Article taken from the Tillage Autumn 2014
Growing an autumn-sown cover crop followed by a spring cereal has emerged as a great tactic for combating herbicide resistant blackgrass in the first year of a five-year rotational trial run by Agrovista and Bayer CropScience on a heavy land site at Lamport in Northamptonshire.
The Project Lamport site has a background infestation of over 500 heads/sq m of highly resistant blackgrass, but spring-sown wheat drilled after an autumn-sown cover crop was almost free of the weed, despite a limited herbicide programme.
The cover crop – a blend of black oats (65%) and purple vetch (35%) called Chlorofiltre 26 – was combi-drilled at 25kg/ha on 3 September and sprayed twice with glyphosate in March before spring wheat was drilled. The latter received only low doses of pendimethalin, flufenacet and DFF as per label recommendations.
A similarly managed plot of spring wheat sown after a traditional overwintered stale seed-bed had been sprayed four times with glyphosate still contained a moderate infestation of blackgrass, says Agrovista technical manager Mark Hemmant.
£150/ha herbicide programme
“Growers are asking if we are going to see £150/ha blackgrass programmes in winter wheat. The answer is yes. But can we guarantee they will work? No, we can’t. We can’t rely on chemicals any more to control blackgrass in winter wheat, so we have to do something different in the rotation.”
Key to the marked difference in blackgrass control was the cover crop residue’s retention of moisture in the soil surface.
“Even though the [spring] crop was direct drilled, the soil after fallowing was dry enough to shatter between the rows, which was enough to stimulate blackgrass to germinate. The last thing we want is to create a seed-bed for blackgrass in the spring = its where a lot of people go wrong,” says Mr Hemmant.
“We know spring cropping offers the most potential when it comes to non-chemical methods – Rothamsted Research literature shows it provides a mean of 88% control. However, establishment is challenging on heavy soils.”
Cover crops help by drying heavy soils at depth and providing soil structure benefits to allow direct drilling.
Growing an autumn-sown cover crop followed by a spring cereal has emerged as a great tactic for combating herbicide resistant blackgrass in the first year of a five-year rotational trial run by Agrovista and Bayer CropScience on a heavy land site at Lamport in Northamptonshire.
The Project Lamport site has a background infestation of over 500 heads/sq m of highly resistant blackgrass, but spring-sown wheat drilled after an autumn-sown cover crop was almost free of the weed, despite a limited herbicide programme.
The cover crop – a blend of black oats (65%) and purple vetch (35%) called Chlorofiltre 26 – was combi-drilled at 25kg/ha on 3 September and sprayed twice with glyphosate in March before spring wheat was drilled. The latter received only low doses of pendimethalin, flufenacet and DFF as per label recommendations.
A similarly managed plot of spring wheat sown after a traditional overwintered stale seed-bed had been sprayed four times with glyphosate still contained a moderate infestation of blackgrass, says Agrovista technical manager Mark Hemmant.
£150/ha herbicide programme
“Growers are asking if we are going to see £150/ha blackgrass programmes in winter wheat. The answer is yes. But can we guarantee they will work? No, we can’t. We can’t rely on chemicals any more to control blackgrass in winter wheat, so we have to do something different in the rotation.”
Key to the marked difference in blackgrass control was the cover crop residue’s retention of moisture in the soil surface.
“Even though the [spring] crop was direct drilled, the soil after fallowing was dry enough to shatter between the rows, which was enough to stimulate blackgrass to germinate. The last thing we want is to create a seed-bed for blackgrass in the spring = its where a lot of people go wrong,” says Mr Hemmant.
“We know spring cropping offers the most potential when it comes to non-chemical methods – Rothamsted Research literature shows it provides a mean of 88% control. However, establishment is challenging on heavy soils.”
Cover crops help by drying heavy soils at depth and providing soil structure benefits to allow direct drilling.