Autumn cover crop/spring wheat sequence offers new approach to managing black-grass

Article taken from the Agronomist & Arable Farmer Summer 2015

To succeed, any development must be innovative and practical.  It’s an ethos that underpins all Agrovista’s research and development, including Project Lamport, which in its second year has already produced dramatic results.

A key feature of this project is the integration of autumn-drilled cover crops followed by spring wheat, a technique that has shown great promise in trials and that is now making a mark on farm.

The principles are straightforward.  Spring cropping offers the most potential when it comes to non-chemical black-grass control, (in the future, it may be the only way to maintain profitable rotations) but establishing crops at this time can be fraught with problems on heavy soils.

Black oats

To overcome this, a blend of black oats (Avena strigosa) and vetch and/or berseem clover is sown after harvest.  This system demands the correct selection of not just species but variety choice – be aware that they are far from being equal.  The key role of this cover crop is to draw moisture out of the soil over winter.  This dries the soil at depth and improves soil structure and biology significantly, enabling a spring crop to be established successfully at the optimum time.

This unique cover crop mixture isn’t there to smother out black-grass – quite the opposite.  Its high, late autumn biomass production allows for a low seed rate, which gives an open structure during the maximum germination period of the weed.  Control comes in the spring when the cover crop and black-grass mixture is destroyed with glyphosate.

This is carried out using a split does of glyphosate plus Companion Gold.  The first spray is applied two weeks ahead of the planned drilling date of the spring crop.  This initiates the destruction of the cover crop, opening it up ready for the second spray – applied a few days before drilling to target black-grass at the base of the cover.

Crop establishment must be carried out with a drill which minimises soil disturbance.  Attempts to incorporate the cover crop or create a deep seed-bed must be avoided as this will encourage a flush of black-grass and/or pull up wet soil.

An additional factor is that maintaining cover crop residue keeps the upper soil damp, which helps minimise soil disturbance between the rows and reduces black-grass germination.  After successful demonstration and dramatic results in 2014, a significant number of growers nationally are trying the technique this season and we expect more uptake this summer.

The heavy-land site at Lamport contained a background infestation of over 500 heads/m² of highly resistant black-grass.  The cover crop was combi-grilled at 25kg/ha on 3rd September.  It was sprayed twice with glyphosate in March before drilling and KWS Willow.  The resulting crop was almost free of black-grass with only two heads/m², despite a limited herbicide programme, and yielded 8.6t/ha.

A similarly managed plot of spring wheat direct-drilled after a traditional overwintered stale seed-bed that had been sprayed four times with glyphosate still contained a moderate infestation of black-grass.

Conventional control in autumn-drilled winter wheat using two glyphosate sprays applied pre-drilling and very robust stacked pre- and post-emergence herbicide applications ranged from 45% in 2012 to 95% last season, falling well below the 98% needed to reduce the seed bank.

Project Lamport

- Fourteen different rotational systems set within a high indigenous black-grass population.
- Incorporates winter and spring cropping, autumn cover crops/spring wheat rotations, traditional fallows, hybrid rye for AD plants, winter wheat/OSR rotation and later drilling of winter wheat.
- All rotations will end up in winter wheat in the final year.
- Success will be based on both on final black-grass control and economic return.

 

04 June 2015

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