Only 47% of the total fertilizer nitrogen applied to the environment is taken up by the plants whereas approximately 40% of the total fertilizer nitrogen lost to the environment reverts back into unreactive atmospheric dinitrogen that greatly affects the global nitrogen cycle including increased energy consumption for NH3 synthesis, as well as accumulation of nitrates in drinking water. In this letter, we provide a mechanochemical method of inorganic magnesium and calcium salt–urea ionic cocrystal synthesis to obtain enhanced stability nitrogen fertilizers. The solvent-free mechanochemical synthesis presented can result in a greater manufacturing process sustainability by reducing or eliminating the need for solution handling and evaporation. NH3 emission testing suggests that urea ionic cocrystals are capable of decreasing NH3 emissions to the environment when compared to pure urea, thus providing implications for a sustainable global solution to the management of the nitrogen cycle.