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Ihere are currently no field calibration data for interpretation of soil S tests in the U.S. Northeast and limited data elsewhere. Given the reduction in the S deposition rate during the past decade in the Northeast, it is imporunt to evaluate the potential for soil testing as a tool for S management in the region. An incubation study was conducted to compare: (i) the accuracy and effectiveness of six S extraction methods to identify an increase in available S; and (ii) S detection in solution using inductively coupled plasma atomic emission spectroscopy (ICP-AES) at 1S2 nm with curbidimetric determination of S using BaCl2x2H2O and a spectrophotometer at 420 nm. The six extraction solutions were 1.0 mol L"' NH^OAc, 0.016 mol L"' KHjPO^, 0.01 mol L"' CaiHjPO^jj, 0.01 mol L"' CaCI^, Morgan, and the Mehlich-3 solution. Four New York soils were treated with six S rates (0,28,56,84,112,168 kg ha~') applied as gypsum and incubated for 4 wk (in the dark, at room temperature, 75% ofñeld capacity, four replications). SulRir test results correlated with $ fertilizer application for all extraction and detection methods; however, the 0.01 mol L~' CaClj extraction with ICP-AES detection of S in solution was best correlated with S added (highest r^, smallest RMSE across all four soils), the regression equation had the largest slope, and this method showed the greatest consistency between the two detection methods. We conclude 0.01 mol L~' CaClj extraction with ICP-AES detection of S is most promising and should be evaluated in field trials. Abbreviations: ICP-AES, inductively couple plasma atomic emission spectroscopy; OM, organic matter.

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