Arable News

  • Written by: Farmers Guide
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Prevent a legacy: exhaust the seedbank

A black-grass legacyis in the making if growers fail to take action, warns eastern

counties agronomistRichard Peake.

 

Favourableconditions from autumn 2013 onwards have led to significant seed return

this summer. Ifaction is not taken to reduce the seed bank now, growers could be

building up manyyears of problems.

 

To maintain orreduce a black-grass population, 97% control is required, says Mr

Peake, noting thatthis target is becoming increasingly hard to reach as resistance

builds withinpopulations.

 

In many cases aherbicide strategy alone wont be enough, he says. Instead

growers need to aimfor more control outside of the crop.

 

Along with a returnto the plough, stale seedbeds are no longer just a good idea

they are essentialon many farms.

 

Mr Peake says, incomparison with last year, harvest is far earlier and where crops

are already in theshed, the stubbles are greening up quickly. This widens the

window for staleseedbeds and is an opportunity that should be grasped with both

hands.

 

It doesnt negatethe need to delay drilling though, he warns. The longer you can

hold your nerve, themore flushes of black-grass you can get sprayed off, which

means less relianceon in-crop chemistry, reduced competition with the crop and

less potential seedreturn. Remember with each extra cultivation youll get even

more black-grass togerminate and greater total control.

 

Barclay CropProtections Pat Crean agrees. Wherever possible growers should

give serious thoughtto delaying drilling, using this window to apply a total herbicide.

This, he says, willdeliver much better levels of control, improve resistance

managementstrategies and place pre-em applications into a time slot when there is

often morefavourable conditions.

 

As a non-selectiveherbicide, Gallup (glyphosate) will not only reduce overall weed

numbers but, moreimportantly, reduce resistant populations.

Thatwill make black-grass control within the coming crop much, much easier.

 

Fully loadedformulations of glyphosate, such as Gallup, need no extra wetters or

other additives,says Mr Crean, but he suggests growers should opt for a water

conditioner in hardwater areas.

 

In many areas, pHlevels of water are above 7, however glyphosate works better in

slightly acidicwater, he explains. Its to do with the way glyphosate binds with

cations in water;adding a water conditioner to the spray tank before the glyphosate

binds-up the roguecations, rather than allowing them to lock-up the glyphosate.

 

According to RichardPeake, application timing is crucial. He suggests growers apply

the final glyphosatetreatment two days prior to drilling or, as a last resort tank-mix

glyphosate with thepre-em but be careful to place seed at a good depth and get a

true pre-em timing,he warns.

 

If the gap betweenpre-drilling glyphosate and drilling is too big black-grass can

germinate and growon. Often only the width of a human hair and less than half an

inch tall, theseblack-grass plants are hard to spot. Nevertheless they can be

effectivelytransplanted by cultivations or drilling.

 

By the time thepre-em is on, transplanted black-grass is a hundred times harder to

kill their rootsand shoots could be beyond the zone affected by the active

ingredients bypost-emergence this black-grass is likely to be a big and robust

plant and almostimpossible to kill.

 

Finally Mr Peake iskeen to point out that high populations of black-grass can easily

overwhelm herbicideprogrammes. Youve got to make the most of opportunities to

eliminateplants before the crop is in the ground, he says.


  • Written by: Farmers Guide
  • Posted:
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