Characterizing Droplet Retention in Fruit Tree Canopies for Air-Assisted Spraying

Abstract

As a mainstream spraying technology, air-assisted spraying can increase the penetration and droplet deposition in the tree canopy; however, there seems to be less research on the maximum deposition volume of leaves. In this paper, the maximum deposition volume of a single leaf and the attenuation characteristics of droplets in the canopy were studied. By coupling them, the prediction equation of the total canopy droplet retention volume was obtained. The single-leaf test results showed that too small a surface tension reduced the total volume of droplet deposition on the leaf. In this paper, when the Weber number was equal to 144.3, the deposition form changed from particles to a water film, yielding the best deposition effect. The canopy droplet penetration test results show that the air velocity at the outlet increased first and then decreased, and the best effect was achieved when the air velocity at the outlet was 10 m/s. At the same time, when the surface tension of pesticides was 50 mN/m, the effect of canopy droplet deposition was better, which was consistent with the results of the single-leaf test. An average relative error of prediction equation of the total canopy droplet retention volume with 15.6% was established.