Article taken from the Pro Operator Autumn 2014
As the blackgrass menace spreads and the cost of controlling it spirals, wheat growers need to ensure they are eking out the best possible performance from their herbicide programme.
“When Atlantis worked no-one took too much notice of the difference good application techniques could make.
“Now people are starting to pay a lot more attention, to get the best out of the pre-ems. In our trials, control ranged from 10% to 95% + simply by changing the application – everything else stayed the same,” says Mark Hemmant, Agrovsita technical manager.
The trials examined the effect of nozzle choice, water volume, spray pressure, adjuvant choice and boom height on blackgrass control. All trials (apart from the last) used a boom height of 50cm. The chemistry comprised Trooper at 2 litres/ha and Herold at 0.3 litres/ha, putting down 240g of flufenacet, 60g DFF and 600g of pendimethalin/ha.
Air inclusion nozzles
Air-inclusion nozzles struggled throughout the trials, especially at 3-star LERAP settings, which were included to show the effect should such restrictions be imposed on blackgrass pre-ems.
Blue03 GuardianAir nozzles, angled forward and backwards alternately along the boom, were tested at 1.5 bar and 10km/hr to deliver 100 litres/ha. “This produced the worst result of the whole trial,” says Mr Hemmant. “Control was around 10% - 15% at best.”
Doubling the pressure to 3 bar, more in line with on-farm practice, had some benefit. “This increased the number of droplets, improving soil coverage. There was more drift due to the higher speed of 14.5km/hr needed to maintain the 100 litres/ha spray volume, but control did improve, rising to about 60%,” he adds.
The effect of drift became more apparent when pressure was raised to 4 bar and speed to 16km/hr. “Control started to fall away – the droplet spectrum was too fine and turbulence was also increased, so fewer drops reached the target,” he explains.
Adding Remix, a parafinnic oil made up of long-chain molecules designed to reduce spray drift, had a dramatic effect when added to the sprayer tank.
“It transformed the control, boosting it to about 85%,” explains Mr Hemmant. “Remix improves the spray pattern giving a more even distribution of herbicide onto the soil, exactly as it is designed to do. “Its long-chain molecules also help to bind the herbicide active to clay and organic matter, keeping it in the surface layer for longer.”
The final air inclusion test used brown 05 nozzles to deliver 200 litres/ha at the 3-star rated application (1.5 bar, 8.5km/hr). “Control was much better than the 03s at 100 litres/ha but still not very pretty.” Increasing the pressure had little effect on efficacy,” he adds.
Flat fans
Flat fans gave much better results Even the basic set-up of red CP 80-04 nozzles at 200 litres/ha (3bar/10km/hr) angled straight down outperformed any of the air inclusion nozzles in the trial, producing around 75% control, notes Mr Hemmant.
Halving the water volume using VP08-03 blue nozzles reduced control by at least 20%, despite angling nozzles alternately forward 30° and straight down to minimise shadowing of the spray by clods, he says. “We used the same pressure but speed rose to over 14km/hr. 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 30° forward and the back line set vertical.
“This ended up doubling the volume to 200 litres/ha but sprayed lots more droplets,” explains Mr Hemmant. “In this trial we probably got over 90% control. And, because of the higher speed, we also increased workrate significantly compared with the red nozzles.
“We then took this a stage further and applied 300 litres/ha by pulling the speed down from 14km/hr to around 10km/hr. This result was incredible – the combination of extra water volume and the large number of droplets optimised seedbed coverage, and we achieved almost 100% control from a pre-em only.
“Compare that with the control achieved with the air inclusion nozzles. The only difference is the application – and you don’t have to pay much to achieve it.”
Boom height
Boom height also has a critical effect on herbicide performance, especially when used without an adjuvant to help reduce drift.
The trials used Liberator at 0.6 litres/ha, plus or minus adjuvant, using a single line of vertical CP 80-03 nozzles applying 150 litres/ha (3 bar/10km/hr).
Liberator alone applied 1m above the soil gave very poor control (20%), notes Mr Hemmant. Its performance was ‘hugely improved’ at the correct boom height of 50cm, due to reduced drift. The effect was less clear where a good adjuvant was used. Remix stood out at the 1m boom height, boosting control to 90%. It also gave a significant benefit at 50cm. Two other commercial adjuvants had little effect in this trial used at either height.
“Some modern sprayer booms may not get as low as 50cm. If that’s the case, I’d recommend using 80° flat fans, twin lines and adding Remix to ensure the best result,” says Mr Hemmant.
Key finding
As the blackgrass menace spreads and the cost of controlling it spirals, wheat growers need to ensure they are eking out the best possible performance from their herbicide programme.
“When Atlantis worked no-one took too much notice of the difference good application techniques could make.
“Now people are starting to pay a lot more attention, to get the best out of the pre-ems. In our trials, control ranged from 10% to 95% + simply by changing the application – everything else stayed the same,” says Mark Hemmant, Agrovsita technical manager.
The trials examined the effect of nozzle choice, water volume, spray pressure, adjuvant choice and boom height on blackgrass control. All trials (apart from the last) used a boom height of 50cm. The chemistry comprised Trooper at 2 litres/ha and Herold at 0.3 litres/ha, putting down 240g of flufenacet, 60g DFF and 600g of pendimethalin/ha.
Air inclusion nozzles
Air-inclusion nozzles struggled throughout the trials, especially at 3-star LERAP settings, which were included to show the effect should such restrictions be imposed on blackgrass pre-ems.
Blue03 GuardianAir nozzles, angled forward and backwards alternately along the boom, were tested at 1.5 bar and 10km/hr to deliver 100 litres/ha. “This produced the worst result of the whole trial,” says Mr Hemmant. “Control was around 10% - 15% at best.”
Doubling the pressure to 3 bar, more in line with on-farm practice, had some benefit. “This increased the number of droplets, improving soil coverage. There was more drift due to the higher speed of 14.5km/hr needed to maintain the 100 litres/ha spray volume, but control did improve, rising to about 60%,” he adds.
The effect of drift became more apparent when pressure was raised to 4 bar and speed to 16km/hr. “Control started to fall away – the droplet spectrum was too fine and turbulence was also increased, so fewer drops reached the target,” he explains.
Adding Remix, a parafinnic oil made up of long-chain molecules designed to reduce spray drift, had a dramatic effect when added to the sprayer tank.
“It transformed the control, boosting it to about 85%,” explains Mr Hemmant. “Remix improves the spray pattern giving a more even distribution of herbicide onto the soil, exactly as it is designed to do. “Its long-chain molecules also help to bind the herbicide active to clay and organic matter, keeping it in the surface layer for longer.”
The final air inclusion test used brown 05 nozzles to deliver 200 litres/ha at the 3-star rated application (1.5 bar, 8.5km/hr). “Control was much better than the 03s at 100 litres/ha but still not very pretty.” Increasing the pressure had little effect on efficacy,” he adds.
Flat fans
Flat fans gave much better results Even the basic set-up of red CP 80-04 nozzles at 200 litres/ha (3bar/10km/hr) angled straight down outperformed any of the air inclusion nozzles in the trial, producing around 75% control, notes Mr Hemmant.
Halving the water volume using VP08-03 blue nozzles reduced control by at least 20%, despite angling nozzles alternately forward 30° and straight down to minimise shadowing of the spray by clods, he says. “We used the same pressure but speed rose to over 14km/hr. 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 30° forward and the back line set vertical.
“This ended up doubling the volume to 200 litres/ha but sprayed lots more droplets,” explains Mr Hemmant. “In this trial we probably got over 90% control. And, because of the higher speed, we also increased workrate significantly compared with the red nozzles.
“We then took this a stage further and applied 300 litres/ha by pulling the speed down from 14km/hr to around 10km/hr. This result was incredible – the combination of extra water volume and the large number of droplets optimised seedbed coverage, and we achieved almost 100% control from a pre-em only.
“Compare that with the control achieved with the air inclusion nozzles. The only difference is the application – and you don’t have to pay much to achieve it.”
Boom height
Boom height also has a critical effect on herbicide performance, especially when used without an adjuvant to help reduce drift.
The trials used Liberator at 0.6 litres/ha, plus or minus adjuvant, using a single line of vertical CP 80-03 nozzles applying 150 litres/ha (3 bar/10km/hr).
Liberator alone applied 1m above the soil gave very poor control (20%), notes Mr Hemmant. Its performance was ‘hugely improved’ at the correct boom height of 50cm, due to reduced drift. The effect was less clear where a good adjuvant was used. Remix stood out at the 1m boom height, boosting control to 90%. It also gave a significant benefit at 50cm. Two other commercial adjuvants had little effect in this trial used at either height.
“Some modern sprayer booms may not get as low as 50cm. If that’s the case, I’d recommend using 80° flat fans, twin lines and adding Remix to ensure the best result,” says Mr Hemmant.
Key finding
300 litres/ha better than 200 better than 100 litres/ha
VP80 better than air inclusion
Twin line better than single
3* rated nozzles setting = poor efficacy