The blending problem has been dealt with in the literature since 1945 in different industrial fields with the general aim of defining the optimal mixture to satisfy the demand under very specific constraints. Our paper proposes an extended version of the traditional LP formulation of the blending problem within the phosphate mining industry. This new “dynamic blending” method takes into account the slight instability of the chemical composition of source ores (SO), the availability of SOs in the mine and in secondary stocks (near the blending plants), storage constraints, the availability of blending processors and the orders to be met. The risk related to an unforeseen order of end-customers is mitigated by proper sizing of safety stocks for some critical SOs combined with the flexibility provided by dynamic blending. This model makes it possible to define the optimal quantities to be withdrawn from each source layer as well as the feeding transfers from the primary stock (mine) to the secondary stock. Dynamic blending allows an upgrade from a fixed-BOM rationale to a dynamic-BOM rationale in relation to SO availability and orders to be met.