LET YOUR oilseed rape crops 'see the light' is the advice as the crop gears up for its big growth spurt following winter.

But, if the main raceme shoots away, the yield potential of lower branches could be significantly reduced and this is where well-timed PGR applications could beneficially hold back stem extension and enable the side shoots to develop simultaneously, according to a crop expert from Syngenta.

Its field technical specialist, James Southgate, said that establishing a stronger structure and leaf canopy will produce higher yields. “Some of the more advanced crops could be expected to lose leaves in the bitterly cold easterly winds through the end of February and early March, but with well-established root structures they are well placed to recover quickly,” he said.

“To encourage branching and even up the crop, they are really going to benefit from an early PGR application (such as Toprex), from early stem extension at GS31.”

Smaller crops, with limited root reserves, however, need nurturing through the coming weeks to increase their green area he said. These may then benefit from a later PGR application, from GS51, to develop shape and branching that will make the most of potential light interception, he advocated.

“With the extending day length, plants are poised to take off and as soon as temperatures rise, crops will rapidly move through stem extension,” said Mr Southgate. “Growers should be prepared to apply Toprex at the optimum point to shape canopy development.”

The objective is to trigger the crop into developing sufficient side shoots to bear seed pods and green leaf area to ensure pod fill and increase oil content. “With a genuine PGR you can shape the crop to improve its overall efficiency. Toprex encourages far greater consistency across the crop, so whilst the onset of flowering on the main raceme may be later, you then get all the side shoots flowering at a similar time – so the flowering is far more intense, but over a shorter period,” he pointed out.

The benefit for the crop is that the yellow flowers physically reflect sunlight, so a shorter duration of flowering means that plant’s green leaves are able to absorb and utilise more energy. It’s particularly evident where the PGR has encouraged stronger side branching and more accessible photosynthetic green leaf.

He added, though, that some small crops, slow to get going in the spring, or that have suffered severe pigeon damage, may be better left without PGR treatment. Ensuring they reach a Green Area Index of 3.5 by the start of flowering should be the priority, he urged.