It would seem that it does not matter if it comes out of a bottle or a bag or box or from a compost pile. All of our organic materials whether plant or animal are accumulating salts which then get released after decomposing.
I see the big problem being when the nutrients are coming from the minerals, either as already water soluble or as in-soluble which will eventually be released by the micro-organisms. This causes a faster and larger build-up of the salts as compared to the smaller amounts released by decomposing 'organic' matter of the same weight. And, the ones released from the decomposing materials are ready to be absorbed by the plant instead of needing some sort of pre-digestion by the microbes or micro-organsims.
The more we learn about the cycle of life the more complicated it seems to get.
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