By Wendy Short
THE 2014 growing season for oilseed rape is going to be very different from last year, a Bayer CropScience conference in Selby heard on Monday.
Dr Sarah Kendall of Adas, pictured below, said one of the main challenges for this season’s growers would be to keep the canopies from growing too large.
The aim should be for a green area index (GAI) of 3-3.5. Results from a trial comparing a plot with a GAI of 3 and one of GAI 5 showed yields of 4.8t/ha and 4.4t/ha respectively.
Dr Kendall reminded growers that it was also important to allow pods sufficient access to light, as they had 60pc of the capacity of leaves to photosynthesise.
“The crops were very backward at this point in 2013, but canopies are much larger this time and we need to control their size,” she said. “A thick canopy of flowers will intercept light, reducing the plant’s ability to photosynthesise and limiting yield potential.
“An over-large canopy can also increase the risk of lodging, although there needs to be a balance, because if it is too small that will also have a negative effect on yield.”
Trial work on row spacings and seed rates had highlighted the crop’s ability to compensate for low seed rates by high plant survival, increased branching and a rise in pod numbers, as well as seeds per pod.
The optimum seed rate was 25-30 seeds per square metre for both hybrid and open pollinated varieties. In cases of spring drought, recommended seed rates were 70-110 per square metre for hybrids and 150 for open pollinators.
Dr Kendall said: “Over-crowding within the row will increase the level of competition between plants, creating stress and affecting establishment.
Increasing the row width from 12cms to 48cms reduced establishment rates by at least 50pc in our trials.
“We also found that similar gross margins could be obtained from row widths of 12cms, 24cms and 48cms at 60 seeds per square metre.
Row widths at 72cms led to poor establishment, however.”
Adrian Cottey, of Bayer CropScience, said the dwindling number of chemical treatments available to tackle pests, weeds and diseases meant plant breeders were focusing on varieties with high resistance and these would come from hybrids. Clubroot and verticillium wilt were two of the main targets, although researchers were still working on varietal development.
The conference was at Stockbridge Technology Centre, near Selby.