Use of Ammonium Sulfate fertilizer

[7george]

I think that nitrates should be preferred as a nitrogen source from the fertilizer. Ammonium nitrogen is being rendered in the soil into nitrates by bacteria in the soil and thus made available for plants as a nutrition. Do we have those bacteria in our soil and does it stays wet long enough for them to work - this is a question.

[Steve Johnson]

I think that nitrates should be preferred as a nitrogen source from the fertilizer. Ammonium nitrogen is being rendered in the soil into nitrates by bacteria in the soil and thus made available for plants as a nutrition. Do we have those bacteria in our soil and does it stays wet long enough for them to work - this is a question.

An excellent question too. Out of the 68 cacti I have in my collection, I'm growing 65 in a soil-less mix, so obviously there's no soil to support bacteria. Does it mean that those 65 plants aren't able to take up N from the Ammoniacal component in the fertilizer I'm using? Inquiring minds want to know, and if Mike gives us an answer, I'll post a follow-up comment.

[MikeInOz]

Do we have those bacteria in our soil and does it stays wet long enough for them to work - this is a question.

Bacteria are absolutely everywhere. You can't avoid them. As long as there is a food source and moisture they are present. All plant roots have bacteria on and around them and they feed on exudates from the roots. Others feed on N as it becomes available. The conversion to nitrate will happen in a cactus mix but perhaps a little more slowly than in, say, a tropical soil in the wet season.

[MikeInOz]

I'm growing 65 in a soil-less mix, so obviously there's no soil to support bacteria. Does it mean that those 65 plants aren't able to take up N from the Ammoniacal component in the fertilizer I'm using? Inquiring minds want to know, and if Mike gives us an answer, I'll post a follow-up comment.

Yep they can absolutely take up nitrate N, ammonium N and probably organic N as well. Different plants have different preferences. It was once thought that plants needed bacteria to convert urea into ammonium before they could use it, but this has been proven wrong - at least in some cases - by adding urea as the only N source in a sterile flask of orchid seed. Once inside the seedling the urea is converted into ammonium with the aid of an enzyme.

[Steve Johnson]

I'm growing 65 in a soil-less mix, so obviously there's no soil to support bacteria. Does it mean that those 65 plants aren't able to take up N from the Ammoniacal component in the fertilizer I'm using? Inquiring minds want to know, and if Mike gives us an answer, I'll post a follow-up comment.

Yep they can absolutely take up nitrate N, ammonium N and probably organic N as well.

Fantastic! Going back to the question of supplementing the 7-7-7 with a little bit of Ammonium sulfate, your response indicated that the complications I'd be dealing with violate a basic rule I've been following for many years -- if it ain't broke, don't fix it. By the way, I went straight to the manufacturer's website, and the Osmocote you get in Australia simply isn't available here in the US. The closest I have is a control release fert I bought from the California Cactus Center when I started building my current collection in 2011. Took a look at the label this afternoon, unfortunately a no-go. I'm more than satisfied with the 7-7-7 plus the Potassium sulfate supplementation I added to my fert regimen this year. I really can't thank you enough for your expert guidance.

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.

Just because he's been growing cacti for 60 years, it doesn't necessarily mean that his results are as effective as you might think. When cacti get the full spectrum of nutrients they need, and those nutrients are in proper balance, they'll be able to reach their genetic growth potential under cultivation. (Mike's term, and much more accurate than mine when I used to call it "optimal growth potential".) When certain nutrients are missing and/or out of balance, cacti can still be grown, but problems will eventually get the better of them. Worst case scenario -- they could die a premature death if those problems aren't addressed and corrected in time. My contention is that Elton pushes his cacti beyond the limits of their genetic growth potential, and IMO acidifying with Sodium bisulfate adds insult to injury.

Before I finish this post, I went back and watched the video Keith shared with us. In fact I was kinda shocked (but not surprised) by the number of dead and dying cacti Elton had in his greenhouses. Now we'll do a compare-and-contrast -- this is a gallery of photos I took in the Huntington Botanical Garden's desert greenhouse in May 2012:

https://www.flickr.com/photos/134602763 ... 9863777449

John Trager has been the curator there for over 20 years, and I know his growing practices. A lot of well-grown plants there -- I can tell you for a fact that he is not loading them up with Ammonium sulfate or acidifying with Sodium bisulfate.

[keith]

this is a gallery of photos I took in the Huntington Botanical Garden's desert greenhouse in May 2012:" wow outstanding

[4d3d3d3]

I'm growing 65 in a soil-less mix, so obviously there's no soil to support bacteria. Does it mean that those 65 plants aren't able to take up N from the Ammoniacal component in the fertilizer I'm using? Inquiring minds want to know, and if Mike gives us an answer, I'll post a follow-up comment.

Yep they can absolutely take up nitrate N, ammonium N and probably organic N as well. Different plants have different preferences. It was once thought that plants needed bacteria to convert urea into ammonium before they could use it, but this has been proven wrong - at least in some cases - by adding urea as the only N source in a sterile flask of orchid seed. Once inside the seedling the urea is converted into ammonium with the aid of an enzyme.

Orchids are weird, as they're among the only plants that absolutely require mycorrhizal fungi for their seed to germinate and depend on the fungi for their survival in the first year or so of life. I wonder if maybe the fungi has something to do with urea nitrogen assimilation in orchids? Not really sure how they could germinate orchid seed in a sterile media without the friendly fungi, sounds like an interesting paper.

On the subject of orchids, if you look at the MSU orchid fertilizer or any other specialty orchid fertilizer (excluding orchid ferts from big box stores like Miracle Gro, etc), the nitrate to ammonium ratio is always very high (~18:1 in MSU orchid).

When plants take up ammonium the roots efflux H+, making the soil around the roots more acidic. Simply using a high ammonium fertilizer alone will cause acidification of the media. I'm no expert and actually I'm pretty low IQ, but seeing as ammonium (NH4+) is a cation, I'd rather not supplement additional ammonium to compete with K+, Ca2+, Mg2+ cations for cation binding spots in my low CEC soil mixture. Nitrate (NO3-) is an anion and so using that as the nitrogen source avoids excluding more of the K, Ca, and Mg cations

[keith]

long ago I read a article that said Nitrate is the most expensive Nitrogen and Urea the cheapest form of Nitrogen.

[MikeInOz]

4d3d3d3 post_id=390267 time=1632446026 user_id=18138]

Not really sure how they could germinate orchid seed in a sterile media without the friendly fungi, sounds like an interesting paper.

They've been doing it for 100 years more or less. The orchid seed in a sterile environment are not exposed to pathogens and the nutrients added can then be taken up by the seed/seedling by-passing the need for fungi which does the same job.

On the subject of orchids, if you look at the MSU orchid fertilizer or any other specialty orchid fertilizer (excluding orchid ferts from big box stores like Miracle Gro, etc), the nitrate to ammonium ratio is always very high (~18:1 in MSU orchid).

There's no need for 18 to1 unless you have no CEC in the mix (hydroponics in other words)

When plants take up ammonium the roots efflux H+, making the soil around the roots more acidic. Simply using a high ammonium fertilizer alone will cause acidification of the media.

Only without the buffering effect of lime etc.

I'm no expert and actually I'm pretty low IQ, but seeing as ammonium (NH4+) is a cation, I'd rather not supplement additional ammonium to compete with K+, Ca2+, Mg2+ cations for cation binding spots in my low CEC soil mixture. Nitrate (NO3-) is an anion and so using that as the nitrogen source avoids excluding more of the K, Ca, and Mg cations

True, but again there is conversion of ammonium to nitrate in a moist, warm and neutral potting mix. That's why we can grow pants with many forms of osmocote (for example) which are mainly all urea and or ammonium N. They are usually repotted before any significant acidification occurs otherwise we need to correct it with calcium carbonate again.