Discrete element modelling (DEM) of fertilizer dual-banding with adjustable rates

Multiple band fertilizer application has gained its popularity due to its advantages over other application methods. However, detailed information in this research area is currently scarce. In this study, a dual-band fertilizer applicator was developed to simultaneously deliver starter and base fertilizer as separate bands into the soil. The working process of the applicator was modeled using the discrete element method (DEM) to examine the effects of machine parameters on the ratio (ρs) of discharged starter and base fertilizer, as well as the separation distance (H) of the fertilizer bands. The DEM model results were validated using both laboratory and field measurements. Model results showed that ρs increased linearly as the working length of the meter roller increased; ρs remained nearly constant when the rotational speed of the roller changed. An increased H was observed at faster machine speeds and smaller spacings of the vertical and longitudinal fertilizer delivery tubes. The DEM model could generate the optimal machine parameters for fertilizer application in the given condition. For wheat, the optimum machine speed was 3.9 km h−1 and the optimum spacings of vertical and longitudinal fertilizer delivery tubes were 66 and 194 mm, respectively. Simulated values of H obtained from the DEM model had low relative errors (11.86% on average) with respect to the field measurements. This showed that the DEM model was able to simulate the dual banding fertilizer application with a reasonably good accuracy.