Story Posted: September 08, 2011

Canola Watch: Let canola mature, Aerate all canola

Issues of the week: Warm days forecast for the coming week will give later canola crops a good chance to ripen further before swathing. If growers have a lot of canola to swath and feel they must swath something, go with the most mature crop first. On hot days, swath in the evening to give plants time to dry down slowly and let the green clearing processes function properly.

Swathing is a good time to flag large weed patches. If these patches surprise you, consider what contributed to these escapes. Are these particular species a challenge for your preferred herbicide tolerance system to control? Could they be resistant to certain herbicide groups? Or did stressful conditions contribute to reduced efficacy or poor crop competition for later emerging weeds? Identifying and recording the location of these weeds at swathing will help you with a management plan for next year.

Swathing is also a good time to scout for disease outbreaks. Clubroot incidence seems to be increasing this year, and spotting the disease now will give growers a chance to implement containment strategies.

When combining in hot conditions, put canola on aeration right away to cool it down. Also check any canola that was binned hot in the past few weeks. It should also be on aeration. Even canola at 8% moisture can start to heat if stored hot.

Crop and weather update
Peace (B.C. and Alberta): Swathing is nearly complete in the north and just starting in the southwest. All other regions are somewhere in between. High temperatures are forecast for the coming week, which will give late crops valuable time to ripen further before swathing.

Alberta: Swathing will be close to finished in south and east central regions by the end of this week. The far south is up to 40% combined. Progress is further behind in west central and north central regions, with only 10-20% of acres swathed. With warm temperatures forecast for the next week, fields will benefit from a few extra days before swathing. Light frost hit some areas but damage appears to have been minimal. Alberta crop report.

Saskatchewan: Combining progresses rapidly across the south and swathing is near complete in central regions. Some north regions still have a lot of canola to swath. Heavy storms dropped large amounts of rain in Canora and Weyburn areas in particular, leaving growers with very wet low spots to swath around. Saskatchewan crop report.

Manitoba: Rainfall ranged anywhere from half an inch to 4”, with the highest around Swan River. Swathing in the province ranges from 35% to 100% complete. The Pas and Swan River regions are the furthest behind but a lot of crop will be swathed this week, despite the rain. Combining in the province ranges from 5% to 80% complete, with 50-60% complete overall. Manitoba crop report.

Fast drydown locks in green
Some elevators are reporting higher green seed counts. Swathing too early and swathing in hot and windy conditions are contributing factors in many cases. Cutting canola in hot conditions leads to rapid dry down and desiccation, which doesn’t give chlorophyll time to clear from immature seed. Waiting until less mature seed is at least firm to roll between thumb and forefinger will help minimize yield reductions from early swathing, but significant curing will still need to take place in the swath to remove green seed.

If growers feel they must swath at less than ideal seed color change, then wait until temperatures cool down in the evening. Night swathing gives the plant 4-5 hours to shut down slowly, and nights are usually more humid, cooler and less windy, providing more moisture for chlorophyll clearing enzymes to function. The next day, plants in the interior and bottom of swaths will continue to be sheltered from warmest temperatures and from wind. With today’s larger swaths, the sheltering benefit of the windrow is that much greater.

Restarting the enzyme process. Enzymes to clear chlorophyll can restart when seed rehydrates to 20% moisture. (This applies only to green seed causes by premature desiccation, not to frost injury. Green locked in by seed damage from heavy frost is not likely to clear even with wet weather.) Moisture levels required to bring canola back to 20% can be more than expected. An inch of rain will not lift canola at 7-8% moisture anywhere close to 20%. Several days of heavy dew, high humidity and additional rain events may be required. These conditions can happen and at this stage of the season, growers have time to be patient with swathed canola.

Swathing early does not mean combining early. This is an important reminder. Canola swathed green can take a lot longer to cure than canola swathed at 50-60% seed color change. Whether growers swath a green crop now or wait a week, combining could occur around the same time. And by waiting to swath, the crop has a better chance of meeting its yield and quality potential.

Click here for tips on how to check green seed levels in swaths without starting the combine.

What a few warm days can do
Growers eager to swath, consider this: With warm temperatures and a bit of wind, canola can gain 10 percentage points of seed color change in three days or less. In a week, canola at 5-10% seed color change, which is generally considered too early to swath, can reach 30-40% seed color change. The ideal swath timing for higher yields and lower green seed counts is up to 60% seed color change on the main stem and with all seed on side branches firm to roll, but if that isn’t an option then waiting for at least 30% can significantly reduce potential losses in yield and quality.

Growers who want to swath green canola today may gain quite a bit by waiting 2 or 3 days, as long as the forecast suggests a low risk of frost.

Cool those bins of hot canola
Canola harvested during this week’s hot weather has to go on aeration to cool it off — even if the seed moisture levels are “dry.” Canola at 10% moisture is at risk of spoilage when put in the bin at 20 C. At temperatures of 25 to 30 C, the spoilage risk is that much greater. Even at 8% moisture, canola is at risk if not cooled down immediately after storage.

Green seeds and dockage, including canola plant material, weed material and insect parts, create additional start points for heating and can make the situation worse. Click here for more tips from a media release issued this week.

An article in the September issue of Canola Digest magazine, which hit mailboxes this week, describes how one Alberta grower lost a whole bin to heating. The canola went in dry so the grower thought it should be OK, even though it had a high green count. When he checked the bin a few month after harvest, the central core was a solid mass. It took him days of work to break it apart and get it cleared out. It sold for $1 a bushel.

Bag storage. Growers considering storing canola harvested at high temperatures in bags or bins without aeration should keep in mind that the higher the initial temperature the longer it will take for that grain mass to cool. Monitor throughout this storage frequently for any signs of heating or spoilage, and be prepared to move the grain at the first sign of trouble.

When to swath multi-stage crops
Check the whole field. The field average may be 30% seed color change, but there could be 2 to 3 different stages within the field. If half the field is just beginning seed color change, growers may want to hold off on swathing. By waiting 3 or 4 days, there is minimal risk of frost damage for riper parts of the field and a huge potential benefit for later parts if frost doesn’t occur. The graph below, based on Canola Council of Canada research, shows a yield increase of 11% when swathing is delayed from 30-40% seed color change to 60-70% seed color change.

If the field has distinct late and early parts, the two parts could be swathed at different times.

Finally, if the late parts of the field are not likely to mature even with an extra week of warm weather, the swathing decision should perhaps be based on what’s best for the plants that are mature. There is no “perfect” time to swath these uneven crops. At some point you have to decide the best time for the majority of plants in the field with the least negative impact possible on the rest.

	Summary results pooled for both 3 and 5 lb/ac seeding rates at all locations based on similar trends observed. Straight cut treatments at 10 of 12 locations produced relative yield of 107% vs 30-40% SCC.

When to swath after frost
While forecast daytime highs are warm for the next few days, some areas may experience light frosts. If frosts do not dip below -2 C, damage is likely to be minor and swathing prematurely may do more harm than good. However, it is important to get out there and check crops to ensure damage is not greater than expected.

Click here for more.

If pods are brittle, straight combining may be best
In a situation where a field has matured more rapidly than expected and the majority of plants are beyond 80% seed color change, growers may be better off leaving the crop for straight combining. Swathing may result in costly losses.

Before giving up on swathing, check the pods and stems. If they are still pliable, shelling losses will be minimal and growers could still swath the crop, especially if they can swath at night or early in the morning when moisture levels are higher. But if pods are rattling and dropping off, then straight combining could be the lower risk option. If straight combining for the first time, consider these few tips:

• Have the cutterbar in front of the reel. Set the reel as far back as possible, as long as it still allows for smooth feeding of the combine. That way, when the reel hits the canola, any pods that break open will drop their seeds on to the platform, not onto the ground. The longer the distance between the cutterbar and header auger, the better to reduce losses.
• Set the reel speed equal to ground speed of the combine. This reduces contact with the pods.
• Avoid combining during hot dry days if the pods are brittle. Cooler days or mornings and evenings with a bit of dew are preferable to reduce pod shatter on impact, but this can present a challenge to combine efficiency if the stems are somewhat green. Depending on seed moisture levels, this may also mean additional conditioning for safe storage.
• Work around low spots with later green seeds and higher weed biomass. These will slow you down and green plant material in the sample could increase the spoilage risk. Swath these areas and combine them later.

Insect update
A few late fields are still under threat. Bertha armyworm is at threshold levels in a few late fields in central Peace and western Saskatchewan regions.

Lygus bug feeding continues in parts of Saskatchewan and around Dauphin, Manitoba. Before spraying, check to make sure they’re actually feeding (lygus cannot penetrate mature leathery pods) and that the crop is more than a week from swathing. Among registered foliar insecticides the shortest pre-harvest interval available is 7 days.

Some Manitoba growers are also reporting high levels of flea beetles. As harvest progresses, flea beetles tend to concentrate in the latest fields. Damage at this stage is usually limited to surface stripping of stems and pods with minimal impact on yield, but these adults carry over into spring. If you see high numbers in the fall make a note to watch closely for seedling damage in nearby fields as your canola emerges next spring.

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