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Urea free fertilizer for orchids

This is a discussion on Urea free fertilizer for orchids within the General Orchid Culture forums, part of the Orchid Culture category; Has anyone else had trouble finding a BALANCED urea free fertilizer? It seems absolutely impossible ...

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  1. #1
    sand_tiger86's Avatar
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    Default Urea free fertilizer for orchids

    Has anyone else had trouble finding a BALANCED urea free fertilizer? It seems absolutely impossible to me. I want to try a balanced fert because I'm sick of having three-four different alternating kinds but I know urea based nitrogen is worthless to orchids.
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    Urea is not worthless to orchids, but it is really only absorbed well through foliar absorption, and the thick cuticle layers on most orchid leaves make that a mostly wasted effort. (Roots have an affinity for ionic species like nitrates and ammonium compounds, and a poor affinity for non-polar ones like urea. The plasmodesmata in the leaves is just the opposite.)

    I honestly think you are worrying unnecessarily about the formula, and the need for a "balanced" one. (I am assuming you mean something like a 20-20-20.) And... if the formula you use has all of the trace elements in it, there is absolutely no need to change formulas.

    Fertilizer is WAY down in the "Maslow's pyramid" of orchid priorities. 95% of the plant is made up of stuff it gets from air and water, and of the remaining small percentage, nitrogen is by far the largest component.

    For a varied collection it is very hard to beat the MSU formulas, whether that is the one for "Well Water" (any water that had appreciable level of dissolved minerals) at 19-4-23, or the "RO" version for use with pure water supplies, at 13-3-15-8Ca-2Mg. And if you want to get really "cutting edge", there's K-Lite, which is derived from the MSU RO formula, at 12-1-1-10Ca-3Mg. I am now at over 3.5 years of using it exclusively @ 30 ppm N at every watering, and I am thrilled with the growth and flowering of my plants.

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    Urea is also readily absorbed directly through the roots, and used by the plant, as shown by research: Phalaenopsis can absorb urea directly through their roots
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    Yes it is, but "readily" is a very subjective term. it is all a matter of degree.

    Nitrate/ammonaical nitrogen is preferentially absorbed by the roots, but nonpolar urea is also absorbed.

    Nonpolar urea nitrogen is preferentially absorbed by the leaves, but polar nitrate/ammonaical nitrogen is also.

    I have yet to see a study delineating the percentages.

    The simple fact of the matter is that, for feeding orchids, which ain't the Einsteins of foliar absorption, a nitrate/ammoniacal source is best.

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    Hi Ray

    You're in luck regarding the percentages, they are given in the abstract at the link I provided:

    "The ⁵N analysis of the younger leaves of each plant shows that urea and ammonium are the two preferred forms of nitrogen absorbed, with respectively 47% and 41% of the total amount, while nitrate is only absorbed to a level of 12%"

    So, the study showed that a higher percentage of urea N was incorporated into the leaves compared to the other two forms.
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    i don't like any of the salt based fertilizers (the brightly colored crystals), they burn my plants and you get that salt build-up on the pots and bark. i only use diluted worm tea now. it is organic, easy to use and make, costs me nothing now that my worms are established. not smelly, not too buggy (for a compost pile) and i have worms to feed my toad. the whole urea discussion seems like a lot of conjecture, and kind of like a marketing ploy anyway. my orchids seem to like the tea, i have been getting blooms and good growth. and i am polluting less, and composting is all natural and good for the environment. i mix the worm compost directly into other kinds of plants' soil. all around good stuff, and the only argument i have ever seen against worm tea is that it may or may not contain a small amount of urea... and that was by a few people desperately arguing how bad urea was for orchids and claiming all should switch to some particular brand, so was probably just marketing...

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    Hi coeruleo

    I think one of the reasons for opinions against urea is that some urea fertilizers used to be poorly manufactured, and as a result contained a significant amount of biuret. Think of biuret as similar to a double urea molecule that isn't good for plants. With better manufacturing today, biuret in urea fertilizers is now pretty low.

    I've not used worm tea, but apparently it works for you. Just be careful that the plants put in your compost aren't virus carriers (such as peppers, tomatoes, potatoes).

    Regarding sand_tiger 86's original question, any fertilizer with an NPK profile similar to the MSUs Ray mentioned should be good (less P required than N or K). Even better is a formulation that adds Ca and Mg plus micro nutrients if these are not in your water supply.
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    Hey, Catt. I have read that Trepanier article many times, and have discounted some of the results due to questionable experimentation, or should I say the drawing of conclusions beyond the scope of the experiment. Consider, for a moment, the fact that the study was done with seedlings in aseptic agar and liquid culture.

    A phalaenopsis seedling under such conditions does not develop the layer of velamen that a plant grown in-pot, in a typical medium, or mounted does. In agar culture, that begins to occur as the moisture level in the medium has begun to dwindle That velamen is more than just the sponge we have always been taught, but plays an active role in what the plant absorbs and doesn't. The fact that those percentages were shown for plant in vitro, does not mean it's true for them ex vitro, which is how we grow them.

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    Ray: The authors included in their abstract "Phalaenopsis roots, probably because of the special nature of velamen, can absorb large amounts of nitrogen directly in urea form."
    At my computer, rather than a cell phone, I can provide a link to the complete article so that folks can read & make up their own minds: Phalaenopsis can absorb urea directly through their roots - **士论文 - 道客巴巴

    The important points I take from the research is that the orchid roots, which did have velamen during the experiment, absorbed significant urea N that was used by the plants. It doesn't make sense to think that plants, if they were evolved to be incapable of absorbing urea through the roots, would suddenly develop the ability to absorb and use significant urea in vitro during this experiment. Instead, it is more logical to infer that the roots were previously evolved to absorb urea for use by the plant, and that this experiment measured this ability. The in vitro culture was (in part) needed to in order to control for / evaluate whether hydrolysis was occurring outside the plant.

    Regarding culture of orchid plants by hobbyists or commercial growers, the take-away point is don't worry whether your fertilizer contains urea or not. Orchids can absorb the urea form of N through the roots, and the plants can make use of it.

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    Quote Originally Posted by raybark View Post
    Yes it is, but "readily" is a very subjective term. it is all a matter of degree.

    Nitrate/ammonaical nitrogen is preferentially absorbed by the roots, but nonpolar urea is also absorbed.

    Nonpolar urea nitrogen is preferentially absorbed by the leaves, but polar nitrate/ammonaical nitrogen is also.

    I have yet to see a study delineating the percentages.

    The simple fact of the matter is that, for feeding orchids, which ain't the Einsteins of foliar absorption, a nitrate/ammoniacal source is best.
    BTW Ray, to clear up a misconception, urea is most definitely a polar molecule. It is asymmetric, similar to a water molecule (water is also polar). You can dissolve one polar substance into another polar substance, which explains why urea is readily dissolved in water (urea is hydrophilic).

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