| 摘要 |
[Objectives] To determine the optimal concentration of topping agents applied by unmanned aerial vehicles (UAVs) to effectively regulate cotton growth and improve production efficiency. [Methods] A field experiment was conducted in Shihezi City, Xinjiang, employing a randomized block design. Five UAV-based chemical topping treatments were applied at dosages of 0.300, 0.525, 0.750, 0.975, and 1.200 L/hm2, designated as H1, H2, H3, H4, and H5, respectively. Additionally, manual topping (CK1) and tractor topping (CK2) treatments, both at a concentration of 0.750 L/hm2, were included as control treatments. During the first 20 d following topping, parameters including primary agronomic traits of cotton (plant height, leaf age, number of fruit branches), dry matter accumulation and distribution, leaf area boll load (LAB), root-to-shoot ratio (RSR), leaf mass area (LMA), and leaf area index (LAI) were examined. At harvest, yield components, lint cotton yield, harvest index, and fiber quality were evaluated. [Results] Twenty days after topping, the concentration of the topping agent applied via UAV did not significantly affect cotton leaf age or the number of fruit branches. Additionally, no significant differences in plant height were observed among the five concentration treatments compared to CK2. However, plants treated with H1 exhibited significantly greater height compared to those treated with H5 and CK1, indicating that H1 was the least effective in controlling vegetative growth. Total dry matter accumulation (TDM), boll dry matter accumulation (BDM), LAB, and LMA all demonstrated an initial increase followed by a decrease as the spraying concentration increased. The highest TDM and reproductive organ dry matter ratio (RRDM) were observed in the H3 treatment. No significant differences were found among treatments for LMA, RSR, or LAI; however, LAB and single boll weight were greatest in the H3 treatment. Fiber quality parameters, including fiber length uniformity, micronaire (MIC), specific strength, and fiber maturity, initially increased and then decreased with increasing spraying concentration, whereas fiber elongation rate exhibited the opposite trend. The H3 treatment yielded the highest average fiber length uniformity and specific strength. [Conclusions] At optimal spraying concentrations, UAV-based application more effectively controls vegetative growth, promotes dry matter accumulation and distribution in cotton bolls, increases single boll weight, and enhances the MIC, specific strength, and fiber elongation rate of cotton fibers compared to manual and tractor spraying of topping agents. In summary, the use of UAVs for spraying chemical topping agents is recommended, with a suggested dosage range of 0.750 and 0.975 L/hm2. |
