Oilseed rape growers are advised to hold off harvesting for as long as possible, after many winter crops flowered up to two weeks later than normal this spring.

“Oilseed rape in full flower in mid-April has a short enough pod fill period anyway,” said Bayer commercial technical manager Tom Sowerby.

“We know that each day of seed filling lost typically reduces its average yield by 1-2%.”

He explained that desiccating OSR that didn’t reach full flowering until the end of April – if not later in some cases – as normal in early July could easily knock 0.75t/ha off a 4t/ha potential crop. 

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“What’s more, with most oil accumulated towards the end of seed fill, the effect on gross output will be even greater.”

If farmers are to capture the maximum output essential in a season in which costs have escalated and rapeseed values have fallen back, patience is the one thing they are going to need.

Especially since well-branched, modern hybrids carry the bulk of their yield lower down the plant in pods that typically ripen seven to 10 days later than those on the main raceme, he said.

“Desiccating crops too early will cut their pod fill unnecessarily short,” he stressed. “It will also stop them taking full advantage of the valuable stay-green benefits of flowering sprays such as Aviator [bixafen + prothioconazole].”

Under these circumstances, Tom advised growers to keep their sprayers in the shed as long as possible this summer.

Rather than bringing combining forward, spraying before the seed moisture drops below the 30% recommended for desiccation will just mean crops take longer to dry, even with the most effective modern Roundup formulations.

Remember that pods at the crop edges, as well as those on the main racemes, ripen earlier than the rest,” he said. “So it’s essential to get into the crop to assess its maturity.”

He pointed out that farmers don’t have to go in with the glyphosate as soon as the OSR has reached 30% seed moisture. “In many cases, it will pay dividends to keep the gate closed for another few days, if not a week.”

Tom said with a statutory delay of 14 days after spraying and up to three weeks until the stems as well as pods are fully fit for combining, this might mean harvesting some bread-making wheat before the oilseed rape.

“But those who have done so in the past have found it worthwhile for the extra OSR output.”