Cereals growers across the country should take advantage of the single best out-of-crop black-grass control opportunity for at least five years by ensuring the most effective stale seedbed or stubble treatment this autumn, advises Bob Mills of Frontier Agriculture.
"Like 2003, black-grass seed dormancy levels are particularly low," he points out. "Indeed, standard Rothamsted testing of black-grass seed samples from 22 UK sites shows fully 59% germinating after two weeks - the highest level recorded since 2001. Unlike 2003, though, most soils now have sufficient moisture in their upper layers to ensure good, rapid germination in the field.
"So we have the ideal opportunity to hit black-grass populations hard to help take the pressure off in-crop herbicides and combat the seemingly inexorable rise of resistance. Our trials and experience show that well-managed stale seedbed programmes can reduce the weed seed burden by 50% or more, making them well-worth the effort; especially when conditions are as favourable as they quite clearly are this season."
Bob Mills stresses that stale seedbeds are particularly effective when used with minimum tillage regimes which keep annual grass weed seeds in the germination zone near the soil surface and preserve soil moisture. But he insists they are equally valuable with land that's been ploughed and pressed to stimulate the germination of any weed seed not buried to a sufficient depth as well as viable seed from previous years ploughed back to the surface.
In both cases, he advocates cultivating as soon after harvesting as possible and consolidating the ground well to conserve the moisture and achieve sufficient soil/seed contact.
"Get it right and you should see a strong initial black-grass flush in 10-15 days this season," he notes. "Volunteer seedlings will also green-up nicely. At which stage I recommend spraying them off with 1.2 litres/ha of Roundup Gold. Its modern formulation gives far more margin for error than a standard 360 glyphosate, especially where it rains soon after application or conditions are otherwise less than ideal. What's more you'll be able to cultivate and drill as little as 6 hours after spraying.
"Alternatively, if you're ploughing and cultivating immediately ahead of the drill and want to control annuals and volunteers, spray off the stubble with a similar rate of Roundup Gold ahead of your final seedbed cultivation.
"A lot of people are content with a single stale seedbed and spray, but it will pay anyone with a particularly difficult black-grass problem to get in two or even three glyphosate treatment cycles this year," Bob Mills adds. "Where black-grass populations are high the first flush of weed growth seems to inhibit further germination, so you'll get a worthwhile second flush if you're prepared to wait another two weeks.
"Yes, it will involve a delay to sowing, but in my opinion no one should be considering early drilling fields with black-grass problems these days. If you've got target site resistance, in particular, you're going to need all the out-of-crop weed control help you can get.
"Controlling bad black-grass in-crop can easily cost you the equivalent of a tonne of wheat. Either that or cost you at least that tonne for failing to control it. This has to put a major question-mark over the value of bringing forward your drilling by a couple of weeks."