Agrovista trials help fine tune outputs

Article taken from Pro Operator Summer 2014

While in many cases output needs to be sacrificed for efficacy, with some products the need for timeliness favours increasing outputs, says Agrovista’s Mark Hemmant.

Agrovista has carried out a large number of replicated trials on forward speed and nozzle choice including field work.

“It’s important to test products in the field as they will be used, not under ideal conditions, especially where we are struggling with the available chemistry or tackling diseases such as septoria or rust.  Simple adjustments can make a big impact,” he explains.

Timing is important for cereal fungicides, he adds, particularly at T1/T2 and while flat fans perform best, sometimes the only way to get these products on in the conditions is to use air inclusion (AI) nozzles.

Nozzle angling can also increase efficacy:  “Angling all nozzles forward can have its benefits, while for blackgrass control or the main cereal fungicide timings angling nozzles alternately forward and down can work.  Alternating nozzle angle can also cut drift and there improve the performance of the product.”

Agrovista is looking at the use of drift retardants to allow flat fans to be employed in conditions liable to cause drift.  “We are aiming to find out if we can still maintain flat fan performance using retardants.  They also need to be tank mixable with the products being applied,” he adds.

Mr Hemmant points out that while AI nozzles are known not to be as efficacious as flat fans, the use of adjuvants such as Agrovista’s Velocity can help.  “We can almost match the performance of a flat fan using Velocity and can get the job done with reasonable efficacy,” he says.

The trials aim to work at rated nozzle pressure of 3 bar but also at 3 – 4 bar.  The results showed flat fan performance declines at 4 bar and drift risk increases, while AI nozzles work better at 4 bar.

Variable buffer zones have helped the industry to retain the use of certain products and offer flexibility, Mr Hemmant adds.  “Where there is a 12m buffer zone, manufacturers can apply to have this reduced if they are sprayed with a LERAP three star nozzle or application.  However, there is little choice of three star nozzles to work at 4 bar to 2 bar and a slower forward speed would normally be required.  “Application aids can be used to meet the three star rating and maintain efficiency, and we have trialled an adjuvant that allows a flat fan to give the equivalent result to a three star nozzle.”

When using Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium) for grass weed control, a fine/medium spray at lower water volume improves efficacy – a blue flat fan 110° nozzle applying 150 litres/ha at 10km/hr works best, ideally with a combination of 30° forward and straight down angling by using angled caps.

Agrovista has also trialled a ‘twin boom’ system, he explains:  “Graminicides are best at 70 litres/ha but the legal requirement is for 100 litres/ha.  So we applied 140 litres/ha with two sets of nozzles, each putting on 70 litres/ha, on either side of a box section boom.  The front row was angled at 30° and the rear row straight down.”

Pre-emergence herbicides are becoming more significant as Atlantis becomes less effective, he says, and to get the best out of residuals, 200 litres/ha in total, but more quickly than with a single nozzle,” he says.

Where operators need to apply pre-ems at 100 litres/ha, Mr Hemmant advices avoiding AI nozzles in favour of a variable pressure 80° flat fan.  “Angling the nozzles alternately forward and down increases efficacy, and the adjuvant, Grounded, is useful, especially if you have to use AI nozzles.”