Establishment trials highlight oilseed rape variety value

Conditions for establishing winter oilseed rape this season are clearly very different to those in 2007 when dry soils delayed germination. But results from Cambridge Arable Technologies trials suggest growers don’t necessarily need to turn to hybrid varieties when the going gets tough.

The work compared six conventional varieties and three hybrids grown in 8m wide strips each 100m long, established by four cultivation regimes all, bar direct-drilling, into a lightly worked barley stubble. It was funded partly by CAT members and breeders.

“We used a plough and press, which produced a lovely, crumbly seed-bed,” says CAT’s Richard Fenwick. “We also had minimum tillage, using a couple of passes with a Vibroflex, subsoiler drilling with a Claydon, and direct-drilling into some untouched stubble.

“Strictly speaking it wasn’t true direct-drilling as we used a conventional Lemken drill on which you can increase the disc pressure to get the seed into the ground about 0.5in deep.”

Unsurprisingly, given the dry seed-beds which had no rain for two weeks after drilling, the “direct-drilled” plots failed so were not taken to yield.

Min-tilling clearly posed the biggest challenge to the varieties, producing both the lowest average yield and widest differences.

“Whereas Claydon drilling gave us an average of 3.32t/ha across the nine varieties, and the plough-and-press regime 3.26t/ha, under min-till we averaged just 2.92t/ha,” says Mr Fenwick.

The extent of the establishment difficulty created by min-tilling also showed in the much bigger yield differences recorded between varieties – 2t/ha between the best and worst under min-till compared with 1.7t/ha and 1.5t/ha, respectively, under plough-and-press and Claydon drilling.

“Indeed, only four of the nine varieties topped the 3t/ha mark under min-till compared with seven and eight from the other two regimes.”

Top min-till performers were the hybrids Excel and Excalibur at 3.45 and 3.33t/ha, respectively. But not far behind were conventionally-bred Catana and Castille at 3.3t/ha and 3.25t/ha, respectively.

Of the two drills, Lemken (above) and Claydon(top), used in the CAT experiments, the latter gave the best results after last year’s dry post-sowing conditions

While conventional ES Astrid did well under Claydon drilling and plough-and-press regimes, it gave only 2.99t/ha from min-tilling as the best of the remaining five varieties.

“It wasn’t surprising to see the two leading hybrids coping so well with the season’s challenge,” says Mr Fenwick.

“They showed clear advantages in autumn vigour to give an average 45% establishment at the end of March compared to just 33% with the pure lines. This more than justified sowing rates averaging 55 seeds/sq m against the 82 seeds/sq m we used for the pure lines,

“Clearly, though, their ability to deal with what we, like most growers, found to be one of the trickiest autumns in recent memory was not simply because they are hybrids. After all, the pure lines Catana and Castille performed admirably under the same challenge.

“Nor was it solely a case of establishment vigour. Castille, for instance, went into the spring at just 22 plants/sq m compared with Es Antonia and Es Astrid at 29 plants/sq m and 37 plants/sq m, respectively. But it comfortably out-performed them both.

“It was clearly more able to compensate for lower plant populations – particularly valuable given the sort of pigeon problems many growers had last winter.”