Air pollution legislation to control fossil fuel emissions and the associated acid rain has worked – perhaps leading to the need for sulfur fertilizers for crop production. A University of Illinois study drawing from over 20 years of data shows that sulfur levels in Midwest watersheds and rivers have steadily declined, so much so that farmers may need to consider applying sulfur in the not too distant future.“We don’t think there are actual sulfur deficiencies yet, but clearly more sulfur is coming out of the soil and water than what is going in,” says U of I biogeochemist Mark David. “As the Clean Air Act and amendments have taken effect there has been a reduction in sulfur emissions from coal combustion, so that the amount of atmospheric sulfur deposited each year is only 25 percent of what it used to be. At some point, farmers are going to have to fertilize with sulfur.”