Any ideas as to what this is?

[hkunberger]

Thank you! This is very helpful and I appreciate you breaking this down for me.
So now I’m wondering, given the limited microbial activity of typical orchid media, which is apparently necessary to convert urea into a safe and usable form of nutrition for plants, what is the safe and effective method of applying it to orchids?

 

[gonewild]

Thank you! This is very helpful and I appreciate you breaking this down for me.
So now I’m wondering, given the limited microbial activity of typical orchid media, which is apparently necessary to convert urea into a safe and usable form of nutrition for plants, what is the safe and effective method of applying it to orchids?

Is it really accurate to assume microbial activity is limited in orchid substrates??

 

[SelectOrchids]

Thank you! This is very helpful and I appreciate you breaking this down for me.
So now I’m wondering, given the limited microbial activity of typical orchid media, which is apparently necessary to convert urea into a safe and usable form of nutrition for plants, what is the safe and effective method of applying it to orchids?

That is the key problem, orchids and many plants can absorb and use directly urea. There are as well orchids that are unable to process nitrate nitrogen too.

Some of the best TC Media for Phalaenopsis have only urea as a nitrogen source, as well as some ammonium, and a low quantity of nitrates. and they are fully sterile. Analysis shows that whatever small quantity of nitrate there is in the media is left untouched.

 

[hkunberger]

Is it really accurate to assume microbial activity is limited in orchid substrates??

I would imagine that there is microbial activity in orchid substrate but not the same as there is in soil. I don’t feed my orchids the way I feed my roses. With the roses I’m essentially feeding the soil so it will feed my roses. I had assumed, and maybe this is an incorrect assumption, that I am mainly trying to feed my orchids directly.
I’m not trying to challenge the use of urea. I’m just trying to understand this

 

[hkunberger]

That is the key problem, orchids and many plants can absorb and use directly urea. There are as well orchids that are unable to process nitrate nitrogen too.

Some of the best TC Media for Phalaenopsis have only urea as a nitrogen source, as well as some ammonium, and a low quantity of nitrates. and they are fully sterile. Analysis shows that whatever small quantity of nitrate there is in the media is left untouched.

So, if I am understanding this correctly, some plants do not need to have the urea broken down and converted in order to use it. They take what they need and leave the rest.

 

[Ray]

So, if I am understanding this correctly, some plants do not need to have the urea broken down and converted in order to use it. They take what they need and leave the rest.

The first part is correct, it I doubt that second one is.

• Some, probably most nutrients are taken up at rates controlled by concentration - if there is a lot present in the rhizosphere, there will be a lot absorbed.
• Some of that uptake may be moderated by the specific ion concentration within the plant - i.e., if it isn’t “hungry” for it, the uptake will be slowed.
• There are some, P & especially K come to mind, that the plant actively pumps into itself, out of proportion to the concentration in the rhizosphere, with the excess stored in cell vacuoles.

 

[hkunberger]

The first part is correct, it I doubt that second one is.

• Some, probably most nutrients are taken up at rates controlled by concentration - if there is a lot present in the rhizosphere, there will be a lot absorbed.
• Some of that uptake may be moderated by the specific ion concentration within the plant - i.e., if it isn’t “hungry” for it, the uptake will be slowed.
• There are some, P & especially K come to mind, that the plant actively pumps into itself, out of proportion to the concentration in the rhizosphere, with the excess stored in cell vacuoles.

Thanks Ray! That makes sense.
Please bear with me. I’m trying to find out if I am understanding this correctly. The main argument against using urea is/was that it requires microbial “helpers” in the substrate to convert it into a usable form of nitrogen for the plant. Since orchids do not grow in the typical soil environment, those microbial helpers are not present (or not present in adequate numbers) to convert the urea into a usable form. However, we now know that at least some plants and at least some orchids are able to take up urea directly without these microbial helpers converting it for them.
Please forgive me if I seem dense! I really am just trying to understand this and I’m very appreciative of everyone’s help.

 

[terryros]

No problem, Ray. You are absolutely right. I have several batches of seedlings growing now at various stages: Phrags, Paphs, Odonts and Cymbidiums. All have shown faster - if not much faster - growth once urea was incorporated into my fertilizer formula. Phrags of all sizes have shown the most dramatic improvement, but the effect has shown all across the board regardless of plant age.

I've grown Cymbidiums since 1959, and thought I had their culture wired. But as I started to up the percentage of urea in the constant feed I use for all genera, the leave took on a bright glossy green and the growth accelerated. I've had to repot some out of season as the roots have pushed the plants out of the pots. Never seen this before. You can teach an old dog new tricks.

There are so many factors, but to my eye it was the introduction of urea that has made a remarkable difference. My practices are different from the norm in many ways, including constant feed at a high level and frequent watering. But this is the one thing that has without a doubt made a big difference for me.

What is your water supply and have you monitored the pH of your solutions(s)?

 

[gonewild]

What about the percentage of UREA that when exposed to moisture is converted to ammonia gas. The conversion is by chemical reaction not microbial.

 

[hkunberger]

What about the percentage of UREA that when exposed to moisture is converted to ammonia gas. The conversion is by chemical reaction not microbial.

The plot thickens!!

 

[Ray]

What about the percentage of UREA that when exposed to moisture is converted to ammonia gas. The conversion is by chemical reaction not microbial.

My understanding is that urea dissolved in water forms carbon dioxide and ammonium hydroxide, both of which are pretty stable up to pretty high concentrations, and should not give us the "urine smell" unless exposed to urease, an enzyme. I soppose some of the ammonia may leave the solution, but it's not much.

I'd bet the smell coming from a bag of urea is realeased by bacteria. They're ubiquitous, after all.

 

[kman]

What is your water supply and have you monitored the pH of your solutions(s)?

We use spring water that we pipe in from about 1.25 miles away, with very low TDS - generally less than 15. As you might expect it has low alkalinity, one of the reasons that a 15-5-15 CaMag is one of the components of our program. The pH of the final solution is 6.5 plus or minus 0.1 over time. We use oyster shell and coral calcium as a topdressing for a few varieties that appreciate a higher pH. Also apply ground dolomitic limestone annually to all the Cymbidiums.

 

[southernbelle]

Well, I'm only changing one thing at a time. I contacted Sue Bottom at St. Augustine Orchid Society who writes regularly for Orchids Mag and has the most comprehensive website info on just about every pest and disease and what to do about it. While she acknowledges the possibility their might be a nutritional component and that many in Netherlands, etc. have an up on us in that area, at this point the cell walls appear to be dissolving inside the leaf structure which caused her to suggest bacterial. She directed me to https://www.hark-orchideen.com/diseases/ which has some similar pictures of the way this started. She suggested Phyton 27 which I have both drenched with and sprayed and have the plant isolated and disinfected as best I could. I've removed the damaged leaves, so fingers crossed. Apparently this has about a 3 week residual, so will keep an eye out and see if I have to repeat. Will report back. I really appreciate all the info. Terry, I will get with you about any need to change my fertilizer once this plant is taken care of.

 

[gonewild]

My understanding is that urea dissolved in water forms carbon dioxide and ammonium hydroxide, both of which are pretty stable up to pretty high concentrations, and should not give us the "urine smell" unless exposed to urease, an enzyme. I soppose some of the ammonia may leave the solution, but it's not much.

I'd bet the smell coming from a bag of urea is realeased by bacteria. They're ubiquitous, after all.

My point about the release of ammonia is that microbes are (maybe?) not required for UREA to provide nitrogen to an orchid plant.
I'm remembering back many years but as I recall if you apply UREA to the surface of moist soil as mush as 40% of the contained nitrogen is rapidly lost to the atmosphere as ammonia. This is why farmers always apply UREA subsurface. Then of course the ammonia has in the soil is available to the roots.
I've always advised not to use UREA simply because you really never know how much N you paid for actually gets to the plants.
Maybe dissolved in water as liquid fertilizer the loss isn't significant but I don't find any data to support that.
Think about opening a package of Miracle Grow that has absorbed humidity and is moist. The smell is ammonia N escaping to the atmosphere so over time you really don't have the nitrogen content you think in your teaspoonful.
That said I'm adding some UREA to my K-lite for my Phrags and results are good.

 

[gonewild]

Because you mentioned the cell walls are dissolving it caused me to remember something. What plant is this? Is there a chance it's genetics come from a cool or cold environments and you are growing in warm conditions?
I'm Peru I collected various species at high/cold altitudes and took them down to warm/hot conditions. Most died quickly and had similar cell destruction to your pictures. Researching why high altitude plants die at low altitudes I found out proteins in high altitude plants dissolve in warm temperatures. Literally the plants turn to mush starting out like what you have.

 

[Arne]

As long as the solution isn’t basic, the main fraction of the ammonia will exist as dissolved ammonium ions. So very little will disappear as ammonia gas below pH 7.

 

[Brabantia]

C'est l'un des problèmes des discussions sur l'alimentation : la plupart des « réponses » sont basées sur des preuves anecdotiques, et il peut y avoir d'autres facteurs impliqués qui ne sont pas identifiés. Oui, les symptômes pourraient très bien être une carence en azote, mais n'est-il pas possible qu'une autre partie de la culture de Souther Belle soit à l'origine de cela ?

J'utilise MSU RO puis K-Lite depuis plus de 20 ans. Ils ont le même rapport nitrate/ammonium. Je n'ai jamais vu de tels symptômes, y compris à l'époque où je cultivais une très grande variété de plantes.

Je ne nie absolument pas les bienfaits potentiels de l’urée. Il est bien connu qu’elle entraîne un « verdissement » rapide des plantes, mais cela vient en partie du fait qu’elle est meilleure en application foliaire que les nitrates et les ammoniums.

Je connais un excellent producteur de paphs qui l'ajoute régulièrement à son régime alimentaire et il prétend en tirer des bénéfices. Mais là encore, j'ai lu des articles sur un excellent producteur qui nourrit principalement ses paphs primés avec rien d'autre que du nitrate de calcium.

Personally, I don't deny the fact that most terrestrial plants assimilate nitrate ion very quickly. As I've already mentioned, during a visit to a major grower in Holland, I found pallets of 20-20-20 in his store and a few 25 kg bags of calcium nitrate. For the past two years, I've been experimenting with the use of 21-7-21 fertilizer on Dendrobium nobile and phalaenopsis, with greater success than when I grew them with the full of nitrate Belgian fertilizer. For Paphiopedilum and Phragmipedium I also use a fertilizer whose nitrogen component is made up equally of ammonium and nitrate, and with this I've seen a marked improvement over a fertilizer containing over 85% nitrate. In my opinion, the problem with nitrate fertilizers may lie in the fact that nitrates are also oxidizing agents. If you use this type of fertilizer to fertilize plants whose roots are constantly wet or damp, it's not a problem, and this is the case in hydroponics and semi-hydroponics. If you water dry roots, there's a great risk of burning them. This is what I've observed on Cattleya roots, for example. Let's not forget either that, for the same total nitrogen content an urea/ammonium fertilizer solution will have a lower conductivity than a fertilizer solution whose total nitrogen is largely made up of nitrate. This means that urea/ammonium fertilizers can be used to produce solutions with a higher concentration of nitrogen than nitrate fertilizers, which is something that manufacturers have clearly understood.

 

[gonewild]

If UREA dissolved in water results in ammonia ions does that count as "salt" content concerning excess dissolved salts?

 

[Arne]

If UREA dissolved in water results in ammonia ions does that count as "salt" content concerning excess dissolved salts?

Yes, the ammonium hydroxide that is formed from urea is a salt. Then, depending on pH, a fraction of the dissolved ammonium becomes dissolved ammonia, which is a gas that can leave the solution over time.

 

[Ray]

If UREA dissolved in water results in ammonia ions does that count as "salt" content concerning excess dissolved salts?

Yes, the ammonium hydroxide that is formed from urea is a salt. Then, depending on pH, a fraction of the dissolved ammonium becomes dissolved ammonia, which is a gas that can leave the solution over time.

And if you let the water evaporate urea will be deposited, and that's certainly a salt.

Many moons ago, when a Genessee NY salt mine flooded, we had to use urea to deice driveways.