By Tom Wolf
Calling Australia the world’s driest continent is a bit like saying the average farm size in Canada is 1,500 acres. Though accurate, such statements completely ignore the variation that underlies these averages. And in that variation lives all the interesting information.
I recently visited Australia and I was surprised by what I learned. Fact is that large agricultural areas of Australia receive more rainfall than most parts of Western Canada. Yes, they have droughts, as do we. And, of course, the central and large parts of Australia’s western regions are very dry. Despite that, receiving 400 to 800 millimetres of annual rainfall in the main agricultural regions is not out of the ordinary in Australia. But even that is not the interesting part.
The spatial and seasonal variation of this rainfall is the foundation of its agricultural and weed-control practices. Let’s look at the spatial variation. In the eastern states (South Australia, Victoria, New South Wales and Queensland), coastal rainfall is highest, tapering as one ventures inland. The Great Dividing Range is a key geographic feature that prevents the highest rainfall areas from being agricultural, and large-scale ag begins west of the range. As one travels north from Victoria, rainfall both increases and also shifts from being predominantly in the winter months in the Mediterranean climate of Victoria and southern New South Wales, to being predominantly summer rainfall in subtropical Queensland. In areas where winter rainfall dominates, cropping is done in that season with land in the summer being fallow. Where summer rains become prominent, the traditional winter crops of wheat, canola and pulses are still grown in the winter, but cropping an additional warm season crop such as cotton or sorghum becomes a possibility.
A summer fallow season is an agronomic necessity when low rainfall is accompanied by temperatures commonly in the mid 30 C range. It is also a challenge to maintain control over weeds that emerge after small showers. Tillage is out of the question for obvious reasons related to soil and water conservation. Chem fallow is the only solution, but the expense of multiple broadcast treatments on difficult to control weeds can be prohibitive.
Enter the spot sprayer. First invented in Queensland by Warwick Felton, who in the 1980s proposed that NDVI signals could be used to differentiate plants from soil and stubble, it is perfectly suited to Australian cropping systems. Although NDVI-based spot sprayers became established in the 1990s, they really flourished with the introduction of the more modern WEED-IT systems in 2009.
A summer weed control program graduates to higher savings on each use of a spot sprayer. By late summer, savings of 99 per cent can be achieved. Producers are depleting the seedbank of summer-germinating weeds to a degree that the pressure on winter in-crop sprays can be reduced.
Local equipment sales reflect this utility. WEED-IT and Trimble’s WeedSeeker aren’t the only spot spray tools that are selling. SenseSpray, a Queensland company, is equipping Case sprayers with their cameras and software. John Deere has made significant sales of See & Spray Select. And several other local companies such as Single Agriculture and InFarm both offer drone-to-tractor solutions where drone-developed maps become prescriptions for the ground sprayer.
But the story isn’t all rosy. Herbicide resistance continues to plague Australian producers, and in the absence of new mode of action discoveries, the existing suite of products is stretched. One way to maintain control of weeds such as milk thistle (Sonchus oleraceus, similar to our annual sowthistle) that are resistant to Groups 2 and 9, is to boost rates of products that are weaker, but still work. Glufosinate is registered for chem fallow in Australia, and using a 200 g/L formulation, they are applying rates as high as 10 L/ha of product. That’s 5.4 L/acre of a 150 g/L formulation, about fourfold the highest label rate of glufosinate here. That can only be economical with a spot spray system. Note that the registration of these rates limits the user to applying sprays on 30 per cent of the area, in order to maintain the lower broadcast rate equivalent. Whether it’s wise to use such high rates is a different question.
The introduction of autonomous sprayers has changed the nature of spot sprays even further. While attending research update meetings in Australia, I met farmers who were monitoring their SwarmFarm robot sprayers while listening to scientists. Through the SwarmFarm app, they can monitor their sprayer’s location and status, its fuel load and its spray tank level. The onboard weather station also provides wind speed and direction, temperature and relative humidity. Delta T. criteria can be set for when the robot suspends spraying and enters standby mode. For example, if the wind gusts are too high, the robot will stop and resume once the situation calms down.
This system makes it possible to basically spray continuously through the summer, moving from field to field and never letting a weed situation get out of control. Because the robots are physically small and light, they don’t consume much fuel. And because they don’t travel very fast, the quality of the job is good. One interesting observation from an owner was that the robot probably does a better job than a human operator. He said that he can program the robot to stop when conditions are too poor to continue. A human would power through, he felt.
Another observation was the weed threshold that triggers a decision to spray a field is much lower with a robot. Because the costs to run it are so low, farmers are initiating a spray with just the slightest weed pressure.
It was interesting to see the large-scale adoption of controlled traffic farming. The farms I saw were all on three-metre wide permanent tramlines spaced 12 metres apart. No heavy wheels will touch the ground outside of these lines. Spray booms are 24 or 36 metres. It’s a small problem for U.S. made sprayers whose 120-foot booms have 72 nozzles on 20-inch spacing. That makes them 36.6 metres wide and removing a nozzle makes them non-symmetrical.
My trip to Australia was amazing. We have much in common with our Aussie friends. We grow the same crops using the same equipment, and we compete for the same markets. We struggle with precipitation. We adapt constantly to remain competitive. And we admire innovative solutions to specific problems. The uptake of spot spraying has not been as high in Canada as first expected. Part of the reason might be that the opportunities for using spot sprays are lower compared to Australia. But it’s great to see the success of this Australian innovation in person and bring the news back to Canada in the hope we can learn from it.
