Article taken from the CPM
Application technique can have a huge effect on the performance of pre-emergence herbicides, according to the latest results from Agrovista trials carried out on a heavily infested blackgrass site at Lamport in Northants.
“In our trials, control ranged from 10% to 95%+ simply by changing the application – everything else stayed the same,” reports technical Manager Mark Hemmant.
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 consisted of Trooper (flufenacet + pendimethalin) at 2 l/ha and Herold (diflufenican + flufenacet) at 0.3 l/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.
Blue 03s Guardian Air nozzles, angled forward and backwards alternately along the boom, were tested at 1.5bar and 10km/ha to deliver 100 l/ha. “This produced the worst result of the whole trial,” says Mark Hemmant. “Control was around 10-15% at best.
Doubling the pressure to 3 bar, more in line with on-farm practice, increased control to about 60%, but drift also rose. But adding Remix, a parafinnic oil designed to reduce spray drift, had a dramatic effect when added to the sprayer tank.
Flat fans
Flat fan nozzles gave much better results, with even the basic set-up of red VP 80-04 nozzles at 200 l/ha (3 bar/10km/h) angled straight down outperforming any of the air-inclusion nozzles in the trial, with around 75% control notes Mark Hemmant.
Halving the water volume using VP 80-03 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/h. Going faster with the finer spray inevitable 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° and the back line set vertical.
“This ended up doubling the volume to 200 l/ha but sprayed lots more droplets,” explains Mark Hemmant. “In this trial we probably achieved over 90% control. And, because of the higher speed, we also increased work rate significantly compared with the red nozzles.
“We then took this a stage further and applied 300 l/ha by pulling the speed down from 14km/h to around 10km/h. 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% control from a pre-em only.”
Boom height
Liberator alone applied 1m above the soil gave very poor control (20%), notes Mark Hemmant, but the herbicide performance was “hugely improved” at the correct boom height of 50cm, entirely due to reduced drift.
Adding Remix boosted control to 90% and also gave a significant benefit at 50cm. “Where you can’t keep the boom as low as 50cm, I’d recommend using 80° flat fans, twin lines and adding Remix to ensure the best result,” he says.
Application technique can have a huge effect on the performance of pre-emergence herbicides, according to the latest results from Agrovista trials carried out on a heavily infested blackgrass site at Lamport in Northants.
“In our trials, control ranged from 10% to 95%+ simply by changing the application – everything else stayed the same,” reports technical Manager Mark Hemmant.
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 consisted of Trooper (flufenacet + pendimethalin) at 2 l/ha and Herold (diflufenican + flufenacet) at 0.3 l/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.
Blue 03s Guardian Air nozzles, angled forward and backwards alternately along the boom, were tested at 1.5bar and 10km/ha to deliver 100 l/ha. “This produced the worst result of the whole trial,” says Mark Hemmant. “Control was around 10-15% at best.
Doubling the pressure to 3 bar, more in line with on-farm practice, increased control to about 60%, but drift also rose. But adding Remix, a parafinnic oil designed to reduce spray drift, had a dramatic effect when added to the sprayer tank.
Flat fans
Flat fan nozzles gave much better results, with even the basic set-up of red VP 80-04 nozzles at 200 l/ha (3 bar/10km/h) angled straight down outperforming any of the air-inclusion nozzles in the trial, with around 75% control notes Mark Hemmant.
Halving the water volume using VP 80-03 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/h. Going faster with the finer spray inevitable 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° and the back line set vertical.
“This ended up doubling the volume to 200 l/ha but sprayed lots more droplets,” explains Mark Hemmant. “In this trial we probably achieved over 90% control. And, because of the higher speed, we also increased work rate significantly compared with the red nozzles.
“We then took this a stage further and applied 300 l/ha by pulling the speed down from 14km/h to around 10km/h. 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% control from a pre-em only.”
Boom height
Liberator alone applied 1m above the soil gave very poor control (20%), notes Mark Hemmant, but the herbicide performance was “hugely improved” at the correct boom height of 50cm, entirely due to reduced drift.
Adding Remix boosted control to 90% and also gave a significant benefit at 50cm. “Where you can’t keep the boom as low as 50cm, I’d recommend using 80° flat fans, twin lines and adding Remix to ensure the best result,” he says.