Influence of six successive annual applications of sulphur fertilizers on wheat in a wheat–canola rotation on a sulphur deficient soil

A 9-yr (1999–2007) field experiment was conducted on a S-deficient Gray Luvisol (Typic Cryoboralf) loam soil at Porcupine Plain in northeastern Saskatchewan. The objective was to compare the influence of six successive annual applications (1999–2004) and the following residual effects for 3 yr (2005–2007) of elemental S and sulphate-S fertilizers on yield, seed protein and total S concentration, and S uptake of wheat (Triticum aestivum L.) in a wheat–canola rotation. Treatments used were combinations of two application times (preceding autumn and before seeding in spring) with two granular elemental S fertilizers (ES-90 and ES-95), one fertilizer containing both elemental S and sulphate-S (Agrium Plus), ammonium sulphate, and a zero-S control. The S fertilizers were applied annually at a rate of 15 kg S ha –1 . From 1999 to 2004, seed yield (3 yr) and straw yield (4 yr), seed protein concentration (3 yr), total S concentration in seed (4 yr), and S uptake in seed (5 yr) and straw (5 yr) of wheat showed significant response to S fertilization. In the first year (1999), ammonium sulphate and Agrium Plus were more effective than ES-90 and ES-95. In the following years (2000–2004), there was no significant effect of S source on seed and straw yield. Sulphate-S containing fertilizers produced greater total S concentration in seed and S uptake in straw (3 yr) and for S uptake in seed (1 yr). There was no effect of timing of S application on seed yield and protein concentration in any year, but autumn application was superior to spring application for straw yield and S uptake (1 yr), and for seed total S concentration and S uptake (2 yr). Residual effects of six previous S applications showed improvement in wheat seed yield until 2006, and straw yield and total S uptake until 2007. Elemental S, especially when applied in autumn, tended to have more lasting residual effects than the other S fertilizer treatments. There was some build-up of residual sulphate-S in soil in almost all S fertilizer treatments after four successive applications, but this was generally higher with sulphate-S-containing fertilizers. Recovery of applied S from 1999 to 2004 in plants was usually higher with sulphate-S fertilizer than with elemental S fertilizer in most years. Recovery of applied S in soil was higher for sulphate-S fertilizers, followed by ES-90, and finally ES-95. Residual nitrate-N in soil was significantly lower in spring-applied ammonium sulphate treatment than the zero-S or other S treatments. Key words: Elemental S, fertilizer, protein concentration, S uptake, sulphate-S, wheat, yield