Holding-off on OSR harvesting crucial this season

Many winter OSR crops flowering up to two weeks later than normal this season makes it vital to hold-off on harvesting them for as long as possible to avoid knocking output badly, insists Bayer commercial technical manager, Tom Sowerby.

“Oilseed rape in full flower in mid-April has a short enough pod fill period anyway,” he observes. “And we know that each day of seed filling lost typically reduces its average yield by 1-2%.

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

“If we 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 we’re going to need, above all else, this summer. Especially so with well-branched, modern hybrids carrying the bulk of their yield lower down the plant in pods that typically ripen 7-10 days later than those on the main raceme.

“Desiccating these crops, in particular, too early will cut their pod fill unnecessarily short,” he stresses. “It will also stop them taking full advantage of the valuable stay-green benefits of flowering sprays like Aviator.”

Under these circumstances, Tom Sowerby strongly advises growers to keep their sprayers in the shed as long as they can this summer. Not least because, rather than bringing combining forward, spraying before the seed moisture drops below the 30% stage recommended for desiccation will just mean crops take longer to dry down, even with the most effective modern Roundup formulations.

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

“At the same time, it’s important to appreciate that 30% is the maximum recommended seed moisture. You don’t have to go in with the glyphosate as soon as your OSR has reached this level. In many cases it will pay dividends to keep the gate closed for another few days, if not a week.

“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 may mean harvesting your breadwheats before the oilseed rape. But those who have done so in the past have found it well worth doing for the extra OSR output.”

Mr Sowerby accepts that holding-off on desiccation carries the risk of increased seed shedding from the earlier-ripening pods, in particular. Which is why he considers the pod shatter resistance pioneered by Dekalb and carried by all Ex varieties so valuable; a trait that independent trials have shown gives an average yield advantage of 6% over varieties that don’t carry it with a one-week delay in harvest, rising to nearly 10% with a two-week delay.

“The harvest timing flexibility pod shatter resistance gives will be especially valuable in capturing the extra output from later flowering crops by holding-off on harvesting with the least possible risk,” he concludes. “It will be very valuable too for crops in which flowering has been extended as a result of damage from flea beetle larvae or pigeons, resulting in uneven stands and pods with a particularly wide range of maturities.”