Laboratory studies on dissolution of nitrogen fertilizers by humidity and precipitation

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 degrees 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.