Study On Spray Drift And Anti-drift Method

Pesticide exposure via spray drift can have a negative impact on residents,livestock and aquatic ecosystems.With the increasing awareness about the potential risk of pesticides,reducing pesticide spray drift and maximizing efficacy are the paramount considerations to make an application.Thus this paper,focused on how to improve the effective utilization of pesticide in wheat field,explored spray drift behavior and depositon of droplet on wheat by learing from existing research.The main conlusions are as follows:Firstly,mathematical model of droplet drift potential index and energy was built by analyzing a large number of laboratory test data.The model was built to predict droplet drift potential with the information of droplet size and velocity.Secondly,wind tunnel was used to research on the influence of liquid characteristcs on DIX(drift potential index)by changing the concentration and density of spray liquid.With the concentration of 0.8%,0.4%and 0.3%,respectively,anti-drift adjuvant Silwet DRS-60,Break-thru Vibrant and Greenwet 360 can significantly reduce the spray drift,especially for TR 80-015.For rotary nozzle,DIX decreased 70.3%and 26.0%with Silwet and Greenwet 360 separately,while Break-thru Vibrant had no effect on it.DIX could be increased by increasing the liquid density.Then Spraytec and PDIA(Particle Droplets Image Analysis)were used to explore the influence of droplet size and velocity on spray drift.DIX decreased as VMD increased,VMD and volume percentage of droplets with diameter<75 ?m were considered to be important factors affecting drift potential.The velocity of spray droplet showed positive correlation with droplet size and spray pressure.By using combinations of nozzle,spray drift could be reduced by making the best use of large and small.droplets.By developing a drift test bench for testing drift potential of boom sprayer which could be an effective alternative for drift assessment when wind tunnel was unavailable.This study followed the ISO 22369-2-2010 standard to measure the drift loss and the potential drift of different nozzles indoor.The test showed that the droplet size and pressure were the main factors affecting drift loss(P<0.05).When using two IDK nozzles,potential drift was minimum because of the larger droplet size which consistented with the result of PDIA test.Spray drift test of boom sprayer in wheat field was done as follows and it was found that by using the combination of nozzles,penetration and coverage differed as the same amount of spray deposition volume.When the droplet size was small,it had a better coverage but could evaporate easily at the same time,when the droplet size was large,the potential of drift could be reduced but the droplet could also be lost as it bounced and rolled off from the leaf surface.Adjuvant Silwet DRS-60 had a better anti-drift effect than other adjuvant while using ST nozzles,it could reduce 50%sediment spray drift and 22%airborne drift which consistented with the result in the wind tunnel.Spray drift testing method was developed to research on UAV(unmanned aerial vehicle),rotary impactor was compared with polythene lines in the wind tunnel to prove its high collecting efficiency and it was found that it could be used to collect small droplet above the ground in field test,petri dishes could be used to collect sediment drift from downwind direction within 20 meters while polythene lines on the frame could collect the spray droplet around the UAV,which showed the patterns of droplet distribution from vertival distance.Finally,spray drift and depositon test of UAV in wheat field was carried on,the results showed that wind speed was positively correlated with the application rate of spray drift based on rotary impactors and petri dishes(correlation coefficient was 0.97 and 0.93,respectively)while it was not well related to DIX of sampling frame.Wind speed had a better influence on spray drift than flight height and flight speed.The 90%drift droplets were located within a range of 9.3-14.5 m of the target area,so a 15 m buffer zone should be considered downwind the spraying field for safe aerial spraying.Dv0.5 and percentage of droplets with diameter ?75?m had very significant effects on spray drift percentage(P=0.01);the risk of drift in agricultural spraying could be significantly decreased not only by reducing the percentage of fine droplets but also by widening droplet spectra.Compared to water,Silwet DRS-60,ASFA+B,T1602,Break-thru Vibrant,QF-LY and Tmax could reduce 65%,62%,59%,46%,42%,19%spray drift,respectively.when water without adjuvants were spayed,90%of drift droplets were located within a range of 10.1 meters of the target area while with 0.8%Silwet DRS-60 adjuvant in water,the distance was shorten to 6.4 meters.In conclusion,spray drift of boom sprayer and UAV was closely related to the concentation of adjuvant in the spray liquid.By using boom sprayer with the combination of nozzles,both small and large droplet could be used properly to mitigate spray drift as well as improving the effective utilization of pesticide in wheat field.