Summary of Late Fall and Early Spring Seeding ofHerbicide Tolerant Canola 1994-98

K.J Kirkland, and E.N. Johnson

Agriculture and Agri-Food Canada, Scott, SK

Introduction

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 is 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.

Materials and Methods

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 (1993-98), chemical fallow (1996), and stubble (1995-98).

Results and Discussion:

Effect of Seed Date on Crop Maturity

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)

Effect of Seed Date on Crop Establishment

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 - 8⁰ 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 temperatures in late April, reduced the cold hardiness of canola and a sudden frost of -5⁰ C on May 1, reduced the canola stand by about 70%.

Effect of Seed Date on Crop Yield

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)

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

* Includes 1996 data - poor establishment of fall seeded canola

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 years, Scott, SK 1994-98)

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 Effect of Seed Date on Yield of Quest Canola in Swift Current (Miller and McDonald, unpublished data, 1997)

Effect of Seed Date on Seed Thousand Kernel Weight and Seed Oil Content

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)

Effect of Seed Date on Crop Height

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)

Future Research Needs

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.

Conclusions

• 1. Fall dormant seeded canola and late April seeded canola advanced flowering dates by up to 35 and 19 days earlier than a mid-May seed date respectively.

  2. Swathing of fall and late-April seeded canola averaged 21 and 18 days earlier than mid-May seeded canola respectively, while combining of fall and early spring occurred 25 and 21 days earlier respectively.

  3. Fall seeded canola established better when seeded on stubble as compared to tilled fallow.

  4. Fall seeded canola, when cold acclimated, has tolerated spring air temperatures as low as -8⁰ C.

  5. On stubble, fall seeded and early spring seeded canola yielded 58% and 55% higher than mid May seeded canola respectively.

  6. On fallow, highest yields have been obtained with early spring canola due to establishment problems with fall seeded canola on tilled fallow.

  7. Late fall and early spring seeding may help stabilize canola yields since it is flowering under cooler air temperatures.

  8. Late fall and early spring seeding generally produced larger seed than mid-May seeded canola.

  9. Late fall and early spring seeding generally produced canola seed with higher oil content.

  10. Late fall seeded crops are shorter than spring seeded crops which could reduce lodging.

TIPS FOR FALL SEEDING

• 1) Seed as close to freeze-up as possible. In the moist dark brown, black, and grey soil climatic zones, set a target seed date near Oct.31. In the brown soil zone, set a target date of Nov. 5 to 7.

  2) Seed at normal seed rates. Studies at Scott indicate a 6 lb/acre seed rate for Argentine canola was adequate.

  3) Seeding a herbicide tolerant canola is recommended since winter annual weeds can be easily controlled with post-emergent herbicides.

  4) Use seed treated with a broad spectrum fungicide (Vitavax RS, Premiere Plus, etc.) A fungicide treatment can make a dramatic improvement in crop establishment.

  5) It is best to place the seed 2 to 1" deep in the soil. Broadcast seeding has caused variable emergence particularly if the soil surface is dry. Deep seeding can reduce emergence and yields as well.

  6) Best results have been obtained when seeding into standing stubble or chemical fallow. Seeding on tilled fallow can result in premature germination in the fall due to fluctuating soil temperature and increase the risk of soil crusting in the spring. Avoid fields that are prone to surface crusting or spring flooding. Problems were encountered at Melfort when using disc openers on heavy clay soils with high levels of crop residue.

  7) Seed place or side-band phosphorus fertilizer at soil test recommended rates. Nitrogen fertilizer can be banded prior to seeding, side-banded at seeding, or broadcast in early spring (late April). Apply nitrogen at soil test recommendations. If seed placing nitrogen, do not exceed provincial recommendations for spring seeded canola. Recent tests at Scott have shown that the potential to damage emergence of fall seeded canola from seed placed nitrogen is similar to spring seeded canola. Sulphur is also an important nutrient for canola production. It can be blended with the nitrogen and/or phosphorus fertilizer application in the fall. It can also be broadcast in the spring. Use a readily available sulphate formulation of sulphur fertilizer.

  8) Watch emergence closely in the spring. Keep an eye out for flea beetles if afternoon air temperatures are greater than 15⁰ C. If more than 25% of the cotyledons are destroyed by flea beetles, then treat with a foliar insecticide.

  9) Emergence of the fall seeded crop normally occurs in late April. A thin stand (15 to 20 plants per square meter) can still produce good yields if the plants are distributed evenly.

  10) Spray for weeds early (1 to 2 leaf stage). The primary weed problems in fall seeded canola are winter annuals (stinkweed, flixweed, shepherd's purse) so early control is necessary. One herbicide application is normally all that is required since the fall seeded crop competes well with late emerging weeds.