Macroelements/microelements must be a costant ratio?

[gonewild]

So from the time of watering to the next watering the concentration of nutrients is obviously increasing.

Sounds like you just described "accumulated salts".

There is a company that produces freeze dried amino acid chelates of micronutrients that they claim to be soluble and compatible with fertilisers. I'm not entirely convinced that the amino acid chelates that I use are necessarily going to stay intact that long in the medium as the microbial population in the mix is probably going to gobble up the amino acids anyway.

And as the microbial population gobbles up the amino acids they may very well excrete the exact nutrients that the plant needs.

Nonetheless, I'm trying this approach which is very similar to what David Campen has been doing, which I think is a good enough idea at least to try out.

Yes, try it to find out.

We tend to focus on the inorganic compounds when looking at natural systems, but there is accumulating evidence that both the organic acids (eg. citric, malic, succinic, fumaric, oxalic) and amino acids (eg. aspartate, glutamate, histidine, and others) are present in easily detectable amounts in aboreal forest soils. Not much work on tropical forests that I could find. Fungi, including mycorrhizal fungi, are known to excrete organic acids to increase the availability of cationic nutrients, and some plants have genes that are involved in the export from roots of malic or citric acid. I seem to remember that mosses do something similar.

Exactly what I have been saying but you have used bigger words! The living organisms are what provide orchids with most of their nutrients in Nature.

The point I'm making is that chelation is not some exotic unnatural mechanism dreamt up by chemists in a lab (EDTA is, for sure, but that has been mentioned above). In what form do wild orchids get their micros from mycorrhizal fungi? I'm not sure this is known, but I'm willing to bet that due to toxicity issues the fungus is going to be transporting these as chelates of one form or another.

This is why we need to look at unconventional nutrient sources and not assume all nutrients come from rain or dust or leaching leaves.

It is likely that fungi growing in our orchid pots are excreting organic acids anyway and whether you are applying chelates or not, some of the micros being assimilated by your plants might well be in chelate form anyway. It's back to the story of beneficial micro-organisms and the interactions between the micro-ecology of the pot and the nutrients we apply.

Yes, and to have the orchids grow well we need to give them some form of artificial nutrient supply until the natural organisms establish themselves in the growing media or on the orchid roots and foliage. When an orchid is put into fresh growing media there are no organisms present to produce nutrients so we need to use fertilizer as a form of artificial life support. The growers that are lucky enough to have beneficial organisms populating their cultures are the ones that say fertilizer content is not important.

 

[Ray]

So from the time of watering to the next watering the concentration of nutrients is obviously increasing. The idea of chelating all the cationic micros is to lengthen the time that they are available by reducing their propensity to precipitate as phosphates, increase their mobility in the medium and thus, hopefully, allow lower concentrations to be effective for longer.

Sounds reasonable, but we must keep in mind that that is good and well with only very low doses; in the commercial nursery world, it is well established that one of the best ways to screw up plant nutrition is by overdosing the micros. Most feed N-P-K only, and apply soluble trace elements only if there's a recognized issue.

 

[DavidCampen]

... in the commercial nursery world, it is well established that one of the best ways to screw up plant nutrition is by overdosing the micros. Most feed N-P-K only, and apply soluble trace elements only if there's a recognized issue.

Really, most commercial orchid growers using RO water use N-P-K only?

Or are you talking about commercial growers who grow in soil, use tap water and do not use greenhouse grade (water soluble) nutrients?

Most people here use RO water, do not grow in soil and use greenhouse grade nutrients.

After all, it was you who said: "Don't let knowledge (or mythology, in some cases) about nutrition in terrestrial plants "contaminate" your thinking about orchids. Sometimes the info applies, but in some cases, it doesn't."

 

[cnycharles]

I believe the statement was specific and didn't mention ro water. In the commercial nursery world (general horticulture world of plant production) plain bagged fertilizer is used unless there is a known deficiency or general need of certain plants or a certain feed used is lacking in a known needed micro. Some nurseries may toss in stem or something like that but usually it's done when a need is perceived. Again generally...
There is often pH adjustment and feeds are often chosen which will tend towards a needed pH, but the micros in that particular feed may not be enough for a particular crop


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[Ray]

Really, most commercial orchid growers using RO water use N-P-K only?

Or are you talking about commercial growers who grow in soil, use tap water and do not use greenhouse grade (water soluble) nutrients?

Most people here use RO water, do not grow in soil and use greenhouse grade nutrients.

After all, it was you who said: "Don't let knowledge (or mythology, in some cases) about nutrition in terrestrial plants "contaminate" your thinking about orchids. Sometimes the info applies, but in some cases, it doesn't."

Right you are, David. I never stated RO, and I wasn't thinking in those terms, but my assertion that overdosing trace elements can screw things up still stands.