Frank Henry1, Ross Ballard2 and Elizabeth Farquharson2
1 Agriculture Victoria, 915 Mt Napier Rd, Hamilton, Victoria, 3300, firstname.lastname@example.org
2 South Australian Research and Development Institute (SARDI), Gate 2B Hartley Grove, Urrbrae, SA,5064
Poor nodulation of faba beans grown on acid soils (pHCaCl2 < 5.5) is considered a major constraint to increasing the area grown to faba beans, increasing grain yield and reducing dependence on artificial fertiliser. To help overcome this problem, rhizobia bacteria with improved tolerance to acidic soils were developed at SARDI and DPIRD. A number of the new acid tolerant strains of rhizobia were compared to the commercial Group F strain WSW-1455 in trials undertaken between 2016 and 2018 within the Victorian high rainfall zone. Several acid tolerant strains showed improved nodulation and grain yield. The rhizobia strain SRDI-970 had significantly higher grain yield (6.2 t/ha) and nodulation score compared to the current commercial strain Group F WSM-1455 (2.2 t/ha) in 2017. While acid tolerant rhizobia are still two years from commercialisation, doubling the rate of the commercial Group F WSM-1455 inoculant may improve nodulation and grain yield providing an interim solution until a new strain becomes available. Acid tolerant rhizobia are not considered a replacement for lime, but rather a complement to a good lime program.