Effects of four consecutive annual applications of elemental S and sulphate-S fertilizers on yield, S uptake and seed quality of wheat

Abstract

A field experiment from 1999 to 2002 was carried out near Tisdale in northeastern Saskatchewan on a S-deficient Gray Luvisol (Typic Cryoboralf) soil to compare the effects of elemental S and sulphate-S fertilizers on yield, seed protein, total S concentration, S uptake, and recovery of applied S in wheat (Triticum aestivum L.) and residual SO4-S in soil. Treatments were combinations of 10 and 20 kg S ha-1 rates applied in autumn and spring for two granular bentonitic elemental S fertilizers (ES- 90 and ES-95), one fertilizer containing both elemental S and sulphate-S (Agrium Plus), and ammonium sulphate, plus a zero-S control. The S fertilizers were surface-broadcast and all plots had a preseeding rotovation in spring to incorporate fertilizers into the soil. Seed (1 yr) and straw (3 yr) yield, seed protein concentration (1 yr), and total S concentration and S uptake in seed and straw (all years except uptake of S in seed in 2001 and 2002) showed significant response to S fertilization. Ammonium sulphate and Agrium Plus were generally more effective compared with the elemental S fertilizers, when there was a significant response to sulphate-S containing fertilizers. Autumn application of elemental S fertilizers was sometimes more effective than spring application, while an opposite trend was observed for sulphate-S containing fertilizers in some cases. The increase in S rate from 10 to 20 kg S ha-1 tended to increase the measured wheat parameters in many elemental S treatments, but for sulphate-S fertilizers the effect was less pronounced. The concentration of total S in seed and straw was relatively more responsive to S fertilization than yield and S uptake, particularly for seed. The effect of S fertilization on wheat was less pronounced in drought years, particularly on seed yield, suggesting that drought rather than S availability was limiting wheat growth. There was some build-up of residual SO4-S in the 0-60 cm depth of soil in many S fertilizer treatments after four successive applications, but there was little or no difference in soil SO4-S between elemental S and sulphate-S fertilizers. In conclusion, the results from four successive annual applications of elemental S and sulphate-S fertilizers in autumn and spring on the same area indicate that bentonitic granular elemental S fertilizers had comparatively less influence on wheat than granular sulphate-S fertilizers and further research to improve the effectiveness of these elemental S fertilizers is suggested. Key words: Elemental S, fertilizer, protein, seed quality, sulphate-S, wheat, yield