| Xinjiang is the largest commercial cotton base in China and an important cotton producing area in the world.The spray application of defoliants is an important link in the realization of mechanized production of cotton harvest.In recent years,the plant protection unmanned aerial vehicle(UAV)has developed rapidly and become the main equipment of cotton defoliant spraying in Xinjiang.However,there are many kinds of defoliants,and the contents and formulation of active ingredients are seriously homogenized.There is no cotton defoliants formulation which is suitable for plant protection UAV.In this study,combined with the spraying technology of cotton defoliants for plant protection UAV,10 kinds of defoliants used in Northern Xinjiang cotton area were selected as the objects,and 7 kinds of defoliants were selected through field efficacy test.The effects of the defoliants formulation,storage time after preparation,and physicochemical properties of the 7 kinds of defoliants on the spraying operation of plant protection UAV were studied.The purpose is to provide theoretical guidance for the scientific use of cotton defoliants by plant protection UAV.The main research results are as follows:1.The effects of 10 kinds of defoliants(Suspension concentrate(SC): BJF,YT,TLB,KC,ZL,TTL,wettable powder(WP): TT,Water dispersible granule(WDG): RTL,Oil dispersion(OD): CS,BL)sprayed by four rotor plant protection UAV were studied.The results showed that the droplet size of TLB was the largest in the upper,middle and lower layer of cotton canopy(402.9 μm,383.4 μm and 380.6 μm),and the droplet size of the other 5 kinds of SC and BL had little difference in each canopy.The droplet size of TT,RTL and CS in the upper part of cotton canopy was larger than that in the lower part.The droplet density of CS and BL was the highest in the upper part of canopy(34.85/cm2 and 28.81/cm2),among the 6 SCs,ZL was the highest(27.12/cm2),BJF was the lowest(13.99/cm2).The droplet density of BJF and KC in the middle and lower part of canopy was significantly higher than the other eight defoliants.The droplet coverage of YT(2.46%),TLB(2.68%),TTL(2.75%)and ZL(2.26%)were better than BJF(1.25%)and KC(1.5%)in the upper part of cotton canopy,and BJF and KC were significantly higher than the other 8 defoliants in the lower part of canopy.The droplet coverage of CS and BL was the highest(4.06% and 4.74%),and RTL was slightly lower than that of CS and BL.The droplet coverage of OD and WDG were significantly higher than that of SC and WP.The average coefficient of variation of 10 defoliants in each canopy of cotton did not exceed 60%,and the uniformity of droplet distribution was good.The defoliation rate of BL was the highest(68.7%,79.6%,94.5%)and ZL was the lowest(47.8%,64.7%,81.6%)at 5 d,8 d and 10 d after spraying.The defoliation rate of each treatment was more than 97% 15 days after spraying.ZL and KC had poor effect on the improvement of boll opening rate,CS had the best effect on the improvement of boll opening rate,and the other defoliants had no significant difference.Choose BJF,TTL,CS,BL,TT,RTL for further research.2.The physical and chemical properties of 6 kinds of defoliants and XSL were studied.The results showed that the suspension rates of TTL,BJF,XSL,TT,RTL,CS and BL were more than 90% when the preparation time was 0 min,while the suspension rates were significantly decreased after 24 h,respectively.With the prolongation of storage time,the effective components precipitated in all treatments,and floccules appeared in the upper part of RTL,CS and BL.The retention of BJF,TTL,TT,RTL,BL,CS and XSL on cotton leaves was5.50 mg/cm2,5.49,4.65,4.24,4.61,5.82,5.20 mg/cm2,respectively when the preparation time was 0 min,while the retention on cotton leaves reached the lowest value after 24 hours,.The retention of BJF and TT decreased by 61.4% and 60.4%,respectively.The retention of XSL decreased by only 43.5%.The retention of WP and WG was the lowest.The contact angle of BJF solution on cotton leaves did not change significantly.The contact angle of TT solution was 0 ° before 3 hours of storage.The content of thidiazuron in the seven cotton defoliant solutions decreased with the prolonging of storage time after preparation.Integrating the physical and chemical properties of each drug solution,the application of the drug solution within 1 h after the completion of the preparation has the least impact on the physical and chemical properties of the drug solution.3.Taking the six rotors plant protection UAV as the spraying equipment,the effects of the storage time after the preparation of the defoliant solution on the droplet deposition and defoliation and boll opening effect were studied.The results showed that except BJF,the droplet size of the other 6 defoliants in the upper canopy of cotton did not change significantly with the storage time.The droplet density of BJF did not change significantly with the storage time.The droplet density of TTL and RTL were 8.6/cm2 and 12.8/cm2 at 0 min,21.8/cm2 and 20.6/cm2 at 24 h,respectively.The droplet density of TTL,RTL and XSL increased with the prolongation of storage time,while the droplet density of TT,CS and BL increased first and then decreased with the prolongation of storage time.TT,XSL,TTL and RTL did not change significantly with the prolongation of storage time,while the other three defoliants changed irregularly.In addition to the influence of the storage time on the droplet density of defoliant,the influence on the droplet size and coverage rate is small.The BJF droplet distribution uniformity is the best,and the coefficient of variation does not exceed 60% within 0min～24.The least uniformity of the droplet distribution is XSL,and the coefficient of variation does not exceed 60% only 6h after preparation.The defoliation rates of BJF,TTL,TT,RTL,BL,CS and XSL were 58.7%,62.2%,57.1%,58.0%,63.1%,65.2% and 57.9% respectively at the time of 0 min,after 7d spraying.The defoliation rates were 45.8%,49.1%,48.2%,32.5%,55.1%,50.7% and 46.2%respectively when the leaves were stored for 24 hours,after 7d spraying.The defoliation rates were 93.5%,91.5%,95.2%,94.6%,93.7%,93.3% and 92.3% respectively at the time of 0min,after 15 d spraying.The defoliation rates were 84.7%,82.0%,84.7%,76.6%,87.9%,85.1% and 72.0% at 24 hours,after 15 d spraying.The defoliation rate of 7 defoliants decreased with the prolongation of storage time,but had little effect on boll opening rate and cotton quality.When the defoliant is placed for more than 1 h,it will have a significant impact on the defoliation rate of the defoliant,so the defoliant should be applied within 1 h after the preparation of the defoliant. |
PDF Full Text Request