A slow-release urea fertilizer based on a natural rubber matrix
thesisposted on 26.09.2012 by Ridha Arizal
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By the year 2000 increase to around SYNOPSIS the world 6 billion population for which output of between 1.5 to 2 times that is an of required. Since the cultivated land areas are expand by only 20%, there will be an absolute expected to agricultural 1980 will be expected need that to the 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 , 0 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% urea.
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