From Havlin, Beaton, Tisdale and
Of the liquid N fertilizers used for direct application in the
United States, non-pressure N solutions are next to anhydrous NH3 in
popularity. In 1995 usage of N solutions was more than 9.5 million
tons, equivalent to approximately 24% of the total N consumed. Some of
the reasons for the rapid growth in use of N solutions are:
I .Easier and safer to handle and apply
than other N fertilizers (especially NH3)
2. Applied more uniformly and accurately than solid N sources.
3. Many pesticides are compatible with N
solutions and both can be applied simultaneously, eliminating one pass
across the field.
4. Applied through various types of
5. Safely transported in pipelines,
barges, and railcars, which are less expensive and hazardous than the
containers required for anhydrous NH3.
6. Low-cost storage facilities can be
used to store them more economically than most other N products.
7. Excellent sources of N for use in
formulation of fluid N, P, & and S fertilizers.
8. Lower cost of production than most
solid N sources.
N solutions are usually produced from
urea, NH4NO3, and water and are referred to as UAN solutions. Each UAN
solution has a specific salting-out temperature, which is the
temperature below which dissolved salts begin to precipitate out of
solution. The salting-out temperature determines the extent to which
outside winter storage may be practiced and the time of year at which
these solutions may be field applied. Salting-out temperatures vary
directly with the concentration of plant nutrients in solution. The most
positive feature of non-pressurized solutions is their ease of handling
and application. Direct application, either broadcast or band applied,
is common. N solutions are often added directly to grasses and small
grains. When grass- lands are not dormant, spray applications of UAN can
cause foliage scorching. A temporary leaf burn, usually lasting for less
than a week, will sometimes occur when broadleaf herbicides and N
combinations are sprayed on small grains.