Sulphur in air and soil

Natural S supplies are insufficient for high crop yields. The S brought down by rain is limited, even in industrial areas, and much of it is lost in drainage. Additional supplies are needed either as fertilizers or as SO₂, which vegetation readily absorbs. The margin between the minimum SO₂ concentration for full growth and the concentration at which damage occurs is wide enough for distribution via the air, without deleterious effects, of such S as is available from the combustion of fuels.