Oilseed growth race ahead in spring warmth

The UK’s rape crop has transformed itself from post-winter lethargy to full speed ahead in less than a week suggests Agrovista’s Mark Hemmant. "The rape crops I’ve walked this week have turned the corner from an overwinter GAI 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."

Added to this Mr Hemmant says that the underlying root systems for most oilseed rape crops is 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 Sunorg Pro [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.

ADAS trials have shown that metconazole will reduce stem height by between 7 to 11 cms, but, manufacturers BASF say that it does a lot more than this. "Its main activity is to reduce apical dominance and so divert growth away from the main stem into branches and roots," says Will Reyer, BASF’s OSR Product Manager. "This allows the canopy to achieve better light penetration and improve photosynthesis. Branching also helps lock the plants together, so reducing lodging and pod shatter."

He adds that "metconazole has also been proven to show positive rooting effects, Sunorg Pro’s use has resulted in 25% more rooting at depth, improved water uptake and yield gains of between 0.22 to 0.34 t/ha in a dry season."

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/m2 compared with around 10/m2 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.

For those uncertain about accurately assessing the GAI of oilseed rape, Agrovista’s Mark Hemmant suggests a failsafe method; "BASF and ADAS set up a photo upload tool to assess GAI; I have 122 photos I’ve taken to upload this weekend!" To access the tool go to www.totaloilseedcare.co.uk. The website also has a joint ADAS/BASF sclerotinia monitoring service. Both services are free to any user.