Publication Date
1989
Description
The 15N natural abundance method for measuring N2 fixation by legumes has compared favourably with other methods (reviewed by Shearer and Kohl, 1986). This method is based on the small difference in 15N abundance between nitrogen (N) derived from N2 fixation and N derived from soil. The proportion of legume N fixed from atmospheric N2 (PN) is calculated using :
PN = (o15Nref - o15N1egume)/(015Nref - B)
where o15N is the per mil 15N excess over atmospheric N2 ; ref is a reference plant which obtains all of its N from soil; and B is the o15N of fixed N (a measure of isotopic fractionation during N2 fixation). Several authors (e.g. Mariotti el al., 1980; Steele et al., 1983) have estimated isotopic fractionation during N2 fixation, but it is unknown how constant that these estimates are. This paper reports on a study examining the effects of host plant, rhizobial strain, nutrition and moisture on isotopic fractionation during N2 fixation.
Citation
Ledgard, S F., "Factors Affecting Isotopic Fractionation During Nitrogen Fixation by Pasture Legumes" (2025). IGC Proceedings (1989-2023). 8.
https://uknowledge.uky.edu/igc/1989/session2/8
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Factors Affecting Isotopic Fractionation During Nitrogen Fixation by Pasture Legumes
The 15N natural abundance method for measuring N2 fixation by legumes has compared favourably with other methods (reviewed by Shearer and Kohl, 1986). This method is based on the small difference in 15N abundance between nitrogen (N) derived from N2 fixation and N derived from soil. The proportion of legume N fixed from atmospheric N2 (PN) is calculated using :
PN = (o15Nref - o15N1egume)/(015Nref - B)
where o15N is the per mil 15N excess over atmospheric N2 ; ref is a reference plant which obtains all of its N from soil; and B is the o15N of fixed N (a measure of isotopic fractionation during N2 fixation). Several authors (e.g. Mariotti el al., 1980; Steele et al., 1983) have estimated isotopic fractionation during N2 fixation, but it is unknown how constant that these estimates are. This paper reports on a study examining the effects of host plant, rhizobial strain, nutrition and moisture on isotopic fractionation during N2 fixation.
