Use of Ammonium Sulfate fertilizer

[astro_ian]

Does anyone have experience using Ammonium Sulfate when watering?

Here are the articles I found about ammonium sulfate and acidic water (Ph 5 - 5.5)

https://chinlecactusclub.org/plant-watering/
https://oklahomacactusdotcom.files.word ... -grow1.pdf

[Steve Johnson]

Does anyone have experience using Ammonium Sulfate when watering?

Here are the articles I found about ammonium sulfate and acidic water (Ph 5 - 5.5)

https://chinlecactusclub.org/plant-watering/
https://oklahomacactusdotcom.files.word ... -grow1.pdf

There are too many things in those articles which are just plain wrong, so I'd like to debunk them before anyone decides to follow their recommendations. I'll begin with Don Campbell's use of 21-0-0 Ammonium sulfate and 20-20-20 fertilizer...

• This comes from a professional horticulturalist on the forum who has been growing cacti and succulents quite successfully for many years. The best explainer of ferts I've ever seen, so many thanks to MikeInOz for what I'm passing along here:
  
  The basic "rule of thumb" -- P lower than N, K higher than both. Using N as a constant of 1, the "ideal" ratio is 1:0.4:1.5. Unless you live in Australia or the UK, the NPK values on fertilzer labels need some explaining. N is the true amount of Nitrogen available to the roots. However, P is reported as Phosphorus pentoxide (P2O5), so %P2O5 on the label x 0.436 = elemental P. K is reported as potash (K2O), so %K2O on the label x 0.83 = elemental K. Don's true elemental NPK values are in fact 21-9.16-17.43. Once again using N as a constant of 1, the ratio is 1:0.44:0.83. The balance between N and P is pretty much ideal, and supplementing the fert with the right amount of Potassium sulfate would strike a good balance between N and K. If he knew about that, got the amount of Potassium sulfate right, and got the dilution right too, he would've been fine. But adding Ammonium sulfate? In that amount? Way, way, way too much N. In his defence, Don was correct about the need for acidifying hard water, and I'll discuss that further in a moment.

• Also in the first article, there's no mention at all concerning minor nutrients and micronutrients. Calcium, Magnesium, and Sulfur are important minor nutrients for cacti, and the importance of micronutrients shouldn't be underestimated either. Even if Don had them in his 20-20-20, excessive N with the addition of Ammonium sulfate would've inhibited their uptake into his plants' roots. End result, nutrient deficiences all over the place (including K!). It's not just about NPK, and IMO fert articles that don't include a discussion of minor and micronutrients are missing the "big picture" of what it all means to the long-term health and growth of our cacti. Sorry, but Don was missing it by a mile.

• The second article came up for discussion about a year ago. I know almost nothing about chemistry, so I wanted to have an actual chemist review it. Check this out:

  https://docs.google.com/file/d/0Bwfo_53 ... l=en&pli=1
  
  This article is incredibly detailed, and to be honest, all the chemistry being discussed there was (and still is) way over my head. If you have a good grasp of chemistry, the answer you're seeking may be in there somewhere.

  Thanks. Now, I am a PhD Chemist but it's been a few decades since I looked at such basic chemistry. That being said the discussion in the paper is not at all clear to me either. It seems like a rather circular argumentation. I don't have the time at the moment to deep dive this. If I get around to it I'll provide a hopefully clearer description here.
  
  That being said I agree with their suggestion to use vinegar (acetic acid) or citric acid instead of the other acids. Both for the reasons they list (no need to account for changes to N/P ratio and the formation of soluble salts) but also safety. Especially, if you're using conc. sulphuric acid make sure to use proper safety PPE and procedures (add acid to water!).
  
  Needless to say the authors don't gain any favours with me making statements about the definition of the pH value like "This is an odd number invented by chemists to confuse people.".

  Not the first time when the assertions made by Roberts and Burleigh couldn't pass the logic test by trained chemists.

Shortly after I joined the forum in November 2011, I stumbled on the second article, and the only worthwhile thing I got out of it was understanding that I need to acidify my tap water. Here's a presentation I wrote back in September 2019 -- perhaps more than what casual growers are willing to do, so this is geared toward hobbyists who aren't quite as casual about how they want to grow their cacti:

http://www.cactiguide.com/forum/viewtop ... 25&t=43525

For those of you who do find pH test strips which produce accurate readings, that's great. However, if you'd like to go with a pH meter, the Milwaukee Instruments pH 600 I mentioned in the presentation may not be the only game in town anymore. The most accurate meters are the ones we can calibrate, and that's what to look for as you search around.

By the way, just a reminder:

http://www.cactiguide.com/forum/viewtop ... =2&t=43816

I know that you're not a new member, but it would still be helpful to know where you live in case you need advice re. your plants.

[keith]

I use vinegar and my soil PH is high but never used Ammonium Sulfate on cactus. I have Used Ammonium Sulfate on my lawn with mixed results sometimes it greens up sometimes it doesn't I thought it had to do with temperature ? That's just throwing it on the lawn in pellet form.

If I mix the Ammonium Sulfate with miracle grow in a bucket of water the grass will green up. The Ammonium Sulfate was a white pellet that turned grey in water.

[Steve Johnson]

I use vinegar and my soil PH is high but never used Ammonium Sulfate on cactus. I have Used Ammonium Sulfate on my lawn with mixed results sometimes it greens up sometimes it doesn't I thought it had to do with temperature ? That's just throwing it on the lawn in pellet form.

If I mix the Ammonium Sulfate with miracle grow in a bucket of water the grass will green up. The Ammonium Sulfate was a white pellet that turned grey in water.

You bring up a good point, and I'm not sure if Elton Roberts realized that the Nitrogen in Ammonium sulfate is like a "sugar rush" cacti can't handle if they get too much of it. Here's the chemical analysis of the Dyna Gro 7-7-7 I've been using for almost 10 years:



That little "sugar rush" of Ammoniacal N is balanced by the Nitrate acting as slower-release N, Nitrate being 2.3 times higher than Ammoniacal. Although it pertains to nonxeric plants, I just found a really interesting article from Cornell University, and the following quote should interest us cactus growers as well:

"Ammonium toxicity

"Often nitrogen is applied at concentrations greater than plants can readily absorb. Plants can take up and store additional nitrogen to use later if nitrogen becomes limiting. Nitrate can be safely stored by plants; but when plants take up and store too much ammonium, cell damage can occur."

This makes a good argument in favor of 2 things:

• Not overdoing it when we fertilize our cacti. How much and how often will depend on the individual's growing practices based on experience.

• Avoid using straight-up Ammonium sulfate on cacti like the plague. A fert properly balanced between Ammoniacal and Nitrate is all you need.

Sadly, Elton Roberts is still considered to be an authority among hobbyists who don't question it -- or don't know that they should.

[keith]

https://www.youtube.com/watch?v=BHc4W6y05jo

Elton does not use vinegar he uses some other powder chemical to lower the PH forgot what it was but here is a youtube of his collection and the talk about acidifiying water . Sound is out on this PC or I could hear what the chemical is ... right about the middle of the video he talks about it

[Steve Johnson]

https://www.youtube.com/watch?v=BHc4W6y05jo

Elton does not use vinegar he uses some other powder chemical to lower the PH forgot what it was but here is a youtube of his collection and the talk about acidifiying water . Sound is out on this PC or I could hear what the chemical is ... right about the middle of the video he talks about it

He says it right at the beginning of the video -- Sodium bisulfate. I understand why he got away from using Sulfuric acid, although I don't know if Sodium bisulfate is necessarily the best alternative compared to citric acid for long-term use. Elton's understanding of chemistry is questionable, so I'd be interested get a take on this from our members who actually know chemistry.

[astro_ian]

Keith thanks for the video link

"Ariocarpus is super slow growing right? " YES" Elton replied " NO " Not if you give them acidic water"
https://www.youtube.com/watch?v=BHc4W6y05jo

15:30 on the video clip. Elton mentioned using Sodium Bisulfate to reach PH 5, ammonium sulfate and small fraction of 20-20-20 fertilizer. He has been growing cactus for 60 years. its been working well and proven to be effective with results. I don't see why would it be bad for cactus.

[DaveW]

Is there anything wrong with using Ferrous sulphate to acidify the water occasionally? I have been adding a few granules to two gallons of water? Not measured the PH though yet.

https://www.lovethegarden.com/uk-en/pro ... ting%20out.

[C And D]

To add to the discussion

I now use "ph Down"
which is phosphoric acid and used for Hydroponics

I have never seen a cactus or succulent grow too fast because of too much Nitrate, but it is possible I guess...
splitting would be a problem, yes, but not that common

But I agree, too much Nitrate is probably not beneficial.

I use a medium low dose of "Grow More" 20/20/20 and the ph Down to about 5.5-6.0 in almost every watering

And nothing grows too fast, it all seems to grow rather slow.

[MikeInOz]

https://www.youtube.com/watch?v=BHc4W6y05jo

Elton does not use vinegar he uses some other powder chemical to lower the PH forgot what it was but here is a youtube of his collection and the talk about acidifiying water . Sound is out on this PC or I could hear what the chemical is ... right about the middle of the video he talks about it

He says it right at the beginning of the video -- Sodium bisulfate. I understand why he got away from using Sulfuric acid, although I don't know if Sodium bisulfate is necessarily the best alternative compared to citric acid for long-term use. Elton's understanding of chemistry is questionable, so I'd be interested get a take on this from our members who actually know chemistry.

Sodium bisulfate should be ok if you only need to add very small amounts to get the pH you want. Generally, sodium is avoided as much as possible in horticulture but it is part of natural systems and a small amount seems to be required. Cacti come from areas subject to complete drying and where there is much less leaching of soil minerals, so they ''should'' be able to tolerate higher salinities than plants coming from wet habitats. Sodium and chloride are usually the first two to cause trouble. I would not use it myself.
I have always used citric acid and used sulphuric (very carefully) for many years before I moved to where I am now.

[MikeInOz]

Is there anything wrong with using Ferrous sulphate to acidify the water occasionally? I have been adding a few granules to two gallons of water? Not measured the PH though yet.

https://www.lovethegarden.com/uk-en/pro ... ting%20out.

Probably ok, as long as you keep in mind that you are adding the trace element Fe each time you do

[MikeInOz]

Ammoinum N promotes top growth and suppresses root growth. Nitrate N does the opposite (although suppression of above ground mass is not quite right, it's more that nitrate does not stimulate it as much as ammonium does. There does seem to be some anecdotal evidence that dry climate plants respond to ammonium more than nitrate but it may be at the expense of a more balanced and resilient growth in the plant. Therefore, it is probably safe to have your ammonium to nitrate ratio about equal to slightly high. I have always used more ammoinum than nitrate for cacti with good results but to use only ammonium sulphate as a program is to be avoided IMO. You could well end up with bloated top growth with a weak root system which is vulnerable to root rot. Straight ammonium sulphate will leach Ca from the mix at a high rate, and unless this is constantly replaced you could have all kinds of problems in the roots. Ammonium is also converted to nitrate in a warm moist mix which is not too acidic over a period of weeks. Another reason to include some form of calcium carbonate.

[Steve Johnson]

Mike, that's why I'm so glad to have you on the forum...

Ammonium N promotes top growth and suppresses root growth. Nitrate N does the opposite (although suppression of above ground mass is not quite right, it's more that nitrate does not stimulate it as much as ammonium does. There does seem to be some anecdotal evidence that dry climate plants respond to ammonium more than nitrate but it may be at the expense of a more balanced and resilient growth in the plant. Therefore, it is probably safe to have your ammonium to nitrate ratio about equal to slightly high.

As I said in my response to Keith on the 14th, the ratio of Ammoniacal to Nitrate in my 7-7-7 is 1:2.3. Would that balance be acceptable, or do you suggest that I add just a touch of Ammonium sulfate to get the ratio closer to equal? If I should, I'll have to figure out what "just a touch" means to determine the right amount.

[MikeInOz]

As I said in my response to Keith on the 14th, the ratio of Ammoniacal to Nitrate in my 7-7-7 is 1:2.3. Would that balance be acceptable, or do you suggest that I add just a touch of Ammonium sulfate to get the ratio closer to equal? If I should, I'll have to figure out what "just a touch" means to determine the right amount.

You're going to complicate things because if you add ammonium you will change the NPK ratio. So to bring that back you will need to add one of the potassium phosphates. So you could use ammonium sulphate + monopotassium phosphate or monoammonium phosphate + potassium sulphate.
You can also use urea as an ammonium source as it is converted into ammonium in the pot within 2 days. It gets tricky! I have all the values in a book so if you choose to go down that path I should have the info. But then you will reduce the concentration of all the other nutrients. That's why I was so pleased to find a controlled release that gave me everything I wanted.

[DaveW]

I have only added a little Ferrous sulphate to the water on an odd occasion. However I Googled "excess iron" for plants and found these since I once read our potting soils in the UK often lacked iron?:-

Interesting is the quote in the link below that iron deficiency is an issue for plants grown on calcareous soils since quite a few of the slow growing cacti grow on these, which possibly Elton's PH 5 watering solves?

http://www.globalsciencebooks.info/Onli ... 57-69o.pdf

https://sciencing.com/effect-excess-iro ... 26745.html

https://homeguides.sfgate.com/effect-ex ... 48927.html