CANOLA SEED SURVIVAL OVER WINTER IN THE FIELD IN ALASKA

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Abstract
Factors affecting seed survival of spring canola (Brassica campestris L. ’Tobin’), over two winters in the field at Delta Junction, Alaska were studied. In October, seeds were placed in polypropylene mesh envelopes and buried. The packets were exhumed the next spring and seed viability was determined. Factors studied included seed age, seed treatment, protection by snow-fence enclosures, burial depth, and spring retrieval date. During the first winter, survival of seeds near the soil surface until March was 65%, but many died during spring. During the second winter, seed viability in March was much lower than it had been in the previous March, but no significant mortality occurred during spring. Freshly harvested seeds generally survived better than seeds which had been stored for 1 yr. Seeds buried well below the soil surface and seeds placed inside snow-fence enclosures survived better than seeds placed near the soil surface outside enclosures. Results indicate that factors such as seed storage and protection from extreme temperatures and temperature fluctuations during late winter and early spring are important determinants of canola seed survival over winter. These factors could help explain why large populations of volunteer canola arise from seeds which have fallen from mature pods, whereas harvested, stored seeds planted during fall or early spring often produce poor stands in Alaska.Key words: Seed survival, seed mortality, seed germination, seed dormancy, seed overwintering, volunteer canola