Inoculation with an enhanced N2-fixing Bradyrhizobium japonicum strain (USDA110) does not alter soybean (Glycine max Merr.) response to elevated [CO2]

Álvaro Sanz-sáez, Katy D. Heath, Patricia V. Burke, Elizabeth A. Ainsworth

Research output: Contribution to journalArticlepeer-review


This study tested the hypothesis that inoculation of soybean (Glycine maxMerr.) with a Bradyrhizobium japonicum strain (USDA110) with greater N2 fixation rates would enhance soybean response to elevated [CO2]. In field experiments at the Soybean Free Air CO2 Enrichment facility, inoculation of soybean with USDA110 increased nodule occupancy from 5% in native soil to 54% in elevated [CO2] and 34% at ambient [CO2]. Despite this success, inoculation with USDA110 did not result in greater photosynthesis, growth or seed yield at ambient or elevated [CO2] in the field, presumably due to competition from native rhizobia. In a growth chamber experiment designed to study the effects of inoculation in the absence of competition, inoculation with USDA110 in sterilized soil resulted in nodule occupation of >90%, significantly greater 15N2 fixation, photosynthetic capacity, leaf N and total plant biomass compared with plants grown with native soil bacteria. However, there was no interaction of rhizobium fertilization with elevated [CO2]; inoculation with USDA110 was equally beneficial at ambient and elevated [CO2]. These results suggest that selected rhizobia could potentially stimulate soybean yield in soils with little or no history of prior soybean production, but that better quality rhizobia do not enhance soybean responses to elevated [CO2].

Original languageEnglish (US)
Pages (from-to)2589-2602
Number of pages14
JournalPlant Cell and Environment
Issue number12
StatePublished - Dec 1 2015


  • Elevated carbon dioxide
  • Free air CO enrichment
  • N fixation
  • Nodulation
  • Rhizobia

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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