Prilled urea 46% incorporates 46% of nitrogen (N) in ureic form, simply absorbed through the leaves of plants. Absorption through the root system is slower, because urea in soil is converted (to be a result of enzymatic hydrolysis) into the ammonia form available for plants, and afterwards into nitrate form. https://codyrzmsf.ttblogs.com/16993485/an-unbiased-view-of-fertilizer-urea-composition