Nitrous Oxide Production from Urea Granules of Different Sizes
- Mario Tenuta and
- Eric G. Beauchamp *
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 NO−3 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 NO−2 concentration. The accumulation of NO−2 and the lower rates of disappearance of NH+4, or appearance of NO−3, 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 NO−2. 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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