Spring canola is the most important oilseed crop produced on the Canadian prairies with 4 - 5M. hectares (10 - 12M acres) grown annually. Traditional seeding dates vary by region but generally occur in the mid-late May period. With the short growing season experienced over much of the region fall frost injury and the associated reductions in yield and quality is a concern to growers. Earlier reports (Austenson and Kirkland 1975 ) indicated that seeding spring canola in late October, to lie dormant over winter, could successfully extend the growing season. They also reported that winter annual weeds were both abundant and highly competitive and made this seeding date impractical. The introduction of herbicide tolerant canola and the associated herbicides which effectively control a range of weeds, including winter annual weeds, could make the late October seeding of spring canola possible.
The objective of this study (1994-1996) was to compare the effect of late fall(LF), early spring(ES) and mid-May(mM) seeding dates on maturity, yield, and quality of glyphosate tolerant canola. Canola seeded in late October emerged in late April and demonstrated excellent tolerance to spring frosts. Glyphosate applied at 440g ai/hectare at the 3-4 leaf stage of canola provided excellent control of winter annual and early germinating summer annual weeds. Later germinating summer annual weeds were not competitive with fall seeded canola.
Canola seeded in late October(FS) and late April(ES) was harvested approximately 15 and 10 days earlier, respectively than canola seeded in mid-May(mM). Yield from LF and ES seeding was 10% greater than the mM seeding, and oil content ranged from 1-2 % higher.
In summary, changing canola seeding dates from mid-May to late October or late April increases the crop's ability to compete with weeds, advances maturity and improves quality. Other possible advantages include; the fit into direct seeding systems, soil conservation, reduced risk of insect and disease attack, utilization of June precipitation and cool temperatures for seed set, improved weed management options and spreads grower's workload.