The Cal-Mag of my dreams?

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

I realize we're going way, way, way OT from the reason I started this thread, but we're getting a lot of good "value added" information, so let's keep it going...

In one of his responses to my "Fertilizers explained" presentation, SDK1 included this chart showing the relationship between pH and nutrient availability:

pH_nutrient_ availability_ chart01.jpg
pH_nutrient_ availability_ chart01.jpg (81.4 KiB) Viewed 744 times
Obviously quite different from the chart Mike posted, so I'll use SDK1's chart to illustrate something:

pH_nutrient_ availability_ chart02.jpg
pH_nutrient_ availability_ chart02.jpg (81.33 KiB) Viewed 744 times
As I said in a previous post, my acidified watering solution starts out with a pH of 5.5 and slowly rebounds up to 7.0 when the mix completely dries out. Not thrilled about nutrient availability of the top 6 elements in the 5.5-6.0 range, so I think this makes a good argument in favor not acidifying so much:

pH_nutrient_ availability_ chart03.jpg
pH_nutrient_ availability_ chart03.jpg (81.3 KiB) Viewed 744 times
I learned about the difference between temporary and permanent hardness from Jerry, so I know that acidification deals only with temporary hardness produced by bicarbonates (mostly Calcium bicarbonate) in tap water. Here's a "what if" question -- what if water remaining in the mix rebounds up above 7 right before it completely dries out? Last time I tested it a few weeks ago, the pH of my tap water is 7.3, so the residual water in the bottom of the pot won't rebound above that. My guess is that it won't be a problem, and I think the cacti would benefit more if I start the watering solution out at 6.0 rather than 5.5 when they're watered. For those of you who'd like to answer the question -- if you agree with my thought here, I'll start recommending that growers should acidify their watering solution to bring it down no lower than 6 whenever they water their cacti.
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jerrytheplater
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Re: The Cal-Mag of my dreams?

Post by jerrytheplater »

Steve Johnson wrote: Thu Feb 02, 2023 7:16 am
I learned about the difference between temporary and permanent hardness from Jerry, so I know that acidification deals only with temporary hardness produced by bicarbonates (mostly Calcium bicarbonate) in tap water. Here's a "what if" question -- what if water remaining in the mix rebounds up above 7 right before it completely dries out? Last time I tested it a few weeks ago, the pH of my tap water is 7.3, so the residual water in the bottom of the pot won't rebound above that. My guess is that it won't be a problem, and I think the cacti would benefit more if I start the watering solution out at 6.0 rather than 5.5 when they're watered. For those of you who'd like to answer the question -- if you agree with my thought here, I'll start recommending that growers should acidify their watering solution to bring it down no lower than 6 whenever they water their cacti.
Steve, it seems to me you are making assumptions of what is going on in the pot after watering. Have you actually tested the pH in your pot at various times during a watering cycle? Do you have anything to back up what you are saying?

Test the pH of just the water you use to make up the fertilizer over the course of the two weeks it takes a pot to dry out. This will tell you what is happening to your water.

Have you tested the pH of your fertilizer solution in the bottle over time? Do you see any change in the pH? Test right after make up and daily over the course of time it takes one of your pots to dry out. This will tell you what is happening to your fertilizer by itself. If anything.

Take some of each of the components of your potting mix and test their pH initially and for a few days afterwards. Use the same water you use to make up your fertilizer. See what you see. You may find only one component is causing a change in pH. Maybe none. Maybe all.

Add some fertilizer watering solution to the individual components of your potting mix and test pH. See how they compare to the water tests.

Add only water to the combined potting mix and test its pH over the course of two weeks. See what happens there.

Its a lot of testing, but it is a great way to really get an idea of what is happening. Of course, none of the above takes account of the action of the plant roots on the potting mix.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

jerrytheplater wrote: Thu Feb 02, 2023 3:06 pmSteve, it seems to me you are making assumptions of what is going on in the pot after watering. Have you actually tested the pH in your pot at various times during a watering cycle? Do you have anything to back up what you are saying?
You make a valid point about my assumptions, but it's not something I haven't already thought about. Your first question poses a problem -- this is the pumice-granite gravel mix I'm using for 64 of my 68 cacti:

Pumice-DG_rinsed04242016_forum.jpg
Pumice-DG_rinsed04242016_forum.jpg (201.76 KiB) Viewed 717 times
I checked out pH testers for hydroponics online, but there's not much of a choice, and the ones I found are more expensive than I'm willing to pay for. Of course a pH tester in the pot would be best, but not the only way to do what I'm after. I realize that the runoff test I described in my acidification "how to" sticky probably doesn't produce valid results, so I just came up with a better testing procedure -- simple without being simplistic. If I don't have the time to lay out the steps tonight, I'll post them over the weekend. And since I have at least another 6 weeks before SoCal's growing season begins, I'll have plenty of time to try the testing procedure for myself. Even if the results aren't a 100% accurate reflection of what goes on in the pot as the mix dries out completely, they'll be a lot better than what I was doing with the runoff test -- in which case I'll need to seriously revise that sticky.
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Re: The Cal-Mag of my dreams?

Post by jerrytheplater »

I thought you bought one of those pH pens from what you posted on a post somewhere on this site. I read them and don't always remember where they are!!
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

jerrytheplater wrote: Fri Feb 03, 2023 3:04 pm I thought you bought one of those pH pens from what you posted on a post somewhere on this site. I read them and don't always remember where they are!!
That's a problem -- so many posts, and the time it takes to dig through what you want can become awfully time-consuming. This is the pH meter I've been using:

Milwaukee_Instruments_PH600.jpg
Milwaukee_Instruments_PH600.jpg (9.8 KiB) Viewed 685 times
Great for testing water in a jar, no bueno sticking it into a pot. A probe-style pH tester in the pot would be great, but what I've found online is way more expensive than what I'm willing to pay for. After I made the mistake of letting the electrodes on my first 2 Milwaukee Instruments pH 600s go dry too long, I started keeping pH 600 #3 in a covered jar so the electrode stays wet all the time. Still going strong, although my bottle of 7.0 reference solution went past its expiration date, so I have another bottle in my Amazon shopping cart. I'll get it (along with the Thinkscale and a packet of Sodium molybdate from eBay) before I try out this testing procedure:

1. Test the pH of my tap water and write down the number -- this gives me a baseline.

2. Make a gallon of watering solution diluted with 1/2 tsp. Dyna-Gro 7-7-7, 5 fluid ounces Potassium sulfate stock solution, 1/4 tsp. TPS CalMag, and 2 tsp. Sodium molybdate stock solution. Test the pH and write down the number if the 7-7-7 and fert supplements have changed it.

3. Add acidifier (in my case, it's the usual 5% white vinegar). The target pH I'm aiming for is 5.5, so I'll "sneak up" on it by adding it in small increments (1/8 tsp. per increment). I'll keep track of how many spoonfuls I added to hit the target, then write down the total amount of acidifier for future reference.

4. Fill a large plastic container about halfway with pumice-granite gravel mix, then fill it all the way up with watering solution. Draw out some of the water, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the number, put the test water back into the container, then put a lid on the container. That's Day 0.

5. Day 1 -- draw out some of the container's water again, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the number. Put the test water back into the container, then put a lid on the container.

6. Continue doing the same each day (that includes writing down the daily numbers) until I reach...

7. Day 7 - draw out some of the container's water one more time, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the final number.

That'll give me 7 days of reaction time between the watering solution and the mix, so I'll have a better idea regarding how much pH rebound may be involved by the time the mix completely dries out in the pot. Unfortunately the test results won't be 100% accurate since a container full of mix and water isn't the same as water being taken up by cactus roots as it dries out (yeah, I know -- evaporation). But if the test is more like 90% accurate, IMO that's good enough. The point of this exercise isn't just for me -- while I may be in the minority, I'm by no means the only one growing cacti in a soil-less mix. If the testing procedure works, I'll revise the acidification "how to" guide accordingly. Since the procedure is designed more for growers taking a soil-less approach, I'll suggest that people growing cacti in soil-based mixes use soil pH testers instead.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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MikeInOz
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Re: The Cal-Mag of my dreams?

Post by MikeInOz »

Steve Johnson wrote: Sat Feb 04, 2023 12:02 am

That'll give me 7 days of reaction time between the watering solution and the mix, so I'll have a better idea regarding how much pH rebound may be involved by the time the mix completely dries out in the pot.
But when the water dries up in the container the minerals (carbonates etc) in the water will be more concentrated and the pH will be higher than what you are measuring and that is what the plants roots will be seeing.
The better way to test would be to use a standardized volume of water (say 200ml) passed slowly through the mix (with a plant in it) and measure that after watering with your solution and then again after it dries out.
An even better way to test pH of your mix is to remove some of it (again a sample that has had a plant growing in it) and use an amount of water to make a slurry. Add enough water to the mix slowly until it is just more than wet. (so there is some free water but just more than no free water if that makes sense. ''Free water'' would be that which drains away from the mix) The ''saturated paste.'' Then insert your probe into that and take a reading straight away if the mix was just watered and drained, or after 10 minutes if the mix is completely dry. Like you said, this is not up to lab standards but will give you some idea of what is going on. In fact you can probably skip reading the mix after watering and just check the dry mix because you know the moist mix will have a lower pH - close to that of your solution. You should probably use distilled water to make things easier. Another thing to consider is that even if the pH will be higher in a dry mix it doesn't really mater because the plant will not be taking up water and nutrients at that time. The important pH is that of the extractable water held in the mix with it's dissolved nutrients.
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

Are there any chemists in the house? Reason I ask is that I'd like to know what happens when the acetic acid in vinegar reacts to the Calcium bicarbonate in my tap water. I couldn't find a direct answer online, but this might get us close...

From Socratic Q&A:
  • What are the products when calcium carbonate and acetic acid react?

    Answer:

    CaCO3 + CH3COOH → Ca(CH3COO)2 + CO2 + H2O

    Ca(CH3COO)2 is calcium acetate.
Calcium bicarbonate is C2H2CaO6, so if someone can let me know the products of a Calcium bicarbonate-acetic acid reaction, I'd like to find out if one of them also happens to be Calcium acetate. If so, I may have an interesting thought worth sharing.
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

Okay, I just signed up for a free website called Quora (https://www.quora.com/), a place where many questions can be asked and answered by knowledgeable people. And when I signed up, I asked about what happens when Calcium bicarbonate reacts with acetic acid. The answer I'm hoping for -- one of the reaction products is in fact Calcium acetate. If that's the answer I get, acidifying temporarily hard tap water with vinegar could be a nice little benefit to our cacti and succulents. Now let's see what happens when I get my answer from Quora.
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MrXeric
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Re: The Cal-Mag of my dreams?

Post by MrXeric »

I'm not a chemist, just familiar with the basic principles at the undergraduate level, but calcium bicarbonate exists only as aqueous solution in the form of [Ca]2+ and [HCO3]- ions in water, in equilibrium with dissolved CO2 and carbonate ions. Similar to aqueous sodium bicarbonate, the acid part in acetic acid will react with the bicarbonate (and carbonate) to produce CO2 and water, leaving you with calcium and acetate in ionic form that will crystallize when dry as calcium acetate.
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Re: The Cal-Mag of my dreams?

Post by jerrytheplater »

Steve Johnson wrote: Sat Feb 04, 2023 10:43 am Are there any chemists in the house? Reason I ask is that I'd like to know what happens when the acetic acid in vinegar reacts to the Calcium bicarbonate in my tap water. I couldn't find a direct answer online, but this might get us close...

From Socratic Q&A:
  • What are the products when calcium carbonate and acetic acid react?

    Answer:

    CaCO3 + CH3COOH → Ca(CH3COO)2 + CO2 + H2O

    Ca(CH3COO)2 is calcium acetate.
Calcium bicarbonate is C2H2CaO6, so if someone can let me know the products of a Calcium bicarbonate-acetic acid reaction, I'd like to find out if one of them also happens to be Calcium acetate. If so, I may have an interesting thought worth sharing.
Calcium bicarbonate and Calcium Carbonate will react very similarly with acetic acid. Both will produce Calcium acetate. If you want a balanced equation, I could probably do it, but you really don't need it in my opinion. I doubt you are calculating concentrations etc.

Edit: I didn't see the post by Steve and Eric before writing my post above. Don't know how I missed them.
Jerry Smith
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2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Re: The Cal-Mag of my dreams?

Post by jerrytheplater »

Steve Johnson wrote: Sat Feb 04, 2023 12:02 am
1. Test the pH of my tap water and write down the number -- this gives me a baseline. You should test a container of tap water right after filling and then a few days later. There could easily be a change.

2. Make a gallon of watering solution diluted with 1/2 tsp. Dyna-Gro 7-7-7, 5 fluid ounces Potassium sulfate stock solution, 1/4 tsp. TPS CalMag, and 2 tsp. Sodium molybdate stock solution. Test the pH and write down the number if the 7-7-7 and fert supplements have changed it.

3. Add acidifier (in my case, it's the usual 5% white vinegar). The target pH I'm aiming for is 5.5, so I'll "sneak up" on it by adding it in small increments (1/8 tsp. per increment). I'll keep track of how many spoonfuls I added to hit the target, then write down the total amount of acidifier for future reference. It would be a good idea to test the pH of the fertilizer water daily for a week too, just to be sure.

4. Fill a large plastic container about halfway with pumice-granite gravel mix, then fill it all the way up with watering solution. Draw out some of the water, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the number, put the test water back into the container, then put a lid on the container. That's Day 0. Doing it this way will not allow you to know which part, if any, is causing a pH change. Make sure you stir up the potting mix before taking your water sample. Filtering is really not needed. Let it settle a few minutes and you are fine.

5. Day 1 -- draw out some of the container's water again, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the number. Put the test water back into the container, then put a lid on the container. Don't forget to stir.

6. Continue doing the same each day (that includes writing down the daily numbers) until I reach...

7. Day 7 - draw out some of the container's water one more time, and filter it with a funnel and a brown paper coffee filter into a small mason jar. Test the pH and write down the final number.

That'll give me 7 days of reaction time between the watering solution and the mix, so I'll have a better idea regarding how much pH rebound may be involved by the time the mix completely dries out in the pot. You will be seeing the effect of the potting mix on your fertilizer solution, if any.Unfortunately the test results won't be 100% accurate since a container full of mix and water isn't the same as water being taken up by cactus roots as it dries out (yeah, I know -- evaporation). But if the test is more like 90% accurate, IMO that's good enough. The point of this exercise isn't just for me -- while I may be in the minority, I'm by no means the only one growing cacti in a soil-less mix. If the testing procedure works, I'll revise the acidification "how to" guide accordingly. Since the procedure is designed more for growers taking a soil-less approach, I'll suggest that people growing cacti in soil-based mixes use soil pH testers instead.
See my comments in red above.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Re: The Cal-Mag of my dreams?

Post by ohugal »

While I do like the thoroughness of the experiment, I think from step 4 onwards the experiment is very different from what is actually happening in cultivation. Can I ask why? Isn't what MikeInOz suggests closer to 'reality'?
I would also like to know if it's better to make up your solution and water right away or not? To test the pH of my tap water, I usually leave it for 48h and then test it. After adding the acidifier, fertilizer, stock solutions, ... I would be inclined to use it immediately.
What is the effect of calcium acetate on your watering solution?
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Steve Johnson
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Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

ohugal wrote: Sun Feb 05, 2023 10:21 am While I do like the thoroughness of the experiment, I think from step 4 onwards the experiment is very different from what is actually happening in cultivation. Can I ask why? Isn't what MikeInOz suggests closer to 'reality'?
I would also like to know if it's better to make up your solution and water right away or not? To test the pH of my tap water, I usually leave it for 48h and then test it. After adding the acidifier, fertilizer, stock solutions, ... I would be inclined to use it immediately.
What is the effect of calcium acetate on your watering solution?
Wait for it -- I'm working on a post that'll change the direction I was going in. For now, I'll just say that the testing procedure I had in mind is unnecessary. I should be ready to post the latest information sometime tomorrow. And I think you may be interested in the answer to your question on calcium acetate.
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Re: The Cal-Mag of my dreams?

Post by ohugal »

(tense music playing) 😁
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Re: The Cal-Mag of my dreams?

Post by Minnesota »

ohugal wrote: Sun Feb 05, 2023 2:49 pm (tense music playing) 😁
a teaser to keep us all reading, and waiting.
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