Stereo Vision Controlled Variable Rate Sprayer for Specialty Crops: Part III. Effect of Travel Speeds on Spray deposition and Ground Loss

Abstract

Highlights Stereo vision controlled variable rate sprayer reduced the spray volume by 44% to 99.6% for the tree canopy volumes from 2.2 to 0.03 m3. The variable rate sprayer increased the ratio of a spray deposit on trees to a spray volume by 16.1% compared to a constant rate sprayer. The application of the variable rate sprayer had 57.6% less ground loss compared to a constant rate application. The travel speeds of the sprayer had no significant impacts in spray deposition, coverage, or ground losses of the applications. Abstract. A prototype of a novel stereo vision controlled real-time variable rate sprayer was evaluated in an apple orchard in order to mitigate the risks derived from the use of crop protection products applied at a conventional constant rate in specialty crops. The effects of its travel speed (from 3.2 to 8.0 km h-1) on spray volume reduction, canopy deposition and coverage, and ground loss were assessed. Test results demonstrated that the travel speed did not influence spray deposition, coverage, or ground losses. The variable rate sprayer reduced the spray volume by more than 44% for the canopy volumes detected in the orchard (<2.2 m3) in comparison to the constant rate spray application. Overall spray volume reductions were 79.1%, 73.8%, 71.0%, and 69.8% when the sprayer traveled at 3.2, 4.8, 6.4, and 8.0 km h-1, respectively, compared to the constant rate applications at a travel speed of 8.0 km h-1. In addition, the variable rate application of the sprayer increased the crop interception, a ratio of a spray deposition to a spray volume, by 16.1% compared to the constant rate spray application when traveling at 8 km h-1. Moreover, the sprayer reduced total ground loss by 57.6% compared to the constant rate application, which would minimize adverse impacts of pesticide applications to non-target organisms and unnecessary pesticide losses to the environment. The results of this study suggest that the prototype sprayer has significant potential as a cost-effective solution for sustainable specialty crop spray applications. Keywords: Crop protection, Depth image, Machine vision, Orchards, Precision agriculture, Pulse width modulation.