Seed colour change is an indication of moisture dry down. The following is an estimate of canola seed dry down rates during ripening based on research of weather conditions during mid-August to early September in different areas across the Prairies. Under cool, wet weather moisture loss in the seed will be less than 1% per day, and may even gain moisture with rain. On an average early fall day, moisture loss may be about 1 to 2% per day. In areas with cool nights (e.g. foothills, Parkland transition zones), and later in September, more typical dry down would be 1 to 1.5% per day. Under warm to hot and windy conditions, moisture loss can be as high as 2 to 3% per day.
A rough guide is that a 10% increase in seed color change occurs with about 5% moisture loss. So the period from 30% seed color change to 50% seed color change would need a 10% drop in moisture. This may take 10 days in cool weather to only 3 days in hot windy weather. Click here for more information on canola maturation and swathing.