Current status and prospects of precise sampling of pesticide droplets

Plant protection machinery to spray pesticides is one of the most effective pest control methods in agriculture. It is necessary to accurately collect and measure the amount of droplets deposition, loss, and drift in the spraying process of pesticides, thereby optimizing the operating parameters of plant protection equipment, while improving the utilization rate of pesticides. Various samplers are available at present for sampling spray deposition, loss, and drift droplets. The selection of the samplers should meet the following requirements. Firstly, high collection efficiencies of samplers were required for the droplets of different sizes in relatively low wind speeds; Secondly, the samplers were not easy to saturate, with a certain sampling volume or area to sample sufficient droplets. A certain sampling volume or area can be used to calculate the deposition per unit area; Thirdly, the samplers should not react with active ingredients or tracers, particularly with high sampling efficiency, and stable recovery rate, where the resulting data can be quantitatively analyzed; Fourthly, the cheap samplers are easy to handle under field conditions. In this study, four types of samplers classified by the analytical approaches were introduced, including the type of image processing, chemical analysis, sensors, and rest. There were special precautions for each sampler. The selection of image processing software, correction of scanned data, and the limitations should be noticed in the type of image processing samplers. Much attention should be paid to the selection of samplers, dye or fluorescent tracer, and the volatility of pesticide active ingredients in the type of chemical analysis samplers; The type and applied scenarios were critical for each sensor and accuracy of sensors in the type of sensor samplers. In addition, there was some adhesion, rebound, or breakage failure, further detrimental to the sampling efficiency, when the droplets came into contact with the sampler. Especially for the type of chemical analysis samplers, special attention should be paid to sampling efficiency and recovery. Except for the selection of samplers, there was a significant effect on the placement position, transportation, and preservation of samplers, meteorological requirements, and sampling test sites. Five requirements or prospects were proposed for the current sampling in the future, including (a) to inspect plant protection machinery before the test, and determine the sampling efficiency and recovery rate of selected samplersfor a high accuracy of sampling, (b) to standardize the sampling or samplers in the development of fast suitable for field sampling; (c) further studies focused on the deposition of droplets containing pesticide active ingredients, (d) to develop new sampling sensors for high sampling efficiency, and (e) to establish a deposition and drift model of plant protection drones. In any way, the standardized and accurate sampling is needed to obtain comparable and highly precise data of pesticide deposition. The finding can make a great contribution to improving the current utilization rate of pesticides, particularly providing potential scientific and technical guidance for the "zero growth" of pesticide usage.