Meet the Johnstones

Stuart and Helen Johnstone are working to improve soil health, sustainability and efficiency on their grain farms in Central Queensland.

The grain producers own and share-farm 2,000 hectares at their properties, Warraleigh and Can-Berra, Banana. Their summer crops include sorghum and mungbeans, with their winter crops being wheat, barley and chickpeas.

Warraleigh is made up of brigalow, softwood scrub with open downs country. For several years now, the Johnstones have been rethinking their farming techniques with a greater focus on soil health and sustainability. One of the most recent steps has been engaging the use of a SwarmFarm robot – a driverless, automated machine with an RBE Engineering boom with Weed-It technology for precision spot-spraying of weeds.

Originally Mr Johnstone built a 24m trail-behind rig, equipped with Weed-It camera-controlled spray units for selective weed control. While he's held onto it, the move to the SwarmFarm unit has become the next natural progression. The lighter overall weight of the unit means less compaction on the paddocks, even if the machine does several more runs than large scale machinery.

The Johnstones are in the process of digitally mapping the entire property with the intention of using the robot to cover other areas as well. Using GPS guidance and a laser bucket, the Johnstones have redesigned their contour banks to improve water retention.

Mr Johnstone undertook some research a few years ago that led him to conclude chemical resistance and the effects it has on soil biology could become a major concern for growers, putting a strain on the suite of products available. So, using precision spot spraying, he has been able to use higher end products less often, with different modes of action.

Apart from the land health and environmental gains, another big win has been not having a person perched on a tractor for hours. It frees up an operator who can be doing something else, Mr Johnstone said.

The robot can run 24 hours a day, depending on fuel and weather conditions. It has an onboard weather station and stops if conditions are outside of spraying regulations to ensure the machine is only spraying when parameters are correct.

Both Warraleigh and Can-Berra are made up of undulating country, which means big rainfall events can have a tendency to run-off. The dryland operation has an average annual rainfall of about 625mm, so every drop needs to be welcomed by open and arable land. It was originally surveyed decades ago, then contour banks were installed to help capture more moisture and prevent erosion.

Since then, the Johnstones have redesigned the contours using GPS guidance and a laser bucket to improve the paddock layout and update those that missed out on the original earthworks program. Mr Johnstone said the contours pay for themselves, particularly after a heavy rain event.

After they have been created, it's just a matter of maintaining them to keep them in good condition. That means getting the laser bucket every 3 to 4 years to clean up the contours and realign where necessary. The contours prevent water from cutting large grooves into the land, which could lead to erosion and lost productivity.

Improved water control on the property also ensures sediment is kept on farm and not washed into local waterways, helping to improve reef water quality.

In addition to the soil conservation measures the Johnstones have put in place, soil health is high on the agenda with mixed species cover crops to further help with soil structure and water retention. This combined with zero-till paddock preparation and adherence to controlled traffic areas all play their part in the productivity focus in their farming operation.

The Johnstones have worked with DAF on a number of trials and projects over the years, looking at best management practices. They are currently hosting a chickpea nitrogen fixation trial with the DAF Regional Research Agronomy team and in March 2023, they hosted a contour bank design and digital terrain mapping workshop, focussed on how to use digital elevation data to better inform erosion management and more accurately install contour banks and waterways into cropping land to reduce sediment loss.

Mr Johnstone recently purchased a high-resolution elevation data map to provide accurate data for undertaking soil conservation works on his property.

As broadacre cropping increasingly looks to more sustainable farming methods, Mr Johnstone said it was important profitability was kept in mind. He explained that it was a balancing act between managing soil health, sustainability and profitability, keeping in mind that pressure from retailers is likely to keep increasing, so utilising better environmental practices will become more prevalent.