I'm pretty sure organic fertilizers are not considered to be salts. Salts are the simple ionic combination of a metal and a near-noble gas from the periodic table of elements. Salts usually dissolve (or ionize) in water. Ammonium sulfate is the combination of the ammonium ion and the sulfate ion.
Corn, alfalfa, cottonseed, feathers, milo, soy, canola, etc. are not of that nature. These are complex, naturally occurring, protein strings usually combined in a cellulose structure with some other carbohydrates tossed around in there.
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San Antonio, TX