Granular fertilizers should have appropriate mechanical strength to resist significant fracturing during the handling and storage process. Graphene (GN) has the potential to act as a high-performance reinforcement for different composites. This paper provides a comprehensive study of the influence of GN concentration on the crushing strength of two fertilizers (monoammonium phosphate (MAP) and diammonium phosphate (DAP)) with different initial hardness. The results show differences in concentration dependence, with optimum concentration of 0.5% GN for MAP and 0.05% for DAP increasing their crushing strength by 1680% and 673%, respectively. The effect of different physicochemical properties of GN, such as method of preparation and specific surface area (SSA) on the crushing strength of the fertilizer was also investigated. Results showed dependence of granules' crushing strength on the method of GN production and their SSA, while GN samples with a high degree of reduction and SSA were more effective than others. (C) 2019 Elsevier B.V. All rights reserved.