The value of a black oat/spring wheat sequence in controlling resistant black-grass has been highlighted for a second consecutive year in Agrovista trials in Northamptonshire
Project Lamport, a five-year rotational project conducted in partnership with Bayer, was set up to develop new ways of controlling black-grass on heavy land. The latest results confirm that a cover crop of the black oat Avena strigosa sown in late summer followed by spring wheat offers excellent control while maintaining a profitable combinable crop rotation, says Agrovista's national trials coordinator, Niall Atkinson.
In 2013-14 this approach plus a limited spring herbicide programme left less than two black-grass heads/sq m in the spring wheat crop, compared with a background level of 2,000 heads/sq m in untreated winter wheat. In 2014-15 exactly the same result was achieved with the same sequence on the same plot.
"Year one seemed too good to be true," says Mr Atkinson. "I really didn't expect to see the same result in the following season, and the fact that yields went up was even better." In 2013-14 the spring wheat after cover crop yielded 8.6t/ha, and the following year 9.7t/ha. This compared with 12.1t/ha and 7.8t/ha respectively in conventionally treated winter wheat, reflecting a sharp increase in black-grass heads from 55 to 274/sq m in those plots.
"We know spring drilling offers the most potential when it comes to non-chemical black-grass control, offering an average of 88% control in trials carried out over differing seasons' says Mr Atkinson.”But it is challenging to establish spring crops on heavy land, so the trick is to find out how we can do this consistently — that's where the cover crop comes in."
The key role of the black oats is to draw moisture out of the soil. This dries the soil at depth and improves soil structure, enabling a spring crop to be established successfully at the optimum time with little soil disturbance, minimising further black-grass germination.
The cover crop is not there to smother out black-grass — just the opposite, Mr Atkinson explains. Its open structure in the autumn helps maximise germination of the weed to help exhaust the seed bank — control occurs in the spring when the cover crop and black-grass mix is destroyed with glyphosate.
"This black oat/spring wheat sequence looks as though it is going to stack up agronomically and financially?' says Mr Atkinson. ”It is starting to look so much more profitable than a traditional autumn-sown rotation treated with conventional chemistry."