Handling and spreading of fertilizers: Part 2, physical properties of fertilizer, measuring methods and data

Abstract

Handling and spreading of fertilizer is affected by the physical properties of the particles and so a knowledge of these properties is helpful in understanding fertilizer handling and use. Methods for measuring the coefficient of friction, the coefficient of restitution, the aerodynamic resistance coefficient, and the breaking force (particle strength) of fertilizers are discussed. Measuring devices for the four properties are developed and their characteristics are described. The results of experiments with these devices are presented. The coefficient of friction is influenced to a minor extent by the velocity relative to the friction surface layer. There was almost no influence of normal load but a significant effect of fertilizer type, friction surface layer and environmental conditions. The coefficient of restitution measurements showed a large effect of the impact surface and smaller effects of particle diameter and fertilizer type. A large difference was found between two methods for measuring the aerodynamic resistance coefficient. A new shape parameter was introduced in this paper, as a parameter to determine the aerodynamic resistance of fertilizer particles. Coarser particles were shown to have a higher aerodynamic resistance coefficient than particles with a smooth surface texture. The breaking force measurements showed that the relationship between strength and particle size depended on the fertilizer type.