Rich in phosphates, this waste matter left by bats & seabirds can be a valuable commodity
As a manure, guano is a highly effective fertilizer due to its exceptionally high ... 
bats can have nitrogen levels approximating that of seabird guano and high 
phosphate levels, but bat guano typically has less fertilizing value than seabird 
guano... [DOC] [TLE] Phosphorus Matters II - Keeping Phosphorus on Farms - The ... [PAR] Jul 23, 2009 ...