Hit grass weeds hard ahead of autumn drilling - Agrii - Connecting Agri-science with farming

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August 4, 2014

Hit grass weeds hard ahead of autumn drilling

Growers must take full advantage of the timely harvest and good soil moisture levels to really hit grass weeds hard ahead of planting this autumn. And wherever possible they should aim to spray off two or even three flushes of stale seedbed weed growth with a quality glyphosate before cereal drilling.

This is the firm advice of Agrii trials manager, Steve Corbett against the background of  serious black-grass, ryegrass and brome infestations in so many crops this year, not to mention the rapidly declining effectiveness of post-emergence herbicides.

“With this season’s oilseed rape coming off well before the end of July, most growers will have at least six, if not eight weeks, before their winter cereal drilling,” he pointed out.  “Indeed, they may even have up to three weeks between wheat harvesting and winter OSR drilling too in many cases.

“Recent rainfall across most of the country also means a good black-grass chit is virtually guaranteed wherever stubbles are managed right, regardless of dormancy levels.

“Our extensive trial work at Stow Longa shows that the degree of control achieved between harvest and drilling is one of the single most important determinants of success these days; all the more so with the sort of seed return we’ll be getting this season.

“Two flushes of stubble weed control are infinitely better than one in reducing the grass weed seed burden ahead of planting and three are even better,” stressed Steve. “This is because each flush of weed seedlings suppresses subsequent germinators. So when the seedbank is high plenty of seedlings are left to emerge in the crop.

“If you get things right this season in our experience you should be able to get a good flush of black-grass within 2-3 weeks. And if you spray it off effectively as soon as it comes through the ground you should get another flush 2-3 weeks later even without further light cultivation.”

Getting stale seedbed management right in Steve Corbett’s experience involves:

  • Good, even straw chopping and spreading;
  • Shallow cultivation immediately after combining with accurately set tackle;
  • Rapid and effective consolidation of the top few inches of cultivated soil;
  • Spraying-off black-grass growth as soon as it is evident (at the 1-2 leaf stage);
  • Using a quality glyphosate with proven efficacy under challenging conditions;
  • Applying the correct rate of glyphosate with the right nozzle and forward speed;  and,
  • Spraying-off at least one further weed flush ahead of drilling.

“We’ve found it well worth taking advantage of the extra power and reliability of an ultra-modern Roundup,” he advised.  “It has the edge over other glyphosates in its speed and efficacy, and its rainfastness and ability to cope with both dry conditions and hard water can be really valuable.

“Unlike many other glyphosates too, it is approved for post-planting pre-emergence as well as multiple pre-planting use. This means that, with care, you can get in an additional round of control to tackle any weeds emerging in the seedbed ahead of the crop if you want to.”

On ground suffering particular grass weed problems, Steve Corbett strongly advises growers to delay wheat sowing until mid-October wherever possible to give even greater time for weed emergence and effective treatment ahead of drilling.

He also points out that their Stow Longa studies have shown major advantages from rotational ploughing, providing it is of sufficient quality to effectively bury the bulk of the black-grass seed at depth and is not followed by ploughing the following year to bring it back into the germination zone. Effective glyphosate treatment and delayed drilling is equally essential here, he adds. This is especially important wherever black-grass seed is well spread throughout the soil profile.