Urea, a white crystalline solid containing *6% nitrogen, is widely
used in the agricultural industry as an animal feed additive and
fertilizer Here we discuss it only as a nitrogen fertilizer.
Commercially, fertilizer urea can be purchased as prills or as
a granulated material. In the past, it was usually produced by
dropping liquid urea from a "prilling tower" while drying the
product. The prills formed a smaller and softer substance than
other materials commonly used in fertilizer blends. Today, though,
considerable urea is manufactured as granules. Granules are larger,
harder, and more resistant to moisture. As a result, granulated
urea has become a more suitable material for fertilizer
blends.
