THE SULPHUR STATUS OF EASTERN CANADIAN PRAIRIE SOILS: THE RELATIONSHIP OF SULPHUR, NITROGEN AND ORGANIC CARBON

Abstract

Surface and subsurface samples of 17 of the most agriculturally important soils of the eastern Canadian prairies were analyzed for total S, sulphate S, total N and organic C. The soils varied in texture from sandy loam to clay loam. Fifteen of the soils were of the Chernozemic order, one was Brunisolic and the other Luvisolic. The subgroups included were Orthic Blacks, Gleyed Rego Blacks, Orthic Dark Greys, Eluviated Eutric Brunisol and Orthic Luvisol. The total S of the soils decreased with depth and was significantly correlated with total N and with organic C. The sulphate sulphur extracted with 0.1 M CaCl2 accounted for an average of 2.6% of the total S in each of the three soil depths analyzed. The calculated N:S and C:N ratios averaged 8.3 and 1.25 (0–15 cm), 7.2 and 14.1 (15–30 cm), and 6.5 and 11.0 (30–60 cm), respectively. The N:S ratios, and to limited extent the C:N ratios, were used to describe the sulphur status of the soils. Soil with N:S and C:N ratios 6.0 and 12.5 (0–15 cm), 5.2 and 13.5 (15–30 cm), 4.7 and 11.4 (30–60 cm), respectively, could have a high potential to supply sulphate S to plants and may not be deficient in plant-available S. Soils with N:S and C:N ratios of 8.7 and 13.5 (0–15 cm), 7.2 and 14.7 (15–30), 6.3 and 11.2 cm (30–60 cm), respectively, may be deficient in sulphur for some crops. However, they may have a high potential to convert total S to sulphate S. Soils with N:S and C:N ratio of 12.4 and 11.2 (0–15 cm), 11.1 and 13.0 (15–30), 10.2 and 9.9 (30–60 cm), respectively, may be deficient in plant-available S and could have a low potential for conversion of total S to sulphate S. Key words: Sulphur status of soils; potential available sulphur