I had a thought of a village who had claimed a wooded area, and every day foraged through it for nettles for their poultices, berries for their pies, etc. But what if this village was big? What if they needed LOTS of berries to feed their dudes, lots of nettles to heal their (minor) wounds? Maybe in that area, they could spread a type of fertilizer to help forageables grow faster?
As to what ingredients make up the fertilizer, i do not know. But hows the idea?