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Background and Objective:
Frost seeding has been shown to give a higher yield at lower cost, but it is risky, and
with the high cost of canola seed, it may not be a worthwhile option. Early seeding, on
the other hand, has outperformed normal seeding and is often equal to the best frost
seeding results. Large and small scale experiments comparing frost seeding to early
seeding and normal seeding have provided information that indicates that the use of early
seeded canola in Manitoba would be a worthwhile development.
The objective of the project was to examine 25 genotypes in small plots at five
locations in Manitoba in order to provide a variety of growing conditions and soil types
under which canola is produced in Manitoba. New canola crop establishment guidelines could
be developed from this.
Procedure and Project Activities:
Twenty-five genotypes of Brassica napus were tested in a small plot, random complete
block at various locations to provide a variety of growing conditions and soil types where
canola is produced in Manitoba. Varieties evaluated were supplied by Svalof Weibull, and
through these screening trials, the most suitable cold tolerant varieties were identified.
Trials were conducted in five locations in 1998 including Elgin, Winnipeg, Dauphin,
Basswood and Gilbert Plains, with successful results from Elgin and Winnipeg. In 1999,
trials were located at Elgin, Dauphin, Sandy Lake and Basswood, with successful results
coming from Elgin, Dauphin and Sandy Lake.
These 25 entries were seeded at four different seeding dates in Minto to determine the
optimum timing for seeding B. napus. Seeding dates in 1998 included 24 April, 02 May, 12
May and 20 May. 1999 dates included 23 April, 13 May, 26 May and 08 June. A bigger spread
than initially planned between seeding dates in 1999 was a result of the heavy rains and
flooding experienced in the spring in Manitoba. In addition, one variety was tested at two
different seeding dates with eight different treatments examined at each date in order to
determine the effects of potassium, phosphate, and a Philom Bios phosphate enhancement
treatment called Provide on cold tolerance.
Finally, one variety was seeded at two different seeding dates with six different
treatments examined at each date. The purpose of this trial was to examine the effects of
early seeding on weed control. Treatments included 1) pre-emergent Roundup once, 2) post
emergent Roundup once, 3) post emergent Roundup twice, 4) Poast and Muster, 5) Treflan,
and 6) untreated check. The 1998 trial was seeded on 02 May and 09 May. The first date of
the 1999 trial was seeded on 23 April, but the trial was lost due to flooding in May.
All varieties tested in the multi-seeding date cold tolerance trial were evaluated for
their tolerance to frost. Plants were grown in two different hardening regimes and exposed
to three different freezing temperatures (-2°C, -5°C, -8°C) for a total of six
treatments. Plants were grown in either a warm or a cool growth chamber to provide the
different hardening regimes. At the one to two leaf stage, the plants were subjected to
the different freezing temperatures. The temperatures were dropped slowly to mimic a
natural occurrence and remained at the target temperature for two hours before raising the
temperature back up to normal. Plant recovery was then observed to determine the hardiest
varieties.
Results and Discussion:
Variety Evaluation and Cold Tolerance
Several varieties were identified
as being among the highest yielding in most trials conducted. In general, yields were
lower in 1999 compared to yields in 1998 and the date of seeding had very different
results for the two years. The general trend for 1998 was increased yields with later
seeding dates. Of the varieties tested, 10 entries had the best yields with the last
seeding date (20 May 1998), 12 entries had the best yield with the second last seeding
date (12 May 1998) and, in most cases, the second best yield occurred in one of the last
two seeding dates. None of the entries in 1998 had the highest yield occurring in either
of the first two seeding dates (24 April, 02 May 1998).
1999 produced much different results. Of the 25 entries tested, 14 had the best yields
with the first seeding date (23 April 1999), 6 entries had the best yields with the second
seeding date (13 May 1999) and 5 had the best yield with the third seeding date (26 May
1999). In most cases, the second best yield occurred in one of the first two seeding
dates. The fourth seeding date had the lowest yield for 23 of the 25 entries.
A possible reason for the different results between years is the variation in weather
for each year. Both 1998 and 1999 were quite atypical of the norm. 1998 conditions were
warm for much of April and early May, but turned quite cool and dry towards the end of May
and early June. Minimum temperatures during this cool spell were just above freezing, and
in one case dropped below freezing to -4°C. There was much frost damage observed in the
general area, but there were no visible physical symptoms of frost damage to any of the
entries in the trial. The different hardening regimes resulting from the changes in
weather may have had a major effect on the final yields. The warm temperatures in April
and early May promoted rapid growth of the plants in the first two seeding dates, and the
plants may not have hardened as well as the plants in the last two seeding dates. This may
have resulted in less vigorous growth during and after the cold spell in May and June for
the first two seeding dates.
In 1999, April provided good drying conditions so the first seeding date was
established at the desired time. However, with May came rain, and precipitation amounts
more than 300% above the norm made it very difficult to get the next three seeding dates
established. The spread between seeding dates was greater than the 1998 dates as a result.
The excess rain did not cause any damage to the trials with respect to flooding. Soil was
saturated for part of the spring, but the plants did not show any signs of water stress so
results of the trial were not compromised by the excess moisture.
Weed Control
Results suggest that using post emergent Roundup or Poast
and Muster for weed control versus pre-emergent Roundup or Treflan alone or no weed
control are recommended to maximize yields. Weeds that had the biggest impact included
wild oats, quackgrass, green foxtail, Canadian thistle and Kochia. The post emergent
Roundup treatments controlled all weeds above. Poast/Muster treatments controlled all
grassy weeds mentioned above, and the resulting canola stand competed very well against
the Canadian thistle and Kochia. The Treflan treatments suppressed the wild oats and green
foxtail, but weeds did eventually establish stands sufficient to compete with the canola
and have a significant impact on yields. Although only one year of data was available for
this trial, and data suggests that there is very little difference in yield with the
different seeding dates.
Fertilizer/Seed Treatment Effects
Only one year of data was available
for this trial, and results were inconclusive.
Development of a Laboratory Conducted Cold Tolerance Test
The hardening
regime had some effect on the tolerance of the varieties to frost. The plants grown in
cool conditions were more tolerant to the frost conditions than the plants grown in warm
conditions. There did not seem to be noticeable varietal differences in frost tolerance.
The biggest factor in determining frost tolerance in canola seems to be the hardening
regime. If the plants start out in a cool spring, they will tend to be more hardy and
tolerant to frost versus plants which start out in a warm spring.
Although results from the two years of field testing are quite different, it seems as
though early seeding would be beneficial in most cases. In a normal year, canola seeded in
late April would be subjected to cool temperatures during germination and emergence,
making it more hardy and tolerant to frost later in the spring. Studies have shown that
even with a significant reduction in stand by 50%, fields will still produce more, in most
cases, than if they were to be reseeded.
The earlier the canola stand is established, the less it has to compete with potential
weeds and, therefore, it should be easier to control weeds. Nutrients should also be
more readily available since the weeds will not have used as many nutrients earlier in the
spring. Earlier seeding also reduces the risk of frost damage in the fall. Frost damage
can be very detrimental to canola in the fall causing immature seeds to retain there green
color, and thus reducing the grade of the canola. Since the crop will be ready to harvest
earlier, the potential for frost damage in the fall will be reduced.
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