SULPHUR FRACTIONS OF SELECTED ALBERTA SOIL PROFILES OF THE CHERNOZEMIC AND PODZOLIC ORDERS

Abstract

Total sulphur, carbon-bonded sulphur, HI-reducible sulphur, easily soluble sulphate, adsorbed sulphate, and sulphate associated with calcium carbonate were determined on seven Grey Wooded profiles and eight Chernozemic profiles, the latter including soils from the Brown, Dark Brown, Thin Black, and Black soil zones of Alberta.A clear dichotomy was observed between the Chernozemic and Grey Wooded (Podzolic) profiles. Organic forms of sulphur predominated in all surface and B horizons, although inorganic sulphate reached high levels in C horizons of some Chernozemic profiles. HI-reducible sulphur accounted for 63% and 71% of the total sulphur of Chernozemic Ah and Bm horizons, but only 33% and 48% of the total sulphur of Grey Wooded L-H and Bt horizons. N:HI-reducible sulphur ratios were much wider in the surface and B horizons of the Grey Wooded profiles than in the Chernozems. Carbon-bonded sulphur decreased with depth in all profiles, representing 17% and 9% of the total sulphur in the Chernozemic Ah and Bm, and 26% and 15% in the Grey Wooded L-H and Bt respectively. Sulphated polysaccharides were isolated from all surface horizons, but in no case accounted for more than 2% of the total sulphur. An inert sulphur fraction, resistant to strong oxidizing and reducing agents, was detected in residues of four samples subjected to exhaustive extraction with hot acid and alkali. This fraction accounted for 2–44% of the total sulphur, the highest value being observed in a Grey Wooded L-H sample.