Oxidation of elemental sulphur and acidulation of calcareous orchard soils in southern British Columbia

The capacity of soils to oxidize S was measured by incubation with finely divided elemental S in 13 calcareous orchard soils from the southern interior of British Columbia. Sulphur oxidation rates ranged from 3.4 to 26 μg S cm−2 d−1. The magnitude of pH decrease in response to added S varied inversely with initial CaCO3 content (r = − 0.58, P = 0.04) and silt content (r = − 0.64, P = 0.02) and directly with sand content (r = 0.64, P = 0.02). Incubation studies with one calcareous orchard soil indicated that finely divided S was more effective over time than other acidulants (FeSO4, Al2 (SO4)3 and H2SO4). A field study was carried out on the same soil. Finely divided and bentonitic granulated S were applied at 4.5 t ha−1 on the grass surface or incorporated to a depth of 15 cm. Incorporated fine S was oxidized to a much greater extent during a 2-yr period than was incorporated grandulated S. However, when surface applied, they were oxidized equally but slowly.