Comparison of B values obtained by two methodologies that use soil as a substrate and their influence on the estimation of the proportion of nitrogen fixed by legumes

Abstract

The B value is required to quantify the nitrogen derived from the atmosphere (%Ndfa) in the Rhizobium-legume symbiosis using the 15N natural abundance method. When the B value of a particular specie is not known, one possibility Is to use as a proxy the B value of a specie from the same genus, but this can cause the estimate of %Ndfa to be inaccurate. In this work, we compared two methodologies for determining the B value of Crotalaria juncea, C. spectabilis, C. ochroleuca and Cajanus cajan, using soil as the substrate. One method involvedgrowing plants in soil and averaging the lowest {delta}15N values of plant shoots (B-minimum), while the other consisted in adding sucrose to soil to immobilize the mineral nitrogen (N-immobilized), and then averaging the shoot {delta}15N values of all plants. Results showed that B values of C. cajan and C. ochroleuca obtained using the N-immobilized method were up to 1{per thousand} lower than those reported in the literature for these species. Therefore, we propose that, at least in these species, B values determined with the N-immobilized method should be used to estimate the%Ndfa.

Plant phenotyping relevance

マメ科植物の窒素固定量推定に用いるB値について、植物体のδ15N測定を基盤とする2手法を比較・検証しており、植物の生理状態の定量法が研究の中心である。

Code and data availability

The supplied blocks contain no public phenotype/trait datasets, images, sensor/3D inputs, author analysis code, trained models, or supplements with availability statements. The paper reports greenhouse 15N natural abundance measurements and ANOVA/LSD analyses (InfoStat software) but provides no deposit, repository, or

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