Apparatus and process for coating particles

A particulate fertilizer composition comprising:

• fertilizer substrate particles,
• said particles having been substantially coated with a coating material by (a) providing a plurality of fluidized bed zones for maintaining the particles in an essentially fluidized condition, (b) providing means in at least two of said fluidized bed zones for applying a coating material onto particles in said fluidized bed zones, to provide a plurality of fluidized bed coating zones, (c) continuously feeding substrate particles into a first fluidized bed coating zone, (d) transferring said particles from a first fluidized bed coating zone to a second fluidized bed coating zone, and (e) continuously removing the particles from the second fluidized bed coating zone, said composition being characterized by its slow, continuous and controlled release with a TVA 7-day release rate of below about 50%, said particles having coatings of varying thickness comprising 3-10% by wt. of the coated particles with a standard deviation from the average coating thickness in the range of 0.1 to 0.71, the average coating thickness varying in an approximately Gaussian curve relationship with the standard deviation being related to the number of fluidized bed coating zones N as 1//N where N is 2 to 100.