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Plant Physiol. Jun 1990; 93(2): 708–716.
PMCID: PMC1062574

Measurement of Nitrogen Fixation by Soybean in the Field Using the Ureide and Natural 15N Abundance Methods 1


Nitrogen fixation by field-grown soybean (Glycine max [L.] Merrill) was assessed by the natural 15N abundance and ureide methods. The field sites (five) and genotypes (six, plus two levels of inoculation on Bragg) were chosen to provide a range of proportions of plant N derived from nitrogen fixation (P). Genotypes K466, K468, nts1007, and nts1116 and Davis were included on the basis of their reported tolerance of the suppressive effects of nitrate on nodulation and nitrogen fixation. Bragg was included as a `nitrate-sensitive' genotype. Seeds of all genotypes were inoculated at sowing with Bradyrhizobium japonicum CB1809 (USDA136). Amounts of nitrate in the soil profile (0-1.2 meter depth) at sowing ranged from 70 (site 3) to 278 kilograms per hectare (site 5), resulting in large effects on plant nodulation, on the δ15N values of nodulated plants, on the relative abundance of ureide-N in vacuum-extracted sap (VES) and stem extracts, and finally on the estimates of P. There was no relationship between amount of soil nitrate at sowing and the δ15N of the plant-available soil N. Correlation matrices of the measured and calculated parameters indicated generally weak correlations between crop growth (dry matter and N) and the parameters of symbiotic activity (nodule weight, δ15N, relative ureide-N); correlations were strong and highly significant between nodulation and the measures of nitrogen fixation (δ15N, relative ureide-N; r = 0.79-0.92). Estimates of P ranged between 0 and 68% (δ15N) and between 6 and 56% (ureide) and were highly correlated (r = 0.97). Results indicated that the ureide method can be used with confidence to assess P by field-grown crops of soybean.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Carroll BJ, McNeil DL, Gresshoff PM. Isolation and properties of soybean [Glycine max (L.) Merr.] mutants that nodulate in the presence of high nitrate concentrations. Proc Natl Acad Sci U S A. 1985 Jun;82(12):4162–4166. [PMC free article] [PubMed]
  • Herridge DF. Relative abundance of ureides and nitrate in plant tissues of soybean as a quantitative assay of nitrogen fixation. Plant Physiol. 1982 Jul;70(1):1–6. [PMC free article] [PubMed]
  • Herridge DF, Peoples MB. Ureide assay for measuring nitrogen fixation by nodulated soybean calibrated by N methods. Plant Physiol. 1990 Jun;93(2):495–503. [PMC free article] [PubMed]
  • McClure PR, Israel DW, Volk RJ. Evaluation of the Relative Ureide Content of Xylem Sap as an Indicator of N(2) Fixation in Soybeans: GREENHOUSE STUDIES. Plant Physiol. 1980 Oct;66(4):720–725. [PMC free article] [PubMed]

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