Management of sulphur fertilizers
Sulphur (S) is an important macro-nutrient in the production of canola, a high protein oilseed crop. In the absence of adequate S, canola yield response to added fertilizer N can be completely eliminated. A study was initiated at Brandon, Manitoba, Beaverlodge, Alberta and Melfort, Saskatchewan in 1996 to evaluate the effect of S fertilizer source, placement and application time on the yield and quality of conventional and zero-till seeded canola and spring wheat. The S, including ammonium sulphate (AS), solution ammonium thio-sulphate (ATS) and bentonite clay based elemental S marketed as Tiger-90 (T-90), were all applied at 18 lb S/ac. All treatments received a total N rate of 90 lb/ac, along with MAP at 40 lb P2O5/ac, or 18 lb P/ac. The broadcast fertilizer S was incorporated only with the conventional tillage plots. Where responses to S were recorded, ammonium sulphate (AS) and ammonium thio-sulphate (ATS) corrected S deficiencies in both the application year, and when re-cropped to canola in the following two years. Only when broadcast did T-90 provide a response equivalent to AS. However, this occurred 24 months after application. When the elemental S was pre-seeding banded or seed placed insufficient sulphate was available after 24 months to correct S deficiencies, resulting in yield reductions. Under severe S deficiencies recorded in 1998 a response was recorded for spring wheat to S. The results of this research indicate that in the northern Great Plains region sulphate-S is required to meet short-term S deficiencies in canola. Use of T-90 elemental S requires that the product be broadcast applied at least 24 months prior to crop requirement to allow for oxidation to plant available sulphate-S. Development of finely ground elemental S products will help to increase the conversion to sulphate-S, meeting crop requirements in a shorter time period after application.
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