When crops are maturing rapidly in hot conditions, swathing before 50-60% seed color change on the main stem may not give chlorophyll time to clear from immature seed. Some fields may require additional moisture — rain — in order to re-hydrate the seed so chlorophyll can clear.
If growers feel they must swath at less than 50-60% seed color change on the main stem, wait until temperatures cool down in the evening and then swath at night to take advantage of those cooler temperatures and any moisture from dew. Click here for more information on rate of crop dry down under different weather conditions.
Open the pods. Just because pods look dry and mature does not mean the seeds are ready for swathing. Sunscald and diseases such as blackleg, sclerotinia and clubroot can make plants look mature but the seeds may still be green. The opposite can also happen where pods look green but the seeds inside are ready for swathing. When assessing a canola crop to see if it’s ready, crack open pods on a number of plants throughout the field. Swathing timing is based on seed color change, not pod color. (Watch the video at the top.)
Irrigation before swathing. Growers will not see a yield benefit from irrigating a field that is one week from swathing. Irrigation two weeks or more before swathing could provide some contribution to yield. Irrigation in the week before spraying may provide a quality benefit if the crop is drying down quickly and the crop is at risk of locking in higher levels of green seed. Note that irrigation just before swathing could increase the spread of sclerotinia within the windrow, especially if you compact the swath with a roller. This could increase the spread of infection from plant to plant. Irrigation in general tends to increase the sclerotinia risk, especially if it causes the crop to lodge.
Other Canola Watch swathing articles: