You raise a good point envirogym with the issue of excessive salt content in widely used chicken manure. As water scarcity grows in a hotter climate, irrigation of salts worsens.
"In arid northwestern China, a severe water scarcity and growing soil salinization are closely related problems that are strongly affecting agricultural development and sustainability"
THERE ARE MICROBES(BACTERIA) THAT CAN BREAK DOWN HEAVY METALS!!! Its amazing how MOTHER NATURE can restore and revitalize damaged soil with the proper nutrients and care!!!