Alternative seeding dates (fall and April) affect Brassica napus canola yield and quality

Brassica napus L, canola production on the Canadian prairies often is limit ed by hot, dry growing conditions in early July and a short growing season. Brassica napus canola seeded in the fall just prior to freeze-up or in the early spring as soon as fields are passable may allow canola to avoid thes e adverse conditions. Our objective was to determine if late October (fall) , or mid- to late April (April) seeding dates improve canola yield and qual ity relative to a mid-May (15 to 20 May) seeding date. Plant density and he ight, phenological development, seed yield, seed weight and seed oil conten t were assessed in plots sown to herbicide-tolerant B. napus canola at thre e seeding dates on five fellow sites and three stubble sites at Scott, SK, from 1994 to 1998. A thinner plant stand occurred for the fall compared wit h spring seeding dates; however, this difference rarely. corresponded with less canola yield. Fifty percent flowering occurred 20 d earlier (June rath er than July), reproductive growth (50% flowering to maturity) was 10 d lon ger, plants were 23 (fall) or 8 (April) cm shorter, and maturity occurred 1 3 d earlier when canola was seeded in the fall and April compared with mid- May seeding. Canola seed yield was 38% greater when seeded on the alternati ve dates rather than the more traditional mid-May seeding date. The yield a dvantage for alternative seeding dates was greater and more consistent on s tubble than on fallow likely because of lack of soil crusting and temperatu re and wind protection from stubble. The response of seed weight to seeding date was similar to that for seed yield, indicating that a portion of the positive yield response to alternative seeding dates was associated with la rger seed size. Oil content also was greater for the fall and April compare d with mid-May seeding dates, but the improvement was smaller (6%) than tha t for seed yield. Fall- and April-seeded canola tolerated spring frosts and avoided adversely hot, dry weather during the flowering period, thus impro ving canola seed yield and quality. Alternative seeding dates provide canol a producers in semi-arid regions with a sustainable option to diversify the ir cropping systems.