"Plants often absorb materials in the soil that are there, but which they do not need. They absorb them only because they are there. Sometimes they are altered, to one degree or another. Materials that are not noxious to the plant may not be altered, and may simply be absorbed thru the roots and carried throughout the vasular system, unchanged. This is why plants grown in different kinds of animal excrement acquire a flavor vaguely remininescent of the kind of excrement used. The substances that provide the reminiscense are chemcicals produced by micro-organisms thriving in the excrement."
Solution?? veganic/ Organic agriculture.
*Plant feed is something to be looked into...