Availability of single spring applications of three sulphur fertilizer sources to grass under humid weather conditions

Abstract

Field experiments were conducted to compare the effectiveness of single spring applications of three sulphur (S) fertilizers (powdered and granulated elemental S, and granulated sparingly soluble gypsum) to supply S to tall fescue grass (Festuca arundinacea 'Festorina') under humid weather conditions of coastal British Columbia. The treatments were three rates (30, 60 and 90 kg S ha-1) of each of the three fertilizers and control (No S) in three plots initiated in1997, 1998 and 1999 in different locations in an uniformly managed field. The relative effectiveness of the fertilizers was detected by plant uptake of S since the site was only marginally S deficient resulting in only occasional yield increases. The fertilizers were also evaluated by the increase of inorganic sulphate in the soil. The plant and soil measurements showed that S was available to the plant earlier from the granular gypsum than the elemental forms, and the powdered form was available slightly earlier than the granular form of elemental S. Some uptake of all three fertilizers occurred early in the season, i.e., by the first cut of the crop, showing that elemental S was oxidized relatively quickly. The delayed uptake of S from the granulated elemental S compared with the powdered form reflected the need for the granule to disintegrate before it could be oxidized in the soil. This study showed that S is not always available in soils at the time it is required by plants within a growing season of multiple-cut grass. Knowing the pattern of the release of S from various fertilizer forms in relation to within-season variations of soil S availability and plant requirement of S can provide the basis for optimum amendment decisions.Key words: S fertilizers, elemental S, sulphate-S, crop response, crop S uptake, soil sulphate, SulFer 95