Parameter Optimization And Effect Evaluation Of Chemical Capping Operation For Multi-rotor Plant Protection UAV In Cotton Fields

[Objective]To study the operational effects of chemical capping for multi-rotor plant protection UAV,propose flight parameters to ensure operational quality,clarify the concentration range of chemical capping agent application,and provide reference for the application of chemical capping technology for UAVs in cotton fields in southern Xinjiang.[Method]Three field trials were conducted with’Tahe 2’as the test variety:（1）Capping method test.Set up three processes:manual capping,non capping,and UAV chemical capping to verify the effectiveness of UAV chemical capping.（2）Parameter screening test for chemical capping operation of UAV.Set up an additive group and a non additive group,each group using a two-factor split zone test design.The UAV operation height is the main zone（2,2.5,3,3.5 m,represented by H1,H2,H3,and H4）,and the UAV flight speed is the sub zone（3,5,7 m/s,represented by V1,V2,and V3）.Measure the droplet density,droplet deposition,and droplet diameter characteristics of the upper,middle,and lower leaves of the cotton canopy layer to evaluate the effectiveness of flying spraying operations;（3）UAV chemical capping agent concentration test.Select Guoguang Guanding^○Rbrand combination medicament（250 g/L meperidium aqueous solution+5%uniconazole wettable powder+92%methyl oleate emulsifiable concentrate）,and set up three concentration combinations,namely,high concentration（1 500 ml+375g+47.5 ml per hectare）,medium concentration（1 200 m+300 g+40 ml per hectare）,and low concentration（900 ml+225 g+22.5 ml per hectare）,to clarify the concentration range of UAV flying spray..[Result]（1）The experimental results of different capping methods showed that the plant height,number of fruit sets,number of green leaves on main stems,and total fruit nodes of UAV chemical capping decreased by 5.95%,8.60%,1.46%,and 12.44%compared to those without capping,and increased by9.74%,40.16%,12.55%,and 9.10%compared to manual capping.The leaf SPAD value,LAI,and single leaf Pn all showed chemical capping>artificial capping>non capping.The dry matter accumulation of roots,leaves,and reproductive organs was chemical capping>artificial capping>non capping,and the stem was non capping>chemical capping>artificial capping.The upper and lower parts of chemical capping had 0.12and 0.17 fewer bolls than manual capping,0.40 and 0.57 more than non capping,and the middle part had0.39 more bolls than manual capping,0.02 less than non capping.The ratio of upper,middle,and lower parts was 0.36:0.40:0.24,which was between manual capping and non capping.There was no significant difference in the ratio of inner and outer bells between chemical capping and manual capping.Compared with manual topping,the yields of seed cotton and lint cotton with chemical topping decreased by 2.08%and 2.95%,with no significant difference,but increased by 13.34%and 16.34%,with significant differences.（2）The results of experiments with different flying parameters showed that:a.In the upper canopy,H2V2 had the highest droplet density,followed by H1V1.The average droplet density of the additive group was 21.78%higher than that of the non additive group;The maximum droplet deposition amount was H2V2,and the auxiliary group reached 0.383 3μL/cm²,no additive group up to 0.266 7μL/cm²;The relative particle size spectrum widths of H3V2,H4V1,and H2V2 droplets were significantly smaller than those of other treatments,and their additive group was significantly lower than that of the non additive group;b.In the middle canopy,H2V2 had the largest droplet density and droplet deposition,followed by H3V1.The average droplet density and droplet deposition in the auxiliary group were 52.80%and 123.12%higher than those in the non auxiliary group;The relative droplet size spectrum width of the auxiliary group was the lowest in H3V1,while that of the non auxiliary group was the lowest in H4V3.The average value of the auxiliary group was 7.62%lower than that of the non auxiliary group;c.In the lower canopy,H2V2 had the highest droplet density,followed by H1V1,with an average droplet density of69.10%higher in the adjuvant group than in the non adjuvant group;The droplet deposition amount in the auxiliary group was the largest in H2V2,followed by H3V1,and that in the non auxiliary group was the largest in H1V1,followed by H2V2.The average value of the auxiliary group was 93.73%lower than that in the non auxiliary group;The relative droplet size spectrum width of the auxiliary group was the lowest in H2V1,while that of the non auxiliary group was the lowest in H4V1.The average value of the auxiliary group was 9.10%lower than that of the non auxiliary group;d.The droplet density and deposition amount decreased with the deepening of the canopy,while the relative particle size spectrum width of the droplets had no significant difference.The total amount of fog droplet deposition in the canopy was the largest with H2V2,and the auxiliary group reaches 0.834 3μL/cm²,0.422 1 for the group without additivesμL/cm².The CV value of droplet deposition in each part was the smallest for the auxiliary group with H2V2,and the smallest for the non auxiliary group with H1V2 and H2V2.（3）The concentration test of UAV chemical capping shows that the capping effect of high concentration chemical capping agent was better than that of medium and low concentration chemical capping agent.The plant height,plant width,and number of main stem nodes of low concentration treatment increased by 8.85%,4.31%,and 13.41%compared to medium concentration treatment,while those of high concentration treatment increased by 11.85%,10.84%,and22.97%,respectively;The total number of fruit branches in the low concentration treatment decreased by12.73%compared to the medium concentration treatment,while the total number of fruit branches in the high concentration treatment increased by 20.39%.From the perspective of material accumulation and distribution characteristics,the total dry matter of stems and leaves of cotton plants under low concentration treatment was significantly higher than that under medium and high concentration treatment,but the dry matter accumulation of cotton reproductive organs under medium concentration treatment was significantly higher than that under low concentration treatment,and the difference between medium and high concentration treatment was not significant.[Conclusion]UAV chemical capping can effectively control the cotton plant type,promote the coordinated distribution of cotton bolls,and maintain a high yield,with similar effects to manual capping.When the unmanned aerial vehicle operated at a height of 2.5 m,a speed of 5 m/s,and additives were added,the deposition and uniformity of group droplets were the largest,and the penetration of droplets was the strongest;Spraying the combination agent of Guoguang Guanding^○Rbrand,with medium and high concentration（250 g/L methylpiperidine water agent 1 200～1 500 ml/hm²+5%uniconazole wettable powder 300～350 ml/hm²+92%methyl oleate emulsifiable concentrate 40～47.5 ml/hm²）,had a good capping effect,which could be used as a reference dosage for production practice.