Fixed nitrogen benefit and inoculation response of field pea

Ross Ballard, Liz Drew, Nigel Charman and Mick lines1, Matthew Denton2 and Jason Brand3
1South Australian Research and Development Institute (SARDI), 2University of Adelaide, 3Victorian Department of Environment and Primary Industries (DEPI).
Peer Review: Jake Howie (SARDI).

Key Messages
• All pea genotypes nodulated satisfactorily with the soil rhizobia at both sites, producing more than 40 nodules per plant. Although some genotypes had fewer nodules, it did not appear to limit their dry matter production.
• Total above ground biomass production of the pea genotypes varied by more than 60% at both sites, and is likely to be the most significant driver of their fixed nitrogen contribution.
• The predicted fixed N benefit of the different pea lines is estimated to range from 80 to 160 kg/ha at Curyo and from 78 to 123 kg/ha at Pinery. The cultivar Hayman performed best.
• Addition of mineral nitrogen was less significant than plant genotype for all measured parameters.
• Inoculation failed to significantly increase nodulation, above ground biomass or grain yield and N concentration. The lack of response to inoculation for field pea was not unexpected given the slightly alkaline soil conditions and the presence of >300 pea rhizobia per g soil. One-hundred rhizobia per g soil are considered adequate for prompt nodulation.