ADAS tests reveal high dormancy in black-grass
26 Aug 2020
After Dr Sarah Cook, Senior Research Consultant at ADAS mentioned the dormancy tests in our Real Results Virtual Farm webinar, we wanted to be among the first to find out the results and what they mean for growers this year.
Sarah said that ADAS annual black-grass seed testing is pointing to high levels of dormancy which, in turn, is likely to lead to protracted germination this autumn.
The test is designed to break dormancy by growing seed in specific conditions over a fortnight; only 24% of the samples germinated.
“Where we’ve high dormancy, like this year, freshly shed black-grass seed could wait until late September/October before germinating,” she explains.
While the result is not unusual for black-grass, it emphasises the need to delay drilling, establish a competitive crop and optimise pre-ems. Choose a robust product like Crystal®, and apply it within 24-48 hours of drilling onto a consolidated clod-free seed.
“Looking back at 20 years of data shows high dormancy is typical for this weed; low dormancy is atypical.”
She adds that dormancy is a natural survival mechanism. “By waiting, seeds are more likely to be moved, either by animals or by cultivation, away from the established mother plant which will compete with new plants for water, light and nutrients. Germinating in late September or October also increases the chances of better growing conditions for vulnerable seedlings.
“Black-grass will eventually come up, so if you've got high weed levels, the usual advice would be to wait and drill late.”
Given what happened last year, Sarah tempers her recommendations. “Leave fields with high populations of black-grass until last, and focus attention on establishing a competitive crop.
“We’ve seen how black-grass thrives in open crops. Last year the wet autumn and winter weather hampered crop establishment. The dry spell that followed furthered black-grass’ advantage; it was well rooted and less affected by the lack of rainfall.
“After last autumn there are fields that need structural remediation, so many growers will be thinking about cultivations anyway, but I’d advise growers to consider how they are going to deal with that in relation to the black-grass seed bank.”
“Where there’s been high seed return this year, growers will probably want to keep that on the surface, encourage it to chit and spray it off. If the surface is clean, they probably don't want to bring up black-grass from deeper in the soil profile, but they may have to do so if the soil structure is broken.”
The latest research suggests buried black-grass can survive for up to nine years. On average, 30% of buried seed degrades per year.
“The most effective way to manage those populations varies considerably field to field, but a competitive crop is always good for black-grass control,” she says.
“Make a seedbed to put a crop into; aim for good surface tillage, with no clods and for a date and seed rate that will optimise emergence. A good seedbed will also optimise herbicide performance."
With resistance to existing post-emergence herbicides continuing to spread and strengthen, pre-emergence herbicides are the cornerstone of chemical control.
Choosing proven active ingredients, in an optimised formulation, is essential. Crystal® contains flufenacet and pendimethalin, widely known to be the most effect active ingredients for controlling black-grass. With contact and residual control, it consistently out-performs competitors.
As well as timely applications onto clod-free, consolidated seedbeds, product performance is optimised by applying Crystal® at the full rate (4l/ha) with 200l/ha of water. Keeping sprayer speeds low, and using low-drift nozzles that deliver fine-medium sized droplets, ensuring even coverage will further control.