Oilseed rape crops put on a growth spurt

The UK’s oilseed rape crop has transformed itself from post-winter lethargy to full speed ahead in less than a week, according to one agronomist.

“The oilseed rape crops I’ve walked this week have turned the corner from an overwinter green area index of 0.4 to 0.6 in the space of three to four days; so it makes the March biomass trigger of 0.8 for a canopy management fungicide almost inevitable, says Agrovista’s Mark Hemmant.

Added to this, Mr Hemmant says that the underlying root systems for most oilseed rape crops are very well established which will encourage further rapid growth following the rise in soil temperature and early nitrogen applications.

“We had thought that the cold winter might have knocked back the need for canopy management fungicides like metconazole, but given the potential for growth easily hitting a GAI of 2 in April, I’d recommend at least one, but more probably two, metconazole sprays during April, one of which can be combined with your sclerotinia spray,” he adds.

The added pressure for this season is that many growers increased seed rates following the memory of the wet cold autumn of 2008. And according to Andrew Blenkiron, who grows 220ha of oilseed rape in Dorset, “every seed planted last autumn has grown and produced a viable plant”. The net result is a lot of thick canopies with plant populations of 20/sq m compared with about 10/sq m in 2009.

“Crops established very well and rocketed away last autumn, and despite the cold winter the populations are still there,” he says. “After the winter plants are greening in the centre, they are robust and look like they have the potential to yield very well.”

For Mr Blenkiron, his thoughts are the same; come April a metconazole spray will be essential to check some of the flourishing growth inevitable after early nitrogen applications.

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