Effect of Seed-Placed Sulfate and Phosphate On the Emergence of Brassicae Crops.

Excess application of fertilizer in the seed-row can lead to seedling damage depending on the fertilizer source and type. Tolerance of Brassicae oilseed crops like canola to seed-row application of nutrients is generally low when compared to many other crops. However, there is little information on their relative tolerance to combinations of seed-row placed sulfur and phosphorus fertilizer. The objectives of this research were to determine the effects of seed-placed ammonium sulfate (AS) and monoammonium phosphate (MAP) fertilizer applied at different rates on seedling emergence of different Brassicae oilseed crops/cultivars under controlled-environmental conditions. Tray experiments were conducted using six treatments consisting of an unfertilized control and five rates of seed-placed S applied as AS in combination with three rates of seed-placed P₂0₅ applied as MAP. Seeds were sown into plastic trays at a depth of 1.25cm with 6 rows per tray, creating a seed bed utilization of approximately 15 %. Emergence counts were taken over a two week period. Rates of seed-row placed AS above 20–30 kg S haˉ¹ were associated with significant reductions in emergence of most Brassica species/cultivars. Addition of 15 to 30 kg haˉ¹ of seed-placed P₂0₅ along with the AS further reduced emergence by about 10 to 15%.  Brassica rapa and Brassica juncea were generally more sensitive to injury from seed-row placed S and P than B. napus cultivars. Differences in sensitivity were also observed among cultivars of a species.