The colour of canola seed on the main stem at swathing is a good indication of the quality growers will get in the bin.
Canola council agronomist for eastern Saskatchewan, David Vanthuyne, said swathing canola when the colour is right will keep yield and quality high and green seed low.
Vanthuyne said the best time to swath is when the average seed colour change on the main stem is at 50-60 percent. At this stage, seeds will have changed colour on at least the bottom half of the main stem in B. napus varieties and on the middle and upper pods in B. rapa.
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“When seeds in the bottom half of the plant have changed colour, seeds in the top, or last formed pods, will be firm and roll between the fingertips.”
To be considered “colour changed,” green seeds must have small patches of colour or spotting. Seeds slowly turn from green to light yellow or reddish-brown to black, depending on the weather and variety. Canola seeds within pods on the main stem will change colour about 10 percent every two or three days.
Traditionally, the swathing window criteria was 20-40 percent seed colour change. Canola council criteria has recently been expanded to include seed colour change from 20 percent to 60 percent. This means an additional 10 days of swathing to maximize seed yields and quality.
Why the change? Jim Bessel, canola council agronomist in Saskatoon, said it’s because of the new varieties being planted.
“We see a lot of the newer varieties designed for the specialty oil market,” Bessel said.
“To get your maximum oil level, you need to let seed mature as long as possible. Let the plant develop to its full potential so it keeps putting oil into the seed. Then, if there’s a premium, you can capitalize on it. Also, oil is heavy, so you get a heavier weight by leaving it longer.”
Bessel cautioned that a longer wait for better maturity increases the odds of shelling.
“You have to manage the crop more carefully. You need to do things like swathing at night instead of during the heat of the day, or try using a pickup reel and play with the pitch adjustment.”
Vanthuyne advised growers to start inspecting canola fields 10-14 days after flowering ends. This is the stage when less than five percent of plants have flowers.
“After assessing the main stem, look at seeds from pods on the side branches to ensure they are firm with no translucency, especially in fields with low plant populations and multiple branches,” Vanthuyne said.
Sampling various parts of the field every two or three days and averaging the percentage of seed colour change will give growers an accurate assessment of the overall maturity of the crop. Plant densities, soil type, topography and moisture availability all affect the rate of seed maturity.
It’s a good idea to walk out and sample at least five plants in various areas of the field.
Hot, dry, windy weather can also cause rapid seed moisture loss and seed colour change.
“We’ve seen seeds on the main stem change from 20 percent to 50 percent in just a few days under these conditions.”
To catch most of the crop at optimum seed colour change, growers with large acreages will need to start swathing at 20-30 percent seed colour change.
“Growers have invested a lot of time and money in their canola crops. Swathing at the optimum seed colour change will definitely help maximize canola returns,” Vanthuyne said.
For a free copy of the canola council’s Time of Swathing Guide, contact admin@canola-council.org or phone 204-982-2100. It is also available at www.producer.com by typing “swathing guide” in the go box.
