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Title: AVAILABILITY OF UREA TO AUTOTROPHIC AMMONIA OXIDIZERS AS RELATED TO THE FATE OF 14C- AND 15N-UREA IN SOIL

Author
item MARSH, KERI - UNIV OF ILLINOIS
item Sims, Gerald
item MULVANEY, RICHARD - UNIV OF ILLINOIS

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2003
Publication Date: 11/20/2003
Citation: Marsh, K., Mulvaney, R.L., Sims, G.K. 2003. Availability of urea to autotrophic ammonia oxidizers as related to the fate of 14C- and 15N-urea in soil. [abstract] In: Abstracts of the 103rd Annual Meeting of the American Society for Microbiology. Washington, DC. Number N-025. p. 402-2003.

Interpretive Summary:

Technical Abstract: Urea is unique among synthetic N fertilizers in that hydrolysis generates CO2, which could stimulate the growth of autotrophic nitrifying microorganisms and thereby promote accumulation of NO2 and NO3. Preliminary culture work with a urease positive ammonia oxidizing organism showed when urea was supplied as the sole C source, nitrification still proceeded. In further work, to ascertain whether urea-C is assimilated by autotrophic microorganisms during nitrification of urea-N, a laboratory incubation experiment was conducted to trace 14C and 15N applied to soil as labeled urea (100, 500, 1000 mg N kg-1). Following incubation at 25ºC for 1, 3, 7, 14, 21, or 29 d, analyses were performed to recover gaseous, extractable, and hydrolyzable forms of 14C and 15N. Results obtained in relating 14C incorporation in the amino acid fraction with 15N accumulation as NO3 were consistent with the stoichiometry that would be expected if C fixation were driven by autotrophic nitrification. Our findings implicate urea C in promoting nitrification of urea N in soil.