It's a fertilizing element for ragweed
Depending on the location, ragweed may begin spreading its pollen... [DOC] [TLE] Ragweed - Ambrosia artemisiifolia  Broadleaf Weeds - WinLAWN ... [PAR] Feb 15, 2016 ... Its removal is intensively sought, because ragweed pollen is one of the ... 
because it is able to absorb huge amounts of the trace elements in the soil.