Delaying drilling of winter wheat crops until after mid-October or later has proven to be an effective tactic for helping to control black-grass. Here are five reasons why it helps and how to maximise the effectiveness of delayed drilling.
By delaying drilling from mid-September to after 15th October, over 30% better control of black-grass can be achieved because around 80% of black-grass plants will have already emerged.
It is important to create a fine, consolidated seedbed that is clod and trash free. Clods will hold black-grass seeds which can then germinate when they break down, while excessive trash will prevent herbicides from reaching the soil. If correct drilling conditions don’t arise, consider spring drilling instead which offers even greater black-grass control.
Where winter slugs are likely to cause damage to crop, apply slug pellets prior to drilling for the best control. This will manage slug populations before seeds are in the ground, meaning they are less at risk of attack. Seeds should be drilled 32mm or more below the soil surface to reduce the number of slugs able to reach them.
The shorter days, cooler temperatures and higher moisture levels typical of late autumn allows pre-emergence chemistry to work more effectively. Soil moisture means the active substances are mobile in the soil and reach the weed germination zone while cooler weather means the herbicide breaks down more slowly giving you longer residual protection.
Residual pre-emergence herbicides can be 25% more effective in later drilled crops and applying a pre-em like Liberator (flufenacet + diflufenican) within 48 hours of drilling will stop 60-80% of black-grass plants from emerging. The sooner a pre-em treatment is applied, the more effective it will be because black-grass roots will not have time to move down to below where herbicide activity reaches. Wheat should be drilled at least 32mm below the soil surface to avoid damage from pre-ems, and the use of a Cambridge roller prior to application will help consolidate the soil surface.
Late drilling offers the perfect opportunity to treat any germinating black-grass plants with glyphosate prior to drilling. Glyphosate should be applied as close to drilling as possible for maximum grassweed control.
Watch Darren Adkins answering some key questions about delayed drilling below:
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