Trials put FAR weed approach to the test
THREE "FAR" herbicide applications (see panel) to sugar beet completes weed control – that is the impression growers got from a BBRO-funded trial evaluating the technique at Morley Research Centre last week.
"The weed control compared to the conventional method is like chalk and cheese," said Martin Lainsbury.
But he was quick to point out that the visual assessments were from only one of three trial sites, and it was only year one of a three-year project.
"By running trials on three different soil types we expect to encounter a wide range of weeds. What is right here at Morley is not necessarily going to be right for all situations," he stressed.
Besides comparing cost and yield from FAR regimes with conventional programmes, the project aims to answer other questions, including:
lDoes a pre-emergence herbicide improve efficacy?
lHow do Flo formulations compare to ECs?
lHow does Debut (triflusulfuron-methyl) fit in a FAR programme?
"A pre-emergence herbicide has proved vital with the conventional programmes this season, but it is not yet clear when and where it is necessary with the FAR technique."
But Mr Lainsbury already has some clear ideas on the importance of formulations. "FAR mixes do need an EC component," he said. That means using a generic EC formulation of phenmedipham or another EC formulation in the mix with the more crop-safe Betanal Flo.
"But at such low rates the crop safety differences between the EC and Flo formulations of phenmedipham are very small."
How Debut fits into the programme should become clear from results on heavy soils at Otley where cleavers and volunteer oilseed rape are more of concern. Early data from that site, and the light land work at Morley should be on display at the British Sugar stand at Cereals 2000. *
• Three-year, three-site BBRO-funded trial.
• 17 programme comparisons.
• FAR best first impression.
• Needs an EC formulation.
Under FAR, low doses of phenmedipham, an activator such as ethofumesate, and a residual such as Goltix (metamitron) are applied repeatedly, ideally weekly. First application is at first weed emergence, and repeats are made until weeds are dead and no more emerge. Its success relies on tight timings, especially in warm weather. "This year there has been a bit more flexibility as weeds have not been growing so quickly. But in warm weather the weekly interval is very important. You are aiming to catch weeds almost before you see them," said Mr Lainsbury.