Major System Changes to Tackle Grass Weed Threats - Agrii - Connecting Agri-science with farming

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November 30, 2012

Major System Changes to Tackle Grass Weed Threats

Large numbers of winter cereal growers are already making significant changes to their tillage and rotations to tackle increasingly challenging grass weed infestations. And more fundamental long-term system changes appear to be very much on the cards.

This is one of the key findings of the latest national grass weed control study conducted by Agrii this autumn.  Involving growers responsible for some 50,000 ha of cropping across England, Wales & Scotland, the study confirms the extent to which grass weed control is becoming more challenging.

Nearly 70%, indeed, are finding control significantly or substantially more challenging these days. The scale of the challenge is definitely greater in the south and east of the country and where minimum tillage is the main establishment regime. Even so, more than half of those in the north and west and a similar proportion of those basing their cereal establishment on the plough report a significantly or substantially increased control challenge.

Overall, some 60% of growers identify black-grass as a problem on a quarter or more of their current winter cereals area, with 30% reporting problems on at least half their acreage. While it continues to be more of a problem in the south and east, 20% of those in the north and west now see problems from the weed on half or more of their winter cereals area.

Brome, wild oats and ryegrass are highlighted as problematic on at least a quarter of their winter cereals areas by 15-20% of growers, with ryegrass causing noticeably greater problems in the north and west. 

With the exception of wild oats where the incidence was very much greater in the past, this is a remarkably similar position to that recorded in a benchmark national study conducted in 1998/9 before the introduction of Atlantis.

The past few years have, however, seen a marked increase in the difficulty of controlling black-grass and ryegrass, in particular. So much so that the vast majority of growers have been forced to increase their typical winter cereal herbicide bill by at least 10% in recent years, with over 40%  having to increase the cost by a quarter or more.

Regardless of tillage regime or location, unreliable pre-planting glyphosate control due to weed seed dormancy or the weather, insufficient time for effective control ahead of autumn drilling and increasing resistance to post-em herbicides are pinpointed as the most important grass weed control challenges.

“Against this background, it’s no surprise to find more than 90% of growers already taking one or more tillage or rotational measures to tackle the grass weed threat,” observes Agrii senior agronomist, Andrew Richards who co-ordinated the study. “Nor to find a similarly large proportion considering major future tillage and rotational changes.

“Delaying drilling to give more pre-planting glyphosate opportunities is by far the most popular immediate non-chemical weed control improvement measure, together with better stale seedbed practice on min-till ground and stubble management practice on ploughed land.

“At the same time, large numbers of growers are increasing winter wheat sowing rates to boost competitiveness, stepping-up rotational ploughing in place of minimum tillage and increasing their use of break crops in the rotation.”

In addition to this, the Agrii study suggests the rate of fundamental change will accelerate in the future. Altogether, two thirds of growers are actively exploring at least one major long-term system change – 40% of these primarily considering changes to their tillage, 30% changes to their rotation, and 30% both tillage and rotational changes.

“Increased ploughing is the most popular longer-term measure being actively considered,” Andrew Richards reports. “Increasing direct drilling, introducing grass breaks or fallows and moving to alternative (late-sown) wheats are also under active consideration by many. And to underline the seriousness of the situation, over half the growers are considering the possibility of reducing their winter cereal growing, more than one in 10 exploring this actively.

“Our study confirms that choosing and using both pre- and post-em herbicides better remains a priority for most,” he concludes. “What it underlines more than anything else, though, is that growers are accepting that this needs to be accompanied by more fundamental system and management change if they are to stay on top of the grass weed problems. Which is where our industry-leading research into integrated control systems across the rotation is proving so valuable.”