Blackgrass control is key cover crops target

Article taken from the Tillage Magazine

Agrovista’s Chris Martin believes the key to using cover crops effectively is to choose the most appropriate mix for the specific purpose, be it soil conditioning, nutrient trapping, fumigation to tackle soil pests, or weed suppression.

“There’s certainly no one mix available which suits all needs,” he stresses.

“We’re looking at a wide range of cover crops to satisfy each and all of these purposes throughout the UK, but I think our most innovative work is where we are using specific covers to help control resistant blackgrass and ryegrass.”

Theory suggests that a black oat and vetch mix should provide several benefits, he says.

“Firstly we’re looking to condition and dry out the soil to introduce drilling windows after the peak blackgrass germination period.”

This should allow autumn crops to be sown later or enable spring crops to be sown on heavy land where neither activity would usually be possible, he explains.

Encourage germination

“The idea is to encourage as much blackgrass to germinate amongst the cover crop as possible.”

Mr Martin points out that the approach differs from others where cover crops are intended to compete with or smother blackgrass, and it has given promising results.

“In establishing the cover crop we employ vigorous cultivation to encourage blackgrass germination.  Everyone knows that the biggest blackgrass flush occurs when we put the drill in the field regardless of stale seedbeds.

“The black oat and vetch mix is also slow to colonise the ground which allows a good blackgrass flush.

“Once the cover crop is established, its massive root structure allows further light cultivation, using a straw rake for example, to encourage a further blackgrass strike.”

Before drilling the late autumn or spring crop, a split glyphosate application is employed.  The first destroys the cover crop, and the second, ten days later, ensures that any shaded blackgrass is killed, he explains.

Direct drill

“We then drill straight into the cover crop using a disc coulter drill with as little disturbance of the soil as possible to avoid setting off another flush of blackgrass.

“We’ve successfully used several drills to achieve this including direct drills such as the Great Plains Spartan and the Moore Uni.  We’re also working this season with strip till drills such as the Claydon.

“We’re also trying cultivator drills, such as the Vaderstad Rapid, getting lower soil disturbance by lifting the cultivation elements out of the ground, and using just the disc coulters.

“Last year’s results demonstrated a dramatic reduction in blackgrass numbers in the following crop without herbicides.”

Spring wheat plots after fallowing and several stale seedbeds throughout the autumn and winter ended up with 55 blackgrass heads/sq m at harvest, he notes.

“This was still a great reduction on the neighbouring winter wheat plots which despite having received and extremely robust herbicide programme often still had several hundred blackgrass heads per square metre at harvest.

“However, the spring wheat following the black oat and vetch cover crop had less than two blackgrass heads per square metre at harvest and yielded an impressive 8.6t.ha.”

Table A – Cover Crop Performance

Crop

Fresh

weight t/ha

Dry

Weight t/ha

%N

Total N

Kg/ha

Oil Radish

24.7

2.7

4.13

115

Winter Turnip Rape

19.5

2.8

3.1

88

Mustard

16.7

2.3

3.1

72

Vetch/rye

19.5

2.2

2.7

60

Kings Vitality mix

22.1

2.6

2.5

67

Kings Structure mix

20.6

3.5

2.0

72

Source: Kings trial Autumn 2014 Essex –

Above ground harvest 18th December

 

Table B – Impact on blackgrass population

Crop

Fresh

Weight t/ha

DM

t/ha

%N

Nitrogen

kg/ha

Potash

kg/ha

Blackgrass

Plants/sq m

Siletina Radish

39.8

4.93

4.6

227

204

4

Defender Radish

31.5

3.02

4.8

147

171

0

Mustard

33.6

6.72

3.52

236

212

103

Winter Turnip Rape

26.9

3.55

3.35

119

163

0

Strigosa Oat

11.4

2.34

2.84

66

62

202

Bare land

4.7

1.45

2.44

35

23

268

Wheat

6.6

1.63

2.9

47

38

504

Source: Kings 3D site, Alford, Lincs 15th January

 
Cover crop establishment best practice

-
Sow as soon as possible after harvest
- Use minimal cultivations
- Direct drilling is ideal
- Consider seed-bed starter fertiliser
- Monitor slugs and flea beetles
- Use high seed rates
- Aim to maximise crop biomass
 

 

08 June 2015

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