The weediest stubbles for many years, courtesy of few, if any, windows for cultural or chemical control make early spring cereal management vital this season.
Spring cereals are an excellent rotational aid to managing difficult weeds like black-grass, rye-grass and bromes as well as annual meadow grass, wild oats and a range of broad-leaves.
But much of their value here lies in the extra opportunities they offer for effective weed control over the winter; opportunities that have been sadly lacking in the wettest early winter in living memory for many.
Competitive
Although spring oats and barleys can be highly competitive once growing strongly, along with spring wheats they are acutely vulnerable to competition during establishment particularly where cold, wet ground and less-than-ideal seedbeds restrict early crop growth.
Performance
Darren Adkins, technical manager at Bayer, says early weed competition seriously compromises the performance of spring cereals with their short growing season and limited ability to compensate.
"At the same time, large numbers of seed heads/weed and a heavy seed return in more open crops will undermine the whole rotational value of spring cropping."
He adds: "On top of a lot more ground to sow this spring, we have very well-entrenched weeds in most stubbles and in some decidedly thin cover crops. Black-grass revels in the wet, and the mild conditions have meant it has continued to germinate and grow strongly through to the new year. The earlier germinators are especially well-established with seven or eight tillers apiece.
"We fail to deal with these effectively ahead of sowing and give our spring cereals the best possible chance to grow away from the challenge of continued weed germination at our peril."
Patience
Under these circumstances, Mr Adkins recommends a robust dose of the most active glyphosate as soon as the ground is fit to travel this spring.
He says patience is essential to give the treatment enough time to work, and to ensure the soil is fit enough for a decent seedbed, good pre-em activity and rapid early crop growth before drilling.
Moving as little soil as possible at drilling - together with high enough seed rates and sufficient attention to early crop nutrition and plant growth regulation - is also crucial.
"Glyphosate uptake and performance is markedly reduced under cool conditions, and there have been serious questions over the performance of some glyphosates following the withdrawal of tallow amine formulations," Mr Adkins says.
"Make sure you use a modern Roundup formulation proven to get more glyphosate into plants more rapidly and reliably at low temperatures; and use it at the right rate for the job.
"For established, young black-grass 720g/hectare of glyphosate should be sufficient. However, 1,080g/ha may be required for particularly thick and well-tillered grass-weeds, with tough perennials needing even higher rates, often up to 1,800g/ha.
"Water conditioners can improve performance in hard water areas. But remember that no amount of adjuvant can make up for insufficient glyphosate. And whatever you do, do not rush your stubble applications. Take as much time and care as you would with any pre-em because you do not have a second chance to get it right."
Getting the right conditions
Soil conditions are far more important than calendar date in spring cereal drilling, in Mr Adkins' experience.
He says the worst thing is drilling into a cold, wet seedbeds that are too rough for much in the way of pre-em activity.
The fact that spring barley and oats can be sown into April means that most growers should have plenty of time to sow into seedbeds that are fine and warm enough for the best establishment and residual weed control.
"Moving as little soil as you can at drilling will wake up the least amount of weed seed," he adds. "If you need to cultivate, top-down working will be best for most soils so you don't bring-up clods and I'd work as shallow as 5cm wherever possible. This should help ensure seedbeds that give the best activity from your Liberator pre-em.
"Where you have gone in early with your pre-planting treatment and held-off on the drilling we have found including an approved glyphosate with the pre-em works wonders too. Even when we couldn't see any emerged black-grass in the seedbed, including Roundup with the Liberator made a staggering difference to the control we achieved."
Mr Adkins says: "If the seedbed is a bit cloddy and soil temperatures are rising rapidly it is all too easy for grass-weeds to have emerged and be beyond residual control before they are immediately visible. Of course, the glyphosate must be on before there is any chance of crop emergence."
Tops tips for managing overwintered stubble
- Apply a robust dose of glyphosate as soon as the ground is fit to travel
- Tailor the rate to weed type, size and pressure
- Give the treatment enough time to work
- Move as little soil as possible at drilling so not to disturb weed seeds
- Use a modern formulation to get glyphosate into plants more rapidly and reliably at low temperatures
- Do not rush stubble applications - take as much time and care as you would with any pre-em
- Where pre-planting treatments were applied early, including an approved glyphosate with the pre-em can boost control
Source: Darren Adkins
