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This article in JEQ

  1. Vol. 29 No. 5, p. 1408-1413
    Received: Nov 18, 1999

    * Corresponding author(s): ebeaucha@lrs.uoguelph.ca
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Nitrous Oxide Production from Urea Granules of Different Sizes

  1. Mario Tenuta and
  2. Eric G. Beauchamp *
  1. S outhern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford St., London, ON, Canada N5V 4T3.
    L and Resource Science, Univ. of Guelph, Guelph, ON, Canada N1G 2W1.



Three laboratory experiments were conducted to determine if urea granule size or a high concentration of urea prills influence N2O production in soil. Urea hydrolysis results in a localized increase in soil pH and an increase in ammonia concentration. Such conditions may adversely affect the nitrification process, thereby increasing the N2O to NO3 product ratio. Also, if anaerobic conditions should occur, the N2O to N2 product ratio during denitrification may increase. In general, under aerobic conditions, increasing the urea granule size from a powder to prill (commercial granules) and to larger granules resulted in increased N2O production. The increase in N2O production as granule size increased was accompanied by an increase in NO2 concentration. The accumulation of NO2 and the lower rates of disappearance of NH+4, or appearance of NO3, indicated that the nitrification process was adversely affected. The appearance of N2O was delayed with increasing granule size. A high concentration of urea prills produced a similar but greater effect than large granules. The appearance and rapid production of N2O was closely related to the rapid disappearance of hydroxylamine and the presence of NO2. The failure to detect hydroxylamine in urea granule-treated soil may have been due to its rapid oxidation to N2O. The proportion of the added urea N transformed to N2O increased with granule size but did not exceed 1.24% of the urea added. A high concentration of urea prills resulted in 2.80% converted to N2O−N.

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