Abstract
Aerial spraying can support efficient defoliation without crop contact. With the recent introduction to unmanned aerial system (UAS) for aerial spraying in China, there is a need to determine the optimum application variables to achieve high efficacy and efficiency with low costs. The present research involved field studies across two annual cotton production seasons in North Xinjiang, China. Four factors, including volume rate (A), tank mix including spray adjuvants (B), flight altitude (C), flight speed (D) and three levels of L9 (34) orthogonal arrays were carried out to optimize the application parameters for three types of UASs. These included different numbers of rotors as follows: four-rotors, six-rotors and eight-rotors. Spray coverage, distribution uniformity (coefficient of variation (CV) of droplet coverage), rates of cotton defoliation and boll opening, application efficiency and cost were measured and assessed. Results showed that: (1) the rates of defoliation and boll opening by aerial cotton defoliant application could meet the requirement of cotton mechanized harvesting; (2) the optimal scenario for the three UASs was A3B2C1D3, Volume rate (A3): 48 L/hm2; Tank mix and concentration (B2): (Tuotulong 225 + Sujie 750 + Ethephon 2250) mL/hm2, Flight altitude (C1): 1.5 m, and Flight speeds (D3) for unmanned helicopters with four-rotors, six-rotors and eight-rotors were 3.12 m/s, 2.51 m/s and 3.76 m/s, respectively. These results can provide guidance for cotton defoliant aerial spraying in China using UAS. Keywords: unmanned aerial system (UAS), unmanned aerial vehicle (UAV), unmanned electric helicopter (UEH), cotton defoliant, aerial spraying, parameter optimization DOI: 10.25165/j.ijabe.20191202.4288 Citation: Liao J, Zang Y, Luo X W, Zhou Z Y, Lan Y B, Zang Y, et al. Optimization of variables for maximizing efficacy and efficiency in aerial spray application to cotton using unmanned aerial systems. Int J Agric & Biol Eng, 2019; 12(2): 10–17.
Highlights
Cotton production is a labor-intensive, low efficient and time-consuming process
Most cotton production processes, including cotton harvesting are mostly dependent on manual work in China
Chemical cotton defoliant sprays, which can promote the process of cotton defoliation, providing important support to cotton mechanical harvesting[2]
Summary
Cotton production is a labor-intensive, low efficient and time-consuming process. In addition to planting, most cotton production processes, including cotton harvesting are mostly dependent on manual work in China. Liao J, et al Optimization of variables for maximizing efficacy and efficiency in aerial spray application using UAS Vol 12 No. type, spray pressure, flight altitude and speed)[13], the physical and chemical properties of the tank mix[14] and the meteorological conditions such as air temperature, relative humidity, wind velocity and direction[15]. The present study is aiming to improve the efficacy and efficiency of aerial spraying using three typical UAS models in China. These sprayers would be used to study the relative effects of different application and tank mix systems in aerial cotton defoliant spraying, to support future optimization by applicators of application volume rate, tank mix and concentration, flight altitude and flight speed to be considered when spraying. Four-rotor aircraft would be used for verifying the feasibility of cotton defoliant aerial spraying using UAS and optimizing parameters range in the first year of study, four-rotor, six-rotor and eight-rotor aircraft would be used for efficacy evaluation and parameters optimization in the second year of study
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