Urea is used in several ways to provide N nutrition for
plants. It is most frequently broadcast and incorporated
(mixed) with soil, or broadcast applied to the soil surface in a solid form. Due to its high water solubility (1,080 g/L
at 20oC or 9 lbs/gal), urea can also be dissolved in water and
applied to soil as a fluid, added to irrigation water, or sprayed
onto plant foliage. It is commonly combined with a solution
of ammonium nitrate to form UAN (urea ammonium nitrate),
where urea accounts for half of the N content.
Despite its widespread use, there are fundamental properties
of urea that necessitate careful management in order to recover
its full nutritional value.