Effect of Air-assisted Spray Application Rate on Spray Droplet Deposition Distribution on Fruit Tree Canopies

Abstract

<abstract> <b><i>Abstract. </i></b> To improve the utilization rate of pesticides and the adaptability of the application machinery to different canopies and to construct a matching relation between the application rate and the characteristics of fruit trees, this article introduces spray droplet coverage rate and deposition as the investigation indexes. Five different application rates were used with the purpose of investigating the effect of the application rate on spray droplet deposition coverage under different canopy characteristics and quantitatively describing the optimum application rates for different canopies. According to the results of the application with under air-assisted sprayer, the recommended spray application rates for the three types of canopies in the present article were 0.25, 0.20, and 0.14 L/tree in average, which is compared with the traditional manual application rate of 0.25 L/tree in average. To achieve the same level of application effect with traditional manual application, the air-assisted application rate for large and medium canopies can be reduced to 0.20Â L/tree in average, this is a decrease of ¹/₅. Compared with the upside coverage rate of the spray droplets, the underside coverage rate of the spray droplets was more significantly affected by the reduction in the application rate. In addition, in the case of a higher spray droplet deposition and a lower dispersion degree, there would be an inconsistency between the spray droplet coverage rate and the deposition indexes. Thus, it is also necessary to measure the uniformity of the spray droplet dispersion on the leaf surface (spray droplet dispersion index) and the effective lethal area of the spray droplets, which will enable a more accurate expression of the application effect.