Aerodynamic properties of six organo-mineral fertiliser particles

Agricultural fertilisers are generally applied by means of centrifugal disk spreaders. The machinery, the working conditions and the physical characteristics of fertilizers (including the aerodynamic characteristics of particles) may affect the behaviour of particles after the discarding from the spreader. We investigated the aerodynamic properties of organo- mineral fertilisers (a class of slow release fertilisers that are less investigated since they are relatively new in the market) using a vertical wind tunnel similar to an elutriator. In the same time, the morphological characteristics of individual fertilizer particles were measured by means of an image analysis procedure. In the study we compare six different fertilisers and we discuss the suitability of the employed methods. The results provide the terminal velocity - Vt (the velocity value that overcome the gravity force of the particles) of the particles, ranging from 8.60 to 9.55 m s(-1), and the relationships between Vt and some physical properties (mass, shape, dimensions) of the fertilizers. Moreover, the results of field distribution trials show the behaviour of the tested fertilizers during practical use. Such data can contribute to enhance the quality of application of these products in field.