Urea as fertiliser

I have always used non-urea fertilisers for my orchids and have been quite content with the results. With a few exceptions. Amongst them a PEOY NFS that has been hanging there without much growth and with a rather pale appearance. I have tried several things like calcium and magnesium nitrate additions etc, but it did not green up. Then I thought: " What the h... lets try Urea, its commonly used as foliar feed so why not make a try?" Ok, I had some pure urea in a canister, dissolved 10g into a liter of water(1%) and started with a slight spray on the surface of the leaves. Not enough to moisten evenly and far from dripping. Covered the rest of the plants as well - again very slight. Voila! next day (or two days later) everything had greened up, the PEOY the most, from yellowish green to more like grass-green. The rest of the plants in my mixed collection of 500plants+(?) also seemed more shiny and darker green. It was like magic. It even seems to have accelerated growth a bit (this I am sceptical to though)?:clap:
I will definitely start to include Urea in my fertilisers from now on, possibly in the water, but definitely as additional foliar feed.
Any comments or other experiences?
P.S. unfortunately no pictures available- well "after" is possible but without "before" its hardly convincing:evil:

The result you saw is not from the "quality" of Urea. The result is because the plant finally got enough nitrogen and that indicates that you have not been applying enough with your regular routine. Either you have been using too weak of a solution of not applying often enough.

Urea is not a good choice to include in fertilizer for orchids.

I don't claim to be an expert but for each and every study that states that urea isn't good for orchids there is a study that says it is.

So I personally can't judge about urea. I personally use a Peters fertilizer ( 21-7-21 + 3%MgO ) of which the N parts is partially Urea based nitrogen and I'm happy with it.

I'll just piss on my plants from now on! :evil:

Marc said:

I don't claim to be an expert but for each and every study that states that urea isn't good for orchids there is a study that says it is.

So I personally can't judge about urea. I personally use a Peters fertilizer ( 21-7-21 + 3%MgO ) of which the N parts is partially Urea based nitrogen and I'm happy with it.

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As I have already explained, when I visited a great Vanda producer in Holland in the technical room I saw many many bags of Peters 20-20-20 and few bags of Calcium nitrate. I must add that they cultivate at high temperature (28 °C 80°F) and that urea is a cheap nitrogen source.
I believe that temperature is the limiting factor for urea and organic fertilysers use for orchids culture in temperate countries… except in "very" heated greenhouses for commercial productions.

Brabantia said:

As I have already explained, when I visited a great Vanda producer in Holland in the technical room I saw many many bags of Peters 20-20-20 and few bags of Calcium nitrate. I must add that they cultivate at high temperature (28 °C 80°F) and that urea is a cheap nitrogen source.
I believe that temperature is the limiting factor for urea and organic fertilysers use for orchids culture in temperate countries… except in "very" heated greenhouses for commercial productions.

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Probably for Vandas with their extensive dependence on atmosphere moisture Urea would work well since almost all of the Nitrogen from urea is quickly released into the air in gas form. Vandas probably suck it up but for other orchids and plants grown in media in pots it is not the best choice.

It is a good choice for the fertilizer makers because it is a cheap source of Nitrogen to put into the bag. For growers it is a poor choice because so much of the Nitrogen never reaches the plants and thus a waste of money.

I've heard that urea needs microorganisms in soil to break it down to be useful, and that's why it's not a good choice for orchids. Is that true?

SlipperFan said:

I've heard that urea needs microorganisms in soil to break it down to be useful, and that's why it's not a good choice for orchids. Is that true?

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Not True.

The Nitrogen in Urea rapidly turns into Ammonia gas in soil.
Ammonia gas inhibits soil microbs.
Ammonia gas can damage sensitive roots.

Urea is designed for use on field crops.

Why use this on orchids when there are better choices?

Google search found this....
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/faq7758

Thanks, Lance. Clears that myth up for me.

It may also be useful that the toxicity of ammonia is pH based. It is highly toxic at pH's above 7.8. Below pH 7 toxicity (if you could call it that) goes way down. This is true even for bacteria species that "eat" ammonia.

So in Bjorn's case it may not be unlikely that pot pH had dropped lower than a good optimal to pick up N from nitrate, but able to pick it up from ammonia.

It's also not inconceivable that a significant shot of ammonia could have altered the pot pH and released a bunch of pent up nutrients.????

So many variables!!!

Obviously none of you got it right Ok lets make it more precise:
The Urea application never, never, NEVER got into the soil, just as a slight spray, drizzle, not enough to wet the leaf surface. And there it rested. Over night the changes to green appeared. Please note, there was no watering or spraying or misting going on during that time. I know what I say is contrary to common "knowledge" but if it works and there are no other variables in the experimental set-up, my scientific education has told me to believe in the observations and look for mechanistic explanations to the observations.
Ok this was not a planned and controlled experiment with double blinds etc. but there was a change in the plants, it was quick (in hours), it had nothing to do with soil and it happened after I sprayed with a 1% solution of Urea p.a. in pure water (rain).:rollhappy:
I have done some googling on the issue and it turns out that used as foliar feed urea is not dependent on urease to enter the leaf(in potatoes), and it is quick-a few hours is enough. It is further claimed that it makes absorption of other nutrients easier. Urea might not be the best nitrogen source for generalised fertilising(through soil) but it seems to be the best for leaf-application. And its not a salt and does hence not burn tissue easily. The below link should be interesting to those that are interested in this issue, it contains quite a bit of info.
http://forums2.gardenweb.com/forums/load/orchids/msg032222191547.html
Those of you that uses Peters 20-20-20 already add some urea, Personally I think that I will stay with my base fertiliser (urea free) and supply with an Urea based foliar feed that i have come over. Its rich in most necessary elements incl. micro.
And yes Rick, I do follow you regarding potassium, I do think it is important to reduce it and increase Ca (and Mg) so I add both to my standard feed.
One thing, as Calcium nitrate tends to react with concentrated fertilises it should not be mixed into the stock solution. It can however be mixed into the diluted water e.g. at the nozzle. I found that magnesium sulphate may be added directly to my stock solution without problems at a rate of 20% (2%Mg). Its best to make a test, take some stock solution and add epsom salt and look for precipitation/haze. If its stable for some days its ok.
In my set-up, I use a 10% fertiliser solution(with epsom salt) hooked up on a Dosmatic that dilutes 1:500. That gives a 200ppm nutrient solution. On the end of the hose I have one of those cheap injectors and here some 200ppm Calcium Nitrate is added as well. (Its actually some 40ppm Ca in the mix). The total mix coming out of the hose is around some 400ppm containing 90ppm N, 10ppm P, 40ppmK, 40ppmMg, 53ppmCa + S and micro. Numbers are approximate
This is in all water btw. and still that Urea application had such an effect.

I understood that you applied it as a foliar application. I still stand by my statement. The reason you saw a rapid "greening" of the foliage is because the plants were low on nitrogen. If you had been applying adequate nitrogen regularly you would not have seen a rapid response to the sudden availability of Nitrogen.

I always foliar feed my plants by drenching the plants with whatever fertilizer solution I'm using. Foliar applications are very beneficial for most nutrients not just Nitrogen.

In my set-up, I use a 10% fertiliser solution(with epsom salt) hooked up on a Dosmatic that dilutes 1:500. That gives a 200ppm nutrient solution. On the end of the hose I have one of those cheap injectors and here some 200ppm Calcium Nitrate is added as well. (Its actually some 40ppm Ca in the mix). The total mix coming out of the hose is around some 400ppm containing 90ppm N, 10ppm P, 40ppmK, 40ppmMg, 53ppmCa + S and micro. Numbers are approximate

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Have you actually measured the ppm coming out of your hose at 400ppm?

I'm having a little trouble following your math, maybe I'm getting a little old? in your 400ppm mix you account for 233ppm, what does the other 167ppm consist of?

In your nutrient ratio you have the answer as to why the Urea greened up your plants..... 90ppm Nitrogen is not enough. It it were enough then the plants would not have changed so dramatically with the Urea application. You could easily double the Nitrogen ppm's in your nutrient ratio.

one other possibility (to study) is that urea is better assimilated by Paphs than N03- form...

please tell more about calcium nitrate reacting with fertilizer?

Lance, I do follow you in saying that somehow the plants were deficient in N if they green up by N addition. My point is how quick it is and the effect overwhelmed me. Even plants growing like weed changed significantly - over night- getting much greener and shinier.It seems to work a little like that stuff housewifes spray on plants to meke them shine "leaf-gloss" or whatever its called. Well it had that effect - and over night. And without any of the stuff getting into the soil. Truly amazing. Whether that is something to aim for is another thing, to me its a bit like putting the plants on steroids - but I like it:evil:.
About the missing ppm: Firstly a disclaimer: My numbers are approximate. Then the reason for the deviation: Over here(Norway, Europe), NPK is given as the elements Nitrogen-Phosphorous-K(potassium): in USA (could be all English-speaking countries for what I know?) and some other places its actually as the oxides: N-P2O5-K2O even if they write NPK.
So my 90-10-40 European NPK is 90-23-48 US NPK. Its confusing, right? You have to take the molar weight of the individual components into consideration doing this transformation. Accordingh to my calculation the factor becomes 0.83 to transform K to K2O and 0.43 for P to P2O5.
Then: Mineral fertilisers are mostly mechanical mixes of water soluble salts of the desired cations like potassium K+, magnesium Mg2+, and Calcium Ca2+. Since these cations are positively charged you also need a counter-charge or anions which are negatively charged. In fertilisers, primarily nitrates (NO3(-)), sulphates (SO4) and phosphorous (mostly as phosphates due to higher solubility PO4(3-).
Nitrogen can be present as ammonium NH4+ or nitrate NO3- (lets forget nitrite its poisonous)and possibly urea that is not a salt but an organic molecule
Suphur mostly as suphates SO4(2-)
Phosphor mostly as phosphate (PO4(3-)
And there are all the other ingredients that make up the fertiliser mix. like borates molybdates etc all containing oxygen.
All this oxygen is not accounted for in the NPK and that is the main reason for not getting to 100 if you start counting ppm's. Take 100g Potassium nitrate (KNO3)as an example. 100g dissolved in 100liter gives 100/100000 =1000ppm These 1000 ppm becomes : 13,9N + 38,7K (46,6 in US)+ 47,4 O
So when you sum up my ppm to 233 out of 400 (=41,8% missing), you get pretty close to the result using potassium nitrate above(47.4% Oxygen) Using other oxygen bearing substances than potassium nitrate makes things more complicated and explains the deviation.
Then Calcium: When salts are dissolved in water they are broken up to cations and anions. The cations are positively charged and are typically metals like K, Mg, Ca, the anions are negatively charged and are typically of non-metals like Nitrogen and Oxygen and Sulphur or Phosporous etc. Ok, the solubility of salts are variable and the least soluble combination tends to precipitate if two solutions are mixes. So in the case of mixing calcium nitrate that has a solubility of more than 100g/100g water (as hydrate) with Potassium sulphate that dissolves 12g/100g water, what happens if you mix equal amounts of say 10% solutions (10g salt in 100g liquid)?
the total volume gets 200ml and the individual concentrations of calciumnitrate and potassium sulphate becomes 5% each. So far so good???
NO! Since calcium sulphate has a solubility of less than 0.2g/100g water, most of the calcium together with suphate will precipitate and get lost as fertiliser. The solubility of calcium sulphate is still some 2000ppm, so it does not precipitate if it is added as calcium nitrate at the nozzle, or for that sake in the bulk volume of water. BUT you cannot mix it in a stock solution.:evil:
This treatise was a bit simplified, if any out there discovers my shortcuts then bear over with me, but its not that easy to popularise the stuff.
If you have questions regarding these things then do not hesitate to ask.

Can a paph (or any plant) absorb nutrients and make enough chlorophyll to noticeably 'green up' the leaves in 24hr?

Might have been 48hours but it was an amazing effect. I would say perhaps visible after 24 hours, but after that, repeated application made a hughe difference. Makes me wonder whether the roots of my paphs get to the N i fertilize with in the regular fertiliser? The roots does look ok though?

Bjorn said:

Over here(Norway, Europe), NPK is given as the elements Nitrogen-Phosphorous-K(potassium): in USA (could be all English-speaking countries for what I know?) and some other places its actually as the oxides: N-P2O5-K2O even if they write NPK.
So my 90-10-40 European NPK is 90-23-48 US NPK. Its confusing, right? You have to take the molar weight of the individual components into consideration doing this transformation. Accordingh to my calculation the factor becomes 0.83 to transform K to K2O and 0.43 for P to P2O5.

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While your conversions to the oxides are right, the numbers are weight percent, not PPM, so those formulas are impossible.

Ray, I might misunderstand you, as you know, English is not my native language and this time I feel uncertain.
Sure, I was inprecise, but I think most got the point. Peters 20-20-20(US) would have been labelled 20- 8.6-16.6 over here. On the other hand; people should remember that 1 ppm is the same as 0.0001%. Just saw that the Wellensteins have treated this quite extensively so I stop here(http://www.ladyslipper.com/minnut.htm) There is a lot of good things written on their pages. The fertiliser issue is well described and I would suggest that anyone having questions lookup their pages.