Unmanned aerial vehicles (UAVs) are becoming increasingly used in agriculture. Many agricultural operations, the involving UAVs are carried out at low flying altitudes, which generates a powerful downwash flow field that changes the shape of plants. To explore the influences of the downwash flow field on the shape of plants, this paper focused on rice plants at heading stage and tested the effect of different UAV flight parameters. The single-factor tests in hover showed that the wind speed at the rice canopy reduced and turbulence intensity of the downwash flow field increased as the UAV flight altitude increased from 2 to 8 m. Moreover, it showed that the degree of rice plant deformation was closely related to the maximum velocity of the downwash flow field. The multifactor field tests showed that the area of rice deformation was shaped like a horseshoe; and the flight altitude (1.5–5 m), flight speed (1–5 m s⁻¹) and payload (0–20 kg) had obvious effects on rice plant deformation with the greatest effect due to payload, followed by flight speed, and flight altitude. When the maximum wind speed was less than 3 m s⁻¹, the downwash flow field did not cause obvious changes to rice plant morphology.

无人机（UAV）正越来越多地用于农业。许多涉及UAV的农业作业都是在低空飞行高度下进行的，这会产生强大的下冲流场，从而改变植物的形状。为了探索下冲流场对植物形态的影响，本文重点研究了抽穗期的水稻植株，并测试了不同无人机飞行参数的影响。悬停的单因素试验表明，随着无人机飞行高度从2 m增加到8 m，水稻冠层的风速降低，下冲流场的湍流强度增加。此外，它表明水稻植物的变形程度与冲洗流场的最大速度密切相关。多因素田间试验表明，水稻变形区的形状像马蹄形。和飞行高度（1.5–5 m），飞行速度（1–5 m s^-1）和有效载荷（0–20 kg）对稻株变形有明显影响，其中最大的影响是有效载荷，其次是飞行速度和飞行高度。当最大风速小于3 m s ^-1时，向下冲洗流场没有引起稻株形态的明显变化。