K.J Kirkland, and E.N. Johnson

Agriculture and Agri-Food Canada Scott, Sk.

Annual crop production in most of Canada’s prairie region is limited by a short growing season, hot, dry periods in July during flowering and seed set and the probability of cool, wet conditions at harvest in September. As a result, yield potential is restricted and crop quality often reduced. Development of a technology that would expand the season by two to three weeks would produce major economic benefits to crop producers in the region.

Research studies to develop alternative seeding dates for canola were initiated at the Scott Research Farm in the fall of 1993. The main study has evaluated canola seeded at three dates; late October (dormant); early spring (late April); and a traditional spring seed date (May 15-20). Herbicide tolerant Brassica napus canola ( RT-73, Quest) was used as it allows broad spectrum weed control, including winter annuals in a single pass post emergent glyphosate treatment. The early years of the study were conducted on Dark Brown soil at Scott with additional locations on Black, Gray Wooded and Brown soil types added in recent years. Tests have been established on tilled fallow (1993-97), chemical fallow (1996), and stubble (1995-97).

Late fall and early spring seeding dates have significantly advanced the maturity of canola to flowering, swathing and harvest by several days compared to mid-May seeding (Table 1). With flowering occurring in early to mid-June the crop can take advantage of the normally cooler, moister conditions rather than the higher temperatures and drier conditions of July. Fall seeded and early spring canola generally reaches 50% flowering around June 10 and June 19, respectively. However, early emergence in 1998 resulted in the fall seeded and early spring seeded canola being in the 50% flowering stage on June 1 and June 17, respectively. Considered over all years of the study this has advanced harvest dates by up to 25 and 21 days for the late fall and early spring dates, respectively.

Table 1. Maximum Maturity Advantage in Days for Fall and Early Spring Seeded Canola (Scott, SK., 1994-98)

Late fall dormant seeded canola established better on stubble than tilled fallow in 1996 and 1997. The absence of trash cover on tilled fallow increases the risk of premature germination with fall seeding due to temperature fluctuations near the soil surface. Surface crusting at the time of emergence reduced fall seeded stands on tilled fallow in 1996. In 1997, the establishment on fallow was reduced due to high spring winds causing sand blasting of the seedlings. (Table 2) . In 1998, emergence was excellent on fallow and stubble for all seed dates (data not shown).

Table 2. Effect of Seed Date on Crop Establishment (plants/m², Scott, SK. 1996-97)

Fall seeded canola emerges extremely early with emergence dates ranging from April 20 to May 1.Early spring seeded canola emergence ranged from 8 to 14 days after seeding while mid-May emergence ranged from 6 to 13 days after seeding.

Fall seeded canola has exhibited good tolerance to spring frosts after emergence. At Scott, it has survived temperatures as low as - 8° C and survived 8 consecutive nights of frost in 1994. However, in 1998 frost did significant damage to fall seeded canola in Swift Current. Early emergence (Apr. 9-12) followed by high air temp.in late April reduced the cold hardiness of canola and a sudden frost of -5° C on May 1 reduced the canola stand by about 70%.

Canola yields on stubble averaged 58% and 55% higher for the late fall and early spring seeding dates, respectively (Table 3). On fallow late fall and early spring seeded canola have averaged 16% and 26% higher yields than mid-May seeding (Table 4). The lower yields associated with the dormant fall seeded canola on fallow are associated with poor crop establishment in 1996. When successfully established, excellent yields for fall seeding were recorded on tilled fallow.

Table 3. Yield of Canola seeded at Three Dates on Stubble (4 site years, Scott, Sk. 1996-98)

Seed Date	Mean Yield (bus/acre)	% of mid-May	Range of Yields (bus/acre)
Late Fall	19.3	158%	12.8 to 26.7
Early Spring	18.9	155%	8.7 to 28.6
mid-May	12.2	100%	7.1 to 16.2

Table 4. Yield of Canola Seeded at Three Dates on Fallow (7 site years, Scott, SK 1994-98)

Seed Date	Mean Yield (bus/acre)	% of mid-May	Range of Yields (bus/acre)
Late Fall*	27.9	116%	12.0 to 44.2
Early Spring	30.4	126%	26.0 to 37.4
mid-May	24.2	100%	12.0 to 39.0

When yields were combined over stubble and fallow, the late fall and early spring seeding date produced 25 and 32% more than the mid-May seeding date, respectively (Table 5).

A study conducted in Swift Current in 1997 found that canola seeded on Nov. 5 yielded 41% higher on fallow and 43 % higher on stubble than canola seeded on May 4. (Table 6). Avoidance of flowering in hot, dry July conditions is necessary to make canola production viable in the Brown Soil Zone.

Table 5. Combined Yields of Canola Seeded on Stubble and Fallow at Three Dates ( 11 site yr Scott, SK. 1994-98)

Seed Date	Mean Yield (bus/acre)	% of mid-May	Range of Yields (bus/acre)
Late Fall	24.8	125%	12.0 to 44.2
Early Spring	26.2	132%	8.7 to 37.4
mid-May	19.8	100%	7.1 to 39.0

Table 6. Effect of Seed Date on Yield of Quest Canola in Swift Current (Miller and McDonald, unpublished data, 1997)

Fall and early spring seeding produced larger seed than mid-May seeding in 1995 and 1996. However, in 1997 the fall seeded canola had slightly lower thousand kernel weights than the other seed dates. This is likely due to the higher than normal air temperatures experienced in early to mid June (Table 7). Thousand kernel weight data has not been compiled for 1998 yet.

Table 7. Effect of Seed Date on Canola Thousand Kernel Weight (grams). Scott, SK. 1995-97

Fall and early spring seeding of canola generally results in higher oil content since the crop is flowering in cooler conditions. When averaged over 6 experiments (1994-97), the oil content of the fall and early spring seeded canola has averaged more than one percentage point higher than the mid-May seeded canola (Table 8).

Table 8: Effect of Seed Date on Percent Oil in Canola (Mean of 6 experiments, Scott, SK.

1994-97)

Fall seeded canola crops are shorter than the early spring or mid-May seeded crops. (Table 9) The shorter crops make them less prone to lodging, which would be an asset in highly productive areas.

Table 9: Effect of Seed Date on Height of Canola (cm) Scott, SK. 1996-97

Numerous agronomic trials on dormant and early spring seeding are underway to investigate; seed dormancy enhancement; seeding depth; seeding rates; seeding methods; nutrient placement; the role of fungicide; seed size; and age of seed lot. Late fall seeding shows tremendous potential and could revolutionize the way canola and other crops are produced. To achieve widespread adoption, it is essential that methods be developed to enhance dormancy (restrict water uptake) and permit seeding in the October 15-20 time period. Widening the seeding date window by a few days would permit producers to seed a significant portion of their acreage in late fall. Abscisic Acid and analogues have been evaluated to control germination, however results have been inconsistent to date. The research program at the Scott Research Farm has extensive studies in progress to investigate and develop possible dormancy enhancers and/or seed protectants to make October seeding a viable option for producers. Development of a protectant that ensures dormancy throughout the late fall but completely disappears when the soil thaws in the spring will be a challenge to both research and industry.