Efficacy Evaluation And Parameters Optimization For Cotton Defoliant Spraying Using Multi-rotors Electric Unmanned Helicopter

In recent years from 2002 to 2017,society's preoccupation with the use of plant protection products has been increased significantly.When pesticides are applied,a portion of pesticides may move to undesirable areas instead of depositing on the intended area,which might result in a lower volume than intended on the target area,damage of sensitive adjoining crops,water and soil contamination,health risks to animals and humans.Maximizing efficacy and minimizing pesticide non-target areas are the paramount considerations when selecting technologies and operating parameters prior to making a spraying application.Many researchers are studying methods and technologies to improve spray optimization.Cotton is one of main industrial crops in China.Spraying cotton defoliant can promote cotton defoliation and boll opening rate,improve the mechanization of cotton harvesting,and then improve the cotton productivity.Mini-micro unmanned aerial vehicle?UAV?has the advantages of height spraying efficacy and efficiency,feasibility and adapting well to environment.On basis of these advantages,UAV is getting its'prevalence in plants protection spraying,and it has broad application prospects in cotton defoliation spraying.The general objective of this research was to investigate the influence of operational parameters on pesticide spraying,evaluate the efficacy,efficiency and cost of aerial spraying,and optimize the parameters for cotton defoliant aerial spraying,ultimately,to improve droplet penetration ability,cotton defoliation spraying efficacy and efficiency.This research was conducted in wind tunnel test and field studies.The main research work and achievement of this research are as follows:?1?Key component and parameters testing for cotton defoliant aerial spraying in wind tunnel The droplet size measurement system in the wind tunnel laboratory is consisted of a liquid atomization system,a laser diffraction particle size analyzer and a data storage and processing system.3,4,5,6 bar spray pressures and 3,4,5 m/s speeds were set up in the experiments,A HELOS Vario laser diffraction particle size analyzer?SYMPATEC,Germany?was used for the droplet size measurement research.The droplet size characteristics of six different types of air induction flat fan hydraulic nozzles were measured,different nozzles are different in flowrate,the flowrate order for six types nozzles are:BFS 11001<BFS 11002<BFS11004<BFS 11005<BFS 11006<BFS 11008.This study focused on the effect of different nozzle types,spray pressures and wind speeds on the D_v0.1,D_v0.5,D_v0.9,%<150?m?proportion of spray volume contained in droplets with diameter below 150?m?,RSF(Relative Span Factor,calculated by D_v0.1,D_v0.5,D_v0.9)and CV(Coefficient of variation for D_v0.5)of the sprays.The following results were investigated:?1?The nozzle type had an extremely significant influence?P=0.000?on D_v0.1,D_v0.5,D_v0.9,%<150?m and RSF,but had no obvious effect on CV?P=0.143?.The spray pressure had an extremely significant influence on D_v0.1,D_v0.5,D_v0.9 and%<150?m?P=0.000?,had no obvious effect on RSF?P=0.219?and CV?P=0.528?.When the air speed was increased from 3 m/s to 5 m/s,there was no significant wind speed effect on any of observation indices?P>0.05?.?2?The nozzle flowrate had a positive‘linear'regression relationship with D_v0.1?R=0.921?,D_v0.5?R=0.937?,and D_v0.9?R=0.914?,while it had a negatively‘linear'regression relationship with%<150?m?R=0.966?.Spray pressure had a negatively‘S'relationship with D_v0.1?R=0.993?,D_v0.5?R=0.999?,D_v0.9?R=0.998?,while it had a positive‘S'relationship with%<150?m?R=0.995?,but it had no significant correlation with RSF and CV.There was no significant correlation between wind speed and each observation index.Flowrate had the greatest significant effect on the spray quality among the three factors of flowrate,spray pressure and wind speed,followed by spray pressure and wind speed.The optimal factors level solution of each dependent variable index was obtained in this study,furthermore,the regression prediction models were established by the Statistical Package for Social Science?SPSS?.?3?On basis of the results of comprehensive consideration,the optimal solution for cotton defoliant aerial spraying was A_2⁵B₁C₁?flowrate:0.8².4 L/min,pressure 3 bar,air speed 3m/s?.?2?Efficacy evaluation and parameters optimization using four-rotors electric unmanned helicopterYR-GSF06 four-rotors electric unmanned helicopter?EUH?was used for the feasibility verifying tests and the primary parameters optimization.The orthogonal test of four factors Volume of solvent?A?,Tank mix?B?,Electrostatic spraying?C?,Flight height?D?and four levels was designed.Droplet coverage,deposition density,deposition rate and distribution uniformity of different different volume,tank mix,electrostatic spraying and different flight height were investigated by water sensitive papers?WSP?.The regression relationships between droplet size,coverage,deposition density and distribution uniformity were investigated and regression models were built.The defoliant rate and boll opening rate of different application parameters were investigated.The regression relations between the indexes and cotton defoliation rate and boll opening rate were analysed using SPSS,and the regression models were built.The results were observed as follows:?1?The order of four factors that affect the droplet coverage and distribution uniformity were ACBD and BCDA respectively.Factors A,B,C,and D had an extremely significant influence?P<0.05?on droplet coverage.Factors A?P=0.020?and C?P=0.042?had an extremely significant influence on droplet deposition density,factors B?P=0.076?and D?P=0.090?had a significant influence on droplet deposition density.Factors B?P=0.046?and C?P=0.037?had an extremely significant influence on CV,factors A?P=0.075?and D?P=0.074?had a significant influence on CV.?2?There was a‘S'negative correlation between D_v0.5 and?a?droplet coverage?R=0.731??b?deposition density?R=0.552?.There was a‘cubic'positive correlation between droplet coverage and deposition density?R=0.800?.There were‘cubic'positive correlation between droplet coverage and?a?cotton defoliant rate?R=0.622??b?boll opening rate?R=0.567?.There were‘S'positive correlation between droplet deposition density and?a?cotton defoliant?R=0.550??b?boll opening rate?R=0.554?.?3?Parameter ranges of testing factors were observed in this part of research:80 L/hm²?A₄?,Tuotulong225 ml+Sujie 375 ml+Ethephon 2250 m?B₂?/Tuotulong 225 ml+Kesheng 562.5 ml+Ethephon 2250 m?B₃?,electrostatic spraying?C₁/C₃?,1.5².0 m?D₃/D₄?.These results provided theoretical reference basis for the further parameter optimization.?3?Efficacy evaluation and parameters optimization using four-rotors,six-rotors,eight-rotors EUHsYR-GSF06 four-rotors,TXA—Xiangnong six-rotors and YR-AU 15 eight-rotors EUHs were used for aeronautical cotton defoliant and parameters optimization on basis of the parameters which were obtained in the wind tunnel and the primary parameters optimization.The orthogonal test of four factors Volume of solvent?A?,Tank mix?B?,Flight height?C?,Flight speed?D?and three levels was designed.Variance analysis,rang analysis,covariance analysis and gray incidence degree analysis method were used in this research.?1?General linear relationship between Leaf Area Index?LAI?and droplet coverage and droplet deposition density were analysed using SPSS 19.0.The results showed that:LAI had an extremely significant influence on droplet coverage?P=0.000?and deposition density?P=0.001?.SPSS19.0 was used for eliminating the influence of LAI on droplet deposition density and droplet coverage,the corrected values of droplet deposition density and coverage were obtained and used in the following analysis after covariance analysis.?2?The order of four factors that affect the droplet coverage and distribution uniformity were ABCD and BCDA respectively.?3?The relationship between the droplet characteristic and cotton defoliation and boll opening rate was more significant after the covariance analysis.It revealed that the LAI had a significant influence on droplets characteristic.With the purpose of maximizing the droplet coverage,deposition density and deposition rate by adjusting droplet size,the relationships between droplet size,deposition density,coverage and deposition rate were analysed using regression analysis.The results showed that there were negative‘S'relationships between D_v0.5 and?a?droplet coverage?R=0.886?,?b?deposition density?R=0.831?.There was‘cubic'positive relationship between droplet coverage and deposition density?R=0.903?.There were positive‘cubic'relationship between droplet coverage and?a?cotton defoliation rate?R=0.826?,?b?boll opening rate?R=0.704?.There were positive‘S'relationship between droplet deposition density and?a?cotton defoliation rate?R=0.817?,?b?boll opening rate?R=0.711?.Correlation models were built,therefore,cotton defoliation rate and boll opening rate could be predicted by the droplet deposition characteristics.?4?Data were analysed using gray incidence degree analysis method,spraying efficacy,efficiency,and cost were taken into consideration.The optimum parameters for the three types of EUHs were:A?Volume?:48 L/hm²,B?Tank mix?:?Tuotulong 225 ml+Sujie 275 ml+Ethephon 2250ml?/hm²,C?Flight height?:1.5 m,the optimum flight speed for YR-GSF06,TXA—Xiangnong and YR-AU 15 were 3.12,2.51,3.76 m/s respectively.With this study,a database with droplet characteristics in wind tunnel and field studies was observed.The results of this research provided technical guidance and theoretical basis for the cotton defoliant spraying using EUH in North Xinjiang.