hydro, then adding high Ca water with high alkalinity will lock out other nutrients like iron via precipitation. I guess if your water report doesn’t have really high residual alkalinity, and your grow medium has good buffer capacity, then high Ca tap water shouldn’t be an issue. Otherwise, it’s probably a good idea to correct the pH or remove the salts via RO.
 

Ca++

Well-known member
Yeah, I really liked nitric acid when I used plain tap water. The other nice thing too, is all metal nitrates have very good solubility, so it can be very useful for flushing overly mineralized soils.

This time around, I’ve switched to citric acid as my pH corrector. Has nice chelating capabilities, and buffering capacity. Also, I wanted to see if there was any benefit to growing plants without any added nitrates. Time will tell!
Nitric is pretty much all available, but phosphoric about 50%. As 50% isn't, the pH has more reason to stay stable. Though I suspect you know this, others may be interested.

I think you are saying you are in soil. There, the ammonium to nitrate ratio isn't generally a thing. I have my eye on this though. An LED user in soil, just used chicken waste tea, and his plants did some LED stuff. Signs somewhat foreign to us before LED. He saw pH as an indicator, but I lost the thread before it got started.

It's a fledging interest. Revolving around the idea of 10% max nh3 we follow. Looking at how we can't control the nh3 uptake except through pH. Then just what excess nh3 would really do. I'm looking toward K with interest. With the mid leaf stripes on my mind. We know the blue light may drive water out of them more than HID did. Opening the stomata another 10% perhaps. It seems those signs can come on rapidly, like a day, so transpiration increases from pumping up the power seem to tie in. It's a lot of info to manage though, based on the little I know at the moment.

If you have some idea what I'm speaking of, look out for it for me please. You might be doing a test grow of interest regarding the N types and LED use.
A big spanner in my thoughts, is how soil plants actually seem a little more resistant to that.
 

Dr.Mantis

Active member
Nitric is pretty much all available, but phosphoric about 50%. As 50% isn't, the pH has more reason to stay stable. Though I suspect you know this, others may be interested.

I think you are saying you are in soil. There, the ammonium to nitrate ratio isn't generally a thing. I have my eye on this though. An LED user in soil, just used chicken waste tea, and his plants did some LED stuff. Signs somewhat foreign to us before LED. He saw pH as an indicator, but I lost the thread before it got started.

It's a fledging interest. Revolving around the idea of 10% max nh3 we follow. Looking at how we can't control the nh3 uptake except through pH. Then just what excess nh3 would really do. I'm looking toward K with interest. With the mid leaf stripes on my mind. We know the blue light may drive water out of them more than HID did. Opening the stomata another 10% perhaps. It seems those signs can come on rapidly, like a day, so transpiration increases from pumping up the power seem to tie in. It's a lot of info to manage though, based on the little I know at the moment.

If you have some idea what I'm speaking of, look out for it for me please. You might be doing a test grow of interest regarding the N types and LED use.
A big spanner in my thoughts, is how soil plants actually seem a little more resistant to that.
Hey, I am a soil grower, but had to switch to liquid feeding due to container sizes. I think I know what you are referencing, and I’ll send you a pm with more info so I don’t derail this thread.
 

Dr.Dutch

Member
Regarding the topic, as long as calcium is dissolved in water, it is plant-available. Calcium in tap water is 100% plant-available.
No calcium in tap water is not available to plants. 😎
I assume the smiley is expressing irony :)


I use nitric, as it burns off the carbon, that leaves as dioxide. While bonding with the Calcium to form calnit. Plants will actively take N, with the Ca along for the ride.
No, calcium nitrate does not form when you add nitric acid to your tap water. For calcium nitrate to form, the concentration would need to be so high that it exceeds the solubility of calcium nitrate (which is quite difficult because it is highly soluble). Instead, calcium sulfate and calcium phosphate will form in your solution first, which are both much more insoluble and than not plant-available. And undissolved calcium nitrate is also not plant-available.

Nitric is pretty much all available, but phosphoric about 50%. As 50% isn't, the pH has more reason to stay stable. Though I suspect you know this, others may be interested.
I believe you might be confusing something. Phosphoric acid dissociates depending on the pH. At a pH around 6, it exists as H2PO4 and HPO4. Both of these forms are plant-available.
 

Creeperpark

Well-known member
Mentor
Veteran
Tap water is an unreliable source of calcium to generalize as a group for everyone to use. If you live in a big City with over a million people vs a small town the water will be different. Recommending tap water to everyone is an unreliable recommendation. If I recommend using tap water that's alkaline I will give a bad recommendation and hurt your plants by the time you get in flowering. If a person is going to grow the best cannabis they can grow, they need to use quality water.
 

Dr.Dutch

Member
If you know what's in your water and calculate it with, it's not a problem.
You are right that the quality can vary (hardly a problem in my country, I don't know how it is in the US).
But the calcium what is in the water is plant available. Regardless of whether the quantity varies.

12. Water Quality

Tap water can be used if it does not contain high levels of sodium, heavy metals, boron, and bicarbonate. Some water sources can have fertilizer concentrations of Ca, Mg, S, and micronutrients. These nutrients are bioavailable and must be included when formulating the nutrient solution. When tap water cannot be used, the most cost-effective water purification method is reverse osmosis (RO), which removes about 97% of the ions in tap water. For critical applications, RO water is often additionally filtered through a deionization column, which removes 90 to 99% of the remaining ions.
In some locations, the use of tap water can result in accumulation of sodium (Na) in recirculating solutions, which reduces plant growth. Elevated salinity reduces leaf growth and development [120], so keeping Na concentrations below 6 mM (138 ppm) is recommended to avoid salinity problems [121]. Reducing Na and other undesirable ions in solution typically requires discarding some of the solution.
High concentrations of bicarbonate in some tap waters increase the alkalinity of the nutrient solution. Bicarbonate can be neutralized to water and carbon dioxide (which leaves solution) through the addition of acid. Continuous acid injection through an injector may be necessary if bicarbonate concentrations are continuously present.
Although we have high-quality tap water with low levels of undesirable elements at Utah State University, we use RO water for hydroponic research studies.
 

Creeperpark

Well-known member
Mentor
Veteran
If you know what's in your water and calculate it with, it's not a problem.
You are right that the quality can vary (hardly a problem in my country, I don't know how it is in the US).
But the calcium what is in the water is plant available. Regardless of whether the quantity varies.
Dr Dutch you guys are lucky to be able to use your tap water. Most people don't know what is in their water. In the US most tap water is modified to raise the pH to stop heavy metals from leaching into the drinking water. When the tap water pH is 9 or above the calcium is not as available as it is when the pH is 6.2. It doesn't matter how much calcium is there. Personally, my tap water is 500 ppm loaded with calcium but with a 9.5 pH it's mostly unavailable. I never recommend tap compared to quality water.
 

G.O. Joe

Active member
Veteran
Or more precisely and according to the solubility of Ca at various pH, salinity, and temperature levels, why should a person think that Ca dissolved in water at alkaline pH is unavailable at that or lower pH?

Would 0.004% solubility be out of line at pH 9?
 

Dr.Mantis

Active member
I think there are some good point being made for both sides, and I think there is actually agreement. However, I believe the differences come down to the use cases and generalizations therein.

Is Ca completely dissolved in tap water at slightly acid, neutral, or slightly alkaline pH plant available? Probably, after all it’s full dissociated and in solution. What is the real world applicability of this? I mean, if I took my pH 8.6 water with 250ppm ca and poured into plants it would cause all sorts of issues. Sure the Ca is available in the water, but at pH 8.6 as soon as that calcium ion sees a phosphate from my soil it’s goin to ppt out as a hydroxyapatite or something. And, as soon as that bicarbonate anion sees a ferrous ion, or manganese ion it’s going to ppt those out of solution as well. So, sure it is “plant available” out of the tap. In the real world though, it’s not great advice to dump high alkalinity tap water on your plants without taking into consideration the other factors. So I tend to agree with creeper on this one.
 

G.O. Joe

Active member
Veteran
Why should a person think that watering soil or promix with plain tap water of pH 9, or especially nute mixture dissolved in same - even more especially if a good chunk of the N is NH4 - changes the root zone pH to 9?

Or that in the real world, hard water instantly precipitates fert phosphate, or Fe and Mn in their usual chelated forms?
 

Dr.Mantis

Active member
If your pH is 9 and your water has high buffer capacity Fe and Mn are going to ppt out pretty quick, especially as the root zone dries up. Likewise phosphate is going to ppt out quite quickly. The solubility constants for these are extremely low. Sure edta and the like can help, but it’s not a magic bullet in all scenarios. It’s true the root zone buffers it’s own pH, but if your dumping liters of pH 9 water with high residual alkalinity it will temporarily overwhelm the root zone buffer capacity. Yes, the roots while gradually bring it back into the ideal range, but one something like cal phos ppts, or Fe ppts and oxidizing to ferric oxide/hydroxide it’s much more difficult to re dissolve.

So to add some more nuance, like you are hinting at, soil and media with high cec can handle tap water better than hydro or soil-less.
 

G.O. Joe

Active member
Veteran
If your pH is 9 and your water has high buffer capacity Fe and Mn are going to ppt out pretty quick, especially as the root zone dries up. Likewise phosphate is going to ppt out quite quickly.

A lot of crops worldwide are watered with alkaline water with no problem. Greenhouses. Lawns, gardens, golf courses.

Perhaps you should start your own "is phosphate bioavailable in hydro in the presence of excess calcium at a pH of 9.5?" thread. An account of hydro with tap water, yes, taking account of the starting ppm, which is a constraint especially at the beginning. (the truth is there was not much difference between GH hard water formula and normal):
 

Dr.Mantis

Active member
A lot of crops worldwide are watered with alkaline water with no problem. Greenhouses. Lawns, gardens, golf courses.

Perhaps you should start your own "is phosphate bioavailable in hydro in the presence of excess calcium at a pH of 9.5?" thread. An account of hydro with tap water, yes, taking account of the starting ppm, which is a constraint especially at the beginning. (the truth is there was not much difference between GH hard water formula and normal):
I’m not a hydro grower, so no, I won’t. However, thanks for sharing those are some nice looking plants! I didn’t read every post, but it looked like you were using lemon juice and later on phosphoric acid to correct your pH?
 

Creeperpark

Well-known member
Mentor
Veteran
A lot of crops worldwide are watered with alkaline water with no problem. Greenhouses. Lawns, gardens, golf courses.

Perhaps you should start your own "is phosphate bioavailable in hydro in the presence of excess calcium at a pH of 9.5?" thread. An account of hydro with tap water, yes, taking account of the starting ppm, which is a constraint especially at the beginning. (the truth is there was not much difference between GH hard water formula and normal):
Thanks for sharing friend. I work in a greenhouse's friend and we used acid infectors to lower the alkalinity. The same goes for golf courses here where I live. The reason is the tap water won't work and causes big problems here. Using acid injectors is so easy to use and it's common practice when there's a lot of bicarbonate or carbonate in the water.
 

Creeperpark

Well-known member
Mentor
Veteran
If you don't know what's in your water and use it, you are putting unknown ppm that can accumulate in the growing media. Some can get by with it and others can't.
 

Three Berries

Active member
When you pH down carbonate laden water that releases the calcium and magnesium in free readily available form. Any time an acid (H+) comes in contact with a carbonate (-) it will reduce the atomic charge to neutral. This is an ongoing process through physical contact with the chemical compounds. It's why carbonates are called a buffer. When the carbonates compound charge is reduced to 0, all used up, then the buffering stops, all the metal elements are available until they again react with something and pH will go down or up depending on what is added pH wise.

None of this takes into consideration of what microbes do as far as breaking down compounds in soil. But they use acids too....
 

Ca++

Well-known member
For a pH below 6, we need more dissolved co2 in the water, than bicarbonates. The acid provides the H that turns the bicarbonates to co2. We see it as burning them off.

I won't provide the equation, as I don't understand it. I just take what I'm told with chemistry.
 

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