Short-term and residual contribution of selected elemental S fertilizers to the S fertility of two Luvisolic soils

Abstract

A 3-yr program was carried out in central Alberta to evaluate the immediate and residual contributions of various fertilizer sulfur sources to the pool of plant-available sulfate in soil. Three elemental sulfur products, a finely-divided suspension and two elemental sulfur + bentonite products, and ammonium sulfate were applied at various rates (0–120 kg S ha−1) in factorial arrangement with various supplemental rates of sulfate (0–40 kg S ha−1). Temporal patterns of plant-available sulfur release varied significantly among fertilizer S sources, suggesting different agronomic niches for the various forms. While ammonium sulfate and the finely divided S suspension provided almost immediate correction of S deficiency, the S-bentonite products appeared be better suited to long-term maintenance of soil S fertility. The relatively slow release of plant-available S in the latter products was attributed to ineffective dispersion of the products in the soil. These slow-release characteristics need to be considered in the formulation of fertilizer recommendations on soils previously amended with S-bentonite products. Key words: Oxidation, plant availability, residual effect, S fertilizers