UAN 32% Solution
What is UAN 32% Solution?
UAN 32% Solution is a nitrogen fertilizer solution composed of urea and ammonium nitrate.
Approximately one-half of the N is from urea, and one-half is from ammonium nitrate.
Nitrogen is available in three forms in UAN 32% Solution--ammonic, nitrate and urea.
One-fourth of the nitrogen is ammonic, one-fourth is nitrate and one-half is urea. It
weighs 11.08 lbs. per gallon, has a pH of approximately 7 and has a negligible vapor
pressure. Each gallon of UAN 32% Solution contains 3.55 lbs. of N.
Does UAN 32% Solution have any other names?
Yes, it is also called Uran, Solution 32 and simply 32% Solution. It may also have other
names in your area.
Are other grades of UAN 32% Solution available?
Yes, in some areas UAN 32% Solution contains 30 or even 28% N. This is done to prevent
crystallization (salting out) in cold weather. UAN 32% Solution will salt out at 32° but
diluting it to 30% N will lower the salting out temperature to 15° and further diluting
to 28% will lower the salting out temperature down to only 1°F.
On what crops can UAN 32% Solution be used?
UAN 32% Solution can be used on just about all crops. It is widely used for sidedressing
cotton, vegetables, corn, beets and other crops. Sprinkler applied UAN 32% Solution is
used for tree crops such as almonds, for cereal grains, potatoes and for many other crops.
How fast is UAN 32% Solution available to plants?
The nitrogen in soil applied UAN 32% Solution is rapidly available to plants. The nitrate
portion (one-quarter of the total N) is immediately available as soon as it reaches the
root zone. The urea portion (one-half of the total N) moves freely with the soil water
until it is hydrolyzed by the urease enzyme forming ammonic nitrogen. After the hydrolysis
of urea three-quarters of the total nitrogen is ammonic nitrogen and it is held to the
clay particles in the soil and not subject to leaching. This ammonic nitrogen is available
to plants. Ammonic nitrogen is converted to nitrate by soil organisms, usually within a
few weeks after application.
Are there solutions in which UAN 32% Solution is a more efficient form of nitrogen than
Generally, dry and liquid nitrogen fertilizers will be equally available to crop plants.
The efficiency of soil-applied nitrogen fertilizers is usually independent of the source
of the nitrogen; adoption of Best Management Practices will lead to the highest efficiency
in any system.
However, university studies have shown that foliar application of liquid nitrogen
fertilizers such as UAN 32% Solution to wheat can be more efficient than broadcast
applications of dry materials. The increased efficiency is due to foliar uptake by the
plant which is more efficient than soil uptake of nitrogen.
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