The study investigated the effect of internal disturbances to the fluid flow in a typical agricultural flat fan nozzle on the liquid sheet structure, wavelength, breakup position, and finally the droplet size distribution. The internal disturbances were generated by a cylindrical insert upstream of the final orifice, and the magnitude war, determined by the insert diameter. The liquid sheet structures were recorded using short-duration photography. The quantitative effects of the insert size on the breakup length and volume median droplet diameter (VMD) were measured using a phase Doppler analyzer (PDA). The results showed that it is possible to increase the droplet size, such that the proportion of spray volume in small droplets less than 100 mu m is reduced by 45%, without significantly affecting the other spray characteristics such as the spray angle and spray pattern at a normal working pressure for agricultural spraying.