The pulse width modulation (PWM) spray system is the most advanced technology to obtain variable rate spray application without varying the operative sprayer parameters (e.g. spray pressure, nozzle size). According to the precision agriculture principles, PWM is the prime technology that allows to spray the required amount where needed without varying the droplet size spectra which benefits both the uniformity of spray quality and the spray drift reduction. However, some concerns related to the effect of on–off solenoid valves and the alternating on/off action of adjacent nozzles on final uneven spray coverage (SC) have arisen. Further evaluations of PWM systems used for spraying 3D crops under field conditions are welcomed. A tower-shaped airblast sprayer equipped with a PWM was tested in a vineyard. Twelve configurations, combining duty cycles (DC: 30, 50, 70, 100%) and forward speeds (FS: 4, 6, 8 km h⁻¹), were tested. Two methodologies, namely field-standardized and real field conditions, were adopted to evaluate the effect of DC and FS on (1) SC variability (CV%) along both the sprayer travel direction and the vertical spray profile using long water sensitive papers (WSP), and (2) SC uniformity (I_U, index value) within the canopy at different depths and heights, respectively. Furthermore, the SC (%) and deposit density (Nst, no stains cm⁻²), determined using short WSP, were used to evaluate the spray application performances taking into account the spray volumes applied. Under field-controlled conditions, the pulsing of the PWM system affects both the SC variability measured along the sprayer travel direction and along the vertical spray profile. In contrast, under real field conditions, the PWM system does not affect the uniformity of SC measured within the canopy. The relationship between SC and N_st allowed identification of the ranges of 200–250 and 300–370 l ha⁻¹ as the most suitable spray volumes to be applied for insecticide and fungicide plant protection products, respectively.

脉宽调制 (PWM) 喷涂系统是最先进的技术，可在不改变喷涂机操作参数（例如喷涂压力、喷嘴尺寸）的情况下获得可变速率喷涂。根据精准农业原则，PWM 是主要技术，它允许在需要的地方喷洒所需的量，而不会改变液滴尺寸谱，这有利于喷雾质量的均匀性和减少喷雾漂移。然而，与开关电磁阀和相邻喷嘴的交替开关动作对最终不均匀喷雾覆盖 (SC) 的影响有关的一些问题已经出现。欢迎对用于在田间条件下喷洒 3D 作物的 PWM 系统进行进一步评估。在葡萄园中测试了配备 PWM 的塔形鼓风喷雾器。十二种配置，^-1 )，进行了测试。采用两种方法，即田间标准化和实际田间条件来评估 DC 和 FS 对 (1) SC 变异性 (CV%) 沿喷雾器行进方向和使用长水敏纸 (WSP) 的垂直喷雾剖面的影响) 和 (2)分别在不同深度和高度的冠层内的SC 均匀性（I _U，指数值）。此外，SC (%) 和沉积密度（Nst，无污渍 cm ^-2)，使用短 WSP 确定，用于评估喷洒性能，同时考虑喷洒量。在现场控制条件下，PWM 系统的脉冲影响沿喷雾器行进方向和垂直喷雾轮廓测量的 SC 变异性。相比之下，在实际现场条件下，PWM 系统不会影响树冠内测量的 SC 的均匀性。SC 和 N _st之间的关系允许分别将 200-250 和 300-370 l ha ^-1的范围确定为最适合用于杀虫剂和杀菌剂植物保护产品的喷雾量。