Particle shape and size distribution
Fertilizer prills have a smooth and glassy surface, whereas the surface of the granules can vary a lot; normally granules are more rough and uneven than prills. The colour of the particle surface can vary according to raw materials applied in the process or due to mineral or organic pigments added to colour the particles.
The particle size distribution is important for spreading properties and segregation tendencies. It is especially important if the component is in bulk blends.