Abstract Aiming at improving fertilizer management by assessing fertilizer dissolution, we compared the hygroscopicity of calcium ammonium nitrate (CAN), ammonium nitrate (NS 27‐4), and nitrate compounds (laboratory grade). Dissolution of N fertilizers was also studied under simulated rain conditions. All compounds were highly hygroscopic, dissolving within 24 h at 90–99% relative humidity and 25 °C. Addition of 2 mm rain to fertilizer granules (3–4.5 mm diam.) was sufficient to dissolve 50% of the compounds. Dissolution rates by humidity or rain were not the limiting step for plant availability.