Thanks, Ken. I had already seen this post. Gotta watch what info you buy into on the internet. The author might be an orchid hobbyist, but he's not remotely qualified to write a dissertation on fertilizer and his references including the German study aren't related to orchid growing. He says "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." Very few crop plants are epiphytes, and the majority of orchids are. So, what he "thinks" in that statement throws cold water on the whole thing, jmho. At the end he says "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." Hmmm.
According to one of my books, and another article the reason orchids can't use the nitrogen in urea-based fertilizer is because it needs soil-borne bacteria to metabolize it into usable form. So only terrestrial orchids can use it readily since their roots are in soil. I want to know where this information came from, too. Some scientist somewhere must have researched this.
My favorite orchid book, "Orchids to Know and Grow" co-written by two horticulture professors at the University of Florida, both of whom have grown orchids for over 20 years makes no mention whatsoever of using non-urea based fertilizers. It looks to me as if they were careful to avoid the question altogether, in fact. So maybe there really hasn't been a properly documented study about it.
Still reading and searching for any kind of research to confirm the whole urea question. Learning a lot along the way, too. I read 9 different culture sheets from the AOS website, and none of them mention non-urea based fertilizer, either! There were two culture sheets for Cattleyas and Phals for "Novice" orchid growers, and they did say to use "orchid fertilizer". But not all "orchid fertilizer" is non-urea either. The fellow who started this whole discussion read the analysis on the package of Miracle Gro for Orchids 30-10-10 at a Lowe's store today and its formulation included 26% nitrogen from urea and only 4% from ammonia sources.
Trial and error by orchid growers over the years gives a compelling argument for the non-urea side, though. i.e. it's what most people think is right, and what most experienced orchid hobbyists and growers do. I'm not giving up my non-urea fert any time soon. But I do want to know if there's real data to support its use just because that other fellow on DG raised the question. He was using regular Miracle Gro on his orchids, and several people advised him to get some non-urea instead. He asked "Why" and opened this can o' worms . . . ps. Jim, mine too.
