Chapter 11 - Swathing, Combining

Harvest Management

Proper harvesting and storage of canola are the final steps in profitable canola production. While good agronomic practices can maximize canola yields and returns, proper harvest and storage management are essential to realize those yields. Seed and quality losses caused by untimely harvesting, inappropriate harvesting techniques, improper handling, inadequate storage, or some combination of these practices, all result in reduced crop value. Therefore, timely harvest and proper storage will help maximize yield, quality and returns.

Swathing vs. Direct Combining Canola

Canola is often harvested with the same swather and combine equipment as cereal crops with some adjustments. Canola can be direct combined, or swathed for uniform maturity and later threshed. Swathing involves cutting the crop and placing it in rows directly on the cut stubble. This hastens the drying rate of the crop, ensures even ripening and reduces the possibility of seed losses from wind and hail. After the crop dries to uniform seed moisture content of 8 to 10% moisture (usually five to 10 days after swathing), it is ready for harvesting.

The advantages of swathing canola are:

• earlier harvest (eight to 10 days) and more even seed maturity—this is particularly important in fields where maturity is uneven
• earlier harvest to avoid fall frost and accelerate dry down, especially in short season areas
• earlier harvest to allow for double cropping or fall seeding
• more flexibility with a large acreage since the timing of harvest is not as critical
• reduced shatter losses during the harvest operation—especially in crops infected with Alternaria
• swathing can be run around the clock (unlike direct combining) to assist with the harvesting of large acreages
• cutting weeds allows a cleaner and drier sample that will reduce the risk of heating in storage and reduce the number of weed seeds that reach maturity

In western Canada, B. napus canola is generally swathed because it tends to ripen unevenly and shatter easily due to adverse weather conditions later in the season. B. rapa varieties can be direct combined because they mature earlier and resist shattering. B. napus can be direct combined after using desiccation or after using a pod sealant or a combination of both (see section on Chemical Desiccation and Pod Sealants).

Swathing Canola

When to Swath

Swath at the proper seed colour change to reduce green seed and seed losses from shelling, and ensure quality required for top grades and prices. The best time to swath for optimum seed yield and quality is when average seed moisture content is 30 to 35%. The colour of the seed is a good indicator of seed moisture content and is more important than the overall colour of the field in determining the stage of crop maturity. Seed in all pods on a plant reach physiological maturity and complete filling at about 40% moisture. Physiologically mature seed loses moisture at about 1 to 3% per day. Seeds slowly turn from green to light yellow, or reddish-brown to brown, depending on the weather and variety. The crop is at the optimum 35% moisture stage for only three to five days under good drying weather.

When field topography, soil type and moisture are similar, the crop will usually mature evenly. However, variability in a canola field usually means the canola matures at different rates. There may be a range of seed colour change in a field—30% in flat areas, shelling on hilltops and 5% in lowlands. Ideally, swath at three different times in the same field—first the ridges, then the side slopes and finally the low areas. However, this is usually impractical. Generally, the flat areas are the highest yielding. Therefore, base the decision to swath on optimizing yield—look at where most of the yield is in the field and swath when that area is ready.

With a large acreage, swath before the crop reaches the optimum seed colour change. If swathing starts when seed colour change is approximately 20%, the majority of the crop can be swathed at or near optimum seed colour change. If 5% or more of the pods are covered with Alternaria black spot disease, swath early to reduce potential shatter losses.

Avoid swathing during hot (30°C), dry weather. Very hot and dry, windy weather after swathing may stop chlorophyll clearing due to low seed moisture. This may result in some immature seed with green colour. The enzyme responsible for clearing the chlorophyll requires moisture. Swath during the cool evening hours, at night, or early morning to allow the seed to dry down at a slower rate. This lowers the chance of green seed and lower oil content. Rain or irrigating the crop will help maintain moisture in the seed. Delaying combining can often allow some of the green seed colour to clear in the windrow.

If conditions are cool and it is late August or early September and frost is coming, consider swathing early (at 10% seed colour change). This can help minimize green seed due to frost. A crop swathed three days prior to a frost will have less potential for frost damage. However, canola seed does not continue to fill while the plants cure in the swath. If the seed has not accumulated its full complement of oil and protein at the time of swathing, no further accumulation will occur in the swath and some potential yield will be lost from immature seed.

Figure 1. Seed Colour Change To Assist in Determining Proper Time of Swathing

Seed Colour Change

The best time to swath for optimum seed yield and quality is when average seed moisture content is 30 to 35%. At this moisture level, seed colour change on the main stem is at 30 to 40%. Most of the seed that has changed colour will be from the bottom third of the stem in B. napus varieties, while in B. rapa varieties some of the middle and upper pods will have seed which has changed colour. When seed in the bottom pods has turned colour, seed in the top, last formed pods will be filled or nearly filled. Canola seed within the pod will change colour an average of 10% every two to three days. Under hot, dry conditions, seed colour change can occur rapidly. When conditions are cool, seed colour change can take longer.

Assessing Your Yield

Here's a list of tips for assessing seed colour change:

• Start inspecting your canola field approximately seven to 10 days after flowering ends. Canola is usually ready to swath about 20 to 30 days after the end of flowering. The end of flowering is defined as the stage when only 10% of plants have any flowers.
• Take time to assess a field. Sample various parts of the field to make an accurate assessment of the overall maturity of the crop. Stand on the road or in the back of your truck box and look at the field. Look at ridge tops, low lands and similar areas, making mental notes how each area appears. Varying plant densities, soil type, and moisture availability affect the rate of seed maturation.
• Walk out and sample at least five to 10 plants in the different areas of the field. Most of the seed in the top pods should be firm, and roll, as opposed to break or crush, when pressed between the forefinger and thumb.
• Using Figure 1, take notes on the seed colour percentage of the plants.

Examine only pods on the main stem. Seed in pods on the bottom third of the main stem mature first and will turn colour much sooner than seed in the pods of the top third of the main stem. Make note of how many pods have Alternaria black spot and what percentage of each pod is covered with the disease.

After assessing the main stem, look at the seed from the pods on the side branches to ensure they are firm with no translucency, especially with low plant populations where the plants have numerous branches.

Count seed with small patches of colour (spotting) or seeds that have changed colour completely as “colour changed.”

Effect of Swathing Date on Yield and Quality

Field scale trials in western Canada have shown that optimum seed yield and quality were achieved when B. rapa varieties were swathed at 40% seed colour change on the main stem. However, the optimum time for B. napus was between 20 and 40% seed colour change (Table 1.)

Table 1. Effect of Time of Swathing on B. napus Canola Yield, Oil and Protein

% Seed Colour Change	Location Years	Yield (%)	Oil Content (%) @ 8.5% Moisture	Protein Content (%) @ 8.5% Moisture
0 to 10%	25	90	40.8	20.7
10 to 20%	25	96	41.5	21.7
20 to 30%	25	100	42.2	21.6
30 to 40%	25	100	42.8	21.6

The trials found that swathing at 0 to 10% seed colour change on the main stem resulted in reduced yield, oil and protein. Swathing at 10 to 20% or 20 to 30% seed colour change had little effect on yield or protein. The variations in oil content seldom exceeded half a percentage point.

Research at Agriculture and Agri-Food Canada in Saskatoon, SK showed that once canola plants are swathed, the seed does not continue to fill (Figure 2). Seed swathed before accumulating its full complement of oil and protein will not accumulate any more after swathing, resulting in potential yield loss.

Figure 2. Effect of Swathing Date on Seed Weight after Swathing

Research studies have shown that time of swathing usually has little effect on green seed levels except under abnormal 1103 Oil Content (%) @ 8.5% Moisture % Seed Colour Change Location Years Yield (%) Protein Content (%) @ 8.5% Moisture 0 to 10% 25 90 40.8 20.7 10 to 20% 25 96 41.5 21.7 20 to 30% 25 100 42.2 21.6 30 to 40% 25 100 42.8 21.6 situations. In all research trials, swathing even prior to seed colour change did not increase the green seed levels. Swathing at a seed moisture content over 45% moisture (0-10% seed colour change on the main stem) reduced average seed size and immature seed turned a reddish colour. Occasionally, reductions in seed size were recorded with swathing at 15 to 20% seed colour change on the main stem. However, under abnormal conditions, swathing too early can occasionally result in green seed when plants are under moisture stress and very hot, windy weather dries out the pods and seed in the swath before chlorophyll has had a chance to clear.

As B. napus has a narrower range in development time (due to fewer branches and pods) than B. rapa, it is possible to swath B. napus earlier without yield loss due to immature seed. This range in development time is affected by any factor that influences the number of branches and pods. Since dense or high population stands of canola have fewer branches and a narrower range in development, swath them earlier. Since low population stands tend to branch more profusely and have a wider range in development, swath them at the higher end of the seed colour change range.

Green Seed

Green seed occurs when the chlorophyll in the seed has not degraded or cleared. Green seed appears to be related not only to variety maturity but also environmental factors. In particular, temperature influences not only the rate of chlorophyll clearing but also the timing relative to seed development, as measured by the decrease in seed moisture content. An inherent difference between the species causes B. rapa to clear its chlorophyll more readily than B. napus during seed ripening.

The majority of the canola green seed problem in western Canada is usually the result of frost. Even a light frost can fix the green colour by damaging the enzymes that clear the chlorophyll in higher moisture seed, preventing additional clearing regardless of how favourable weather conditions may become. A killing frost also causes rapid dehydration of seed and plant tissue. The seed enzymes that clear chlorophyll work rapidly at high temperatures but slowly at low temperatures. Freezing temperatures have much less effect on seed chlorophyll content at lower seed moisture levels. Seed at 20% moisture is safe from frost damage. Swathing one to three days prior to freezing temperatures may reduce seed chlorophyll levels by allowing for a more rapid seed dry down when compared to standing crops at the same stage of maturity. The time required to dry down the swathed crop to a “safe moisture” level is always dependent on the weather conditions experienced following swathing.

To minimize high green seed:

• Swath B. napus varieties at 10 to 15% seed colour change on the main stem to reduce the risk of frost damage in short season areas.
• Start swathing large acreages early to reduce crop windrowed at too late a maturity stage. B. napus canola can take 15 to 22 days to progress from 10% seed colour change to 35% seed colour change on the main stem.
• Avoid swathing too early in hot, dry weather (30 to 35°C). The heat can rapidly dry the crop resulting in shatter losses from swathing too late or excessive seed shrinkage from swathing too early.

Chemical Desiccation and Pod Sealants

A chemical desiccant usually produces more uniform crop ripening by chemically drying down all green vegetative growth. Canola must be desiccated at the correct stage to optimize yield and seed quality. Desiccation may also reduce the incidence of pod shatter and seed loss, making it an alternative to swathing.

For B. rapa varieties, desiccation can eliminate the need to swath while providing some weed control. However, B. napus cultivars are more prone to shatter than B. rapa cultivars. Desiccation and direct-combining should only be considered for B. napus canola in:

• heavy crops that lodged early and have weeds grown through the crop
• crops that mature unevenly due to topography or uneven stand establishment
• where swathing machinery is unavailable
• in late maturing fields, which may not mature in time under normal conditions before a killing frost

For B. napus varieties, a heavily lodged crop canopy may help prevent shatter loss by wind. Check your provincial recommendations for current information on registered desiccants.

When seed is mature but before pods become dry and split, pod sealants will slow pod dry down and prevent the movement of moisture into and out of the pod, reducing shatter losses. Combine timing is crucial for minimizing shatter losses as the sealant efficacy diminishes with time and from repeated rains. Sealants slow crop dry down and harvest by five to 14 days. This could be a concern in shorter season growing areas.

Swathing Operation

Types of Swather

Swathers can be either self-propelled or power-take-off driven. 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 manoeuverability. Regardless of the equipment used, the windrow must flow smoothly through the swather without bunching. Stands that are exceptionally tall, thick or lodged and tangled make it difficult to lay an unbunched swath. Bunching leads to 1104 uneven drying and combining problems as well as development of diseases such as sclerotinia stem rot under wet or humid weather conditions. At the bottom of bunched or heavy swaths this disease can damage up to 50% of the canola pods. Therefore, a swather must have the following essential features to handle canola:

• At least 1.1 m (3.5') depth (front and back) of the table or platform to handle the crop material.
• A large throat opening of 1.0 to 1.3 m (3.3 to 4.3'), which is at least as wide as the distance between the draper belts.
• A vertical clearance of up to 1 m (3.3') under the swath opening to allow large swaths to pass through without interference.
• A throat opening free of projections that may catch or bunch the swath as it passes through the machine. It’s important to avoid bunching as this leads to both harvesting and drying problems.
• A swather with ample reel and table adjustments to handle the range of crop conditions. The major problem is the amount of material in heavy crops to be forced through the throat of the swather.
• An adjustable draper belt speed.
• A divider capable of separating heavy and tangled crops. Difficult crop conditions may require specialized attachments on the swather 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 swather. 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 divider of which the double knife with two moving blades appears to be the best suited for all crop conditions since it reduces the shatter loss in drier crops.
• Canola crops do not often flatten 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 during swathing.

Swather Operations and Setting

Cut the crop just under the pods to reduce the amount of crop passing through the throat, without missing any of the lower pods. This leaves a maximum amount of stubble on which to lay the windrow and ensure adequate air circulation through the swath. Such swaths tend to settle into the stubble and escape wind damage. This also minimizes the amount of material that must be handled by the swather and combine. If bunching occurs, adjust the width of cut, height of cut and the forward speed of the swather so that the throat of the machine will handle the swath without bunching. For best results:

• Set the reel as high and as far forward as possible with the batts at the top of the crop to hold plants gently against the knife.
• Make the reel rotation speed slightly faster than the ground speed of the swather. This speed will just lay the cut material gently back on the table to avoid shelling.
• Use a middle-range belt speed for most swathers. A fast draper belt speed tends to produce a hollow twisted swath; a slower belt produces a more compact swath, but it may bunch and sit high on the stubble. A mid-range speed will usually cause the cut crop to become slightly tangled and easier to pick up at harvest. The need to create a formed canola swath is not as critical as in cereal crops.

In areas where light fluffy swaths could be lifted and blown by the wind, a light roller pulled behind the swather will help anchor the swath in the stubble. Set the roller so that it just anchors the swath into the stubble without shelling any ripe pods. Excessive pressure on the roller will produce a swath that is too compact to dry quickly and difficult to pick up without shelling the canola. Leave the swath as high as possible in the stubble so that the combine pickup can slip under it without tearing the cut crop.

Combining Canola

Harvesting Swathed Canola

Swathed canola is ready to harvest under normal conditions about five to 14 days after cutting—when seed temperature and moisture content have dropped to 10%, which is considered a safe storage level. Most seed will be mature with little or no green colour. Use a moisture meter to ensure correct timing. If there is green seed present, allow a few more days in the swath for further colour change. Green seed may change colour in the swath but does not change significantly once combined and stored.

Before combining, use a crush strip to determine the amount of seed that is green inside. A small percentage of green seed will reduce grade (No. 1 Canada allows 2.0% distinctly green, while No. 2 Canada and No. 3 allow 6.0 and 20.0% respectively). The use of wide swathers on tall, heavy crops can result in very large swaths that can take longer to cure, especially at the centre of the windrow. Bunching in the swaths also may contribute to a green seed problem as the crop dries out and cures unevenly. In addition, during wet or overcast weather, sclerotinia stem rot may cause significant yield loss in heavy or compact swaths. In Alberta, yield losses of up to 30% from stem rot have been estimated in the windrow during wet fall weather. Canola swaths dry more quickly than cereal swaths after a rain or heavy dew so combining can begin sooner. Canola combines well under conditions that may be too moist for cereals. The chances of taking off top grade canola are much better under rainy conditions than with cereals.

Direct-Combining Canola

Direct combine canola crops that have been desiccated or that are uniformly mature and relatively free of green weeds or Alternaria disease. In western Canada, field scale trials have shown that B. rapa varieties lend themselves well to direct combining. However, B. napus varieties had a higher risk of shatter losses when over-ripe (Table 2).

Table 2. Effect of Swathing Versus Direct Combining Canola on Yield, Oil and Protein

Treatment	Location Years	Yield (% of Swathing)	Oil Content (%) @ 8.5% Moisture	Protein Content (%) @ 8.5% Moisture
B. rapa (S)*	24	100	40.4	20.3
B. rapa (DC)	24	99	40.6	20.3
B. napus (S)	28	100	42.8	20.1
B. napus (DC)	28	89	43.5	19.9

S= Swathing DC= Direct Combine

Canola is ripe when the pods are dry and rattle when shaken. Seed is dark brown to black or yellow in colour at maturity depending on variety. Stems may still be partly green at this stage. Bottom pods on the plant ripen first and at harvest some of the small top pods may still be greenish. Green pods will usually pass through the header unthreshed. Start harvesting when overall seed moisture has fallen to 10% moisture or less and green seed is minimal.

At 10% moisture and above, seed in storage can heat rapidly on hot days, particularly if there is a significant proportion of immature seed. To avoid shatter losses, harvest B. napus varieties without delay when green seed levels are low and seed moisture reaches 10%. The longer a ripe B. napus crop stands in the field, the greater the potential for shatter losses. Rain on a standing crop increases the potential for shatter losses as it promotes saprophytic organisms growing on the pods.

Reduce shatter losses by combining:

• a ripe crop at higher seed moisture levels and drying the seed
• in the cooler part of the day
• at night when pods are damp from dew
• when wet with rain
• at night during periods of very hot weather

However, seed moisture levels must be continuously monitored to ensure they do not exceed safe storage levels.

Combine Harvesting Operations and Settings

Before harvesting, check combines completely. Cover holes or cracks with plastic tape or a silicon rubber-sealing compound, especially in the table, front elevator and grain tank. When leakage occurs it is usually through the stone trap, the top of the feeder housing, or through the lower inspection doors on the elevators.

In addition to repairing leaks, it’s important to keep combines in good mechanical condition. Worn or loose chains such as feeder conveyors, internal conveyors and elevators may cause seed cracking. Make certain that cylinder bars are in good condition and properly aligned. Missing or torn straw walker curtains, broken sieves and loose drive belts can result in seed dropping out of the back of the combine.

Combine operating speed must be set at the specifications detailed in the operator’s manual and then fine tuned for conditions in the field.

Swaths 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 shatter losses. The aluminium pick-up is more suited to bunched swaths. 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. Wide large capacity, open-front headers may be capable of handling more than one swath.

Windrow Pick-Up

To minimize front-end pod shatter losses on a swath pick-up equipped combine, adjust swath pick-up speed and forward travel speed so that the windrow will be gently lifted without tearing or pushing. Set the swath pick-up to run just under the swath. If the swath pick-up is too high or the speed too fast, the swath will be dragged and jerked up onto the table. On the other hand, if the speed is too slow, the swath will be pushed and bunches of crop will be fed into the auger.

Dividers and Reels

A major problem in direct combining tall canola is ensuring freedom from blockages at the dividers and header components to maintain a smooth crop flow through the combine. Long dividers or vertical power dividers can be effective in preventing crop blockages. A normal batt reel is usually satisfactory, but in heavy lodged crops a pick-up or finger reel is desirable. To minimize shatter losses, set the reel well back and as high as possible to act as a precaution against stems falling forward. Set the reel speed to gently assist the crop into the combine. A reel that is set too low or too fast will result in shatter losses.

Front Auger and Elevator

Adjust the table auger as high as possible. If the adjustment is insufficient to give 8 to 10 cm (3 to 4") clearance, it may be necessary to slot the adjustment holes. If the clearance is too small, the stems will be broken, the pods threshed open, and seed may be lost. The front elevator carries a much bigger volume than is normal for cereal straw. Check carefully for tension and freedom to float.

Cylinder Speed and Concave

Canola is not a difficult crop to harvest. In fact, under normal conditions most of the seed threshes out in the front or in the elevators. Set the cylinder speed at about 60% of that used for cereals. Set at 650 to 700 rpm for small diameter (46 cm, 18") cylinders, and 450-600 rpm for large diameter (61 cm, 24") 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. Too slow a speed reduces the capacity of the combine. Slow the cylinder speed to where the amount of cracked seed is just acceptable.

Avoid breaking stems and pods and keep unthreshed pods to a minimum. This will reduce overloading the sieves and allow seed separation without excessive dockage or load on the return conveyor. Make sure the concave is wide open (40 to 50 mm at the front, 1/3 to 1/5"). Keep the clearance at the rear narrow - from 3 to 13 mm (1/100 to 1/20").

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, lift them 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 seed is 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 depends more on a shaking separation and less on wind separation. While it is necessary to reduce the fan speed, allow enough wind to maintain a “live” sieve. Direct air 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. Set the fan at half to three-quarter speed. Where shutters control the wind, set them less than half open. Too high a fan speed will blow canola seed out with the chaff and allow a large number 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. Open the top sieve or chaffer enough for good separation (1/4 to 1/3 open, or 6 to 10 mm (1/50 to 1/25"). This will keep the seed from going over the top and out the back of the combine. Ensure that air lifts the chaff on the sieve with a shaking action conveying the material along. Raise the chaffer extension slightly (5 to 10°) at the rear and open it 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.

Adjust the lower sieve depending on the sample seed quality in the grain tank. If too much residue is present in the tank, close the sieves slightly. If the sample is overly clean, seed may be going back to the return conveyor, so open the sieves slightly. A lower sieve setting at 3 to 6 mm (1/100 to 1/50") will usually be sufficient. Excessive returns result in seed crackage and the overloading of one section of the combine resulting in 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 over threshing. 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 their weight a small percentage of this admixture may be acceptable. In areas with high temperatures 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. Stop harvesting until the temperature falls later in the day.

Grain Losses

High seed losses 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 kg/ha (0.02 bu/ac) is equal to 23 seeds of B. napus and 42 seeds of B. rapa per square metre remaining in the field. Average harvesting losses in the field can range from 10 to 50 kg/ha (0.2 to 1 bu/ac). 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. A reduction in the meter reading is a signal that the feed rate may be increased in order to improve productivity. Changes in crop conditions often occur during the day. The loss monitor will indicate when combine adjustments are necessary to compensate for changing weather conditions.

References