On-the-field simulation of fertilizer spreading: Part 1 - Modeling

- A model for dynamic fertilizer spreading on non-flat fields was developed.
- Some of the model input data are randomly sampled from distributions.
- The ballistic flights of particles are updated at each new position of the tractor.
- The Modeling assumptions were validated by various bench measurements.

The field elevation and its variation represent a disturbance in the spreading process that is not handled yet by centrifugal spreaders. This stems in part from the knowledge gap regarding the possible application errors of fertilizer on non-flat fields. To address this issue, a new model has been developed, integrating both the field elevation and the tractor motion. The model was employed in the paper (“On-the-field simulation of fertilizer spreading: Part 2 - Uniformity investigation”). The model was based on transformation matrices to update the initial conditions of the ballistic flight of particles in the field coordinate system at each new position of the tractor, as it moves along a given trajectory on a given DEM (digital elevation model). An experimental validation was conducted using a radial bench in different static configurations, which also provided the unknown input data for the model. High correlation coefficients were found between the characteristics of the simulated and measured spread patterns, even where, in the simulation, the model parameters were fixed and the spreader inclination varied. Thus, in addition to proving the reliability of the model, the measurements also helped determining the limits of validity of the assumptions within which on-the-field simulations can be carried out.