Influences of wind vortex intensity of rotor UAV on rice morphology and yield

During pesticide spraying operations, the downwash airflow generated by the rotor UAV disperses the rice canopies with different wind vortex intensities, resulting in different degrees of morphological changes of rice sheaves in the target area. However, it is inconclusive whether it will affect rice yield. In this paper, dispersed canopy parameters and rice yield data through experiments of conventional flight operation and unconventional hovering operation were collected, aiming to conduct a comparative analysis of the effects of UAV wind vortex intensity on the morphology and yield of rice sheaves in the spraying operation. The results showed that in the conventional flight operation, the wind vortex had little effect on rice morphology and yield. Due to the influence of the short downwash airflow, the rice canopies were rapidly dispersed and produced a restorable canopy-vortex patch. After the UAV withdrew, the rice canopies recovered immediately. In the unconventional hovering operation, with the increase of vortex intensity, the rice canopies forged unrestorable canopy-vortex, which caused significant changes in rice morphology and eventually led to a yield reduction, of 1.21% at preliminary heading stage, 9.05% at full heading stage and 4.87% at mature stage. The experiments indicated that wind vortex did not affect rice during conventional plant protection, while the unrestorable canopy-vortex patch caused by the prolonged operational duration in unconventional hovering operation did affect rice morphology and yield, especially after the full heading stage.