Chemical concentration and spatial uniformity of a premixing in-line injection system attached to a variable-rate orchard sprayer

Authors: ZHANG, ZHIHONG - Kunming University Of Science And Technology; Zhu, Heping; WEI, ZHIMING - Shandong Academy Of Agricultural Sciences; SALCEDO, RAMON - The Ohio State University

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2021
Publication Date: 12/20/2021
Citation: Zhang, Z., Zhu, H., Wei, Z., Salcedo, R. 2021. Chemical concentration and spatial uniformity of a premixing in-line injection system attached to a variable-rate orchard sprayer. Journal of the ASABE. 64(6): 1977-1987. https://doi.org/10.13031/trans.14113.
DOI: https://doi.org/10.13031/trans.14113

Interpretive Summary: Disposal of tank mixture leftover is a common problem associated with existing standard constant- and variable-rate sprayers for pesticide applications. To solve this problem, a premixing in-line injection system was developed. Before its adaptation, however, this new technology must be thoroughly investigated to demonstrate its capability to discharge spray deposits on targets with consistent concentration accuracy and uniform concentration spatial distribution. In this research, the premixing in-line injection system was integrated into a laser-guided variable rate intelligent spray system. Outdoor experiments were conducted to assess the chemical concentration accuracy and concentration spatial uniformity on targets at different heights. Variables included different combinations of target chemical concentrations, viscosities of simulated pesticides, and duty cycles. A vertical spray patternator was used to position spray targets at different heights to quantify spray mixture concentration and uniformity discharged from individual nozzles on the sprayer. Test results demonstrated that the accurate and uniform concentrations were achieved across different heights on the vertical patternator, and spray mixture uniformity from measured samples fell in desirable and acceptable level ranges defined in the pesticide application guidelines by USEPA and USDA. Therefore, the premixing in-line injection system would have potentials to be used in laser-guided variable-rate sprayers to further reduce chemical waste through elimination of tank mixture leftovers.

Technical Abstract: Pesticide spray application efficiency is highly dependent on chemical concentration accuracy and its spatial distribution uniformity. In this research, the performance of a newly developed premixing in-line injection system attached to a pulse width modulated (PWM) variable-rate orchard sprayer was evaluated. The chemical concentration accuracy was determined with respect to spray deposition with fluorescent tracer technique, and spatial distribution uniformity of chemical concentrates at different heights was determined with spray deposits at different heights on a vertical spray patternator. Outdoor experiments were conducted with 27 combinations of target chemical concentrations (1.0%, 1.5%, 2.0%), simulated pesticide viscosities (1.0, 12.0, 24.0 mPa·s) and various PWM duty cycles. For each injection loop, the amounts of both chemical concentrates and water discharged into the mixing line were measured separately in response to preset target concentrations. Test results demonstrated that measured concentrations across the patternator heights, simulated pesticide viscosities and duty cycle combinations were consistent. For all treatments, the mean absolute percentage error (MAPE) of measured concentrations was 6.96%, indicating chemical concentration accuracy of the system was acceptable; the mean coefficient of variation was 3.35%, indicating concentration spatial distribution uniformity of the system was desirable. In addition, there was little variation in concentrations of spray mixtures collected at different heights on the patternator. Thus, the premixing in-line injection system could adequately dispense chemical and water to produce accurate concentrations and uniform spray mixtures for variable-rate nozzles to discharge to targets.