Growing maize provides as great opportunity totackle grass weeds in the rotation, including difficult to control black-grass.Pre-emergence herbicides have proven increasingly useful in helping the cropestablish and giving greater flexibility to the whole weed control programme,according to Tony Boole of Wiltshire-based agronomists and contractors, BooleCrop Specialists.
For arable farms with a black-grass burden, maizeenables the chance to encourage a flush of pre-dominantly autumn germinatingseeds, which can be killed off with glyphosate. Black-grass will germinate atsoil temperatures as low as 6C, whereas maize is typically not drilled in thespring until soils reach at least 10C, which often gives the chance to repeatthe process to lower the weed burden whenever opportunities arise.
Into the spring, Mr Boole advocates starting theherbicide programme with a Dual Gold based pre-emergence application,particularly where grass weeds are a problem. We do look to get the Dual Goldtreatment on as soon as the crop is drilled, no matter how dry the soilconditions, he advised.
Inevitably there is sufficient soil moisture forsome weeds to germinate, which we are looking to effectively stop. Typicallyhe advises a tank-mix with pendimethalin to further enhance the residualactivity and improve persistence against more of the broad-leaved weedspectrum.
Without that pre-emergence treatment there isalways a huge flush of weed competition as soon as there is any rain, headded. And then if it stays wet it is difficult to find the spray windows toeffectively tackle weeds before they start to aggressively compete with themaize crop.
Pre-emergence treatment certainly buys time andflexibility to tailor the follow-up treatment more effectively. Mr Boolehighlights that, in some instances, he has found the pre-emergence has beensufficient to see the crop through. But usually he will walk the crop andselect the most appropriate post-emergence treatment from a range of activesand application rates.
Core to many of his post-emergence treatments hasbeen the broad-spectrum activity of mesotrione. For Mr Boole, Calaris has beenthe preferred option, where he believes the inclusion of terbuthylazine adds extra strength for controllingknotgrass and speedwell that are typically a particular problem on mixeddairy/arable rotations. Milagro can be included in the tank mix wherepost-emergence grass weeds are also a target.
Whatever the post-emergence mix used, he points outthat the earlier the weeds can be controlled the better for the crop. We dohave some flexibility to adjust rates and product choice according to the sizeof the weeds, but for cost efficacy and the agronomy of the crop early controlis more effective.
Mr Boole reported that maize stubbles wereparticularly clean this year, which was a clear indication that the herbicidestrategy had been effective and reinforced the valuable benefit of maize in therotation for grass weed control.
Tony Boole highlights one of the keys to successwith the pre-emergence treatment is getting the right seedbed; too often earlyseason seedbeds can be cloddy that compromises application and herbicideactivity. The difference with a firm, fine seedbed is immense. And the cropgets off to a better start, so it is usually worth the wait and the effort, headvised.
Applications by Tony and his son, Robert, are madeusing angled DEFY nozzles facing forwards and backwards to give the bestpossible coverage of the soil surface, with a water volume of 200 lt/ha havingproven to give the best results.