Plant-N derived from N2-fixation (N2-fixed) and the percentage of plant-N derived from N2-fixation (% Ndff) were determined for four field-grown soybean lines by several techniques. The objective was to determined which technique would distinguish between the lines on the basis of their N2-fixing abilities. Variables in the techniques included method (total N or 15N isotope dilution), plant sample (seed, shoot at physiological maturity and whole plant) and placement of control (non-nodulating soybean) plots. Estimates of N2-fixed generated by isotope dilution were. on average, higher than those generated by the difference method (total N). Greater distinction between the genotypes was possible using the difference method than with isotope dilution. Separation of genotypes on the basis of N2-fixed as estimated by isotope dilution was not affected by the tissue sample used (seed, shoot or whole plant).
ASJC Scopus subject areas
- Soil Science