Blackgrass Management – Tips4 September 2023
With blackgrass levels soaring this summer after early drilling, ProCam agronomist Gary Webster says it is now crunch time to employ all available techniques to bring numbers back down.
Mr Webster said: “Last season presented a perfect storm. Little control was achieved in stale seedbeds. Crops were drilled early. Then, with the wet March and April, blackgrass just tillered and tillered. With high levels of blackgrass seed shed, even 95% control will leave a lot behind.
“New herbicide chemistry is available, but there is no silver bullet, so we need to get every little step right from day one.”
In response Mr Webster highlighted a five-point plan for the season ahead:
1. Admit you have a blackgrass problem and have a clear control policy
Because so many arable operations can impact on blackgrass survival, you have to get everyone on the farm bought in to a policy of controlling it, said Mr Webster. “Get everyone to agree: we are going to defeat it,” he urged.
2. Re-examine your rotation
This may not just be a question of deciding whether to grow a winter break crop as a way of tackling blackgrass, you may need to consider two-year spring cropping.
3. Delay drilling
The later that drilling can be delayed, the better – for example from mid-October onwards – but adapt your farm practices accordingly, Mr Webster advised.
“If drilling later, get a contractor to help, so you can get drilled up in the shorter window. It might cost you more, but the payback will come when you have got grass weeds under control. You also need faster-developing varieties to compensate for later drilling, and higher seed rates will be needed to maintain the correct density of tillers.”
4. Pay attention to machinery
Ensure combines are properly cleaned down between fields, so blackgrass seed is not spread around the farm, and avoid cultivations that mix weed seeds through the soil profile, Mr Webster explained.
“Residual herbicides work in the top inch or so of soil. So if you mix weed seeds through the soil profile, those that germinate from deeper will grow through the herbicide layer unaffected. If you have really high blackgrass seed shed this season, you may need to plough them down.”
5. Use herbicides correctly
It is not only a case of choosing the correct herbicides, said Mr Webster, it is important when and how they are applied.
“Warm soils last autumn meant residual herbicides were being broken down in days rather than weeks. By drilling later, when there is more soil moisture and it is cooler, herbicides are taken up better and remain active for longer in the soil.
“In addition, use the correct nozzles and keep spray water volume up at 200 l/ha. This will give better soil coverage. And keep sprayer speed down to 6-12 kph. Contractors may want to go faster, but this increases spray turbulence which affects spray deposition. For similar reasons, keep boom height down to 50cm from the ground.”