Quantification of symbiotically fixed N 2 by faba bean and allocation of 15 N among above-and below-ground components of faba bean, canola, and barley on a Gray Luvisol

Ji-Dong Gu, William B McGill

Research output: Contribution to journalArticlepeer-review

Abstract

This study was carried out to estimate N-15 allocation into different components of the above- and below-ground plant parts, and
to quantify biological N-fixation in faba bean using N-15 dilution method, and both canola and barley as reference crops. Four samplings
were conducted during the crop growing season, both above- and below-ground plant parts, and soil were sampled. The above-ground
plant was fractionated into leaves, stems, shell, and seeds for faba bean and canola; and dead-leaves, live-leaves, stems, sheaths, husks,
and seeds for barley. Roots were extracted from soil by root-washing technique and further separated from dead debris by water floatation
and hand-picking. N-15 excess of faba bean above-ground parts was lower than its roots, but the reverse was true for the non-legumes
(canola and barley). N-15 fractionation was apparently taking place in various plant parts. Reproductive organs of faba bean had lower N-15
excess than the vegetative ones, but reproductive organs of non-legumes (canola and barley) had higher N-15 excess than the vegetative ones.
N-fixation in faba bean was quantified by using N-15 dilution method with either canola or barley as a reference crop, the quantity of N
derived from atmospheric fixation was 183-199 kg N/ha/yr in the above-ground parts of faba bean and 18-22 kg N/ha/yr in faba bean roots
by September 1, when faba beans were not fully matured. Either canola or barley can be a valid reference crop for N-fixation estimation in
N-15 dilution method. Total difference method agreed with N-15 dilution method with less than 10% variation in this study. A peak of
N-fixation was observed after faba bean flowering and the rate of N-fixation during this period was 4.0-4.7 kg N/ha/day. This study provides
the key inofmration for the quantity of N-fixation from atmosphere in faba bean growing on this soil of Canada.
Original languageEnglish
Pages (from-to)21-31
Number of pages11
JournalApplied Environmental Biotechnology
Volume3
Issue number1
StatePublished - 2018
Externally publishedYes

Keywords

  • dinitrogen fixation
  • N-15 dilution method
  • Gray Luvisol
  • soil improvement
  • Rotation

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