| Corn is China’s first large crops, but its applications are not standardized for prevention and control of corn borer, corn armyworms and other pests, so it is easy to bring chemica loss, excessive pesticide residues, environmental pollution and other negative issues. Thus this paper, focused on how to improve the effective utilization of pesticide in corn, explored spray atomization process and deposition behavior of droplet on corn by learning from existing research.The main conclusions are as follows:Firstly, mathematical model of droplet adhesion-broken critical point with minimum wrong number of samples was presented by analyzing a large number of laboratory test data. Combination of kinetic laws, droplet adhesion-broken energy model was builtSecondly, atomization characteristics of pesticide and droplets distribution properties were studied to search theory basis for improvement of effective pesticide utilization. The results showed that missible oil solution could make the length of spray film reduced significantly, the edge of spray film broken aggravated, the number of perforation broken increased obviously and the droplets size enlarged significantly compared with tap water and water dispersible granule solution. With the increase of adjuvant concentration, the length of spray film area were all decreased first and then increased; the structure of atomization sheet occurred morphological changes to varying degrees; the droplet size were all increased first and then decreased. Adjuvant had more effect on atomization progress of water dispersible granule solution. Missible oil and adjuvant solution allowed air induction nozzle to produce liquid droplets entertaining gas. The diameters of droplet changed wavily along with boom sprayer, and peak appeared in the center of the test area for ST and IDK serie nozzles. The impact angle between droplets and the target fell into three types:<90°,=90°,>90°. Compared with horizontal target, the deposition of50°target was decreased by one third that was determined by movement of droplet. By variance analysis, it was found that when the target was placed at an angle of50°, the deposition amounts changed significantly between the seven test points. Thus it indicated that the target angle was main induction factor for droplet distribution characteristics causing distinct differences on liquid deposition. The study with high-speed camera found that droplet deposition state significantly affected by simulation target surface properties, placement angle, and movement direction of droplet.Thirdly, microscopic surface structure of maize leaves and leaf sheaths affecting droplet deposition behavior was studied by scanning electron microscopy. It was found that the corn leaves sides have similar structural units. The back of the blade had no knitting bands and hook hair, and the space of stomata bands was smaller, the stomatal density was larger. The structure of corn leaf sheath was composed of epidermal hook hair bands and stomata bands. Compared with leaves, it had smaller stomatal density, and longer hook hair with larger number. The results supplied a certain theoretic basis for droplet deposition behavior.Finally, according to the above scientific conclusion from experimental study, the verification of correctness for above theory in production process was performed to find an effective way to improve effective pesticide utilization of actual production.By laboratory test to study the factors affecting droplet deposition behavior deposited on corn leaves, the result displayed that nozzle type, different parts of the corn leaves and the movement direction of the droplet significantly affected the state of droplet deposition. After statistical analysis, droplet adhesion-broken critical curves were got for different trajectories droplet impacting with corn leaves horizontally and50°degree placed. According to droplet adheres-broken critical energy model, the droplet adheres-broken critical energy range on the corn leaf were could accurately displayed. After analysis for all factor affecting droplet deposition,it was found that droplet with higher energy was more easily broken regardless of whether adding spray additives and angle of target; critical energy value of droplet adhesion-broken was not a single value, but possessing certain range. Critical energy range of the same droplet affected by ajuvant, droplet trajectory and target angle depended on its droplet size and speed.Adjuvant could speed up the rate of pesticide spread on maize leaves and leaf sheathes, but the rate ultimately depended on the properties of target. The angle of targets placed, nozzle types had significant effect on the deposition rate and droplet coverage. For the same serie nozzles, the bigger the nozzle type was, the lower the deposition rate was; the bigger the angle of targets placed was, the lower the deposition rate was. After adding assistant reagent, the deposition quantity reduced significantly on the horizontal surface of the leaves, and the droplet coverage mostly increased in a certain degree on the surface of the leaves, while on the surface of the leaf sheath was just the opposite. Integrated comparison of liquid deposition rate, spray process with small flow rate and small particle size was not only conducive to the effective deposition of pesticide on corn leaves, and conducive to effective deposition of pesticide active ingredients on the leaves. This was consistent with conclusion from drolet deposition behavior.After field trials, deposition rate and droplets coverage varied with the size of the droplets and the flow of nozzles, and the overall trend of deposition was:the bigger the nozzle type was, the lower the deposition rate was; the deposition rate decreased from the upper layers to to lower layers; the deposition rate was bigger on the central region of the leaves than on the base regions of leaf, than on the leaf sheathes; adjuvant could significantly decrease deposition rate on the central region of the leaves and increase deposition rate on the base regions of leaf and leaf sheathes, the increment was proportion to the flow rate of nozzle and the droplet size. Small flow rate with small dropletsize spray should be applied for improvement of the pesticide deposit and total effective deposition of pesticide active ingredients on the central part of leaves; small flow rate with big droplet size spray should be applied for improvement of the pesticide deposit and total effective deposition of pesticide active ingredients on base regions of leaf and sheath.In order to determine the acess of effective pesticide depositon and utilization, active ingredient content of chlorantraniliprole in corn leaves was tested, and the results revealed that active ingredient content of pesticide was proportional to the height of corn plant. Whether adding adjuvant, active ingredient content of pesticide sprayed by ST110-02nozzle was more than other nozzles. And it was also higher than that without additives groups. In conclusion, final active ingredient content of leaves was not only related to liquid loss of small spray, but also to closely related to the concentration of pesticide active ingredient of spray liquid; adjvant decreased deposition rate of on the central part of leaves, but active ingredient content of leaves could be improved by increasement of deposition rate on on base regions of leaf and sheath. Thus spray with a small capacity and smaller droplet was the effective access for pesticide utility. |
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