A laboratory study to evaluate the agronomic utilization of industrial lump sulphur by-product in alkaline soil

A laboratory experiment was carried out to investigate the possible utilization of lump sulphur coming from petroleum desulphurization in reducing pH of soils at high alkalinity reaction, as substitute of commercial elemental sulphur. An alkaline soil (pH = 8.37) was added with different amounts of lump sulphur (So) equivalent to 0, 1, 2.5, 5 and 10 t ha-' and modifications induced on chemical and biochemical parameters such as pH, EC, sulphur oxidation, total (TOC) and extractable (TEC) organic carbon, microbial biomass-C content (MBC-content), soil basal respiration, arylsulphatase (ArS-ase), o-diphenoloxidase (0-DPO) activities and total hydrolytic activity (FDA-hydrolysis). were monitored. Changes in soil microbial community was also investigated. Results showed that lump sulphur oxidative capacity of soil strictly depends on soil moisture level. As a consequence of sulphur oxidation soil pH decreased until a minimum value of 7.68, at the highest dose of lump sulphur added, within60 days of incubation. Significant increases of soil EC were also observed within 120 days. No significant changes in ArS-ase, o-DPO activities and FDA-hydrolysis were observed, while basal respiration indicated an initial stress suffered by the soil microbial community as consequence of sulphur addition. A shift in the microbial community towards sulphur-oxidizing bacteria was also observed in all sulphur treated soils.