G.A. BAHNISCH¹, R.A. DATE², N.J. BRANDON² and P. PITTAWAY¹

¹Department of Plant Production, University of Queensland, Gatton College, Queensland, Australia
²CSIRO Tropical Agriculture, St Lucia, Queensland, Australia

Abstract

The need to inoculate Desmanthus virgatus cv. Marc in 8 clay soils from central and southern Queensland was investigated in a glasshouse experiment, by comparing growth of uninoculated plants with that of plants inoculated with the effective Rhizobium strain CB3126 or inoculated and fertilised with N. The success of the inoculum in forming nodules in competition with indigenous strains was tested using a serological method. The N-fixation effectiveness of indigenous strains of Rhizobium compared with CB3126 was evaluated in a second glasshouse experiment.
Significant (P < 0.05) plant growth responses to inoculation with Rhizobium strain CB3126 were recorded in 4 soils, 100 days after sowing. In two of these soils, a response was recorded 56 days after planting. Leaf production was increased relative to the uninoculated controls by up to 96%, 56 days after sowing, and up to 90%, 100 days after sowing. The strain CB3126 accounted for 35–96% of nodules 56 days after planting and 23–98%, 100 days after sowing. Uninoculated plants in 6 of the 8 soils formed nodules. Indigenous strains of Rhizobium isolated from 5 of these soils were at least 60% as effective as CB3126.
This study demonstrates that Desmanthus virgatus responds to inoculation with Rhizobium strain CB3126 when sown into soils with few or no native Rhizobium. Although no response to inoculation occurred in 4 of the 8 clay soils used in the trial, inoculation with the commercially available strain CB3126 is recommended for all soils as a normal part of the sowing procedure.