A comparative study on the spraying effect of orchard wind sprayers under different air supply modes

Abstract:【Objective】Pest control is one of the important aspects in orchard management, and mainly depends on spraying pesticides. With the change in climate across the seasons, pesticides are sprayed 8- 15 times in orchards in a year, and the workload accounts for about 30% of the total management work. Therefore, machinery for plant protection in orchards is very important. The performance of spraying machinery directly determines pest control result and thus the economic profit of the orchard. Evaluat- ing the spraying effect of orchard sprayers under different air supply modes based on liquid consump- tion, droplet distribution in the crown, attachment of droplets to the lower surface of the leaves and the penetration performance of the droplets provides technical reference for the design of the wind convey- ing system of air blast sprayers used in orchards.【Methods】The 450 type turbofan sprayer from Vicar, Italy, and fxl7b- 18 / 440 tower type and FXD / 340 circular fan type sprayers from China’s Taizhou Xinyi Agricultural Machinery Co., Ltd. were selected as the research objects. We will use water sensi- tive paper, hot wire anemometer (QY-AM-4204, Handan Qingsheng Electronic Technology), Taihong tractor (TH804-3), rotational speed tester, thermometer and hygrometer (AS847), box ruler (3m), tape measure (30m), stopwatch and other instruments to test. The test was carried out at an ambient tempera- ture of 15-20 °C, a humidity of 40%, and a northwest wind speed of 3 m · s- 1. The operation speed was 1.25 m · s- 1. Two rows of trees were selected as the experimental block in the orchard. Six fruit trees (three trees in each row) with well-developed canopy were selected for the test, which was carried out in accordance with the national standard of air supply sprayer. Through this field experiment, the charac- teristics of droplet deposition and canopy distribution were compared and analyzed.【Results】1) Under the same operation condition, the tower type and circular type sprayers saved about 36% and 33.3% liq- uid consumption, respectively. 2) The distribution of droplets was concentrated in the middle and lower layers of the canopy in all the three models and the difference was between 17.28% and 29.51%, while droplet distribution in the upper layer created by the turbine type sprayer was significantly less than the other two models and the difference was between 66.65% and 69.03%. Under the droplets national stan- dard of 20 drops·cm-2 for orchard spray, the upper layer in the treatment of air assisted sprayer had less drift and thus a higher liquid utilization rate; 3) Droplet density difference between the upper and the lower leaf surface in the treatment with the turbo air assisted sprayer was 9.60%, and the difference in the groups with the other two types was 39.48%-42.70%. The results showed that the turbo air assisted sprayer was more uniform than the other two types and the adhesion effect on the lower leaf surface was better; 4) According to the analysis of variance, the penetration performance of the three models was similar.【Conclusion】The turbine air sprayer has less liquid consumption, less drift, and less im- pact on the quality of fruits, and is thus more suitable for orchard spraying.