Urea as fertiliser

[Rick]

bjorn, about your plant being insubstantial(?) and more prone to rot - maybe the light is a bit too low so it stretches. this could lead to thin cell walls. the word is that too much ammonium type fertilizer can make plants grow too lushly, which can lead to possible disease. also if a plant can normally grow too quickly, it can be deficient in both calcium and phosphorus. calcium moves at one speed and sometimes if it isn't available all the time in a small amount a fast-growing plant can outpace the movement from the roots to the rest of the plant. with things like mums that can grow very quickly, have large floral structures (lots of branching and flowers), a lack can cause brittleness, less branching and flowers. not exactly sure how this would translate to orchids though I noticed when I was trying a too-low phosphorus fertilizer things that grew quickly would have problems. actually also for larger plants a breeze can help toughen up plants. movement causes some plant cells to react and toughen cell walls and slow upwards growth. air jets over the top of easter lilies have been used in lieu of growth regulators to keep them shorter. I think that you can use too much nitrate fertilizer for orchids (my opinion based on work, reading and seeing discussions here, not experimental), but I believe a balance of different types could be the most benefitial, and from Rick's experiments, one with less potassium and more calcium.

Lots of soft growth (often with lots of blooming), poor substance, susceptability to rots is very much in line with too much N and K with inadequate Ca/Mg. Ca (and Si) needs to get incorporated into cells walls for better substance (and disease resistance). Excess K blocks uptake of divalent cations (Ca/Mg), which in turn reduces uptake of PO4.

In general for all bio (ion pumps) and substrate ion exchange (in bark and CHC) the K will always win out for adsorption if Ca or Mg is not present at higher concentrations than K. A moderately soluble top dress of something with Ca/Mg in the potting mix will offset standard fertilizer NPK imbalances, but you get faster (and I think more controlable) results if your fertilizer and irrigation water always contains more Ca than the K present in fertilizer.

Keep in mind that unless you are using very soft water or RO water there is probably at least 5-20 ppm of Ca and 3-7 ppm of Mg present in standard surface waters. I could guestimate these values better if I at least know the hardness of the water used.

Noticing the sanderianum thread that Wendy just posted, even though she uses a heavy K fertilizer and rain water, the potting mix contains a substantial amount of "limestone screenings".

After the large multi growth multis I've lost over the years that grew and bloomed like crazy for 5 years going into slow burn demise, I'm now to scared about pushing that much K over extended periods of time with only potting mix sources of Ca/Mg for backup.

 

[Sirius]

Rick,

I am using 13-3-15 MSU fertilizer at a rate of 3/4 teaspoon per gallon of R/O water for a concentration of 75 ppm. This fertilizer also contains 8 Ca and 2 Mg. I flush every fourth or fifth watering with pure R/O water.

Where can I buy the source of additional Ca you are adding to your water?
How much additional Ca would you recommend that I add to bring my Ca up to a beneficial level (in tsp amounts)?
How much additional epsom salt would you recommend that I add to bring my Mg up to a beneficial level (in tsp amounts)?
I read that you also add Mg to your flushes. Is that with or without the addition of extra Ca?
Would adding extra Mg without adding extra Ca be beneficial or harmful? I don't have any Ca, but I have a huge bag of epsom salts.

 

[cnycharles]

http://www.orchidmix.com/cat4.htm

if you have a wholesale or other plant nursery around you, you might be able to get a 25 lb bag for not much money. robert's flower supply is just one orchid place I saw that has calcium nitrate, think c.l.a.n. orchids also had it (googling orchid supplies calcium nitrate). might find cheaper from greenhouse supply catalog place, but might be 25 lb bag shipped might not be cheap anymore. robert's sells it in 1lb and up quantities

 

[Rick]

Rick,

I am using 13-3-15 MSU fertilizer at a rate of 3/4 teaspoon per gallon of R/O water for a concentration of 75 ppm. This fertilizer also contains 8 Ca and 2 Mg. I flush every fourth or fifth watering with pure R/O water.

Where can I buy the source of additional Ca you are adding to your water?
How much additional Ca would you recommend that I add to bring my Ca up to a beneficial level (in tsp amounts)?
How much additional epsom salt would you recommend that I add to bring my Mg up to a beneficial level (in tsp amounts)?
I read that you also add Mg to your flushes. Is that with or without the addition of extra Ca?
Would adding extra Mg without adding extra Ca be beneficial or harmful? I don't have any Ca, but I have a huge bag of epsom salts.

My present method of use with MSU is 1/4 tsp/gal of MSU, 1/4 tsp of Calcium nitrate (the dihydrate is fine) and 1/4 tsp of anhydrous MgSO4 (but hydrated epsom salts is probably fine too). The MgSO4 is harder to dissolve, so I put this in first and mix until dissolved, then I add the other two items. I also add a 1/4 tsp of kelp extract.

Since my dilute well water has some calcium in it already (~12 ppm) I don't add any more calcium nitrate to it for the flushes.

Alternatively I've been flushing with my dilute well water to which I add 1/4 tsp/gal of EPSOMA peletized lime. Mix and settle for about 5 minutes, and discard the settled solids. The pH of this is still <8.0 and will add a small jolt of alkalinity with the Ca/Mg.

 

[Roth]

Alan Moon at the Eric Young qualified urea as essential to grow their plants properly some years ago.

Rick, your schedule looks OK, but there is way not enough ammonium to my taste in your program. Ammonium is required by a number of orchid species as a prefered source of nitrogen ( there was a study by Arditti about 40 years ago about that, well a compilation, but it was right). As a matter of fact, soe genuses like dendrobium phalaenopsis and some cattleya can grow in vitro with only nitrate nitrogen, but paphs, some Blc, and phals need absolutely to have ammonium, and for some, even urea...

MSU, I tried it and did not like it at all in terms of growth speed and color, so I went back to an ammonium/urea/some nitrate fertilizer for all of my plants. As an aside the Tokyo Orchid Nursery uses a very high ammonium/low nitrate fertilizer, loaded with P too, as a slow release. In Taiwan, they use another slow release that is very high in ammonium and ureafoam (which decomposes in ammonia with time). The Orchid Zone was using the old 30-10-10 all urea, then they used the Jerry's Grow that was a 50/50 blend of ammonium and urea. Norris Powell was using an ammonium only fertizer, and for me, I tried to use a calcium nitrate/potassium nitrate based fertilizer, but the leaf color quickly became dull ( like many photos I see on the internet, have to be honest). I like my plants to be very dark green, like in the wild or like healthy plants. They reward me by growing very fast then...

There is a large study in New Zealand under way, using many different potting mixes, and fertilizers. So far, the plants grown in a MSU type fertilizer with only nitrate as a source of nitrogen are about half size the ones grown with a fertilizer including urea and ammonium, with a marginal quantity of nitrate. The results will be published in a year or so, it is done by an university, with all the requirements, including the statistician...

What is true, however, when feeding nitrate only and low P to phalaenopsis, in the first time, they seem to become darker.

However, after a few weeks for deflasked seedlings, and a few months for mature plants, the effects start to be opposite, the plants are stunted, so they look nice, dark green, but grow at half speed. Later, some plants collapse by a kind of chlorosis...

 

[Bjorn]

A speculative approach

This thread is getting very interesting. Particularly as we now have got some new contributions. Input from Xavier is always welcome; and these things with urea - well at least I find it utterly fascinating.
Unfortunately, English is not my native language, so I have problems with the nuances of the language; but here is a proposal/idea::rollhappy:
I will try to write it in a condensed form, some of you do obviously not have time to read things carefully and we are all sometimes a bit "blocked" in our own mindset
I have been googling the issue lately and found a lot information, sometimes contradictory - which makes me go crazy. However after sorting and perhaps "filtering" these are the outcome:
Plants can assimilate NH4+ and NO3- through the roots
Urea disintegrate to NH4+ through NH3 in soil quite easily.
Urea can be assimilated through the leaf - at least for potatoes and obviously my orchids.
Urea acidifies soil. BUT first the production of NH3/NH4+ makes the soil alkaline - at least locally. Its when the Ammonia/um is oxidised to NO3- that the acid is formed. Nitrosomas produce nitite from ammonium and nitrobacter oxidise the nitrite to useful nitrate. Not straight forward is it? This happens in soil, in the cornfields. But do we know that nitrification is actually contributing much for orchids? And particularly epiphytes? What about humus ephyphites?
Let us imagine that we are plants growing in the jungle. The availability of nutrients is rater scarce so we have become very efficient in sourcing whatever comes our way.
What is coming our way, what is the source of it?
1)In the rain comes a solution of nitreous oxides commonly known as nitric and nitreous acids. Here is a source of Nitrate - grab it:drool:
What else?
2)droppings? Birds droppings contain uric acid. I have been unable to find how it is used by plants but it is a well known fertiliser(guano) My own experience from the days I had chicken tells me that composting Chicken droppings produce a lot of NH3 if it gets wrong. So Here is a source of NH3/NH4+
3)Decaying plant matter? Source of N in plants? probably proteins and amino-acids.
4) Misc. blue-green algae has the ability of synthesising amines and amino-acids. Possible source?

What does 2)-4) have in common except for being available N-fertilisers? Yes, they all contain Amino-groups -NH2 or easily gets broken down to ammonia(in the case of birds droppings).
Of course the amines also break down to NH3/NH4+.

All of the sources 2)-4) have to be oxidised to get into the "useful" NO3- ion. Then I ask you: Frankly, would you recon that plants would adopt to the ammonium or the nitrate as primary N-souce based on this reasoning? Particularly the epifytes should have much easier access to nitrogen though the NH3/NH4+.
And here we arrive at Urea: If the plants prefer ammonium over nitrate, why is urea so bad? And if the plants prefer nitrate, why should the evolution lead to a preference of the (perhaps) least available nutrient?
Of course, this is merely speculations; it could of be that all the water and Nitrogen-sources available to the orchids is so full of nitrosomas and nitrobacter that it all transform to nitrate, or at least most of it? - I do not know. Anyone having info on the chemistry of seepage water in the jungle?oke:

 

[Ray]

It's well-established in the bedding plant industry that ammonium-based nitrogen tends to accelerate internode elongation, while nitrate does not (I think I have that correct - it's been a while), so they are utilized at different times of the growth cycle. How that pertains to orchids, I have no idea, but I can tell you that my paphs grow like weeds using the MSU RO formula (18:1 nitrate:ammonium) exclusively, and each growth is about twice the size they were when I used Dyna-Gro "Grow" formula (1.7:1 nitrate:ammonium), so I detect no stunting of growth..

 

[Ray]

Rick - I was thinking about your blend of MSU/CaNO3/Epsom salts.

Using the septahydrate Mg source, a 1/3-each blend gives you about a 9-1-5-16Ca-0.7Mg fertilizer formula. Is that sufficient mag?

 

[Rick]

Rick - I was thinking about your blend of MSU/CaNO3/Epsom salts.

Using the septahydrate Mg source, a 1/3-each blend gives you about a 9-1-5-16Ca-0.7Mg fertilizer formula. Is that sufficient mag?

Those rotten waters of hydration!!!

Actually I use anyhydrous MgSO4 and not Epsom salts

I would like to see more like 4-5 for Mg and not 0.7

Please double check the MSU contribution for Mg (the "pure water") has a few ppm of it to start with, so I don't think you should end up with <1ppm)

 

[Rick]

From looking at some of the published work I added to this thread or the other thread on nutrition (from the GA extension website). The alkalinity values really push the choice of nitrogen.

Roth you mentioned in another post that you were growing in hard water conditions (at a GH in Europe). Alkalinity is generally high too in hard water conditions.

According to the GA extension paper, urea/ammonium is the prefered nitrogen source as alkalinity goes up.

Conversely for those using soft or RO based waters with very low alkalinity, Nitrates appear to be the preffered choice of N.

Although closely linked, pH and alkalinity are not 100% the same. pH of hard water systems are generally under 8.0 s.u. even with alkalinity values close to the hardness levels (>200 mg/L). Also soft waters can have high alkalinity and a pH approaching 9.0 (just add baking soda, NaHCO3), and the theoretical pH of pure water (alkalinity = 0) is pH 7.

I'm using dilute well water as my base water. Hardess 20-30 and alkalinity ~15 (very low). pH is usually around 6.5.

I use primarily nitrates for N source. I just started with MSU because it was the fad thing to do at the time. However, it looks like the alkalinity / Nitrogen discussion is pertinent to the results I've been seeing for the last couple of years. I am gettin very big luxuriant dark green leaves, and very pleased with present growth results for just about all species including paphs.

I need to post some pics of some P. mastersianum seedlings that I am presently growing. They have very good color and size for about 1 year out of flask. They are big dark and shiny with a vague pattern like the textbook description. Much better than my almost demised parent plant.

 

[Rick]

Rick - I was thinking about your blend of MSU/CaNO3/Epsom salts.

Using the septahydrate Mg source, a 1/3-each blend gives you about a 9-1-5-16Ca-0.7Mg fertilizer formula. Is that sufficient mag?

At 1/4 tsp per gal of the Robert's version of MSU pure water (12-6-13 7Ca-2Mg) that's essentially half strength

6-3-6.5 -3.5Ca-1Mg (granted the P and K are "phosphate and potash" not ion).

I'm actually using dihydrate CaNO3, and the anyhydrous MgSO4

So that should come out to a bit less N and Ca and a bit more Mg.

 

[Ray]

Ah HAH! Thanks.

 

[Rick]

Xaviar

Here's a couple of mastersianum 17 months out of flask. Baskets are 4" for scale.

 

[SlipperFan]

:drool:

 

[Jim Toomey]

Holy Crap, they are huge!

 

[Roth]

Xaviar

Here's a couple of mastersianum 17 months out of flask. Baskets are 4" for scale.

Superb plants... Three things however:

- The NZ trial includes MSU and various potting mixes, and MSU is clearly a vast disaster compared to several others fertilizers tested, and various potting mixes ( the trial is on phalaenopsis clones, few thousands plants for the trial, so it is indeed an interesting one going on, not a hobby size thing...), however you are using kelp extract, which could well make a huge difference... I used in fact something quite close to what you are using as a fertilizer, and that's the best performing fertilizer in the trial, as of today ( the trial will be completed by blooming huge phalaenopsis Japanese style, to push the trial to the end, so we don't know until they bloom hehe...). The best performer as of today was a ( per weight) 2-1-3 calcium nitrate, magnesium nitrate, and Peters 20-20-20, at about 1g total per L microsiements. Monthly use of a 10-52-10.

The EYOF used as well a product called Maxicrop every other month, and another guy (who was a conman, but very good grower) in england was doing beautiful paphs flasks, and growing a lot of orchids in rockwhool with great results, using maxicrop and calcium nitrate blended...

- You are using moss ( where I don't hehe), and apparently there is algae on it, heavily. It could well make a byproduct that feeds the plants

That would be really interesting to know what percentage of the growth comes from amino acids or NO3... My general feeling, including in-vitro, is that some genus prefer one source of nitrogen ( like many crops do anyway), and within the genus, some species, and specific populations prefer different conditions too. As an example in flask, for the last replate, the real doritaenopsis and the phalaenopsis pot-plant have a very different media, to get perfect seedlings.

I discussed that by accident with Clone Biotech in Taiwan, who have their own lab, and massive, perfect phal nursery. He told me, well that's funny you have two different last replate media, because we use your orchiata, we use NZ sphag moss, but for the doritaenopsis, we MUST get cheap chinese sphagnum moss to get the fastest growth...

Mastersianum from Ambon has heavily mottled leaf for about 20% of all the plants, and plain/mildly tesselated leaf for the remaining. The ones from Ceram have only yellowish green leaf, and can be really huge ( I mean 80+cm leafspan). The color is different, and the former grow on leaf litter, very deep shade. The latter grow on limestone, very alkaline and mineral soil. The same applies to different colonies of volonteanum and violascens. Apparently, when plants from one type grow very well, the others don't, in the same setup and growing conditions. Violascens grows on limestone outcrops, where the 'papuanum types of violascens' grow in fern roots...

Praestans, gardineri, and praestans red leaf have similar acid or alkaline colonies ( in fact I find the big roth-size praestans to be extremely easy to grow, the wilheliminiae/pygmy gardineri too, but the normal gardineri are less easy to grow for me...). Add to that that glanduliferum is a tree epiphyte... Same for philippinense, the very rare 'Sabah' type of philippinense, which is clearly the best type, grows in Sabah on fern roots, exceedingly acid. The philippinense in the Philippines prefer alkaline, to very alkaline growing conditions. That's clear there is clonal variation to expect...

 

[NYEric]

At 1/4 tsp per gal of the Robert's version of MSU pure water (12-6-13 7Ca-2Mg) that's essentially half strength

6-3-6.5 -3.5Ca-1Mg (granted the P and K are "phosphate and potash" not ion).

I'm actually using dihydrate CaNO3, and the anyhydrous MgSO4

So that should come out to a bit less N and Ca and a bit more Mg.

Great! You can mix me up a batch and let me know what to use it on!

 

[Rick]

http://www.hort.purdue.edu/rhodcv/hort640c/nuptake/nu00001.htm

Link to nitrogen uptake in higher plants. The chemical and non-plant interactions in the rooting zone are connected. but here is a synopsis of what the plant is doing internally.

pH (alkalinity) plays an important role in choice of Nitrate vs ammonia.

Here's another link (a Bill Argo article through Ray's site).

http://www.firstrays.com/PDF/Part 3 - Fertilizers.pdf

There's a table that shows % ammonia based on alkalinity

 

[Rick]

Rick - I was thinking about your blend of MSU/CaNO3/Epsom salts.

Using the septahydrate Mg source, a 1/3-each blend gives you about a 9-1-5-16Ca-0.7Mg fertilizer formula. Is that sufficient mag?

I weighed out 1/4 tsps of calnitrate 4H2O and MgSO4 anhydrous, and they were 1.44g and .888g per 1/4 tsp respectively.

This comes to 45 mg/L N, 64.5 mg/L Ca and 47.3 mg/L Mg

If 1/2tsp of MSU is ~80mg/L N

Then 1/4 tsp is
40mg/L N, 20 mg/L PO4, 43mg/L K 23mg/LCa and 6.6 mg/LMg

Adding back in the Ca, N and Mg from supplements should be:
85N - 20PO4 -43K - 87.5Ca - 54Mg

as % I think that should come out something like:

13-3-7 13Ca and 8Mg

 

[Ray]

Sorry to resurrect this after a month, but I found some textbook info that seems to confirm some of what was shared here, so went back and reread this thread.

According to Horst Marschner, in Mineral Nutrition of Higher Plants (a real "snoozer", but contains some good explanations), the chapter on nutrient uptake by leaves describes gaseous uptake (primarily ammonia) through stomata, while solution uptake is through the leaf cuticle. However, it also shows how that uptake mechanism is only significant in cases of mineral deficiencies (as Lance stated).

Also of interest is the fact that in solutions, nonpolar urea is taken up by the leaves faster than the polar nitrate and ammonium ions. (By contrast to roots, which via several different mechanisms, take up ions almost exclusively.)

So I guess the upshot of this is that foliar feeding using urea is not a bad strategy - but only if your plants are nitrogen deficient.