Crop inspection vital to time oilseed rape desiccation correctly

Regular crop inspections will be crucial to ensure glyphosate desiccation sprays are correctly timed in oilseed rape crops, says Richard Elsdon, technical manager for United Oilseeds.

Any crops following last autumn’s wet conditions, and severe pigeon and frost damage, are very patchy, he says. “Crop maturity, even within fields, is going to be very variable.”

That’s going to make pre-harvest management tricky. “Growers need to inspect their crops as often as possible in the run-up to harvest. For many farmers, applying glyphosate at exactly the right time will be difficult to judge, but regular crop inspections will help to maximise crop yields and reduce the risk of rejections at the crushing plant.”

Don’t be tempted to go by last year’s treatment date, or by the colour of the crop as seen from the gateway, he warns. “Both of these methods are likely to give the wrong answer.”

The only reliable way to decide on timing is to inspect the seeds from the middle pods on the main stem of several plants, he says. “It is important to split open a number of seeds and to make a judgement accordingly. At least two-thirds of the seeds from plants that are growing away from the headland and tramlines should have begun to turn from bright green to a pale green or yellow colour with a splash of brown on them.”

At that stage crops should be sprayed, preferably with a modern Roundup formulation, within four days, he says, or if the weather turns cool within seven days.

“Glyphosate applied at this stage will have barely any effect on pod splitting or seed losses, as the pods will still be pliable enough to withstand any damage caused by the sprayer’s wheels.”

Correct glyphosate timing will also enable easier combining – as any weeds will be completely dry and dead by harvest – and more efficient seed separation.

A Claas study using a Lexion 580 with a 9m Vario cutter bar showed a correctly-timed Roundup-treated plot could be combined 50% faster at 6kmh compared with 4kmh in an untreated plot.

That increase not only results in direct savings in fuel and labour costs, but also means a larger area can be cut at the optimum time to maximise crop quality, says Monsanto‘s Manda Sansom.

Extremely variable crops might need patch spraying at different times, Mr Elsdon says. “For most farmers this level of precision will be unfeasible. In these cases, growers must be even more vigilant to ensure most of the crop is ready to be sprayed to avoid load rejections.”