Article taken from the Farmers Guide
Spray application technique can have a dramatic effect on the performance of pre-emergence black-grass herbicides in winter wheat, latest Agrovista trials show.
In a good year in the field 80 per cent or more control might be achieved, but, more often, 60 per cent is the norm and much less in a poor year, especially when seedbeds are dry, says the company. However, poor application technique can also have a huge effect on efficacy, it adds.
“To get the best results from pre-ems you want good soil coverage,” say Agrovista technical manager, Mark Hemmant. “In our trials, control ranged from 10-95+ per cent simply by changing the application – everything else stayed the same.”
Air-inclusion nozzles struggled in the trial, says Mark, with control at around 10-15 per cent at best.
Flat fans
Flat fans gave much better results with even the basic set-up of red VP 80-04 nozzles at 200 litres/ha (3 bar/10kph) angled vertically outperformed any of the air inclusion nozzles in the trial, producing around 75 per cent of control, notes Mr Hemmant.
Halving the water volume using a VP 80-03 blue nozzle compromised control by at least 20 per cent, despite angling nozzles alternately forward 30 degrees and straight down to minimise shadowing of the spray by clods, he says. “We used the same pressure but speed rose to over 14kph. Going faster with the finer spray inevitably created more drift.”
Adding another line to the sprayer using the same nozzles, pressure, and speed transformed the result. Front nozzles were inclined forward 30 degrees and the back line set vertical.
“This ended up doubling the volume to 200 litres/ha and also produced lots more droplets,” explains Mr Hemmant. “In this trial we probably got over 90 per cent control. And, because of the higher speed, we also increased work rate significantly compared with the red nozzles.
“We then applied 300 litres/ha by reducing the speed to around 10kph. This result was incredible – the combination of extra water volume and the large number of droplets optimised seed-bed coverage, and we achieved almost 100 per cent control from a pre-em only.
Boom height can also have a critical effect on herbicide performance, he acknowledge, adding that herbicide performance was “hugely improved” at the correct boom height of 50cm, entirely due to reduce drift.
Application trials details
Key Findings:
Spray application technique can have a dramatic effect on the performance of pre-emergence black-grass herbicides in winter wheat, latest Agrovista trials show.
In a good year in the field 80 per cent or more control might be achieved, but, more often, 60 per cent is the norm and much less in a poor year, especially when seedbeds are dry, says the company. However, poor application technique can also have a huge effect on efficacy, it adds.
“To get the best results from pre-ems you want good soil coverage,” say Agrovista technical manager, Mark Hemmant. “In our trials, control ranged from 10-95+ per cent simply by changing the application – everything else stayed the same.”
Air-inclusion nozzles struggled in the trial, says Mark, with control at around 10-15 per cent at best.
Flat fans
Flat fans gave much better results with even the basic set-up of red VP 80-04 nozzles at 200 litres/ha (3 bar/10kph) angled vertically outperformed any of the air inclusion nozzles in the trial, producing around 75 per cent of control, notes Mr Hemmant.
Halving the water volume using a VP 80-03 blue nozzle compromised control by at least 20 per cent, despite angling nozzles alternately forward 30 degrees and straight down to minimise shadowing of the spray by clods, he says. “We used the same pressure but speed rose to over 14kph. Going faster with the finer spray inevitably created more drift.”
Adding another line to the sprayer using the same nozzles, pressure, and speed transformed the result. Front nozzles were inclined forward 30 degrees and the back line set vertical.
“This ended up doubling the volume to 200 litres/ha and also produced lots more droplets,” explains Mr Hemmant. “In this trial we probably got over 90 per cent control. And, because of the higher speed, we also increased work rate significantly compared with the red nozzles.
“We then applied 300 litres/ha by reducing the speed to around 10kph. This result was incredible – the combination of extra water volume and the large number of droplets optimised seed-bed coverage, and we achieved almost 100 per cent control from a pre-em only.
Boom height can also have a critical effect on herbicide performance, he acknowledge, adding that herbicide performance was “hugely improved” at the correct boom height of 50cm, entirely due to reduce drift.
Application trials details
Background black-grass population – 400 heads/m²
Crop – Solstice winter wheat
Sowing date 28 September
Seedbed – dry, firm, small to medium clods
Chemistry – 240g of flufenacet, 60g DFF and 600g of pendimethalin/ha.
Applied 2 October at 50cm boom height onto a dry seedbed
No useful rainfall until week beginning 17 October
No post-emergence treatments applied
Key Findings:
300-litres/ha better than 200 better than 100
VP80 better than air inclusion
Twin line better than single
3* rated nozzles settings = poor efficacy