Evaluation of real-time stereo vision-controlled variable rate sprayer performance in grapevine shoot detections and spray application

The use of plant protection products (PPP) for plant protection can be substantially reduced by applying PPP on plants only. A novel variable–rate sprayer with a stereo vision system to apply PPP only to grapevines was developed for vineyard applications. The stereo vision system was evaluated as a grapevine shoot detection sensor under various conditions in average grapevine shoot lengths (4.1–29.1 cm), travel speeds (3.2–8.0 km h-1) and outdoor illuminations (12,718 – 67,912.0 lx). A real-time variable–rate sprayer prototype with two air assistance levels at the air outlet (low (air speed of 5.9 m s-1) and high (11.3 m s-1)) tested for its spray performance against a conventional sprayer. The results show that the stereo vision system detected 95.1 % to 99.8 % of grapevine shoots in average under various conditions, and no influences of the shoot size, outdoor illuminations, and travel speeds on the shoot detection were observed under the test conditions. The prototype sprayer had up to approximately 2.8 times more spray deposit averages compared to the conventional sprayer, which was a significant increase (p < 0.05). Insignificant increases of spray deposit on grapevine shoots next to the sprayer, and spray drift to an adjacent row were observed from spray applications with low and high air assistance. A similar trend was observed in spray coverage data. These results demonstrate that the novel stereo vision real-time variable rate sprayer is feasible for vineyard applications.