ABSTRACT

Canola, grown on 25-30% of the annual crop acreage in Western Canada, requires a high level of management and knowledge for maximum yield potential. Matching fertility and seeding rates with new hybrid canola cultivars is required to understand the new genetics and may also be a tool to manage weeds and disease in the crop year. A field study was conducted in 1998 to evaluate the integrated effects of fertility, seeding rate and time of weed removal on hybrid canola (cv. Invigor 2153) and an open-pollinated canola (cv. Exceed). Both varieties were herbicide tolerant (HT) to glufosinate. These cultivars were compared under low, normal and high fertility at four seeding rates in Lacombe, Alberta and Melfort, Saskatchewan. Canola emergence was higher with Exceed compared to Invigor 2153 when seeding rate was by weight. However, when seeding by plant population, Invigor 2153 was significantly higher in emergence compared to Exceed. Seed yield was higher and time to maturity reduced with Invigor 2153 compared to Exceed, regardless of when seeding by weight or by plant population. Fertility had little effect on enhancing crop yield, however, higher fertility generally increased the time to maturity and the incidence of disease and/or lodging. Seed yield was unaffected when weeds were removed early or late with Exceed, however, the more vigorous Invigor 2153 yield potential was reduced as weed removal was delayed to the six leaf stage of canola. The interactive effects of agronomic factors can provide a means of manipulating the yield potential of canola varieties.

INTRODUCTION

Canola, grown on 25-30% of the annual crop acreage in Western Canada, is a major crop on the Canadian Prairies and requires a high level of management to achieve maximum yield potential. Cultural practices define crop performance and can have a large impact on yield and economic returns. Seeding rate has been studied extensively in Western Canada indicating that a wide range of variable results. Moderate seeding rates of 6 kg/ha were optimal for crop performance in several studies (Kondra 1975, 1977), whereas, Clarke and Simpson (1978) suggested that higher seeding rates could result in higher yield. Others observed that seeding rates used in a number of studies had no effect on yield (Christensen and Drabble 1984, Degenhardt and Kondra 1981). Brandt (1992) reported that seeding rates of 8, 12 or 16 kg/ha resulted in similar yield of yellow mustard, however crop development was hastened by increased seeding rates. The comparison of hybrid versus conventional canola has been studied less extensively. Van Deynze et al. (1992) reported that hybrids produced 50% more dry matter and 24% more seed yield than conventional cultivars, however hybrids were significantly later to 50% flowering and maturity than the conventional cultivars. The time to 50% flowering displayed a linear response to varying seeding rate, with increases in seeding rate from 3-9 kg/ha reducing the interval by approximately 1 d. Days to maturity paralleled those for 50% flowering with a linear decrease in days to maturity occurring with an increase in seeding rate. Small decreases (1.7 d) in crop development do not justify using higher seeding rates. In addition to seeding rate and variety, fertilizer differences required to optimize production depend on the yield potential of the crop (Grant and Bailey 1992). Matching fertility and seeding rates with new hybrid canola cultivars is required to understand the new genetics and may also be a tool to manage weeds and disease in the crop year. Our objective was to determine the interactive effects of cultural practices on open-pollinated and hybrid canola production.

MATERIALS AND METHODS

Field experiments were conducted in central Alberta (Lacombe) and in northern Saskatchewan (Melfort) in 1998. Prior to seeding, cultivated oat was cross-seeded into the plots to supplement the natural weed infestation. A hybrid HT canola ‘Invigor 2153’ and an open pollinated HT canola ‘Exceed’ were planted on barley stubble with a Conserva-Pak double-shoot seeder equipped with knives on 30 cm row spacing. Fertilizer (N, P₂0₅, and K₂O) was banded beside and below the seed during the seeding operation at 50, 100 and 150% of soil test recommended rates in Lacombe and 67, 100 and 133% of soil test recommended rates in Melfort. Treatments included four seeding rates of 2.2, 4.5, 6.7 and 9.0 kg/ha. Individual plot size was 3.5 X 15 m. The experiment was designed as a randomized complete block with four replications in a factorial arrangement. In a related experiment, ‘Invigor 2153’ and ‘Exceed’ were planted on barley stubble with the same seeding equipment at seeding rates of 100, 150 and 200 plants / m². Weeds were removed when the canola was in the two, four and six leaf-stage with Liberty Link (glufosinate) at the recommended rate (500 g ai/ha). Emergence, flowering date, maturity date and yield were determined from all experiments.

RESULTS AND DISCUSSION

Emergence of the hybrid canola was 30 and 13% lower than the open-pollinated canola when seeded by weight (Table 1). The seed weight of ‘Invigor 2153’ was 55% greater than the seed weight of ‘Exceed’, resulting in lower plant populations. In a related study, emergence of ‘Invigor 2153’ was 20% higher than ‘Exceed’ when seeded at the same population (Table 1). The percent survival was 44% and 37% for the hybrid and open-pollinated cultivar, respectively.

The hybrid canola ‘Invigor 2153’ yielded 30% higher, flowered three days earlier, and matured two days earlier than the open-pollinated canola ‘Exceed’ at Lacombe in 1998. In Melfort, ‘Invigor 2153 yielded 11% higher, flowered the same day and matured three days earlier than ‘Exceed’.

Seeding rate did not effect yield at either Lacombe or Melfort, however the 6.7 and 9.0 kg/ha seeding rate reduced maturity by two days compared to the lower seeding rates at Lacombe and by 4 days compared to the low seeding rate at Melfort (data not shown). This may or may not be agronomically important when the cost of hybrid seed is considered.

A significant cultivar x fertility interaction was detected for yield at Melfort. The open-pollinated ‘Exceed’ yielded similarly at all fertility rates, whereas, the hybrid canola yield decreased as fertility level increased to 133% of soil test recommendation (Table 2). This is contrary to what others have seen in preliminary studies (Allan Eadie, personal communication) where the high yielding hybrid may require more fertilizer to achieve optimum yield (Grant and Bailey 1992). The higher fertilizer applications caused increased disease problems (Lacombe) and severe lodging that resulted in reduced yields, particularly with the hybrid at Melfort in 1998. Unusually dry conditions in the spring of 1998 may have limited canola response to fertilizer at both locations.

In another study at Lacombe, early time of weed removal may be more effective when combined with plant competition to compete with weeds (data not shown). Time of weed removal was more important at lower seeding rates than higher seeding rates at a study in Lacombe. Consequently, higher seeding rates can reduce weed competition, however it is yet to be determined if the cost of hybrid seed is more effective than the cost of herbicide, or some combination of both inputs. The hybrid yielded 17% higher than the open-pollinated cultivar and matured 9 days earlier.

SUMMARY

Cultivar, seeding rate, and time of weed removal may become important tools in managing canola in Western Canada. The new hybrid canola varieties are higher yielding and in this case earlier maturing than the conventional canola variety. Seeding rate may play a role in maturity of canola as well as a method of weed management.

Further research is needed to determine if these effects are consistent under other growing conditions, and to determine the influence late emerging weeds have on ease of harvest and weed seed banks. Given more favourable early spring moisture conditions, we would anticipate a positive canola response to fertilizer.

ACKNOWLEDGEMENTS

The authors express their appreciation to L. Michielsen, B. Pocock, Trina Alexander, and Jim Pocock for plot maintenance and technical assistance.

REFERENCES

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