I think a component of the discussion that is being missed is the microbial populations in different people's orchids. Specifically the phosphate and potassium solubilizing bacteria associated with their orchids- if you lack theses functions in the microbial populations that live in and on your orchid roots then you are forced to overcompensate with increased additions of these nutrients.
Applying phosphorous as a salt and without appropriate microbial helpers means that your plant really only takes up phosphorous when it is in its ionic form in solution... the massive increase in concentration that occurs as evaporation and dry down cycles happen causes the phosphorous to be complexed with cationic species which become much harder for your orchid to take up. In a natural system there is a balance between phosphorous immobilization and mineralization/solubilization that dictates the availability of ionic phosphorous. Increasing phosphorous fertilizer without the appropriate microbiology just drives your orchid and media towards immobilization. Additionally, the organic forms of phosphorous that are contained in micro life are an important source of phosphorous as these organisms growth and death releases these organic forms which are less likely to form insoluble complexes. In systems with low organic matter (like most orchid mixes) the deleterious effects of excess salts on microbial populations are much more pronounced. If you combine this with the over use of synthetic pesticides which are harmful to nutrient cycling organisms and it becomes no surprise to me that people start compensating with higher feed rates. There is nothing wrong with this... other than you lose a lot of resilience and efficiency in your growing system.
You can meticulously balance nutrient ratios, or you can use microbes and be lazy but that's just my $0.02. I'd rather use less salts and preserve and promote the functional organisms I've inoculated into my orchids.
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