Abstract
Urea is one of the spirited input materials for plant growth. However, more than half of conventional urea applied to the soil may not reach the plants and be washed off by rain and irrigation water. The high lost proportion results not only in economic losses but also in environmental pollution. Alleviation in cost and nitrogen pollution is possible by mitigating the nitrogen release rate and synchronizing it with the plant’s need. A wide range of synthetic and natural materials are being tested for production of slow-release fertilizers. Each one of these materials has its own merits, with accompanying disadvantages. This study critically reviews the most featured natural and synthetic materials pertaining to the slow-release urea industry. The focused review was aimed at elaborating the benefits and limitations of polymeric and nonpolymeric coating materials, release mechanism of conventional and coated urea, methods to characterize the coated urea, slow-release characteristics imparted by a coating to the coated urea, and release patterns of conventional and coated urea. This discussion was further extended to commercially available coatings and slow-release potential of superabsorbent, urethane, and starch-based coatings.
About the authors
Muhammad Yasin Naz is working as a research scientist with the director of Hybrid Energy Systems (HES) research at the Universiti Teknologi PETRONAS (UTP), Malaysia. He holds a MPhil degree in Plasma Physics from Quaid-i-Azam University, Islamabad, Pakistan, and a doctorate degree from UTP dealing with atomization of non-Newtonian fluids. From 2009 to 2012, he worked as a lecturer in physics at the University of Agriculture Faisalabad, Pakistan. With a very diverse research background, he has contributed to scholarly works on atomization and sprays, rheology, slow-release coatings, nanotechnology, plasma discharges, fluidized beds, erosion-corrosion of flow-lines, and electromagnetics. His research achievements include two silvers and one bronze from Science and Engineering Exhibitions, most publications award from UTP for the year 2013–2014, best paper award, and research productivity award for the year 2013.
Shaharin Anwar Sulaiman is an associate professor in the Department of Mechanical Engineering at Universiti Teknologi PETRONAS (UTP), Malaysia. He graduated in 1993 with a BSc in mechanical engineering from Iowa State University. He earned his MS. in thermal power and fluids engineering from UMIST in 2000 and obtained a PhD in combustion from the University of Leeds in 2006. He joined UTP in 1998 and is presently director of the Hybrid Energy Systems research group in the university. His research interests include air-conditioning and ventilation, combustion, sprays and atomization, and biomass energy. He is also a member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and Malaysian Energy Professionals Association (MEPA) and a corporate member of the Institution of Engineers Malaysia (IEM).
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