Assessing when to desiccate oilseed rape crops is critical in maximising yields and achieving effective desiccation prior to harvest.
This is especially important given that timings may differ several days between conventionals and modern hybrids grown at lower plant populations.
“Workload pressures and the overwhelming desire to get harvesting means some crops are often being sprayed at least a week before they should be,” says Hutchinson’s technical development director David Ellerton.
See also: Growing hybrid oilseed rape Academy
He explains that more than a third of the pods in well-structured, hybrid canopies may be immature at the traditional spray timing for conventional crops grown at relatively high plant populations, says Dr Ellerton.
David Ellerton’s glyphosate tips
- Select an area of the field representative of the crop
- Pick 20 pods from the part of the canopy bearing the bulk of the yield
- If at least two-thirds of the seeds have changed from green to brown in at least 15 pods, the earliest stage for spraying has been reached
- Repeat in other several areas of the field to check for consistency and spray within 4-7 days
In contrast, conventionals bear most of their yield on the main raceme.
“Therefore, for the greatest yield, oil content and sample quality, spraying should be delayed until the bulk of the pods are sufficiently ripe,” he advises.
“This can be 7-10 days later than those on the main raceme. So it’s important to apply the Roundup spray timing guidelines (see box right) to the area of your canopy bearing the lion’s share of the yield rather than the main raceme.”
Oilseed rape grower Andrew Gloag agrees that timing is crucial for effective desiccation.
“We are going in with a pod stick at the end of this week, which is at least a fortnight before the glyphosate.
“We don’t want to go too early as plants need to lose some of their waxiness to effectively get good uptake. We found stems were not properly desiccated and were sappy if sprayed too early.”
Mr Gloag is growing hybrid crops at a lower population of 45-50 plants/sq m and he explains that it results in bigger, stronger plants which take more desiccating.
To time his spray, Mr Gloag opens 20 pods from the main raceme and as soon as seed is rolling firm in the hand or turning from a green to brown colour, then he will go in with the glyphosate.
“And because we are using a pod sealant, we are confident that we can leave rape for up to 21 days [from glyphosate spraying] for harvest.”