Straight combining canola – tips

Straight combining scenarios

Canola crops ideal for straight combining will have the following characteristics:

  • Pod shatter resistance. Canola crops with this trait are less likely to experience pod shatter while waiting to harvest the crop. This gives some flexibility on combine timing (harvest may not have to occur the moment the crop is ready). Not all seed that claims to have pod shatter resistance will have an equal level of resistance.
  • Knitted. The crop should be well knitted and slightly lodged to reduce potential seed loss through pod shelling and drop. If a large proportion of the plants appear to move independently in the wind, they will be at higher risk for shattering loss as the plants senesce and dry down.
  • Pod integrity. If a lot of pods have been damaged by frost, drought, hail or insect damage, this may not be a good candidate field for straight combining. Hail will typically cause more damage to a standing crop than a swathed crop.
  • Uniformity. Unevenly matured fields can be difficult to straight cut, particularly when the plant and stalk material does not dry down well. Field topography can play a large role in the evenness of maturation. Pre-harvest aids or swathing should be considered in a field with uneven growth stages.
  • Minimal green weed growth. Weeds may stay green longer, and make straight combining much more onerous on the combine. Green material may also end up in the hopper, increasing the storage risk.
  • Low disease. The crop should be relatively free from blackleg, sclerotinia stem rot, clubroot and alternaria, as these diseases can result in premature ripening, which increases shattering losses.
  • Low frost risk. Canola seed is at significant risk for fall frost damage until seed moisture drops below 20 per cent. This moisture drop will take much longer in a standing crop, and as such, late maturing crops are poor candidates for straight cutting. They will be much more vulnerable to yield loss, and to downgrading from frost damage when standing.

The decision to swath or straight combine is less clear with:

  • Late crop. Swathing may be preferred over straight combining when crop is immature with an elevated frost risk. But don’t swath too early. In most cases, waiting is probably the better option but the decision depends on (at least) two things: (1) How far advanced is the crop? (2) How cold will it get? Suggestions based on four scenarios.
  • A heavy frost. Pod splitting or pod drop due to tissue damage from heavy frost usually starts within a day after the frost event. If the canola crop is still sound, growers can probably stick with a plan to straight combine. If frost damage is heavy, getting brittle plants into a swath could protect them from wind whipping, but swathing means handling brittle crops twice. Details. Would you sleep better if the crop was swathed? If yes, swathing is probably the best decision. Note that if the crop is fully mature and almost ready to straight combine, frost provides some extra dry-down of green stems. 
  • Lodged crop. Severely lodged or excessively branched canopies may be candidates for straight combining because, if swathed, the low cut may leave minimal stubble to anchor swaths in high winds. Swath or straight combine lodged canola?
  • Thin crop. Short or thin crops will not produce a windrow that rolls nicely, and may not have the stubble to hold that windrow and prevent it from blowing. Straight combining eliminates the risk of swaths blowing. Thin crop also whips more in the wind, so pod shatter resistance is a benefit. Also, thin crop may not feed well when straight combined, which could mean substantial losses at the header. 
  • Uneven crop. Swathing may be the best option to manage extreme variation in maturity, and delayed swathing will let more of the latest seeds reach maturity. Straight combining could mean early-maturing plants will start to shell out (though pod shatter resistance reduces this risk) but it gives late-maturing plants more time to mature. If using pre-harvest glyphosate in this situation, remember that it must applied after the crop is at 30 per cent seed moisture, or less. If a large percentage of plants have not reached this stage, it can result in elevated glyphosate levels in the seed. Pre-harvest aids (see the next section) are not a treatment for uneven fields.
  • Weedy crop. Crop with green weed growth or crop re-growth may be better for swathing. With an uneven crops, desiccation may be required to dry down weeds and those very late canola plants to facilitate straight combining. Hold off on desiccation as long as possible to let as much of the crop mature, then go in with desiccant a few days before harvest. 

Pre-harvest aids

A pre-harvest spray to help prepare canola for straight combining may not be required if warm, dry days allow for natural dry down of the crop and weeds.

Pre-harvest spray applications have two goals to prepare a canola crop for straight combining – weed control and desiccation.

  • If weed control is the goal, assess the weed situation before spraying. Moderate to heavy infestations of annual or grassy weeds should be sprayed out pre-harvest. Good control can be provided pre-harvest for perennial weeds as well. If waiting for post-harvest, weeds need up to four to six weeks of regrowth after harvest and may need three times the active ingredient for the same control. 
  • If desiccation (crop and weed dry-down) is the goal for straight combining, this decision should wait until just before harvest – for two reasons: (1) Crops may dry down naturally, especially if conditions are warm and dry. (2) Diquat desiccant can only be applied once the crop has 90 per cent brown seed throughout.

For details on products and timing, read the Canola Encyclopedia on pre-harvest options for canola.

Harvest timing

Canola harvest can be delayed when crop is straight combined. (This is not always the case. For example, if snow falls on canola before harvest, standing canola is often ready to harvest before swathed canola.) The extent of the delay can depend the farm’s expectation of “ready”. Consider these three approaches to straight combining timing:

1. Based on acceptable seed moisture. Straight combining will start earlier if the decision is based on dry seed, but combining may be less efficient. Green plant material may limit capacity, plugging may be more frequent, threshing losses may be difficult to reduce, and green material may be difficult to chop and spread, causing issues for future operations in that field.  Green leathery pods will often pass through the rotor and be spit out the back, unthreshed. This can be hard to correct without cracking good seed.

2. Based on dry pod material. This approach should strike a balance between acceptable seed moisture (not too low) and a decent amount of plant material dry down for ease of harvest. Unthreshed losses should not be an issue. Disadvantages are that it takes longer to reach this stage, the pods will start to become more susceptible to shattering (most notably in non-shatter tolerant varieties), and stalk material is likely still going to be on the green side, which can drain the machine capacity. Watch your sample for green material that would lead to greater storage risk.

3. Based on dry stalks. The key advantage with this approach is a much easier and faster harvesting experience. The disadvantage is that it can take significantly longer to reach this stage (especially later in the season or in areas that tend to be wet and/or cool) or it could require a pre-harvest aid to achieve. Seed moisture could also end up very low. The plant material will tend to break down a lot more readily, and the primary loss point may end up being the cleaning sieves (chaffer or shoe) rather than the rotor.


PAMI ran a three-year project (2014-16) to compare three header types for straight combining canola: rigid auger, draper and extendable knife. The rigid header had the highest losses overall, and was by far the worst for losses in the middle of the platform. Extendable knife and draper headers had lower losses in the middle of the platform.

Crop dividers. The PAMI project also found that all three straight-cut headers had fairly high losses at the crop dividers. PAMI compared fixed, vertical knife and rotary knife dividers. Vertical knife and fixed dividers had lower losses than the rotary knife divider.

Ontario Canola Growers Association ran a one-site field study in 2012 to compare shatter loss and yield differences between three straight cut headers: New Holland 35-foot CF740 flex header, Case-IH 40-foot draper header, and John Deere modified 30-foot Model 930 with the flex pan removed and replaced with a solid pan with an 18-inch table extension. The modified header also had a vertical side cutter. Canola seed loss was 76 per cent less with the modified header and 60 per cent less with the draper header when compared with a regular flex header.

With standing crop, header loss can occur if the reel hits canola pods and seeds fall to the ground, not on the header. Keep the reel as slow as possible. Specialty headers with knives that stick out in front of the reel can reduce these losses in canola. 

Other header considerations: Keep the knives sharp. Add an after-market shield (Crop Catcher from Michel’s) over the feederhouse to keep canola seeds in the combine. 

Stripper headers. Stripper headers can be effective in the Brown Soil Zone on farms with a complete system to seed into tall stubble. Canola Watch podcast on stripper headers.

Combine settings

Standing canola will often have higher levels of green within the stems. For this reason, straight combining canola often requires combine settings different from swathed canola. Consider these settings: (1) speed up rotor RPMs to handle greener plant material, (2) take wires out of the concave to release canola seeds faster, and (3) pull back the rotor vanes to keep crop inside the rotor for more rotations.

To check these settings, disengage the chopper and check the back of the combine for losses. Look for intact pods that may suggest a required adjustment to concave settings. Look for broken seeds. These will be part of an overall assessment of loss.


All canola should be conditioned immediately after combining to cool it down, even out the temperature throughout the bin and remove any moisture released through natural seed respiration that occurs in the first hours to weeks after harvest. 

Green dockage from straight combined canola, due to its potential for higher-moisture stalk and pod material, could increase the storage risk. Concentrated areas of chaff could be a start point for spoilage, even in a bin where the seeds test dry. Storage risk factors