华北旱地土壤硫施用量指标

Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L^-1 CaCl₂ was nearly equivalent to that by 0.25 mol L^-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L^-1 Ca(H₂PO₄)₂ solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L^-1 Ca(H₂PO₄)₂-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L^-1 KCl (40 ℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.

Indices of sulfur-supplying capacities of upland soils in North China