| | Swathing canola | Combining canola
Proper harvesting and storage of canola are the final steps in profitable canola production. Canola can be harvested, stored and conditioned with small losses in yield and quality using the same equipment and facilities that are used for cereals. Seed and quality losses can be large due to untimely harvesting, inappropriate harvesting techniques, improper handling or storage. A more detailed discussion can be found in the Canola Grower’s Manual.
Canola can be direct combined (straight cut), or swathed (windrowed) then combined later using a pickup header. Deciding which technique to use is based on:
- the species/cultivar inherent shattering characteristics
- the need to accelerate harvest to avoid fall frost .
- field variability
- weather conditions prior to and during harvest
- weed or disease conditions
- the thickness of the crop stand
In Western Canada, when canola is swathed, it is to reduce shattering, to avoid adverse climatic conditions (wind, frost, snow) and to promote more even ripening. B. rapa varieties may be direct combined since they mature earlier and are more resistant to shattering than Argentine varieties. Many canola producers use direct combining. Under certain conditions direct combining can provide better capture of crop yields. Direct combining is covered in more detail below.
Swathing is preferred in short season areas to accelerate dry-down of the crop by up to 10 days, and thus reduce the exposure to harvest problems like early fall frosts or snow storms. It allows for a more even maturation and drydown of the crop. Accelerating harvest can also allow more time for fall seeding of winter crops. Swathing kills and desiccates green weeds, which allows easier threshing and reduces weed seed contamination in the grain. Canola crops with significant levels of Alternaria pod spot should be swathed early since this disease causes increased pod shattering and drop in ripening crops. Unlike direct combining, swathing can be performed around the clock, if necessary, which helps when harvesting large acreages.
Swathing Canola
Canola crops can be swathed by most self-propelled or power-take-off driven windrowers. The draper belt style of windrower is superior to the auger style in reducing crop damage. Self-propelled machines are more suited to heavy, tall stands or in undulating fields that require greater maneuverability. The swath must flow smoothly through the swather without bunching. Bunching leads to uneven drying and combining problems as well as development of diseases such as sclerotinia white stem rot under wet or humid weather conditions. A swather should have the following features to handle canola:
- Sufficient depth (1.1 m front and back) of the table or platform to handle the crop material.
- A large throat opening 1.0-1.3 m that is at least as wide as the distance between the draper belts.
- A vertical clearance of up to 1 m under the window opening to allow large windrows to pass through without interference.
- The windrower should have ample reel and table adjustments to handle the range of crop conditions experienced with canola.
- The draper belt speed should be adjustable.
- The divider must be capable of separating heavy and tangled crops. Difficult crop conditions may require windrowers to be fitted with specialized attachments to assist with the feeding of the crop. The vertical knife is similar to the sickle bar knife of the windrower, but it is in a vertical position on the divider end of the windrower. In a lodged and tangled crop, the vertical knife operates far more efficiently than a cone or looped steel rod divider as it improves the division of the crop and reduces "bunching" problems. There are several types of dividers of which the double knife with two moving blades appears to be the best suited for all crop conditions as it reduces the shatter loss on drier crops.
- Some producers uses rollers behind the swather to anchor the swath and make it less likely to be blown around in a strong wind. High shelling losses can occur if high winds move the swath once cut.
- Swathing the field parallel to prevailing winds can reduce the risk of wind losses.
Canola crops do not often lodge so badly that a conventional swather with a batt reel will not handle them, but in difficult conditions, a pickup reel set well forward, will help.
Field staging for optimum time of swathing
Gauging the correct time to swath canola is more important and difficult than with cereals. Swathing at the optimum stage will reduce shattering compared to late swathing, and reduce green seed content and increase seed size/oil content compared to early swathing.
Time of swathing is crucial to maximizing crop returns. Check out the canola plants to determine where most of the pods occur. If the plant has little branching, then main stem, pod seed colour change should be used to determine the right time to swath. If the majority of the pods occur on a heavily branched plant, then seed maturity on the branching stems becomes paramount. Main stem pods from different parts of the field should be examined for maturity and thus readiness for swathing. Uneven ripening over the field often complicates the swathing assessment – hilltops are often much riper than low spots. Estimate what the average crop maturity and where the majority of yield potential exists in the field and use that area to estimate when to swath. Seed ripening varies on the same plant -- pods at the bottom of the plant are formed first and will mature before pods higher up or on side branches.
Seed color is more important than the overall field, straw or pod color when gauging the optimum time to swath. When the seeds reach 35 to 40 % moisture they turn from green to light yellow, reddish brown, or brown, depending on the cultivar. In the fall in western Canada, ripening seeds lose moisture at about 1 to 3 % moisture per day, depending on the weather.
The optimum stage to swath canola is when 30-60% of the seeds have color change. Small patches of color change are counted as changed. When seeds in the bottom pods have turned color, seeds in the pods near the top of the main stem and on side branches are green but filled or nearly filled. However, these later formed seeds should be checked to ensure they are firm and will roll, not squash, when pressed between the thumb and forefinger. Canola seed does not continue to fill once swathed – they will only dry down.
Growers with many canola fields should start swathing canola at 30% seed color change in order to finish their last field before surpassing 60% seed color change. Very hot and dry, windy weather during and after swathing may prematurely halt chlorophyll clearing in green seed due to low seed moisture, and in such weather swathing should be delayed to the end of the swathing window. Thin canola stands have more side branches that mature later – thus swathing should also be delayed in such situations.
On the other hand, if conditions are cool and a frost or snow storm is forecast, swathing as early as 10% seed color change could be justified to minimize green seed or harvest difficulties. In order to reduce green seed due to frost, the field must be swathed about 3 days prior to the frost.
Green seed caused by frost damage will NOT degreen in the swath, whereas green seed caused by rapid drydown during hot weather may degreen if rain rewets the seeds above 20% moisture.
Canola fields with significant pod spotting due to Alternaria also should be swathed early to reduce shatter losses and pod drop. Unusually heavy, late infestations by flea beetles or lygus bugs may also benefit from early swathing rather than spraying insecticide beyond the allowable pre-harvest window.
Direct combining canola
Recent research in direct combining canola has shown it is a viable harvest alternative to swathing in some circumstances. In B. napus, conditions favourable for direct combining include having a crop canopy that is slightly lodged and knitted together, even maturity across the field, few, green weeds (or else sprayed with a desiccant), the pods should not have been exposed to many wet/dry cycles due to showers or heavy dews; and the crop should not have significant Alternaria pod spotting.
Advantages to direct harvesting are as follows:
- Fewer operations and machinery costs are less.
- Lower risk due to high winds moving the swaths
- Less green seed
- Higher oil content
- Possibly higher yields
- Once dry, you can harvest the canola even if rain has dampened the pods.
Disadvantages to direct harvesting
- Higher chance of pod splitting.
- Greater potential for pod drop
- Green stalks can slow dry down and cause problems with combining.
Recent research from the ARC, AAFC and the Alberta Canola Producers Commission has shown straight cut canola is a viable alternative to swathing, most of the time. 30% of the time losses from direct harvesting is at least 2 bushels/acre and 15% of the time losses would be 5 bushels/acre. Newer harvesting headers have also reduced hearder losses significantly from straight cut. With our higher yielding hybrid canola varieties there is more branching and knitting together of plants. At 5 lbs of seed per acre, the straight cut canola yields were equivalent to yields from crop swathed at 30 – 40% moisture. At 3 lbs/acre of seed, the straight cut canola actually outyielded the swathed canola by 12%. Some seed companies have also bred line of canola with a greater resistance to shattering, thusly making straight harvesting the crop less risky.
Key points for successfully straight cutting canola include a dense, crop stand to maximize the crop knitting together to prevent wind actuated pod shelling. You get this with high seeding rates and high plant populations. Areas with a short growing season may not be the best place to try straight cutting canola as you need enough heat units to mature the crop. Straight combined canola needs to be put in aerated bins to get the temperature down after harvest. Moisture content above 10% can be a problem.
Combining Canola
Canola is ready to combine when seed moisture has dropped under 10% -- under normal conditions this is about 5-10 days after swathing. Most seeds will be mature with little or no green color. A moisture meter is essential to ensure correct timing. Before combining, use a crush strip to determine the amount of seeds that are not green inside. A small percentage of green seeds will reduce grade. If green seed is present due to rapid drydown, not frost, and it is early in harvest, the swaths may be left longer to clear more green during subsequent wet weather. However, during wet or overcast weather, sclerotinia white stem rot may cause significant yield loss in heavy or compact windrows. Yield losses of up to 30% from stem rot have been estimated in the windrow during wet fall weather in Alberta. Leaving the swaths to reduce green seed also runs the risk that prolonged wet fall weather will delay combining until very late fall or the following spring, resulting in yield and quality loss. Canola windrows dry more quickly than those of cereals after a rain or heavy dew so combining can begin sooner. Canola combines well under conditions that may be too moist for cereals.
Windrows are picked up using a rubberized draper belt, an aluminium draper fitted with fingers or direct cut open front headers. The rubber belt type pick-up with rubber or synthetic fingers is preferred in canola as the gentle action helps to reduce shattering losses. The aluminium pick-up is more suited to bunched windrows. Direct cut headers require crop lifter attachments for the width of the windrow to lift the windrow into the header. The rest of the cutter bar may be covered to prevent or reduce the amount of green second-cut stubble entering the combine.
Cylinder speed and concave
Canola is not a difficult crop to harvest. Often most of the seed threshes out in the front or in the elevators. Consult the combine manual for proper settings. Cylinder speed should be about 60 percent of that used for cereals – 650 to 700 rpm for small diameter (46 cm) cylinders, and 450-600 rpm for large diameter (61 cm) cylinders. Excessive cylinder speed causes seed cracking and skinning and excessive smashing of pods and stems, which may then be difficult to remove from the seed. A speed that is too slow reduces the capacity of the combine. Slow the cylinder speed to where the amount of cracked seeds is just acceptable.
Stems and pods should be broken no more than necessary and unthreshed pods kept to a minimum. This will reduce overloading the sieves and allow seed separation without excessive dockage or load on the return conveyor. The concave should be wide open (40-50 mm at the front). Clearance at the rear should be narrow, ranging from 3-13 mm.
Straw walkers
Unthreshed pods, broken pods and stems returned from the walkers tend to overload the sieve and the return conveyors. If baffles are fitted over the walkers these should be lifted as high as possible to allow a smooth flow of stems.
Wind adjustment, chaffer and clean grain sieve
Proper adjustment of fan and sieves for the cleaning action is important since canola seeds are light and can easily be blown out of the combine or remain mixed with the chaff. Unlike the cleaning action for cereals, the cleaning action for canola should depend more on a shaking separation and less on wind separation. While it is necessary to reduce the fan speed, enough wind must be used to maintain a "live" sieve. Air should be directed as uniformly as possible under the entire length of the sieve to keep the sieve "alive"; otherwise, stems, pods and seed will move over the sieves in a mat and losses can be high. The fan should be set at half to three-quarter speed. Where the wind is controlled by shutters these should be less than half open. Too high a fan speed will blow canola seed out with the chaff and allow large amounts of pods in the return. Start with a lower fan speed and gradually increase it until separation of chaff and seed occurs with no seed being blown over the chaffer sieve.
There is a close relationship between adjusted fan speed and sieve openings. Closing the sieve tends to direct the air to the rear rather than up, but at the same time tends to increase air velocity through the sieve. The top sieve or chaffer should be opened enough for good separation (1/4 to 1/3 open, or 6-10 mm). This will keep the seed from going over the top and out the back of the combine. Air should lift the chaff on the sieve with a shaking action conveying the material along. The chaffer extension should be raised slightly (5-10 degrees) at the rear and be open enough to allow unthreshed pods through to the return. A chaffer opening that is too narrow, coupled with insufficient wind, can result in high seed losses.
The lower sieve should be adjusted depending on the sample seed quality in the grain tank. If too much residue is present in the tank, the sieves are likely too open. If the sample is overly clean, canola seed may be going back to the return conveyor so that the sieves should be opened slightly. A lower sieve setting at 3-6 mm will usually be sufficient. Excessive returns result in seed crackage and the overloading of one section of the combine with resultant high seed losses. If the returns are too high, there may not be enough wind, the top sieve may be too open, or the cylinder-concave is overthreshing. The best seed sample will be made when humidity is high, for example at night or soon after a rain. During high daytime temperatures (over 30°C) smashed pod pieces will contaminate the sample, but because of its light weight a small percentage of such admixture may be acceptable. In areas with high temperature during harvest, skinning of the seed will often occur during the hottest part of the day, and the problem cannot be corrected by further adjustments. It then becomes necessary to stop harvesting until the temperature falls later in the day.
Grain losses
High losses of seed out of the front and the back of the combine are possible if adjustments are not correct, therefore, frequent checks and readjustments must be made in the field. A loss of 1 lb/acre is equal to 2 seeds of B. napus and 4 seeds of B. rapa per square foot remaining in the field. Average canola harvesting losses in the field are 50 to 100 lb/acre. A standard grain monitor, suitably adjusted, is satisfactory for canola seed. The loss monitor can warn of changes in the grain loss rate but it does not accurately measure the amount of loss. The loss monitor will indicate relative changes in loss rate. An increase in the meter reading is a signal to reduce the feed rate by slowing down. The loss monitor will indicate when combine adjustments are necessary to compensate for changing weather conditions. |
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