If the available sulphur supply is exhausted before pods or seeds are formed, the resulting yield loss can be devastating. At that stage, the problem can be treated with a topdressing of ammonium sulphate fertilizer or with liquid sulphate-sulphur. Symptoms of sulphur deficiency at flowering are easily seen from a distance. Flowers deficient in sulphur look white or very pale compared to healthy canola, even in the same field. At that stage, a foliar liquid sulphate-sulphur application can still restore the yield.
Preliminary results indicate that canola yield can be restored with sulphate.
Dr. Malhi set up a field experiment at two locations in 1998 to determine if yield can be restored by an application of sulfate fertilizer at sowing, bolting and flowering. Methods included broadcast with incorporation, sidebanding, seedrow applied, and topdressed granular or foliar application at bolting and flowering. Preliminary results indicate that canola yield can be restored with sulphate fertilizer during the growing season, probably as late as the early flowering stage, says Dr. Malhi. Adequate rainfall will be critical, he adds, to move broadcast types of topdressed sulphate sulphur fertilizer down into the subsoil where roots can intercept it. Applied in warm, dry conditions, foliar product will stay on the leaf surface and be absorbed for immediate response.