Use cultural control and chemical combination to tackle high black-grass populations, trials show
Ploughing, increased seed rates and timely herbicide applications were the most effective control measures in 2014 black-grass trials, Bayer CropScience has revealed in a recent study.
Affectionately known inside Bayer CropScience as the ‘black-grass busting trials’, the research programme takes fields with exceptional black-grass populations and measures the impact of traditional approaches to control, both cultural and chemical.
“Most sites had a background population of over 1,000 plants/m2,” says Miles Taylor, crop agronomy co-ordinator at Bayer CropScience.
“They replicate what growers might do if they’d taken on land with a big black-grass problem, but with the added benefit of control plots allowing us to measure the impact of commonplace cultural and chemical methods.”
According to Mr Taylor the most striking outcome of the trials is the effectiveness of tailoring programmes to the field history and, in particular, the location of seed within the soil profile.
“At some sites it’s relatively apparent which cultural controls are likely to have the greatest effect. For example, at a site in Buckinghamshire that hadn’t been ploughed for over eight years, bringing the plough back into the rotation reduced the number of plants in the following crop by 51 per cent.
“One site in Suffolk demonstrated the value of increasing seed rates from 250/m2 to 500/m2 by delivering a 55 per cent reduction in black-grass seed heads.”
Further analysis of ten independent market support trials also re-emphasise the importance of application timing for Atlantis WG (mesosulfuron + iodosulfuron).
“Bayer CropScience has been assessing the effects of application timing for Atlantis WG since the product was in the development stages, nearly 15 years ago. Since then there have been thousands of trials but only two years when, on average, a later spring-time application led to better efficacy.
“In those cases we had very abnormal weather conditions. And while we don’t know what this year holds, all the evidence suggests that autumn applications of Atlantis WG will out perform spring applications.”
Mr Taylor advises growers to implement cultural controls as much as possible before deploying a robust herbicide programme, an action which reduced seed heads by 96% in the following crop.
“Reducing a big population requires patience and perseverance; it’s a war of attrition,” he says.
“Delay drilling as long as possible. It will provide time for multiple stale seedbeds and put pre-em applications back to when ideal conditions are most likely.
“Black-grass needs light, water and nutrients - restrict its access to these essentials by increasing crop competition, for example by increasing seed rates and sowing more competitive varieties.
“And persevere with the objective of an autumn post-em application. Take advantage of every spray window to pick off the worst-affected fields, even if the crop looks relatively clean after pre-em applications.”