Agrii R&D insight – Soil Management For Blackgrass Control

David Langton – Crop Nutrition Technical Manager

Agrii technical manager, David Langton warns 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.

Armed with latest results from our long-term system trials on fields with serious multiple herbicide resistance near Huntingdon, he highlights cultivation flexibility, multiple stale seedbeds and delayed drilling as particular opportunities for tackling problem fields.

“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-grass plants/m2 in our OSR compared to 123 plants/m2 from ploughing after ploughing.”

Where rotational 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 blackgrass, while generating higher margins over establishment and chemical costs; providing they are accompanied by effective stale seedbeds. “If we are to rise to a black-grass challenge we really need to know our weed,” David concludes. “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.