Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling

Per Ambus, S.O. Petersen, J.F. Soussana

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Urine deposition by grazing animals is known to, induce large NO emissions as a result of increased nitrification and denitrification in the soil. This is brought about by the increased N availability from the urine, in combination very likely also with increased organic C availability. Possible sources for C include the urine itself, increased solubility of soil C, lysis of microbial cells and leakage of C from scorched roots. The objective of this experiment was to test the hypothesis that: (i) urine deposition causes an increase in root-derived degradable C compounds in the soil, which (ii) fuel denitrification activity and N2O production. The study took advantage of carbon-13 pulse labelling the plant tissue combined with application of nitrogen-15 labelled synthetic urine as an attempt to identify the sources of N2O. Over a 6 weeks course, the CO2 evolved in response to urine application was equal to the quantity of organic C added. Immediately after the application, 87% of the respired CO2 appeared to be from the urine, and respiration of plant-derived C was temporarily decreased. The cumulated amount of respired C-13 plant carbon, however, was unaltered by the urine treatment indicating that root death was not a significant source to available C. Nitrous oxide emissions accumulated to 7, 59, 142 and 77 mg N2O-N m(-2), respectively, for control (0N), low urine N (LUN), high urine N (HUN) and high mineral N (HMN) treatments. Pair-wise comparisons indicated that HUN > LUN (P < 0.03), whereas HUN = HMN (P < 0.18). The N2O emission factors were 0.3% for the urine treatment, independent of urinary urea concentration and 0.15% for mineral N (NH4+). The N-15 isotopic data indicated that denitrification of soil NO3- was the sole source for N2O production in the urine-affected soil after 12 days of incubation. The initial source of N2O could not be identified because of lack of ability to detect the soil (NO3-)-N-15. The source of N2O from added NH4+ was ambiguous since the isotopic signals of N2O, NH4+ and NO3- could not be discerned. Approximately, 50% of the urinary-N, independent of urea concentration, and 72% of the NH4+-was recovered after 6 weeks of incubation. This finding, in combination with the difference in the NO losses, emphasizes the potential to control N-emissions from urine patches through dietary control of the urine N-content. (c) 2006 Elsevier B.V. All rights reserved.
    Original languageEnglish
    JournalAgriculture, Ecosystems & Environment
    Volume121
    Pages (from-to)84-92
    Number of pages1
    ISSN0167-8809
    DOIs
    Publication statusPublished - 2007

    Bibliographical note

    This article may be downloaded for personal use only. Any other use requires prior permission of the author and the publisher

    Fingerprint Dive into the research topics of 'Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling'. Together they form a unique fingerprint.

    Cite this