Building biomass, building yield in oilseed rape crops

Despite the range of variety traits available to oilseed rape growers, still the most desired attribute for an oilseed rape variety is vigour.

It is one of the main factors responsible for the dominance of hybrids in the market and the characteristic most apparent to oilseed rape growers.

Driven by its vigour and disease resistance, RGT Kanzzas followed a strong 2023 performance in Agrii variety trails by finishing the second highest yielding variety in 2024, says David Leaper, Agrii seed technical manager.

This was an average of four sites located across the country.

“One thing that we have looked at is late autumn biomass, looking at how big the plants are going into winter,” he explains.

“What has driven our variety choice over the last few years are varieties that grow relatively quickly, producing a big plant with a nice thick stem.

“Not only are they better at coping with cabbage stem flea beetle (CSFB), but they are also less vulnerable to weather conditions and pigeons.”

Agrii measures biomass using a 1-9 scoring system. The trials are analysed in late autumn and springtime to give two measures of vigour: how the variety is established and how quickly it gets going after the winter.

Both are critical parameters in post-neonicotinoid oilseed rape agronomy. For example, Agrii has evidence showing how early spring oilseed rape biomass helps offset the effects of flea beetle larvae, says David.

Early spring vigour is a factor Agrii correlates against assessed levels of CSFB.

David says they see a close correlation between spring vigour and lower CSFB symptoms, a key factor in how Agrii choose varieties to bring to market.

© Ragt Seeds Ltd

“Generally speaking, the higher the biomass, the lower the symptoms.”

Foliar disease resistance is another important factor that can greatly aid oilseed rape agronomy.

Light leaf spot has become a particular challenge because it cycles in the crop from an early growth stage right through the year.

Yield losses tend not to come from a loss of green leaf area but from infections spreading onto the pods and stems, causing pod abortion and premature ripening.

The protracted period for controlling light leaf spot can aslo be a drag on variable costs, with multiple fungicide applications necessary to keep on top of the disease in susceptible varieties.

“The one outstanding characteristic of Kanzzas is the light leaf spot resistance. It has the highest rating for LLS of any candidate variety assessed by the AHDB.

“This disease is important across the country, not just in Scotland; it is prevalent everywhere. The races vary a bit across the country, giving variations in different trials, but Kanzzas is very consistent.”