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Nitrogen in fertilizers and the truth about Urea

Posted by painterart z9 SF, CA (My Page) on
Mon, Mar 24, 08 at 22:22

Sorry for being late on the discussion about fertilizer. It is all a matter of finding time. the one thing I want to dispel is that urea is not good for plants or orchids contrary to often what is written about it. I posted a similar post to this one years ago on this forum, but information gets lost especially when there is a lot of misinformation.

Almost all published studies done on fertilizers and plant nutrients have been done on crop plants. I do think though that much of this is transferable to orchids.
Most orchids can absorb nitrogen directly in the forms of cationic ammonium ion (NH4+), the anion nitrate (NO3-), and urea. The nitrogen in the ammonium ion (NH4+) is available immediately to the plant for the production of amino acids and other compounds. Nitrate nitrogen (NO3-) on the other hand has to be reduced in order to be used by plants.

Nitrate nitrogen is more "time released" then urea. Ureas nitrogen availability is more the middle ground between nitrate and ammonium. Urea hydrolyses into ammonium (NH4+) and C02. This breakdown of urea can take place in the surrounding soil, bark or coir and in the roots and leaves of orchids. The urease enzyme breaks down the urea in leaves and roots. Urea is readily absorbed by roots and leaves and can be used in foliar feeding. While urea is broken down in a growing medium and the resulting ammonium nitrogen is absorbed by the orchid, it is not necessary as orchid can directly absorb urea and break it down within the orchid. Contrary to older orchid book statements urea does not take a year to break down, and can be used by orchids directly.

Ammonium Nitrate NH4N03 is like a quick fix nitrogen drug for plants, as the plants readily take up both ammonium NH4 and nitrate N03. Because ammonium is directly assimilated into plant metabolism and growth, it benefits only work in very good light conditions or in correcting nitrogen deficiencies. Many orchids grow in a constant swing of moist to dry to moist, and I imagine this is also the case with orchids use of nutrients as they become available then unavailable. The use of ammonium in this situation is probably advantageous. Excesses of ammonium in plants can cause many problems in plants reducing their ability to absorb and utilize other nutrients.

Urea only provides nitrogen in the form of ammonium NH4. Nitrate nitrogen can be stored by plant. Orchids or plant preferences for ammonium or nitrate nitrogen is directly related to their ph preference for growing (acid medium growing plants have a preference for ammonium, plants with a preference for a alkaline growing medium prefer nitrate nitrogen), though both nitrogen sources are used by plants throughout the ph range. For these reason and others, the highest growth rate is a mixture of nitrogen supplied by both ammonium and nitrate.

This is a very condensed explanation, and it is still a very long post. I just hope it is coherent enough. I realize that the most controversial statement made is probably the ability of plants and I am sure orchids to take up urea directly through their leaves and roots. The initial study for plant uptake of urea is Hartel, H (1977) Wirkung einer Harnstoffernahrung auf Harnstoffumsatz und N-Stoffwechsel von Mais und Sojabohnen. PHD Thesis, Technische Universitat, Munchen.

Other books used in this post are Mineral Nutrition of Higher Plants, Horst Marschner, 1995, Academic Press and
Hydroponic Food Production, Howard M. Resh, PhD, 1995, Woodbridge Press Publishing Company

Mark Sullivan


Follow-Up Postings:

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RE: Nitrogen in fertilizers and the truth about Urea

Mark,

Quite coherent--and in a nutshell--with footnotes! How did you do that?!

Thank you!

Sweetcicely


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RE: Nitrogen in fertilizers and the truth about Urea

A few other things about fertilizer:

1. Urea is not a salt. This confusion probably comes from the fact that urea is found in the waste product of animals which does contain salts. Urine does have salts in it and also urea, but urine and urea are not the same thing. The body makes urea to get rid of nitrogen. Urea will form a salt with a strong acid.

2. Any time you see nitrate in a fertilizer that is a salt, like potassium nitrate.

3. The white build up that can develop in mediums and on pots can be salts or calcium or a combination. The build up and its composition has probably more to do with your water quality then fertilizing unless you fertilize heavily.

4. Pick a fertilizer with a list of micronutrients, calcium and magnesium- MSU , Cal Mag fertilizers fit the bill. Calcium could almost be considered a macronutrient. Lack of calcium shows up as leaf tip die back. The leaf tip is brown and not desiccated. Leaf tip die back is hard to diagnose as it can be cause by over watering, cold temperatures, draft, and bacteria. Bacteria is a secondary problem. Desiccated leaf tip die back that is ash gray with successive black lines, kind like waves will form on a beach with debris, is fungal.

5. Dyed candy colored fertilizer is a marketing job aimed to appeal to a certain segment of the market. Most that I have seen are poor fertilizers.

Mark Sullivan

"How did you do that?" Built up over years of combating myths over nitrogen. The footnotes help eliminate arguing back and forth and give people who want to learn more a place to look. Warning the two books above are tombs and not light reading.


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RE: Nitrogen in fertilizers and the truth about Urea

Mark,

Thank you very much for sharing your knowledge and references. This is really good information. I haven't thrown out my urea based fertilizer.

I heard Alan Koch of Gold Country Orchids speak last week. Alan briefly touched on the use of urea in fertilizers used for orchids. He urged listeners to consider urea based nitrogen as a part of fertilizer regimens.

More and more, I am hearing experts suggest that their choice of fertilizer(s) isn't any one in particular. Recent recommendations are to rotate among several good ones, especially those which provide supplemental calcium, magnesium and the various elements provided in small quantities as noted in the MSU formulations in addition to the N-P-K.

--Stitz--


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RE: Nitrogen in fertilizers and the truth about Urea

Thanks for jumping in, painterart. I really appreciate all this wonderful and useful information. It's going to take me a little while to absorb and understand all of this! Liz


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RE: Nitrogen in fertilizers and the truth about Urea

  • Posted by paul_ z4/5 MI (My Page) on
    Tue, Mar 25, 08 at 18:48

Interesting, Mark. Be interesting to see if more orchid specific investigation will be done in the future with regards to urea uptake/use.

Only very minor 'correction' to your 2nd post --

"Warning the two books above are tombs and not light reading."

I believe the word you were looking in reference to the books was "tome". A "tomb" is a place/vault in which to bury the dead. ;-D ...at least I hope they aren't "tombs" 8-O

: )


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RE: Nitrogen in fertilizers and the truth about Urea

Mark,

"How did you do that?!" ~ strictly rhetorical applause :)

One thing I learned in two semesters was that chemistry is not light reading. As for Wirkung einer Harnstoffernahrung auf Harnstoffumsatz und N-Stoffwechsel von Mais und Sojabohnen, I'm satisfied to translate "Corn and Soybeans" and to trust the chemistry to you.

Thank you for the concise and Useful distillation.

Sweetcicely


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RE: Nitrogen in fertilizers and the truth about Urea

Mark, very nice summary! We've read some of the same articles.

There are questions, aren't there always? Re: the direct absorption of urea by roots, has it been established that orchids contain the enzyme urease for internal breakdown? I know the question has been posed. Also, there is some concern that when urea hydrolyses in the medium, the ammonium not absorbed can create an inappropriately acidic pH. This would seem to pose a risk particularly for orchids grown moist in absorbant mediums such as paphs in sphagnum and chc, where fertilizer tends to accumulate.

One of the more interesting statements made in your post was the observation that plant preference for urea or nitrate nitrogen is directly related to their pH preference for growth. In the case of orchids, I believe the going generalization is a pH preference in the range of 5.5 to 6.5, only slightly acidic. With paphs preferring a neutral to slightly basic pH.

At this point the question for me seems to be lifting away from *whether* orchids can metabolize nitrogen from urea (the answer seems to be "Sure!").

However, since most fertilizers we hobbyists use seem to specialize in either urea or nitrate nitrogen, the question still can be asked whether urea offers the *best* source of nitrogen for orchids in general - why or why not?. I for one (and I imagine many others) would prefer not to have to switch off fertilizers for whatever reason - light, heat, choice of medium, genus, whatever. Nitrate based fertilizers with micronutrients seem to offer stability and predictability, as well as being the logical choice (given an option) since orchids are not acid-loving plants.

Since most of us seem to feed our orchids frequently, if not constantly, the time-released character of nitrate nitrogen you mentioned, plus a plant's ability to store it, would not seem to be a liability at all. In fact, it seems that over time it would be a levelling factor that feels appropriate for maximizing orchid growth potential as the result of supplying them with a consistent stream of nutrients - without the concern of acidifying any medium we may happen to be using.

That's just my take. I don't really know. And one great thing about growing plants is that over time we adapt to them and they adapt to us. There is no miracle fertilizer, no miracle medium. It's so personal.

Enjoyed your post,

John :>)


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Sorry for the late reply. Sometimes life gets in the way and there isn't enough time in a day.
When you ask whether it has been established that orchids contain the enzyme urease for internal breakdown it's a complicated question. John probably knows this but for those that don't, Urease is a protein that acts as a catalyst in breaking down the urea molecule. I don't know of any studies on orchids that say that orchids produced this protein like in the crops that have been verified to produce the urease on their own. I would not be surprised if orchids did but it wouldn't be in the quantities of the crops studied. It really doesn't matter as urease is found in a number of different bacteria that are ubiquitous. These bacteria are found in and around the roots, leaves, potting medium, mounts and as part of fungi. So urea is readily broken down. Urea is readily absorbed through leaves and roots because it has a neutral charge. Ion exchange is driven by both chemical and electrical potential differences. Depending on what the chemical and electrical potential is in the root/cells in relationship to outside the root will determine how much, how fast the cationic (positive charge) ammonium ion (NH4+) or the anionic (negative charge) nitrate (NO3-) is absorbed. The chemical and electrical potential differences can work together, or oppositely, during ion exchange. PH is also a facture in ion uptake.

On the question " the ammonium not absorbed can create an inappropriately acidic pH. This would seem to pose a risk particularly for orchids grown moist in absorbant mediums such as paphs in sphagnum and chc, where fertilizer tends to accumulate."
Many things: All fertilizer that I have seen has some ammonium component to them. Ammonium is naturally produced in the breaking down of organic matter. Nitrate is a salt. http://en.wikipedia.org/wiki/Nitrate Urea and ammonical nitrate are not. Which form of nitrate would you rather see accumulate? I dont think with the reduced fertilizer level used with orchids the accumulation of fertilizer is that important in that the medium will break down before the fertilizer accumulates to such a detrimental point. This is especially true if growers flush often and with sphagnum moss which has a short life as a medium. The bogs sphagnum moss grows in have a pH of 3.5 to 5 and sphagnum has a similar acidity. http://mossplants.blogspot.com/2008/01/peat-moss-saga-part-3-as-i-mentioned_5856.html The acidity is partly why sphagnum moss is used in bringing back sick orchids. Sphagnum moss has great anti bacterial and fungal qualities plus a high cation exchange capacity. While fertilizers may have a short term effect on changing pH in a medium, I dont think it will make sphagnum moss or coir significantly more acidic in the long run especially if your fertilizer has calcium in it and you use municipal water to which lime is added to keep the pipes from corroding.

While on sphagnum, the following passages will help give a better idea of how cation exchanges work and how nutrients get into roots as mentioned in the first paragraph:
"Sphagnum moss has a high cation exchange capacity (which is the reason why it is used extensively in plant propagation either as sphagnum moss or in its decomposed peat moss state) which is to say that sphagnum moss has the ability to transfer nutrients extremely well; due predominantly to unesterified polyuronic acid molecules. By exchanging nutrient cations such as calcium magnesium, potassium, and sodium for hydrogen ions, sphagnum moss lowers the pH of its surrounds."
http://www.moutere.com/stories/storyReader$54
"An ion is an electrically charged atom or group of atoms. Ions are important to all life since it is in ionic form that many nutrients are passed into cells and waste products are passed out of cells. Acidity is determined by the concentration of hydrogen ions. An acid is a substance that generates hydrogen ions when dissolved in water and the greater the resulting hydrogen ion concentration the more acidic the substance is and consequently, but seemingly paradoxically, the lower the pH. Sphagnum cells selectively absorb mineral ions from and release hydrogen ions into the surrounding water. A growing Sphagnum plant is continuously creating sites at which this exchange of ions can take place and the major active substances at those ion exchange sites are uronic acids, which constitute 10-30% of the dry mass in Sphagnum. The uronic acids are held in the cell walls as a polymer, commonly referred to as sphagnan. Sphagnum plants also contain a variety of phenolic compounds. There is evidence that uronic acids are responsible for ion exchange at low pH levels, with the phenolic compounds working at higher pH levels. In Sphagnum plants the concentrations of the phenolic compounds are lower than those of the uronic acids."
http://www.anbg.gov.au/bryophyte/ecology-sphagnum.html

From John: "In the case of orchids, I believe the going generalization is a pH preference in the range of 5.5 to 6.5, only slightly acidic. With paphs preferring a neutral to slightly basic pH." "Nitrate based fertilizers with micronutrients seem to offer stability and predictability, as well as being the logical choice (given an option) since orchids are not acid-loving plants."
John, I hope I dont come across as picking on you because on the contrary you ask very educated questions and bring up some thought provoking points. First of all I consider anything below 6 to be fairly acidic. Orchids have a wide range of pH habitats. Orchids that grow in and around bogs have a very low acidity of 3.5 pH to 6 pH habitat. There are many orchids that grow on limestone (calcium) outcropping in southeast Asia which like a high pH including as you mentioned many paphs but not limited to paphs. Epiphytes are more neutral in their growing environment. Rain is acidic to now a day very acidic because of sulphate released into the air primarily from coal burning. The habitat pH of a plant does dictate to some degree what nutrients a plant absorbs and needs. The optimum pH for in take of all nutrient elements needed for growth by plants is 6.3 to 6.5 pH with a wider shoot for range of 6 to 7 pH. This is the pH range you should shoot for in your fertilizer solution for most orchids. Orchids that grow in a very acidic habitat the fertilizing should be on the more acidic side and weak. If you fertilize using municipal water you dont have to worry too much about hitting this pH range as fertilizer makers have tap water in mind when formulating their fertilizers. If you use rainwater or reverse osmosis you need to worry about pH because of lack of buffering. Well water can bring up an arrange of issues or be fine. From Hydroponic Food Production mentioned in the first post: " Iron, manganese, and zinc become less available as the pH is raised from 6.5 to 7.5 or 8.0. Molybdenum and phosphorus availability, on the other hand, is affected in the opposite way being greater at the higher pH levels. At very high pH values the bicarbonate ion (HCO3-) may be present in sufficient quantities to interfere with the normal uptake of other ions and thus is detrimental to optimum growth."

The source of nitrogen I think is not of great importance compared to making sure the fertilizer you use has all the micronutrients plus calcium and magnesium. The purpose of my original post was that someone should not worry about whether the fertilizer they use has urea or not. Urea is not a salt. It is not bad for orchids. Urea free fertilizers are a market ploy exploiting common myths that have been circulating for a long time. You can think of it this way: In nature, organic nitrate (small quantities in animal poop) is not as prevalent as urea on ammonium. Before fertilizers were synthesized and readily available, orchid growers used organic fertilizers high in urea with no problem.

As far as tome verses tomb mistake, I saw that mistake once I reread the post after posting it. Actually every time I post I see mistakes but you cant take a post back once it is out there. I am not a writer by nature the reason for "painterart" and not "fiction writer" or something like that.

In school I always thought it was a good play between tome and tomb. Any book that you could stand up on it side went from tome to tomb as in tombstone. Conceptual art. After reading that sentence you probably will always see a thick book as a tombstone.
=%>)
Mark Sullivan


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RE: Nitrogen in fertilizers and the truth about Urea

Hi Mark. Your posts have been very interesting, and I appreciate your willingness to discourse on this touchy topic. As for me - not at all knowledgeable in chemistry -- I just want to pull together enough of a working acquaintance on the subject so I can go my own way, so to speak. But it's like a hydra. You find the answer to one question and two more questions replace it.

Following is an article arguing the presence of urease in orchids.

Dear all,
The claim that urea 'releases' its nitrogen too slowly to be useful as a fertiliser for orchids, is indeed, as Marty Epstein has pointed out, a myth, which however is widely spread and even used by manufacturers of orchid fertilisers ("formulation 100% urea free!"). A bit of literature study will reveal that many plant propagating media rely on urea as a (cheap!) source of nitrogen. As most of you will know, flasking media basically are nutrient ('dilute fertiliser') solutions which normally are solidified by a gelling agent. If it indeed were true that nitrogen cannot but become available after degradation of urea by soil-bound bacteria, I'd be curious to know how orchid seedlings are able to grow (and grow well!) on sterile media in which urea is their sole source of nitrogen...
Sincerely,
Simon M. Wellinga / SymPhyto - Laboratory for in vitro plant propagation
Heerenveen, The Netherlands

Still, I wonder whether it's a tad premature to dismiss the development of urea-free fertilizers as entirely market-driven. I don't remember the early commentaries from presumably trustworthy sources on urea free fertilizers to be based on a "urea is bad for orchids" platform, but, rather, on results. It was more along the lines of nitrate being better - given the common peculiarities of modern orchid culture, as opposed to growth in the wild. Once "everyone" started arguing about it, the topic stratified into good and bad, which as we know, rarely is a helpful perspective.

John

Here is a link that might be useful: Orchid-Talk


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Wow, Mark and John, I'm exhausted reading all that. Very interesting but I find it so confusing. This has been an on-going argument for so long I'm not sure how important it is.

I've used urea based fertilizers for years. Because I change fertilizers depending on the seasons, I can't for sure tell any difference. I use Miracle Grow in the summer because it's easy and I can use the hose. I use MSU, Dynagrow, whatever - I've never lost a plant to urea, and haven't noticed any difference in growth or bloom because of the fertilizer I have at hand.

I'm not a big feeder, and my plants don't seem to suffer a lack of it. At least as far as I can tell. Plants growing in less than optimum conditions (indoors, poor light)don't need the amount of fertilizer a greenhouse or outdoor plant does.

I'm still fooling around with Ph and think water quality is probably more important or at least equally so.

Interesting information though,

Jane


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It's exhausting after awhile. Back in the 90's, I accepted that orchids were light and not particularly fussy feeders, I diluted 20-20-20 to one quarter strength and used it as a constant-feed with a clear drench every month. I didn't even think about water quality. Luckily, it was good, and the practice was simple and seemed to work just fine.

Then I started growing under more demanding circumstances than a windowsill, warmer temps and brighter, more consistent light, so I wanted to be sure I was giving the plants enough support. By that time people were talking about mineral content in water, RO, PPM, acidity and all that.

No one is saying what the professional houses did before the orchid hobby took hold, but in view of the basic fertilizers available from back in 70s when orchids were still fairly rarified to the average joe, it seems they had great success with basic materials - but who really knows what-all they were doing?

That said, one can expect valid advances over a period of time, which, while possibly market driven, don't necessarily deserve to be tagged as ploys. That is not meant to be a criticism of Mark - just an observation that each person needs to exercise their own discretion, just like other facets of growing - depending on how involved one wants to be. The trick is separating the wheat from the chaff - and there's a lot of chaff.

J


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I completely agree....

Jane


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Mark, thank you for taking the time! I find this info very interesting and helpful.

Thanks everyone!

Carol


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RE: Nitrogen in fertilizers and the truth about Urea

What an interesting and thought-provoking thread. Thank you all!

Marci


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RE: Nitrogen in fertilizers and the truth about Urea

  • Posted by jank US10 (My Page) on
    Sat, Apr 5, 08 at 17:45

My head is swimming but am beginning to understand that I don't necessarily have to steer clear of urea in formulas. Now to figure out how to get my city water with a pH of 9.0 to a level to make better use of all those delicious trace elements!
Thanks all for your generosity of research and knowledge. Have printed the thread for my notebook to go back to later to digest some more.
Jan


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RE: Nitrogen in fertilizers and the truth about Urea

Hello John,

Yes, I know Simon Wellinga and Marty Epstein. In fact if you look at that thread you will find my name on two of those posts. There are things in my first post on that thread that I wouldnt totally agree with now, 7 years later. Much of what is in my second post on that thread is copied to the first post of this thread. What you write on the web can last a long time.

You wrote "Still, I wonder whether it's a tad premature to dismiss the development of urea-free fertilizers as entirely market-driven." While the marketing of urea free fertilizers only started in the 90s, fertilizer makers have been able to make urea free fertilizers since fertilizer have been synthesized. The ability to develop urea free fertilizers hasnt been recent, just the marketing has.

You wrote: "I don't remember the early commentaries from presumably trustworthy sources on urea free fertilizers to be based on a "urea is bad for orchids" platform, but, rather, on results. It was more along the lines of nitrate being better- given the common peculiarities of modern orchid culture," This is a fine statement if you know of the research to prove it.

I did a quick (not an exhaustive search) for research that compared growth with different nitrogen forms using orchids and found:

"Effects of different forms of nitrogen sources in the culture media on the growth of Cattleya young seedlings" http://ci.nii.ac.jp/naid/110000220415/ The best growth was a medium combining NH4 and NO3 (ammonium and nitrate). Most of the nitrogen forms produced normal growth in the experiment including various combinations and just NH4 ammonical nitrogen. High concentrations of nitrate (NO3) and urea limited growth. This is not surprising any high concentration of any fertilizer element will limit the uptake of other elements. I would hardly conclude from this study that people should only buy fertilizers with ammonium nitrate. One study on seedlings of a cattleya hybrid in a lab doesnt translate into conclusions for orchid hobby growers growing many species, usually mature orchids in greenhouses, windowsills or lighted growing areas.

"Nutritional Conditions Required for the Non-symbotic Culture of an achlorophyllous Orchid Galeola septentrionalis" http://www.jstor.org/pss/2431830 "An amino acid mixture and urea were good nitrogen sources, but allantoin, ammonium salt and nitrate were poor ones. Nitrite and uric acid inhibited growth." This says very little for us other than you probably want to use urea if you grow orchids with no chlorophyll. I understand from the title growing without a mychorrizal relationship as non-symbotic, but relying on bacteria I would still call symbotic.

Trying to find more studies, I went to look at the websites of fertilizers companies that sell urea free fertilizers to see what claims they make and what research they point to if making the claim that a urea free fertilizer is better. In googling "Orchid Fertilizers + Urea free" to bring up some manufactures names and guess what popped up eighth from the top but this thread on the GardenWeb. This thread hasnt been around long and isnt even finished. Very circular and scary how fast that happened.

BetterGro, Grow more, JR Peter Jack professional, and Gublers Pro Blend all say urea free but from what I can tell none make any claims on their websites that this is better or any claims at all. JR Peter makes fertilizers with urea and without. Pro Blend is probably a contracted repackaging of a fertilizer. On Botanicares Pure Blend Pro, Botanicare doesnt appear to have a website. A few websites that sell Pure Blend Pro make this statement: "Essential elements are not derived from harmful chemicals such as a urea and high concentrates of ammonia nitrate." This is a nonsensical statement just on the surface. Urea, ammonia and nitrate seem to be harmful? They kind of imply that non-essential elements are maybe derived from harmful chemicals or they would start their sentence "All elements..." High concentrations of any elements can be harmful and there are plenty of other elements in fertilizer that can be harmful.

Dyna gro makes an overall claim that their fertilizer is better then everyone elses but I am sure all do. As far as about urea from Dyna -grow: Urea Free Formulas - No harmful urea that can burn roots. Of course they dont provide anything to back up that claim. I couldnt find any study to support that claim.

So I would say that touting that a fertilizer as urea free is exploiting misconceptions that are prevalent with orchid growers about urea. Why is there any debate? I dont believe that the source of nitrogen in fertilizer makes any great difference unless you are foliar feeding.

If nitrate is better - given the common peculiarities of modern orchid culture do you know of studies that back up that claim?

Mark Sullivan


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Hi Mark. No I certainly don't know of any such articles.

You wrote: "So I would say that touting that a fertilizer as urea free is exploiting misconceptions that are prevalent with orchid growers about urea"

I agree with that statement. I don't mean to deny or defend the exploitation of the idea, or the misleading of growers. My point is that it makes no sense to discredit the idea simply because it is being exploited. It's a logical point, not a factual one. As you yourself pointed out, urea-free fertilizer has been around much longer than the exploitive marketing. So, I want to know why, and its pertinence, if any, for orchid culture.

Thanks for your patience and for sharing your time and scholarship.

John


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John, why are you being so obstinate about this issue? I have to ask because I considered you a friend and I know that Arthur meant you no harm in his earlier contributions in the other thread but you blew us both off rather angrily as hostile to your ideas. We were not hostile and neither is Mark but your last post shows your agitation because his ideas haven't completely aligned with yours. This debate has been going on for years, years. You say you want to know, I don't know how much more it needs to take if the sheer volume of data in Marks last several posts most of which I haven't even begun to absorb isn't convincing enough. I agree, its confusing, maybe confusing enough that there isn't a clear answer which means that having either a pro urea or a nay urea stance is incorrect but perhaps the approach of hedging ones bets and using a little of all three available sources of nitrogen is the wisest course. Why does that sit so badly with you?

H


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I hope that Mark has not formed that impression. If so, Mark, please let me say I had absolutely no intention of communicating annoyance or hostility, or to test your patience. On the contrary, your knowledge on the subject obviously far exceeds my own. I suspect that I have a somewhat stiff writing style, which can be misinterpreted as frostiness. When I intend to be frosty, it is generally unmistakeable, to wit:

Howard, I really can't imagine where you possibly get off telling me when I should and should not be satisfied with my own question. This is not a matter upon which you have any right to an opinion, however impressed you personally may be with a large volume of information which you, as stated, have not absorbed.

Regarding the thread to which you refer, and in deference to Arthur, he was very kind, and far exceeded me in good manners - I appreciate his forbearance in the face of my own lapse.

John


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John, when you want to know something, you have to in the words of Petrichor (the Scientist) "run some trials".
It is no good telling him as i did that Diatomite is good stuff. He just says "did you run some trials."
So most of the stuff you read or hear in the orchid world is like that. Just ideas, unscientific, word of mouth, the chaff as you say.
In amongst all that chaff are pearls of wisdom, little hints, that just might improve orchid culture.
I can understand what you are trying to achieve, that is the optimum fertilizer/fertilizing program for the orchids you grow in your particular growing conditions. But, i think that there are so many variables that perhaps you are seeking the impossible.

Thank you Mark for the detailed explanation.


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Wow didn't know this thread was still going. I for one love these 'technical' posts. I think this forum has gotten too basic. I love digging around topics like these. Very interesting and Mark's explanations are great.

I still use urea fertilizers, never stopped. Never really understood the argument. I never saw any difference. Too many other variables. The biggest change I've seen in my growing conditions would be increased light over winter. I'm getting blooms on plants I've had for years without blooms. Same fertilizer regimen. Because I use RO and rain water during winter, I am more concerned regarding the addition of trace minerals.

I'm playing around with pH to see if I notice anything different and so far I haven't. I continue to use urea based fertilizer as well as non-urea.

Jane


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I agree, Jane we could use a little more depth here. Arthur, I absolutely agree with what you said. The thing is that orchids have been cultivated for more than 150 years, a substantial part of that time by professional growers for the competitive cut-flower market who must have developed some pretty successful and consistent practices to stay in business. So the way I see it is that a lot of "tests" have already been run. I'm a traditionalist and my thing is reconstruction so it's like putting together a puzzle. Maybe are is no theories, no time-honored practices that are handed down quietly from generation to generation. Maybe the grail is a myth. But Im a romantic, what can I say?

John :>)


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John, I bet there are time-honored practices that are handed down, like grandmas recipes - 'a little of this, a lot of that' and you get the perfect pie, unless the weather is too humid. My mom made a killer Lemon Meringue Pie, but only when the weather was dry. No one could understand why her meringue was always so perfect and we would wind up with a soupy mess. Dry weather - so simple.

Growing is sort of like that. Keep notes and sometimes you realize something actually works, over and over again. Pass it along.

Hey Arthur, a peal of wisdom and a 'real trial' which worked and will again. Stick a bunch of Cattleyas under a bunch of octopus lamps during a dark, dreary N.East winter and you get flowers. Not one other change. Same windows, same temps, same fertilizers and not one repotting. Just a whole host of 23W CFL's, cords strung all over and I got flowers. That was the only variable in my trial. Pass it along....

Now Howard, finals must be right around the corner. It will soon be all over and you will fly. Hubby told me he saw a rose called 'Howards Light.' I said, "no, no, it must be an orchid!"

John, don't change a thing. Stay the same romantic, intelligent, charming person. No, no, the grail can't be a myth!

Had a week from hell and when I thought it couldn't get any worse it did. Then this morning, the air felt of Spring, my Mari's Song opened three beautiful buds and all was well with the world.

Jane


 o
RE: Nitrogen in fertilizers and the truth about Urea

No worries John, I feel no hostilities from you or frostiness. Just inquiring minds want to know.

I will repeat though "The source of nitrogen I think is not of great importance compared to making sure the fertilizer you use has all the micronutrients plus calcium and magnesium. The purpose of my original post was that someone should not worry about whether the fertilizer they use has urea or not."

I think people look at fertilizer as a quick and easy thing that they can change and feel like they are doing something to help their plants. Things like adding more light throughout the year, increase humidity, better control of temperature, regulating ph take more effort and/or cost more.
Jane is on to something when she says "The biggest change I've seen in my growing conditions would be increased light over winter. I'm getting blooms on plants I've had for years without blooms." and Jan when she says "Now to figure out how to get my city water with a pH of 9.0 to a level to make better use of all those delicious trace elements!"
One thing everyone can do that is not expensive is get a water quality report from their municipal water district. This should be free. Some cities require them to be given to customers. San Francisco customers get a water report twice a year. The reports maybe online. The report will tell you things like ph, hardness, and about minerals and pollutants in the water. These can vary from spring to fall. I suspect with Jans tap water ph of 9 that her municipal water source comes from a river that flows through limestone, maybe like the Colorado. She may find she gets plenty of calcium and magnesium in her water and doesn't need it in her fertilizer.

As far as nitrogen forms in fertilizers, it maybe good to cover your bet with all three as they have varying times of utilization, but I think over time it doesn't mater. I think the different nitrogen forms are present in the potting mix after each fertilizing and get used the next time, washed out, or help break down your potting medium.

John to help you search for a holy grail in fertilizer you may look at these:
1 Simple sugars after all that is a big part of what the plants are making. Jerry Grow- no longer made as far as I know - exploited this. Works better in highlight and warm to hot weather. Needs more scientific study.
2. Nickel as a trace element. It is use by plants as a catalyst in urease enzyme so it is never used up, but plants grow. I have only seen one fertilizer that had nickel in it made by Hydrofarm. I have no idea if they still make it or not.

I do think you can grow orchids fine with urea free fertilizer relying on ammonical nitrogen and nitrate. I will mention two things that havent been mentioned so far and are needed in the break down of nitrate to ammonia to be use by plants. Two enzymes are required. Nitrate reductase involving two electron reduction of nitrate to nitrite. The other enzyme nitrite reductase involving a six electron reduction to transform nitrite to ammonia. As you can see there are a lot more steps to get from nitrate to ammonia then with urea.

Cheers,
Mark Sullivan


 o
RE: Nitrogen in fertilizers and the truth about Urea

I have 2 Phaleonopsis that have survived from when I was working and did not know how to look after them. They only have leaves.This year I fed them urine diluted 1 part to 30 parts water once monthly. Both have developed fine new leaves and the one which had very few roots now has grown several more. I cannot see any detrimental effects for this fertilizer on them. Swedish gardening experts recommend diluted urine to fertilize with. Last year the results on my cherry tomato plants (dilution 1-10) were so good I asked if I could use diluted urine to fertilize houseplants and orchids. I was told houseplants can be (dilution 1-20), orchids, succulents and cacti can be (dilution 1-30), indeed with the exception only of some rockery plants everything can be fertilized with diluted urine. Therefore I have used it to fertilize all my plants and today I noticed the first buds on one of my cherry tomato plants which I subsequently have transplanted into a larger container as it is only plus 8 C outside as yet. My cutting of Busy Lizzy is full of flowers and my cutting of Impatiens New Guinea has opened its first bud. I have not noticed any negative effects of using diluted urine on any of my plants, on the contrary they are thriving as never before.


 o
RE: Nitrogen in fertilizers and the truth about Urea

^^^recycling at its finest.


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