Abstract
An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to 56 days to study the effect of factors such as temperature, pH, soil moisture, and organic C additions on N release. The N release rate from RLCU was shown to be increased with increasing temperature and decreasing coating thickness. It was unaffected by the addition of lime to raise the pH or organic carbon sources to increase microbial activity. Although a slight effect of soil moisture was noted, it was not pronounced. Urea release tended to be in two stages — a constant diffusive stage in which, it is postulated, urea was still dissolving within the granule and diffusing to the soil at a constant rate and a slower logarithmic stage where the rate of release decreased with time.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Allen S E, Hunt C M and Terman G L (1971) Nitrogen release from sulfur-coated urea as affected by coating weight, placement and temperature. Agron J 63: 529–533
Dawson M D and Akratanakul W (1973) SCU — the effect of soil temperature and moisture. Sulf Inst J 9: 14
Hashimoto I and Mullins R C (1979) Dissolution of sulfur-coated urea in soils. I. Wax-sealed sulfur-coated urea. Soil Sci Soc Am J 43: 1165–1168
Hauck R D (1984) Technological approaches to improving the efficiency of nitrogen fertilizer use by crop plants. p. 551. In: Nitrogen in Crop Production. R D Hauck (ed), Am Soc Agron, Madison, WI
Jarrell W M and Boersma L (1979) Model for the release of urea by granules of sulfurcoated urea applied to soil. Soil Sci Soc Am J 43: 1044–1050
Jarrell W M and Boersma L (1980) Release of urea by granules of sulfur coated urea. Soil Sci Soc Am Proc 44: 418–422
Lunt O R (1968) Modified sulfur-coated granular urea for controlled nutrient release. Trans 9th Int Congr Soil Sci 3: 377–383
Lunt O R and Oertli J J (1962) Controlled release of fertilizer minerals by encapsulating membranes. II. Efficiency of recovery, influence of soil moisture, mode of application and other considerations related to use. Soil Sci Soc Amer Proc 26: 584–587
Marsh W H, Fingerhut B and Miller H (1965) Automated and manual direct methods for determination of blood urea. J Clin Chem 11: 624–627
McClellan G H and Scheib R M (1975) Texture of sulfur coatings on urea. In: Advances in Chemistry Series (J R West, ed), 140: 18–32. Amer Chem Soc, Washington, DC
Moore W P (1987) Attrition resistant controlled release fertilizer. US Patent 4,711,659. Date issued 8 December 1987
Oertli J J and Lunt O R (1962) Controlled release of fertilizer minerals by encapsulating membranes: I. Factors influencing the rate of release. Soil Sci Soc Proc 26: 579–583
Prasad M (1976) The release of nitrogen from sulfur-coated urea as affected by soil moisture, coating weight, and method of placement. Soil Sci Soc Am J 40: 134–136
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Christianson, C.B. Factors affecting N release of urea from reactive layer coated urea. Fertilizer Research 16, 273–284 (1988). https://doi.org/10.1007/BF01051376
Issue Date:
DOI: https://doi.org/10.1007/BF01051376