Arable News

  • Written by: Farmers Guide
  • Posted:

Don’t overlook stale seedbed opportunities

The relatively narrow window between harvest and drilling may tempt many to overlook cultural grass weed control methods

The relatively narrow window between harvest and drilling may tempt many to overlook cultural grass weed control methods such as stale seedbeds and instead place over-reliance on already stretched chemical options, but doing so will store up future problems, growers are warned.Hutchinsons’ technical manager Dick Neale (left) urges growers to fundamentally change their approach to grass weed control, particularly for black-grass. “If we blindly drill from mid-September onwards, we could be in a real mess next year,” he comments.Black-grass is also spreading to areas where it previously was not an issue, such as Scotland, and the efficacy of the main chemical option – Atlantis (mesosulfuron + iodosulfuron) – is falling as more cases of enhanced metabolism resistance (EMR) occur where growers have over-relied on the chemistry in the past, he says.”But at least with EMR resistance, if we can take the chemistry out of the system for three or four years, there is a good chance it may work well again when brought back in as part of a sustainable grass weed control strategy.”Maximise cultural options
Where black-grass is a major problem, he suggests growers should aim to get at least three or four stale seedbeds in between harvest and drilling. “If this means you have to drill a bit later, then so be it. Maybe you will lose some yield from later drilling, but that’s got to be better in the longer-term than drilling early and getting the same, or worse, yield penalty from a field that’s full of black-grass – and spending 120/ha trying to control it, but failing.”Trials at Hutchinsons’ National Black-grass Centre of Excellence near Brampton, Cambridgeshire, show that shallow cultivations immediately behind the combine to a depth of no more than 50mm work best to encourage black-grass germination in a stale seedbed. Growers should ensure all soil is cultivated and include a second angled pass where machines with wide tine spacing (eg pigtail tines) are used. Land should then be rolled once, and maybe twice, to conserve soil moisture and encourage black-grass germination.Hutchinsons’ trials at its National Black-grass Centre of Excellence, Brampton, in June“The key then is to never let black-grass get too big before you spray it off,” he advises. “Never let it get bigger than two leaves as this prevents the build-up of root exudates in the soil which can stop the germination of further black-grass seed.”For spraying off stale seedbeds he recommends 360g ai/ha of glyphosate plus adjuvant, or alternatively 1-litre/ha glufosinate-ammonium. “It is more expensive, but we can’t expose black-grass to multiple doses of glyphosate without potentially adding to resistance pressure in the long-term. The benefits outweigh any extra cost.”Ploughing may be an option in some instances, especially where there is likely to be a large amount of black-grass seed returned to the stubble post-harvest. “In these cases, ploughing is a worthwhile ‘clean start’ option, but as a long-term strategy it can be flawed as you end up ploughing-up problems again next year.”Spring cropping is no silver bullet
Spring cropping problem fields is often seen as an answer to alleviating black-grass pressure, but in many cases growers are left disappointed, Dick says. “Spring cropping gives you extra management time, but unless you make the most of that time by getting in as many stale seedbeds as possible you are simply delaying problems until spring. As soon as you disturb the soil in spring, black-grass will germinate and in many cases it can then be harder to control.”In addition, much of the worst black-grass is on heavy land which does not lend itself to spring cropping, adds Midlands Cropwise agronomist Andrew Wright. “If you were going down the spring cropping route it would mean having to get a stale seedbed in February or March, which you just can’t do on a lot of land. “Even for autumn sowing in this area [Leicestershire] you can happily drill until early or mid-October, but you wouldn’t really want to leave it any later than that.”
While herbicide resistance is not a major issue in his area, he believes black-grass is generally becoming more prevalent and is getting harder to control on both heavy and light land. “It’s emerging all year round now, so whenever you move soil you’re likely to get a flush of black-grass. It’s no longer confined to that relatively brief flush 12 days after drilling to the 12 weeks after autumn drilling.”An added dimension to black-grass control this year is the amount of fallow ground following the failure of 50 per cent of oilseed rape crops in his region, Mr Wright notes. “People are treating this fallow land as a stale seedbed ahead of getting crops in by mid-September. But if that’s the case you’ve got to manage the stale seedbeds correctly between now and drilling to get at least three kills of black-grass or more if possible.”


  • Written by: Farmers Guide
  • Posted:
Prev Story:Cultivations costedNext Story:Don’t tolerate rats