Determining the effect of wind on the ballistic flight of fertiliser particles

With the increase in working widths for applicators, granular fertiliser particles spread by centrifugal spreaders have more extensive airborne trajectories. In the field, particles can be subjected to wind which can cause their trajectories to change. In this paper, a 3D ballistic model was developed describing the motion of fertiliser particles taking wind effects into account. The physical properties of eight commonly used fertiliser types were determined: particle density, size distribution and angle of repose. X-ray micro computed tomography was used to determine the shape of the particles and estimate the corresponding drag coefficient. Using these parameters in the newly derived ballistic model, the effect of wind on individual fertiliser trajectories was quantified for each fertiliser type. Three wind directions (head- tail- and crosswind) were analysed for two windspeeds: 3 and 6 m s−1. The magnitude of the effect was strongly dependent on the physical properties of the fertiliser type, the windspeed and wind direction. Simulations showed that a windspeed of 3 m s−1 already can affect the landing position of individual fertiliser particles by several metres. Generally, particles with lower density, smaller size and a more irregular shape were more sensitive to wind.