Nitrogen fertilizers contain its nutrient in different forms and are thus to be evaluated differently according to its attributes and efficacy. Ammonium nitrate (AN) and calcium ammonium nitrate (CAN) both contain nitrogen in the form of ammonia and nitrate - they simply differ from each other through the lime content of CAN. Due to this lime the handling of calcium ammonium nitrate is safer (does not underlie ADR-rules like AN), more efficient and the soil acidification is considerably lower. The bigger and evenly shaped smooth granules with the round kernels are the reason for a better spreading pattern of CAN compared to AN.
Urea is containing nitrogen in amide form. The advantage here is a high nutrient concentration of 46%. Furthermore urea does not have a corrosive effect on metals. Disadvantageous is a kind of uncertainty in its efficacy: amide-nitrogen has first to be converted by the enzyme urease to ammonia and nitrate, which is then available for the plant root. The time of conversion is very much dependent on the soil humidity and the temperature and can take very long under dry and cold conditions. During this conversion process gaseous ammonia is produced which can pass off the air. Those losses of nitrogen can under adverse circumstances amount up until 15 %. A soil incubation after spreading is preventing those N-losses. In all areas where a fast and ensured nitrogen effect is necessary, CAN shall be the first choice.