Evaluation of a sprayable elemental sulfur fertilizer under field conditions in Alberta

Elemental sulfur (ES) fertilizers have high S content but may not be effective in the year of application due to the time required to oxidize. Rapid oxidation may be possible if the ES has a large surface area in contact with the soil. We evaluated the efficacy of Sulgro 70, a micronized ES fertilizer that is sprayed onto the soil surface, in eight field trials in southern and central Alberta over a 2 yr period. Under dry conditions in southern Alberta, the relative efficacy of Sulgro 70 to increase S supply to ion-exchange membranes was 22% during the first 4 wk period after seeding and 53% during the second 4 wk period after seeding, compared with ammonium sulfate (AS) sprayed on the soil surface. Under wetter conditions in central Alberta, the relative efficacy of Sulgro 70 to increase S supply was variable (51%–201%) during the first 4 wk period after seeding and 56% during the second 4 wk period after seeding. Based on increases in biomass S concentration in three trials where the unfertilized control had low S concentration (<3 g S·kg −1 ), the relative efficacy of Sulgro 70 was 34%. Canola seed yield was not increased by application of AS or Sulgro 70 in any of the trials. Sulgro 70 sprayed on the soil surface oxidized appreciably during the first 8 wk after seeding and, with suitable management, has the potential to meet canola S requirements in the year of application.