Smart Spray Analytical System for Orchard Sprayer Calibration: A-Proof-of-Concept and Preliminary Results

Efficient chemical spray applications are vital to reduce off-target drift, economic losses to tree fruit growers, and negative environmental impacts. It is thus important to adequately calibrate and adjust orchard sprayers for intended applications. This technical note describes the design, prototyping, and field evaluation of a sensor-based smart spray analytical system (SSAS). The SSAS is equipped with units for spray capturing and volumetric quantification, air-assist velocity measurement, system actuation and control, and data acquisition and wireless transmission. The spray liquid and air-assist velocity quantification units are assembled on a custom-made mobile frame for vertical stop-and-go movement to provide measurements at eight distinct sampling heights above ground level. The data acquisition and transmission units autonomously log the data on-board and transmit wirelessly to a receiving computer with time and height stamps for real-time graphical visualization. All these autonomous processes are guided by a custom programmable single-board computer. The SSAS was preliminarily evaluated for spray liquid and air-assist velocity pattern assessment of an air-assisted orchard sprayer in four sets of spray trials. An average spray liquid recovery of 14.03% and pertinent coefficient of variation (CV) of 10.73% were observed. An average CV of 11.93% was observed in the air-assist velocity patterns. Overall, the SSAS provided measurements within acceptable ranges of variation. This system can thus minimize the experimental errors, time, and efforts involved in conventional assessments of sprayer attributes, thereby providing a reliable solution for orchard sprayer calibration and adjustment.