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Spray deposition inside multiple-row nursery trees with a laser-guided sprayer

H. Zhu, H. Liu, Y. Shen, Hengyu Liu, R. H. Zondag
Journal of environmental horticulture 2017 v.35 no.1 pp. 13-23
Quercus rubra, Tilia tomentosa, air-assisted sprayers, algorithms, canopy, computers, container-grown plants, horticulture, leaves, pesticides, spray coverage, spray deposition, trees, variable rate application
Multiple-row container-grown trees require specially designed sprayers to achieve efficient spray delivery quality. A five-port air-assisted sprayer with both automatic and manual control modes was developed to discharge adequate spray deposition inside multiple-row tree plants. The sprayer resulted from integration of a high-speed laser scanning sensor with a sophisticated nozzle flow control system, an embedded computer with a touch screen, a Doppler speed sensor, a specially-designed algorithm and an air-assisted sprayer base. It was able to detect target tree presence and measure target tree size, shape and leaf density. The sprayer then controlled spray outputs of each nozzle to match tree structures. The sprayer was tested for its sprayer deposition quality inside canopies in a four-row sterling silver linden field (Plot #1) and another six-row northern red oak field (Plot #2). Tests were conducted with the sprayer in variable-rate application (VRA) and constant-rate application (CRA) modes. The average spray deposit on foliage of trees was 1.37±0.47 µL cm-2 from VRA and 1.29±0.42 µL cm-2 from CRA in Plot #1, and was 2.15±0.57 µL cm-2 from VRA and 2.72±0.94 µL cm-2 from CRA, respectively. In comparison, spray coverage on foliage of trees was 19.8±3.0% from VRA and 20.9±4.3% from CRA in Plot #1, and was 27.9±3.7% from VRA and 30.5±5.4% from CRA, respectively. The newly developed air-assisted sprayer in both VRA and CRA modes would be able to discharge adequate spray deposition inside multiple-row tree plants while conserving pesticide.