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Schweiger, P; Hofer, M; Hartl, W; Wanek, W; Vollmann, J.
(2012): N-2 fixation by organically grown soybean in Central Europe: Method of quantification and agronomic effects
EUR J AGRON. 2012; 41: 11-17. FullText FullText_BOKU

Abstract:
The purpose of this study was to quantify the impact of effective nodulation on yield and quality of organically produced soybean and to assess three methods for the quantification of symbiotic N-2 fixation. We used (i) the natural abundance (NA) method which relies on isotopic differences in shoot N between the N-fixing legume and non-fixing reference plants, (ii) a method independent of reference plants that is based on within-soybean N isotopic fractionation and (iii) the xylem solute method, in which the proportion of N transported into shoot material in the form of ureides that are specific to N-fixing soybeans is quantified. Effectively nodulated soybeans produced greater yields of better quality than non-nodulated soybeans in three separate experiments conducted on fertile, organically managed fields. Employing the NA method with non-nodulated soybeans as reference plants, symbiotic N-2 fixation contributed 40-52% to overall N uptake by nodulated soybeans. These estimates for the percentage of soybean N derived from atmosphere (%Ndfa) were significantly increased when isotopic data from naturally occurring weeds were used in the calculation. Xylem ureide concentrations were not correlated with %Ndfa determined by the NA method. NA-determined %Ndfa were closely correlated with differences in the isotopic composition between soybean shoot N and root including nodule N (Delta delta N-15 = delta N-15 shoot -delta N-15 root). Further studies are required to assess the potential suitability of Delta delta N-15 to quantify soybean %Ndfa independent of reference plants. (C) 2012 Elsevier B.V. All rights reserved.
Authors BOKU Wien:
Vollmann Johann
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Find related publications in this database (Keywords)
Soybean
Symbiotic N-2 fixation
Nitrogen isotope
Natural abundance
Ureide method


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