Impact of canopy opener working height on spraying effect of a high clearance sprayer

This study was aimed to solve the problem of low spraying effect in spraying deposition on both sides of maize leaves with different height canopy by traditional high clearance sprayers. The spray effect can be improved by installing the canopy opener on the boom sprayer. The deflection model of the maize stalk was established by the interaction process between the canopy opener and the maize stalk. Based on the model, combined with the measurement of the structure and material property parameters of maize stalks in the bellbottom period, the finite element simulation and the high-speed video acquisition system experiment in the soil-bin were carried out under different working heights of the canopy opener (0.6 m, 0.8 m and 1 m). The test results showed that the bending angle of the stalk increased with the decrease in the working height of the canopy opener, and when the working height was reduced to a certain level, the stalk would break due to excessive disturbance. The simulation data and the high-speed image data have a good consistency, which is also consistent with the analysis results of the established theoretical model. The spraying effect of the canopy opener was further verified through field experiments, and the results showed that the canopy opener can significantly improve the uniformity of the droplets deposited in the canopy at different heights as well as in the adaxial and abaxial leaves. And this effect was increased with the decreasing of the working height of the canopy opener. Taking into account the seedling damage rate and the spray effect, the performance was better when the working height of the canopy opener was 0.8 m. At this point, the ratio of the droplet coverage rate and the droplet deposition density on the lower and middle canopy to upper canopy were 57.29% and 54.67% for lower to upper canopy, 75.64% and 72.41% for middle to upper canopy ratio. In addition, the ratio of the droplet coverage rate and the droplet deposition density on the abaxial and adaxial leaves were 78.82% and 65.85% in the upper canopy, 63.88% and 60.81% in the middle canopy, 58.39% and 54.64% in the lower canopy, respectively. The coefficient of variation of the droplet coverage and the droplet deposition density within canopy at different heights was 27.59% and 30.18%, respectively. This study provides theoretical basis, method and data support for the selection of the working height of the spraying opener during the bellbottom stage in maize cultiv