Australia
October 18, 2010
An economic benefit of more than $200 per hectare may be gained by choosing the best method and timing of canola harvesting, according to new Grains Research and Development Corporation (GRDC)-funded research.
Maurie Street, Grains Orana Alliance (GOA) research and extension manager says the timing of windrowing canola can have a significant impact on canola yield and profitability.
“The GRDC-funded GOA research at Dubbo and Coonamble shows windrowing timing had a limited effect on oil potential in canola in the trials but direct heading is a viable option to harvest canola and in this case maximized profitability,” Mr Street said.
“Delaying windrowing or direct heading has resulted in significant increases in yields of canola in these trials.
“What these trials have done is demonstrate the potential economic benefit gained by getting it right.”
Mr Street says by adhering to best management practice growers have gained up to $140/ha compared to windrowing too early by as little as five days.
However they have also demonstrated some further gains to delaying windrowing further than BMP recommendations. In one trial up to an extra $120/ha for a five-day delay later than BMP.
The process of windrowing requires the plant be cut off from the root system when the pods are still green and pliable enough not to shatter.
Mr Street said the process of severing the plant tops from the root system rapidly terminates many of the key processes within the plant, namely, photosynthesis and respiration.
“These effect both plant growth, and in this context, grain-fill. This termination of a plants primary function may have then had the potential to effect how immature seeds may further develop after windrowing,” he said.
“Characteristics such as final grain size, density and oil content that develop in the late stages of plant growth may be influenced.
“Desiccation with a product such as RegloneTM that rapidly removes photosynthetic area could potentially have a similar effect.
“Any seed that has already reached maturity at the time of windrowing/desiccation would be expected to be unaffected by the timing of such an operation.”
Mr Street says for the immature portion, the question is how much will be able to reach its full potential between windrowing/desiccation and harvest compared to if it was left standing and able to mature naturally as it would be if it was to be direct headed?
As the timing of windrowing advances, the proportion of the crop that has achieved its full potential for its environment increases or in the case of direct heading where the crop is allowed to mature naturally all seed is able to reach its true maximum.
Crop production will be maximised by leaving the crop to mature as much as possible by itself. However as the crop matures and yield increase the risk of pod shatter also increases.
“To determine an ideal windrow timing a balance must be made between potential yield maximisation by delaying windrowing or desiccation, against the potential increases in yield loss through shattering,” Mr Street said.
He said growers should consider how much seed has already reached maturity when considering ideal windrowing timing.
“This should be weighed against the growers risk adversity or other advantages offered through windrowing.
“These may include longer harvesting windows, less exposure to hail damage, less risk of shattering due to high winds.
“Potential risks in terms of pod shattering may be managed by use of products such as Pod CealTM.”
Advances in machinery may also help minimise the potential losses in direct heading situations. Modern headers with draper fronts or conventional fronts with extendable tables may also limit any potential losses, Mr Street said.
“The limited nature of these trials does not allow for an adjustment to current BMP recommendation for windrowing to be put forward. However an ideal windrowing time is about maximising yield by delaying windrowing but not to an extent of jeopardising any of these gains to pod shatter.”
Mr Street says that a number of consultants in the area feel that windrowing time had been creeping earlier in fear of pod shatter. However these trials demonstrate the lost yields could be a much larger risk. At the Cooamble site last year you could have lost 25 per cent of the pods to pod shatter and been no worse off than windrowing too early.
Treatment
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Windrowing Timing
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Assumptions of Crop Maturity %
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Total % of Crop Physiologically Mature
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% At Risk of Not Reaching Full Potential
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|
Early windrow
|
10% seed colour change in middle 1/3 of the main stem
|
Assume bottom 1/3 mature, plus 10% of middle 1/3, nil top 1/3
|
36% seed is potentially already mature
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64%
|
|
Ideal windrow
|
50% seed colour change in middle 1/3 of main stem
|
Assume bottom 1/3 mature plus 50% of middle 1/3, 10% of top 1/3
|
53% seed is potentially already mature
|
47%
|
|
Late windrow
|
70% seed colour change in middle 1/3 of the main stem
|
Assume bottom 1/3 mature plus 70% of the middle main stem, 50% of top 1/3
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72% seed is potentially already mature
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28%
|
|
Reglone
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70% of all pods have changed colour
|
70%
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70%
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30%
|
|
Direct head
|
All seed mature
|
100%
|
100%
|
0%
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