Canola Straight Combining or Swathing (8/25/11)
These losses primarily were from preharvest shattering and combine shattering losses. Studies conducted with farmer-size combines at Minot in 2005 and 2006 demonstrated that timely straight combining can achieve similar or better canola yields compared to swathing. Straight-combined canola tended to have lower harvest moisture, darker seed color, lower green seed, and higher test weight. About 15 to 20 % of canola in North Dakota is currently straight combined successfully by the growers.
Presently, Diquat is the only product labeled for use as a preharvest desiccant in canola. Growers can maintain excellent yield and quality if the Diquat application is timed properly and the crop harvested in a timely manner. Diquat should be applied when 60 to 75% of the seeds have started to turn color. Canola seeds mature in the bottom pods first, while the last seeds to mature are in the top pods. Apply the desiccant when seed in the middle pods (or 60 to 75%) have started to turn color. Research has shown that when the desiccant is timed properly, crop quality parameters, including yield, test weight, oil content, seed loss, green count and grade, generally were similar for desiccated canola compared with swathing.
Diquat applied too early may result in lower yield and seed quality, with a trend toward higher green content. Diquat requires a seven-day preharvest interval. Canola harvested 14 days after application will have lower green content than canola harvested seven days after application. Fields with excessively lodged canola may be difficult to desiccate because the spray droplets may not be able to penetrate the canopy. Therefore, swathing may be the better choice for lodged canola.
Swathing canola at the optimum stage of ripening reduces green seed problems and seed shatter losses, and ensures the quality required for top grades and prices. Swathing can begin in canola at 60% color change (http://www.canolacouncil.org/chapter11.aspx ). When canola plants consist only of stems, stem branches and pods, the crop probably is very near the optimum time for swathing. Seeds in all pods on a plant complete filling (physiological maturity) at about 40% moisture and then slowly turn from green to light yellow or reddish brown, brown or black, depending on the variety. In hot (90 F), dry weather, canola seed can go from 10 to 50% seed color change in just three to five days or less. Once filled, seeds rapidly lose moisture at about 2 to 3 percentage points or more each day, depending on the weather.
Inspect fields every two to three days when some color change occurs in the first-formed pods on the bottom of the main stem. To determine when a field of canola is ready to swath, examine plants from different parts of the field. The stage of maturity in an evenly maturing field will vary from plant to plant and from area to area within the field. When examining the plants, take into account varying soil types, low-lying areas, available soil moisture and exposed early ripening areas.
Examine only pods on the main stem. Seeds in pods on the bottom third of the main stem were formed earlier and will turn color much sooner than seeds in the pods on the top third of the plant. When the overall moisture content of seed from the total plant averages 30 to 35%, about 30 to 40% of the seeds in pods on the main stem will have changed color or have started to change color. Seeds with only small patches of color should be counted as color changed. The color of the seed is more important than the overall color of the field in determining the stage of maturity. Most of the seeds that have changed color will be from the bottom third of the main stem. When seeds in the bottom pods slightly turn color, seeds in the top, last-formed pods are filled or nearly filled.
For more information see: http://www.ag.ndsu.edu/pubs/plantsci/crops/a1171w.htm
Hans Kandel - Extension Agronomist Broadleaf Crops
Brian Jenks, NDSU Weed Scientist