Evaluation of nitrogen-15 tracer techniques for direct measurement of denitrification in soil. IV. Field studies
- Univ. of Illinois, Urbana (USA)
Field studies were conducted to determine whether underestimation occurs in measuring evolution of nitrous oxide (N{sub 2}O) using an {sup 15}N-tracer technique based on the assumption of isotopic uniformity. Microplots of 58, 553, or 1684 cm{sup 2} in area were treated with {sup 15}N-labeled KNO{sub 3} (68.5 atom % {sup 15}N) at the rate of 100 kg N ha{sup {minus}1}. Isotope-ratio analyses of the NO{sub 3} in soil cores collected from on plot of each size showed considerable spatial variability in {sup 15}N enrichment, but measurements of N{sub 2}O evolution from these plots by gas chromatography (GC) and mass spectrometry (MS) usually did not differ significantly (0.05 level), demonstrating that appreciable error does not necessarily arise in the use of {sup 15}N-tracer methodology to measure denitrification of NO{sub 3} that is not isotopically uniform. In a subsequent study, replicate atmospheric samples were collected from three plots of each size following rainfall or irrigation for analysis of N{sub 2}O by GC and MS. The measurements differed significantly (0.05 level) for approximately 60% of the collections that were made; however, the magnitude of the difference was usually small compared to spatial variability in N{sub 2}O evolution. Significant differences occurred more often with medium or large plots than with small plots, and the greater value was usually obtained by GC. The extent of the difference was not affected by increasing the period of enclosure used in collection of atmospheric samples, but it was affected by subsequent application of fertilizer (25 kg N ha{sup {minus}1}), which led to serious underestimation by MS of N{sub 2}O evolved from most of the medium and large plots.
- OSTI ID:
- 5414666
- Journal Information:
- Soil Science Society of America Journal; (USA), Vol. 52:5; ISSN 0361-5995
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DENITRIFICATION
TRACER TECHNIQUES
NITRATES
MEASURING METHODS
NITROUS OXIDE
SOILS
COMPARATIVE EVALUATIONS
ERRORS
FERTILIZERS
GAS CHROMATOGRAPHY
ISOTOPE RATIO
MASS SPECTROSCOPY
NITROGEN 15
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMATOGRAPHY
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NITROGEN COMPOUNDS
NITROGEN ISOTOPES
NITROGEN OXIDES
NUCLEI
ODD-EVEN NUCLEI
OXIDES
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
510200* - Environment
Terrestrial- Chemicals Monitoring & Transport- (-1989)
510101 - Environment
Terrestrial- Basic Studies- Radiometric Techniques- (-1989)