The best modern hybrid oilseed rape varieties have come through one of the toughest winters on record with markedly better and more consistent canopies than their pure line contemporaries, reveals state-of-the-art Green Difference Vegetative Index (GDVI) scanning of field scale trials on commercial farms across the country.
The canopy measurements of seven hybrid and three pure line varieties grown in strips of around 800m2 in 14 Dekalb trials from Dundee in the north east to Exeter in the south west – were undertaken this spring with the most objective electronic technology available.
Measuring the vegetative biomass of crops through a combination of green and infra- red reflectance, the GDVI scans carried out by Dekalb product development manager, David Leaper show hybrid varieties averaging 7.4 on the 1-9 vigour scale developed through extensive 2010 calibrations.
This compares with an average of 6.4 for the pure lines despite their considerable sowing rate advantage – 60-80 seeds/m2 against the hybrids’ 40-60 seeds/m2.
Average all-site canopy scores varied from 6.2 for the worst variety – a currently available pure line – to 7.9 for the best – one of the latest development hybrids.
“Interestingly too, we recorded almost double the variation in average pure line canopy score across the 14 sites as we did in the hybrids, most of which are our development varieties, ” reports David Leaper. “Equally, a good 40% of all the hybrid canopies scored over 8.0 and only around 12% scored 6.0 or less. This contrasts markedly with just 23% and over 46% respectively for the pure lines (Table 1).
Table 1: Dekalb Strip Trials – Overwintered Canopy Measurements
“Overall, the hybrids have clearly come through the winter in noticeably better shape than the pure lines in our strip trials,” he points out. “As so often, though, the averages hide some interesting specific differences.
“Clearly, the hybrids have also over-wintered far more consistently across the range of site drilling dates and establishment conditions. And within the hybrids, there’s an obvious gap between DK ExPower and our other leading development varieties and a current RL standard included in the trial series – not one of ours I’m happy to say.
“Indeed, the standard hybrid had an average all-site vigour score and across-site consistency very similar to the pure lines while DK ExPower was one of the most vigorous and consistent of all.
“Recorded under strictly commercial management from a range of establishment regimes, these differences underline the advantages in establishment vigour, speed of early development and winter hardiness our next generation Dekalb hybrid breeding programme is allowing us to introduce into UK cropping,” says David Leaper.
“Together with far superior disease resistance, these characters are giving growers the best possible opportunity to consistently maximise their OSR production potential year-in, year-out regardless of conditions at the least input cost.
“We know from experience that better established, better rooted oilseed rape crops are far better able to take advantage of spring nitrogen. We also know these crops require markedly less N to build the optimum canopy. Which means either they require less fertiliser overall or the fertiliser can be saved for later application where it will make a far greater contribution to yield. In either case it adds up to valuable extra margin.”
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