GRDC releases chemical mixing and batching guide

The guidebook is a key outcome of a four-year GRDC extension investment into spray efficiency and efficacy, which also included hands-on sprayer calibration and application workshops for growers.

Seventeen full-day workshops have been delivered, with the remaining three to be run in 2023.

The guidebook showcases day-to-day practicalities, with grower case studies for various enterprise sizes, each bringing different concepts, ideas and creative engineering to spray operations.

For Phil and Tom Longmire, who crop 5700 hectares near Esperance over six adjoining properties, spraying operations are logistically complex.

"Timeliness of spray operations is critical for their success, and this is contingent on the capacity you have available - both labour and equipment," Tom said.

"We have upgraded our spray equipment over the years, customising it to the area of crop we need to service, but probably the key efficiency gain is how we use our limited labour source, particularly for mixing and batching chemicals."

The Longmires use a tag-team approach to allow for the pre-batching of chemical granules and dry product for the next spray operator.

This means products have time to dissolve and can be pumped straight into the spray units.

"Each year we spray around 40,000ha," Tom said.

"When spraying, on average we cover 1000ha per day, which equates to five to six spray-tanker loads per day."

The case studies included in the guidebook cover a range of operation sizes (both grower and contractor) and crop mixes in different rainfall zones.

They explore the individual requirements - such as farm infrastructure, equipment and staff management - required to service their spray operations.

WA spray application specialist Bill Campbell said the guidebook contained information on chemical formulations and the correct mixing order, with a summary covering combining common agricultural chemical formulations together with a brief overview of common mishaps that can occur and tips on how to avoid them.

"Fastest is definitely not always the best when it comes to mixing chemicals," Mr Campbell said.

"Always follow label recommendations and check product compatibility and manufacturers' mixing guidelines.

"Use good-quality water and consider using an adjuvant to improve the physical compatibility of certain tank mixes.

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"When mixing a batch for the first time, conduct a jar test that replicates the tank mix.

"This will reduce the risk of financial losses and time-consuming and environmentally unfavourable situations, in cases where the mix doesn't turn out as intended."

Every farming operation is different, so it is important to match spray capacity with the needs of the farming operation and to understand any limitations.

There must be sufficient capacity - both labour and equipment - to spray in a timely manner with the allowance of downtime due to weather conditions (wind, rain, heat), drift considerations or physical logistics (shifting sprayers or equipment, moving chemicals).

GRDC grower relations manager Jo Wheeler said the workshops were an example of how the GRDC's National Grower Network (NGN) operated.

"The National Grower Network has been established to support meaningful engagement with grain growers, improve understanding of local issues and assist in the development of investments that are locally relevant and have on-farm impact," Ms Wheeler said.

"Growers love to look over the fence to see what their neighbours are doing to improve their production practices.

"The guidebook takes this one step further by including grower experiences on mixing and batching from a wider geographic area."