Canola harvest: Is direct heading a serious option?

Jon Midwood,

Southern Farming Systems

Keywords:  canola, windrowing, direct head, desiccation

Take home messages

• No one harvesting technique gives consistently the best results but consideration of other options to windrowing will give growers a better ability to manage their risk
• Ideal windrow timing is a balance between leaving the crop standing as long as possible to maximise yield, while minimising shattering losses.
• With the possible registration of Glyphosate, pre harvest in Canola, direct heading becomes a serious alternative to windrowing. 

Canola is an indeterminate plant, which means it flowers until limited by temperature, water stress or nutrients. As a result, pod development can last over 3–5 weeks, with lower pods maturing before higher ones. Most canola in Australia is currently windrowed but an increasing number of growers are switching to direct harvesting as improvements in varieties are making direct harvesting of canola more of an option and the additional cost of the windrowing operation is putting pressure on the crop margin.

The following are some guidelines for getting optimum results from windrowing, direct heading following natural ripening, or following desiccation. In any one season none of the three techniques is consistently the best but it may enable the grower to minimise their exposure to risk by looking at the pros and cons of each.

Windrowing

This technique is likely to be the most widely used as the majority of canola is currently windrowed

Advantages: By cutting the crop and placing it in a windrow on the stubble;

• the pods and seeds will ripen faster than a standing crop (by as much as 8–10 days)
• windrowed canola is much less susceptible to wind and hail damage than a thin standing crop, especially if it has been desiccated with diquat (Reglone®),
• seeds will reach a uniform harvest moisture content of 8% earlier than desiccation or direct heading and in some cases it can help with uncontrolled or herbicide resistant weeds. 

Disadvantages:

• additional cost
• in very wet seasons the crop can deteriorate in a windrow
• the optimum timing only lasts 4 – 6 days depending on the temperature and humidity;
• the use of contractors may compromise timing
• windrowing timing is determined by % change in seed colour which is a compromise allowing for the variability in the weather post windrowing
• going too early can lead to yield losses of up to 10% and reduced oil content whilst windrowing too late makes the crop far more susceptible to shattering losses

Timing: Collect pods from the main stem of a number of plants and from different positions in the canopy. The optimum time for windrowing is when the top third of the plant has mostly green seeds. These should be firm but pliable when rolled between the thumb and forefinger. The middle section of the plant will have 80% of seed green or green-red and be very firm but pliable and the other 20% may be red-brown to light brown. The bottom third of the plant will have dark brown to black seeds.

Direct Head

Recent research in direct cutting canola has shown it is a viable harvest alternative to windrowing in some circumstances. Favourable conditions for direct heading include having a crop canopy that is slightly lodged and knitted together, even maturity across the paddock, few, green weeds (or else sprayed with a desiccant).

Advantages:

• reduced cost - no windrowing or desiccation costs
• crops dry out faster after wet weather than a windrowed crop
• allows the crop to maximise yield potential and oil contents
• suits rocky areas which can be a problem when windrowing and reduces the risk of harvester blockage that can occur with windrows  

Disadvantages:

• in variable crops the wait for ripening can expose crops to wind damage and thicker crops can take a considerable time to ripen evenly.

Timing: The general colour of the crop is a poor guide on when to harvest, use seed moisture content.

The addition of pod sealants is an extra management aid when direct harvesting, it helps by reducing pod shattering and by allowing crops to achieve their full yield potential. When sprayed on to the crop it provides a unique elastic, semi-permeable membrane over the filling pods. Timing is earlier than the optimum time for windrowing.

Desiccate followed by Direct Heading

The most common desiccant is diquat (Reglone®) which is registered for aerial application.

Advantages:

• useful on variable soil types as it allows more even crop ripening
• ideal for weedy crops and crops dry out faster after wet weather than a windrowed crop.

Disadvantages:

• shedding losses if you have to use ground rig;
• shattering losses can be very high in windy conditions and it’s expensive, especially if applied by air

Timing: The correct time for desiccation is when 70–80% of seeds have changed colour in middle pods, which is when the crop has passed its optimal windrowing stage. The crop will be ready to harvest within four to seven days after the desiccant is applied, depending on the size and density of the crop.

Other desiccants like Roundup are regularly used pre harvest on canola in Canada and Europe. This provides far slower senescence of the plants and so pod shattering is considerably reduced and with the benefit of superior end of season grass weed control. An application has been submitted for Roundup Attack® to be registered pre-harvest in canola.  The timeline for registration is likely to be early 2013 and it will cover all canola types (RR, CLR, TT, CON) and various application techniques - sprayed under the cutterbar of the windrower and also over the top of standing canola.

Contact details

Jon Midwood
Southern Farming Systems, 23 High Street, Inverleigh, 3321 VIC
jmidwood@sfs.org.au