Het effect van PWM op driftreductie van een spuitdop: Effecten van Pulse Width Modulation op druppelgroottes, -snelheden en drift(reductie)

Pulse width modulation (PWM) systems are used in agricultural spray applications to change the applied rate of plant protection products without having to change the pressure on the application system or the nozzle. The assumption is that this can be done without major effects on other spraying characteristics which contribute to off-field spray drift, such as droplet size and speed. Previous studies, as well as this study, however show there is an effect of applying PWM to spraying characteristics of the used nozzle and consequently on spray drift. In this study, 3 different nozzle types at 4 different PWM duty cycle settings were measured using a PDPA system. The results show that both droplet speed and droplet size are effected using PWM. For the Dutch authorities, drift reduction of nozzles used in downward spraying is determined using the IDEFICS model. Nozzles used for up- and sideward spraying are classified for drift reduction by comparing the V100 (volume fraction in droplets smaller than 100 μm) to reference nozzles. For both situations the percentage drift reduction decreases when the PWM duty cycle decreases. With this reduction there is the possibility that a nozzle should be classified in a lower nozzle drift reduction class when using PWM at specified settings.