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|Title: ||A slow-release urea fertilizer based on a natural rubber matrix|
|Authors: ||Arizal, Ridha|
|Issue Date: ||1988|
|Publisher: ||© Ridha Arizal|
|Abstract: ||By the year 2000
increase to around
output of between 1.5 to 2 times that
required. Since the cultivated land areas are
expand by only 20%, there will be an absolute
1980 will be
use of nitrogen fertilizers as the most limiting factor in
agricultural output must be increased. The most popular
nitrogen fertilizer today is urea.
Food and Agricultural Organization of the United Nations
estimated that 40-70% of nitrogen fertilizers are wasted
through leaching, ammonia volatilization and denitrification
during application causing serious environmental problems.
It is doubtful that the present available method commonly
used in agriculture can increase agricultural output without
any consequences for the environment.
The heavy use of nitrogen fertilizers has been blamed for
increasing the nitrate content in drinking water especially
in' Western Europe. Nitrates could cause methaemoglobinaemia
in babies and cancer in adults. The EEC has expressed its
concern by limiting the amount of nitrate in water intended
for human consumption.
One of t!1e approaches most often suggest'ed to avoid losses
of nitrogen from agricultural 'land is by using slow-release
nitrogen fertilizers of which Sulphur Coated Urea (SCU) is
probably the most widely known commercial slow-release
fertilizer. However, the cost of producing SCU has limited its development as a commercial product and because of its
brittleness, coatings may crack during shipment.
Natural rubber due to its specific properties can be mixed,
using the conventional method of rubber technology, forming
a flexible rubber-urea matrix having slow-release characteristic
when immersed in water. Work showed that the release
rate increased with urea concentration and temperature. A
special "split feeding" mixing technique was developed
during this work and found necessary for a good product to
result. Unlike urea which is dissolved within seconds in
water, the rubber-urea matrix slowly releases up to 50% of
its urea d~ring8 weeks soaking period at 25 c.
Leaching experiments using soil columns showed that the
matrix could regulate the release of urea. Ryegrass was
used for pot growing experiment in green house conditions to
examine the rubber-urea matrix's fertilizer ability.
Undiluted commercial urea damaged the young grass plants
during germination while the matrix didn't cause any adverse
effects. The results, with normal watering (harvested on
week 10), demonstrate that nitrogen content of grass without
urea ,addition was 2.14% of its dry weight. With commercial
urea, the leaves contains 2.53% nitrogen. 'The pot growing
experiments with the rubber-urea matrix (70% urea) produced
grass with 2.76% of nitrogen in the grass while with other
rubber-urea matrix compositions (75% urea) then 3.03% of
nitrogen was found in the grass leaves. Higher watering
levels reduced the nitrogen content of the grass in all
cases, except for the case the rubber-urea matrix having 75%
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Materials)|
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