Calcium ammonium nitrate, a related material
made by mixing ground limestone with concentrated
ammonium nitrate solution, has a higher nitrogen content,
between 21% and 27.5%. In the 1990s this material supplied
about 80% of the nitrogen fertilizer use in Holland
but has since been declining in the world market (4).
Calcium ammonium nitrate (CAN) is a nitrogenous
fertilizer produced by treating ammonium nitrate
solution with powdered limestone. It is a white to grey
chalky powder, with the color depending on the
limestone used in the manufacturing process. Made with
dolomitic limestone, the fertilizer contains 20%
nitrogen, 6 % calcium and 4 % magnesium. If the quantity
of limestone is smaller than that of used ammonium
nitrate, the nitrogen content can go up to 28 % CAN is
preferred to ammonium nitrate in acid soils. The most
common grade of CAN contains about 21% nitrogen,
corresponding to 60% ammonium nitrate.
Several methods are employed for manufacturing
calcium ammonium nitrate. A concentrated ammonium
nitrate solution is mixed with powdered limestone to
obtain calcium ammonium nitrate granules. These are
cooled, dried and coated with a suitable material.
Other calcium compounds used for manufacturing
CAN are ground calcite or dolomitic limestone, chalk,
marl or precipitated calcium carbonate. The mixing is
done quickly to avoid decomposition of ammonium
nitrate. The granules contain 25 % nitrogen, half of which
is in a nitrate form and the rest in an ammoniacal form.
The fertilizer is water-soluble and useful to many crops
and soils; the nitrogen available to plants is relatively
resistant to leaching because of its ammoniacal form.
Technologies of both prilling and granulation can be
used for producing CAN. The prilled form is conditioned
with china clay, kieselghur or calcined Fuller's earth in
amounts ranging from 1 to 3% to improve the product
characteristics during storage. To improve the product
hardness, some manufacturers use pug mill to add
ammonium sulphate equivalent to 0.3 to 0.5% of the
sulphate (SO42-).
Calcium ammonium nitrate is widely used as a
fertilizer in Europe and the USA. It supplies nitrogen and
calcium to all crops and soils. As CAN is not acidforming,
it is good for acid soils. However, it is
hygroscopic and difficult to handle because it absorbs
moisture from the air and becomes sticky. Therefore,
once a bag is opened, its content has to be used the same
day.
CAN is marketed under different trade names, like
Ammonium nitrate limestone (ANL), Cal-nitro,
Nitro-chalk, Nitrammoniacal, etc.
