Canada
August 10, 2009
The
Canola Council of Canada
(CCC) is advising growers in some parts of the Prairies to take
more samples than they usually would in order to determine time
of swathing.
"The spring frost that hit most of the prairies caused thin
plant stands in many areas, resulting in more branches and more
pods throughout the plant," says Tiffany Martinka, CCC agronomy
specialist. "When this is the case, there is often delayed and
uneven maturity. That makes determining time of swathing a much
more complex challenge."
Low plant densities of 2 to 3 plants/ft2 will cause canola
plants to branch up to 4 times more than those in optimum plant
densities of 7 to 14 plants/ft2, says Martinka. "This extra
branching can delay seed maturity as much as three weeks
depending on environmental conditions. If the canola plant has
marginal increases in secondary branching (up to double the
normal), growers can still use the main stem to determine if the
crop has reached the optimum time of swathing of up to 60% seed
colour change. However, if secondary branches are 3 to 4 times
the normal, growers need to assess the entire plant, because a
higher proportion of the total yield will be carried on those
side branches. Look for seed colour change in the pods at the
base of those side branches, and the seed in the upper pods
should be firm and dark green. If at least 30 to 40% seed colour
change over the whole plant can be achieved it will help
minimize yield losses and green seed issues."
"With low plant densities, the entire field may be maturing
unevenly," says Martinka. "Growers should assess fields for
variability, and they should take samples from many locations to
determine where the majority of plants are staged. Where there
are multiple stages within a crop, the ideal time for swathing
may be at a point where some pods are almost ready to shell,
while some seeds are barely changing colour."
Once seed colour change starts to show up at about ten days to
two weeks after flowering, it is a good idea to be sampling
fields every two to three days. For an accurate assessment of
overall maturity, the CCC advises taking more samples from
non-uniform fields, and then averaging the percentage of seed
colour change. In some cases where the range of maturity is very
wide, growers may need to weight that average to favour the most
abundant crop stage (largest areas within the field, or the
greatest proportion of plants in individual samples). For more
help with this situation, check out Swathing and Harvesting
Multiple Stage Canola Crops available on-line at
http://www.canolacouncil.org/.
"To be considered sufficiently changed in colour, green seeds
must have at least small patches of colour or spotting,"
Martinka says. "Some varieties will show pod colour change long
before the seeds do, while the opposite is true of other
varieties. This is why it’s so important to check for seed
colour change, not pod colour change".
"Swathing late in the day and during the night will reduce
shattering of riper plants and also minimize green seed issues.
At the very least avoid swathing during the heat of the day,
especially at 30 plus degrees. Also, for any later maturing
crops, remember that the canola often needs a minimum of three
days in the swath to allow sufficient dry down to protect
against fall frost damage".
For a free copy of the Canola Council’s Time of Swathing Guide,
visit
https://canola-council.merchantsecure.com/canola_resources/product12.aspx.
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