Focus on Soil management for black-grass control
Appropriate soil management can play a major part in controlling your black-grass before it controls you, growers and agronomists were advised at the latest national Soil & Water Management Centre improvement event in Lincolnshire.
Agrii technical manager, David Langton warned that a strictly limited chemical arsenal, growing weed resistance and increasing climatic uncertainty make it vital to manage soils and tillage as effectively as possible to minimise the pressure on in-crop herbicides.
Opportunities for tackling problem fields
Armed with latest results from the company’s long-term system trials on fields with serious multiple herbicide resistance near Huntingdon, he highlighted cultivation flexibility, multiple stale seedbeds and delayed drilling as particular opportunities for tackling problem fields.
“We’ve conducted carefully controlled trials on the same challenging heavy land fields at Stow Longa for more than 10 years now,” he explained.“Not surprisingly with a marsh weed like black-grass, these have shown that rectifying drainage issues and cultivating to facilitate water infiltration are key areas for improvement.
“In our latest trials with Lemken, ploughing stood out as the best way of reducing black-grass in a single season, giving us nearly 100% control in our 2010/11 wheat through effective seed burial. Indeed, with 100 black-grass ears/m2 taking almost exactly 1t/ha off wheat yields, we recorded a net benefit of £100/ha over our shallow min till regimes after accounting for the extra £45/ha cost.
“It’s important to stress, though, that ploughing needs to consistently bury the seed below 3” in the profile. And ploughing two years in a row can lead to greater problems by bringing up non-dormant black-grass seed buried the previous year. Ploughing after direct drilling wheat the year before, for instance, resulted in an average of just 6 black-grassplants/m2 in our OSR compared to 123 plants/m2 from ploughing after ploughing.”
On this evidence, rotational ploughing certainly looks to be a better bet that a complete return to the plough. Careful ploughing approximately every three years – when time and conditions allow – is suggested as the best option for badly-infested ground.
Where ploughing is not a viable option, extensive studies at Agrii farm trial sites with particular grass weed problems show some reduced tillage regimes can be almost as effective in controlling black-grass, while generating higher margins over establishment and chemical costs; providing they are accompanied by effective stale seedbeds.
“Good stale seedbeds plus the cheapest available black-grass herbicide – glyphosate – are essential here,” David Langton insisted. “Thiscan eliminate up to 90% of the season’s potential black-grass population. But it must be done correctly and is dependent on sufficient soil moisture.
Early Germinating Black-Grass
“The fact that early germinating black-grass can suppress the germination of other black-grass seed means two cycles of two stale seedbed treatment in a row tend to be better than one, although it’s important to appreciate that not all glyphosates allow this on the label.
“Under these circumstances, delaying the drilling of the worst black-grass fields to give time for repeated pre-planting control can be enormously beneficial wherever conditions allow. As, of course, is a robust pre-em programme in wheat, wherever possible, and effective propizamide/carbetamide treatment in OSR.
“If we are to rise to a black-grass challenge which is just as great for many today as it was before the advent of Atlantis, we really need to know our weed,” David Langton concluded. “As well as its resistance status, we should identify where it is both in the field and in the soil profile. That way we can utilise the tillage and other soil management tools at our disposal in the most cost-effective, integrated control approaches.”
For more information, please contact: