Canola producers spend time, effort and money ensuring their canola crops get off to a good start in the spring and have enough nutrients to produce optimal yields.
But some of that time, effort and investment could be lost if a producer makes the wrong decisions at swathing time.
“A bad (swathing) decision can cost you,” said Jim Bessel, senior agronomist with the Canola Council of Canada.
“But there are no absolutes. Every year, when we start looking at swathing and timing of swathing in relation to seed colour change, it’s always a discretionary decision because of the environment that we deal with … and the conditions at that particular time in that particular year.”
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Determining the proper time to swath a crop can be tricky.
To ensure optimal yields, quality and oilseed content, producers should monitor their fields closely as the crop nears maturity and base swathing decisions on percent of seed colour change.
A few years ago, the canola industry recommended that producers begin swathing when 30 to 40 percent of the seeds on the main stem were showing some evidence of seed colour change.
More recently, canola agronomists have been advocating swathing when 50 to 60 percent of seeds are showing some change. That percentage will usually result in bigger seeds, more oil, higher yields and lower greenseed counts, said Bessel.
“The 30 to 40 percent seed colour change was what the industry felt was a good point to be at with the cultivars that we had a few years ago,” Bessel said.
Bessel reiterated that actual swathing decisions are always influenced by other factors such as manpower, workloads, canola acreage and weather forecasts.
“Again, a lot depends on the number of acres you have to cover and what’s in the forecast,” he said.
When assessing a crop for maturity, Bessel said producers should walk into the crop and examine seeds on the main stem and branches.
Canola seeds taken from pods on the bottom of the main stalk will change colour first.
Examine seed from pods near the bottom of the main stalk and move upward to pods from the middle third of the main stalk and the top of the main stalk.
Seeds from the top of the stalk often won’t show evidence of seed colour change but they should be solid and resist crushing when rolled between the fingers.
Seeds that are soft, wet and mushy when rolled suggest that swathing should be delayed.
Often, canola plants will mature at different rates within the same field depending on moisture levels, soil characteristics and field topography.
If the different parts of a field cannot be swathed at different times, then swathing decisions should be based on an overall assessment of the entire field.
Identify areas in a field where the yield potential is highest, assess what percentage of the field these areas cover and base decisions accordingly.
Swathing during hot, dry or windy weather is not recommended. Seed dry down may occur too rapidly and chlorophyll levels could remain high, resulting in high greenseed counts.
The enzyme responsible for clearing chlorophyll from canola seeds requires some moisture to perform its job properly.
If necessary, producers should consider swathing their crops in the evening, at night or in the morning hours. Swathing in a light rain or under damp conditions can also be beneficial if extremely rapid dry down is a concern.
Frost can also result in elevated greenseed levels but the impact of frost is reduced when seed moisture levels are low.
In general, seed at 20 percent moisture or less is safe from frost damage.
In some cases, swathing before optimal seed colour change can reduce damage caused by a killing frost.
A crop swathed three days prior to frost is less likely to suffer frost damage although some yield and quality loss may be encountered because the crop was cut when seed was at less than optimal maturity levels.
“Generally, the longer you can leave a crop to mature naturally, the better off you’ll be,” said Bessel.
“You’ll have a larger seed with more oil and therefore more weight and that should translate then, in essence, to more bushels pr acre.”
“As far as quality is concerned, if you can leave it to mature to that (50 to 60 percent seed colour change) level, your risk of greenseed content will be basically nil because full maturation has been allowed to take place,” he said.
HOW TO DETERMINE OPTIMAL SWATHING TIMES
•Start inspecting crops approximately seven to 10 days after flowering, considered complete when flowers remain on about 10 percent of the canola plants in a field. Canola is usually ready to swath 20 to 30 days after flowering is complete.
•Evaluate plant stands closely and assess maturity rates and yield variations on hilltops, ridges and in lowlands. With a proper assessment, producers will have a better idea of optimal swathing times.
•When sampling plants for maturity, sample five to 10 plants from several different areas of the field and focus first on the main stem. Seeds from pods on the bottom third will turn colour sooner than those on the top third. Optimal swathing time is when 50 to 60 percent of seeds from the main stem show colour change.
•After assessing seed from pods on the main stem, examine seed from pods on side branches to ensure they are firm and not translucent.
