Temporal trends of sulfur levels in soils of northwestOhio(USA) between 2002 and 2014

Sulfur (S) is an essential nutrient for plant growth. Despite increasing reports of yield responses of crops to S fertilization, there is limited information about changes in the soil test concentrations of S. This study used a soil chemical analysis dataset from 2002 to 2014 to evaluate changes in soil S and other nutrient levels. The soil-test database comprised 8,428 topsoil samples (0-20 cm depth layer) collected from 143 farm fields located in the northwest (NW) Ohio counties of Defiance, Paulding, and Williams. Except for S, the database showed no significant changes in soil chemical properties from NW Ohio between 2002 and 2014. Soil sulfate (SO42-) levels have linearly decreased by 63% from 2002 to 2014, reaching the range of concentration considered deficient for the main cereal crops. With no changes in soil organic matter (SOM) and pH, this result was attributed primarily to enactment of air quality regulations, since soil SO(4)(2-)decreases were directly correlated with the reductions of SO(2)emissions (-70%), SO(4)(2-)in rainwater (-66%) and deposited (-52%) in NW Ohio between the years of 2002-2013. Furthermore, combined increasing crop yields and insufficient compensation by fertilization had role on decreasing soil SO(4)(2-)levels. Current fertilization practices and wet deposition of S have not been sufficient to balance S removals from soil leading to the declines in the soil test S levels. It is imperative to paid more attention to practices that maintain soil S fertility levels to avoid yield penalties associated with soil S deficiencies.