Response of forage grass to sulphur applications on coastal British Columbia soils

Abstract

Little is known about the S requirement of coastal British Columbia soils. Spring gypsum applications increased yield in two and decreased yield in one of six forage grass rate-of-application field trials. Yield effects did not occur at every cut. At the sites where yield depression was observed, the effect primarily occurred at the intermediate rates and S concentration increased with increased rate of application. Luxury uptake of S (increased S concentrations without a yield effect) showed residual effects occurred into the third season after application, despite the abundant winter precipitation common in the area. Yields were affected in a form × rate × time trial, but not at every cut. Powdered elemental S was available to plants sooner than Agri-Sul (an elemental S fertilizer), but neither as quickly as gypsum. Four of five traditional soil test S extractants were significantly correlated with first-cut uptake of S in the control treatment, with the bicarbonate extraction having the highest coefficient (r2= 0.29). The smaller amount of sulphate in calcium chloride compared to the other extractants showed soil adsorption. Soil S tests are required to manage S for optimum yield without accelerated soil acidification. Key words: S fertilizer forms, S rates, gypsum, elemental S fertilizer, Agri-Sul, plant S uptake, soil S tests