Appraisal of the nitrogen-15 natural-abundance method for quantifying dinitrogen fixation

Journal Article · · Soil Science Society of America Journal; (United States)

DOI:https://doi.org/10.2136/sssaj1990.03615995005400020018x· OSTI ID:5511890

Bremer, E; van Kessel, C ^[1]

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1. Univ. of Saskatchewan, Saskatoon (Canada)

Several investigators have questioned the use of the {sup 15}N natural-abundance method of estimating N{sub 2} fixation because of variability in soil {delta}{sup 15}N and small differences between the {delta}{sup 15}N of soil N and atmospheric N. Investigations were conducted to compare the {sup 15}N natural-abundance and {sup 15}N-isotope-dilution methods for estimating N{sub 2} fixation of field-grown pea (Pisum sativum L.) and lentil (Lens culinaris Medik.). Spatial variability was assessed at three sites by determining the {delta}{sup 15}N of non-N{sub 2}-fixing plants. Seasonal variation in {delta}{sup 15}N for spring and winter wheat (Triticum aestivum L.), flax (Linum usitatissimum L.), barley (Hordeum vulgare L.), rape (Brassica napus L.) and lentil was determined at one site. Comparisons between {delta}{sup 15}N and {sup 15}N-enriched isotope-dilution methods for estimating N{sub 2} fixation by lentil were conducted at several sites over a 3-yr period. Variability in {delta}{sup 15}N of the reference plant was site dependent: the {delta}{sup 15}N ranged from 2.8 to 9.3 at the first site, 3.4 to 8.8 at the second site, and 3.5 to 6.2 at the third site. The average {delta}{sup 15}N of four of the five non-N{sub 2}-fixing plants increased from 5.4 at 42 d after planting to 6.9 at the final harvest. The fifth non-N{sub 2}-fixing plant, rape, accumulated most of its N during the first 42 d after planting, and its {delta}{sup 15}N value declined from 8.1 at 42 d after planting to 7.3 at the final harvest. Estimates of N{sub 2} fixation were not significantly different in 18 out of 21 comparisons; in two comparisons in the {delta}{sup 15}N method and in one comparison the {sup 15}N-enriched method provided higher estimates of N{sub 2} fixation. Overall, both methods appeared to provide equally reliable estimates of N{sub 2} fixation for lentil.

• OSTI ID: 5511890
• Journal Information: Soil Science Society of America Journal; (United States), Vol. 54:2; ISSN 0361-5995
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
NITROGEN 15
NATURAL OCCURRENCE
NITROGEN FIXATION
BARLEY
BIOASSAY
CEREALS
ELEMENT ABUNDANCE
EVALUATION
FLAX PLANTS
LEGUMINOSAE
WHEAT
ABUNDANCE
GRAMINEAE
ISOTOPES
LIGHT NUCLEI
LILIOPSIDA
MAGNOLIOPHYTA
MAGNOLIOPSIDA
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PLANTS
STABLE ISOTOPES
540230* - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (1990-)