Victorian agronomist Chris Dunn reminds younger growers that responsible chemical use for optimal weed control involves both confidence and caution

When Chris Dunn was starting out as an agronomist some 15 years ago, he sometimes saw young growers in summer filling up boomsprayers wearing footy shorts, singlets and thongs.

Such scenes are long gone, but it is an image that has stayed with him and one that underlies his promotion of responsible chemical use through his work. “We want people to use herbicides safely – for themselves, for the environment, their neighbours and their crops,” he says.

Responsible chemical use reduces not only health risks but also the contamination of off-target crops, which can come with significant financial cost. Similarly, there is a financial benefit in ensuring herbicides are working efficiently on intended weeds.

“Cropping is expensive, so if you’re spending more money on herbicides, you want to make sure that you are hitting your target at the right time with a properly calibrated boomspray,” he says.

Working with Nutrien Ag Solutions out of Elmore in Central Victoria, Mr Dunn facilitates forums run by Craig Day from Spray Safe and Save that are targeted at younger growers and farm employees.

“We’ve seen a generation shift with younger growers coming home to the farm, and they often get handballed the boomspray jobs, so we want to make sure that they have had the proper training,” he says.

“It’s easy to be blasé if you don’t understand the risks, and we don’t want young people going on to a boomspray and making mistakes or putting themselves in danger. So this is a good way of helping them to be as successful and as safe as possible.”

Chris Dunn. Photo: Melissa Marino

Practical tips

Mr Day, a spray application expert, grower and boomspray contractor from Cowra, NSW, has been delivering spray application industry training days for GRDC after feedback from growers through GRDC’s National Grower Network. The training is full of simple, practical tips for safe chemical use that can be easily implemented.

For example, he advises people to buy a dedicated spray calculator rather than risk contaminating their smartphone by using its calculator when filling up a boomspray. He also suggests keeping a box of disposable gloves handy so that if there is a nozzle blockage or other complications, you are not touching herbicide with bare hands.

Attendees leave the sessions feeling more confident and also more cautious, and this is a balance that leads to better outcomes on-farm, Mr Dunn says.

We’ve had people who have never sprayed before leave knowing they can do the job, confident their boomspray will be set up correctly,” he says. “So their confidence is increased around how to do things well, but they are also more cautious because they are aware of the implications if they don’t.

Nozzles to reduce drift

Mr Dunn says unsafe chemical practices are often unintentional and, when they do occur, commonly involve spray drift.

With more pulses in rotations, and in his region where grapes, tomatoes and olives neighbour broadacre crops, it is important that herbicides remain in their intended paddock, he says. This can be achieved by knowing the correct conditions in which to spray and using the right equipment for those conditions.

“For example, one type or one set of nozzles doesn’t cut the mustard all year round. You need to have at least two different sets of nozzles for spraying at different times of year – in-crop and over summer.”

In summer, when there is a higher risk of spray drift through weather inversions in early morning or late evening, a nozzle that produces a very coarse (or coarser) droplet should be used, Mr Dunn says.

Mr Day brings a boom and a range of nozzles to his small-group information sessions, which involve demonstrations on how to calibrate the equipment so it complies with industry standards while maintaining peak performance.

He also uses water-sensitive paper that turns blue on contact with water to demonstrate how coarser nozzles do not compromise coverage.

“There has been concern that coverage wouldn’t be as good with a very coarse or extra coarse droplet, but Craig and others have shown that you can actually get better results because we’re getting less losses and more droplets down to the target,” Mr Dunn says.

A spray plan

Mr Dunn says nozzle selection is just one part of responsible and effective chemical use, which also involves other elements such as boomspray height and speed. With multiple factors to consider, it is important to have a spray plan in place.

At his sessions, Mr Day develops spray plans with individuals by looking at boomspray type and speed, nozzle choice and spacing, water rates and pump pressure, among other issues. Growers can then keep this document to share with partners and employees.

Mr Dunn says he has also learnt much from Mr Day’s presentations, using them as a basis for the advice he provides. “I’ve taken something different away from every session I’ve been to, and even though I’ve been multiple times I still learn from it every time.”

If growers cannot attend a specialist spray forum, Mr Dunn suggests they seek advice from their agronomist or ask them to source specific information if they do not have it to hand. He is also exploring options for further training in spray application for agronomists to build region-specific knowledge.

Mr Dunn says optimal and responsible spray application not only reduces health and financial risks while increasing profit, but it also feeds into industry sustainability by building goodwill around farming practices among the broader community.

Through appropriate training and advice, growers can help maintain this social licence to operate while continuing to access a broad range of available tools to do the job.

More information: See GRDC Factsheet Practical tips for spraying, GRDC Standard Nozzle Selection Guides.