On-the-field simulation of fertilizer spreading: Part 2 – Uniformity investigation

•Application maps on realistic regular and irregular non-flat fields are given.•Application errors are in the form of overapplication and underapplication areas.•Application errors magnitudes are outside tolerable levels of ±5% on flat fields.•The uniformity can be manageable by the use of various control devices. Modern centrifugal spreaders use active control devices to manage various disturbances affecting the spreading uniformity on flat fields. Yet, non-flat fields that are also likely to cause application errors, are still not taken into consideration. This was highlighted in some experimental studies, limited to the case of single spread patterns on regular non-flat fields. In this study, overall spread patterns uniformity was investigated through simulation. The model used was presented in the paper (“On-the-field simulation of fertilizer spreading: Part 1 – Modeling”). Using computer generated DEMs (digital elevation models), several cases were investigated: regular fields were represented by a longitudinal and side slope, and irregular fields by a longitudinal and side slope break. The results obtained were in the form of application rate maps, showing the areas of overapplication and underapplication. These areas were also characterized by the mean longitudinal and transverse application rates, which gave the application errors magnitudes. The latter were in the case of irregular fields, up to a maximum of +45%, and a minimum of −25%, around the theoretical value of 100% for a perfectly uniform area. These application errors were mainly attributable to altered ballistic flights range, caused by the difference between the tractor and spread surface inclination, and to a lesser extent, by the work of the gravity. These results allow bridging the knowledge gap around overall spread patterns uniformity on non-flat fields. They can also help in developing new active control devices.