For Phil and Tom Longmire, who crop 5700 hectares near Esperance, Western Australia, 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 says.

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.

The key to their operations is a self-contained, mobile batching and mixing rig; a flat-top tautliner Curtainsider truck with tri-axle trailer. The set-up includes two Handler IV 870-litre-capacity batch-induction systems.

The truck contains up to six 1000L shuttles, half with direct suction plus three cone-bottom measuring vats, fitted with a Sotera chemical induction pump, each vat with their own independent circuit.

“This avoids cross-contamination for smaller volume products, for example, grass-selective herbicides, insecticides or adjuvants,” Tom says.

Tom and his father run two spray units: a SP Goldacres 8000/36-metre Arag Seletron and a Fastrac 8330 3m Beverley 7000/36m Arag Seletron. Both units have shared coverage and individual nozzle control.

Each year we spray around 40,000ha. When spraying, on average we cover 1000ha per day, which equates to five to six spray-tanker loads per day.

Water is sourced from dams and rainwater after good rainfall and 50,000L tanks are located at each fill location.

“Our fill time using the batch system is 12 to 15 minutes and, if time is limited during filling for complex loads, the Beverley spray operator completes batches between fills to improve the efficiency of the SP Goldacres spray unit.

“Having three measuring and batching systems that are completely separate and have their own direct induction of chemicals means we can avoid contamination.”

Always on the lookout for further efficiency gains, Tom has a wish list that includes an additional cone-bottom measuring vat – to make a total of four – and an additional rinsing sprinkler on the triple-axle batching trailer.

Tom and Phil have shared their spray operation knowledge with attendees to the GRDC spray workshops, which are run by spray application specialist Bill Campbell. These are now documented in the new Mixing and Batching for Agricultural Chemical Application – A Technical Guide With Case Studies of Australian Grain Growers And Spray Contractors available from GRDC’s website.

Read more: Mixing and batching chemicals  – a key to spray efficiency.