Two farmer’s sons have harnessed image analysis to build a spot sprayer for docks. We visited for a closer look…

Docks are nothing if not tenacious. As someone said: “Dig ‘em up, burn ‘em, and the smoke will grow.” Over in Bavaria this endearing quality is a problem for livestock farmers, not just for dock’s unpalatability to cattle but also because a local area-based payment depends on a raft of conservation measures – which includes a ban on blanket-spraying grassland.

Automation up, inputs down With this in mind, mechatronics students Andreas Breher and Simon Cordella produced a camera-controlled spot sprayer. They called it the RumboJet, pairing the dock’s Genus (Rumex) with Jet (as in fan nozzle) and adding a nod to Boeing. Before it came along, docks on the Cordella family’s 40ha grass were spotsprayed by hand, a lengthy pastime and a bit hit-and-miss on application rate.

Blanket spraying would call for 200-400l/ha, so that was the target to reduce: the RumboJet lowers it to some 30l/ha. The actual figure varies with infestation, though the developers say typically 90% less liquid is used. Seeing red The RumboJet uses infrared cameras to recognise dock leaves from their distinctive shape and colour. It’s a 9.0m trailed unit, with each 1.50m of boom width packing one camera, one LED, one processor and up to 15 solenoid valves.

The cameras capture 90 photos every second, passing them to processors (each a 1.4gHz Raspberry Pi) for analysis. Once a dock plant is spotted, the processor signals one or more electronic MOSFET-based switches to open for a pre-set time, despatching a burst of spray onto the plant.

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