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Urea
is a white crystalline substance with the chemical formula
CO(NH2)2; it is highly water soluble and contains 46% nitrogen.
Urea is considered an organic compound because it contains
carbon. It was the first organic compound ever synthesized
by chemists; this was accomplished in the early 1800s.
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Answers
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| How
is urea made? |
Urea is made by reacting carbon dioxide (CO2) with anhydrous
ammonia (NH3) under 3,000 psi pressure and at 350° F.
CO2
+ 2NH3 > CO(NH2)2 + H2O
The
removal of water that occurs during the reaction is referred
to as "dehydration." The resulting molten mixture is further
processed into either prills or granules.
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| What
is the difference between granular urea and Prilled urea in
term of physical appearance and application? |
Granular
urea is somewhat larger in size than are prills, but the color
will be the same as is the application technique.
Is it related to how the spreader machines/ applicators use
bigger granulation, and hand/manually spread use prill /smaller
granulation?
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| Is
urea use increasing? |
Urea use is up substantially. In the western U.S., for
example, urea use has increased from 28,000 tons in 1955 to
390,000 in 1989, a 15-fold increase. Urea is the fastest growing
dry nitrogen fertilizer used by farmers.
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| What
role does urea play in world commerce? |
Urea
is the major fertilizer traded in international commerce.
In the very near future urea is expected to account for more
than 50% of the nitrogen fertilizer in world trade. When compared
to other dry fertilizers, urea has captured more than 65%
of the world trade.
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| Why
is there such a shift to urea in world trade? |
Urea
has a number of advantages over other nitrogen fertilizers.
Urea is safer to ship and handle, it is less corrosive to
equipment, it has a higher analysis than any other dry nitrogen
fertilizer and it can be used on virtually all crops. Urea
can be stored and distributed through conventional systems.
It can be applied in many different ways from sophisticated
aerial application equipment to a farm spreading urea by hand.
Urea is also highly water soluble so it moves readily into
the soil. The high analysis means a reduced transportation
and application cost per pound of nitrogen.
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| How
much nitrogen does urea contain? |
Urea
is 46% nitrogen. This is the highest concentration dry nitrogen
fertilizer available.
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| How
much nitrogen does urea supply? |
Urea
supplies more nitrogen per ton of product than any other dry
fertilizer. It contains 46% nitrogen; this means that each
ton of urea supplies 920 lbs. of nitrogen. For comparison,
a ton of ammonium sulfate supplies only 420 lbs. of nitrogen
and a ton of ammonium nitrate supplies only 670 lbs. of nitrogen.
The higher nitrogen content means lower transportation and
application costs per pound of nitrogen.
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Does
urea "tie-up"
in the soil? |
Urea
itself is very mobile because it is a neutral molecule, it
has no charge and is not attracted to soil particles. This
means it can rapidly move into the soil following irrigation
or rain. Once in the soil, however, it is rapidly converted
into ammonic nitrogen, which is attracted to the soil particles,
thus preventing leaching loss.
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| What
is biuret? |
Biuret
is formed during the manufacturing of urea. It is two urea
molecules joined together accompanied by the removal of an
ammonia molecule. Biuret is of little concern for soil-applied
nitrogen fertilizers, but it can be toxic when nitrogen fertilizers
containing biuret are foliar-applied to sensitive crops such
as citrus or pineapple.
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| What
is the best nitrogen fertilizer for aerial applications? |
Urea
is the best source of nitrogen for aerial application. Because
urea has the highest analysis (46% nitrogen), it has the lowest
application cost per pound of nitrogen. The uniform area granules
mean that applications can be accurately calibrated and evenly
spread. Urea can be practically dust-free and, under most
conditions, it does not absorb moisture and cake up.
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| How
does urea compare with ammonium sulfate? |
Urea has over twice as much nitrogen as does ammonium
sulfate; 46% versus 21%. That means there is more than twice
as much nitrogen per ton of fertilizer. In addition, urea
is less acid forming, is more water soluble and less corrosive.
Ammonium sulfate does supply sulfur, but it is usually less
expensive to apply urea and a sulfur material such as elemental
sulfur.
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| How
does urea compare with ammonium nitrate? |
Urea
contains about one-third more nitrogen, is less corrosive
than ammonium nitrate and is less prone to caking. In addition,
all the nitrogen is in the ammonic form and, until nitrification
occurs, it is less subject to leaching or de-nitrification
than the nitrate portion of the ammonium nitrate.
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| Is
the nitrogen in urea different from nitrogen in "organic fertilizers"
in terms of plant nutrition? |
No;
the ammonic nitrogen or nitrate nitrogen taken up by plants
is chemically identical regardless of the source. Nitrate
or ammonium that results from urea application is indistinguishable
from the nitrate or ammonium that results from manure application.
A plant utilizes inorganic ions, and the source of these nutrients
is irrelevant to either the yield or quality of the fruit,
grain, or vegetative matter produced by the plant.
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