Effect of UAV prewetting application during the flowering period of cotton on pesticide droplet deposition

Ji Jin,Weixiang Yao,Xianju Wang,Yubin Lan

doi:10.15302/j-fase-2018232

Abstract

Prewetting process can reduce the contact angle between the droplet and the leaf blade, so that the droplet can more easily wet and spread, thereby increasing the quantity of deposition. To improve the effectiveness of pesticides on cotton leaves, prewetting by single-rotor electric unmanned aerial vehicles (UAV) was studied, focusing on the effects of pesticide deposition on cotton leaves during the flowering period. Cotton leaves in 0°–30°, 30°–60°, 60°–90° leaf blade angle ranges (angle between the leaf blade and the horizontal plane) were examined. In the first experiment, four different prewetting volumes (0, 1.6, 3.2 and 4.8 L) were sprayed by a single-rotor electric UAV on four cotton plots (plots A–D) each with an area of 120 m2, and then each area was sprayed with a 0.8% (w/v) ponceau 2R solution by another single-rotor electric UAV. The results revealed that with no prewetting, droplet deposition quantity decreased with increasing leaf blade inclination. After prewetting, the mean droplet deposition quantity on plots B, C and D increased by 39.8%, 9.7% and 24.9%, respectively. The prewetting rate of 1.6 L per 120 m2 had the most significant effect on improving the deposition of droplets. It was also found that the mean droplet deposition quantity in each leaf blade angle range increased after prewetting. For the leaf blade angle range 60°–90°, this increase was the most pronounced, with 0.043, 0.062, 0.057 and 0.048 mL·cm−2 in plots A–D, respectively. Also, droplet deposition uniformity in the leaf blade angle range 60°–90° was better after prewetting. These results should provide a valuable reference for future research and practice to improve the effectiveness of pesticides applied to cotton by aerial applications.

Highlights

The flowering period of cotton is from flowering to boll opening, which is the most sensitive period for water supply, with a high incidence of pests and diseases[1,2]
This paper reports an experiment using a small, single-rotor, electric unmanned aerial vehicles (UAV) spray with different prewetting capacity based on the precision operating flight parameters obtained by a light airborne BeiDou Real-time kinematic (RTK) differential system
To further demonstrate the effect of prewetting on the deposition on cotton canopies with different leaf inclination angles, the prewetting volume was divided into four levels, and the deposition quantities on leaves of different inclinations analyzed by least-significant difference test (P = 0.05)

Summary

Introduction

The flowering period of cotton is from flowering to boll opening, which is the most sensitive period for water supply, with a high incidence of pests and diseases[1,2]. It is important to ensure full water supply and pest control during the flowering of cotton[3,4]. The spraying of pesticides by UAV usually involves low volumes and high concentrations with small droplet size because of the UAV weight and tank limits[8,9]. Cotton usually has a high planting density with dense foliage during the flowering period[11], so it is imperative to ensure effective droplet deposition of pesticides on cotton leaves

Methods

Results

Conclusion