IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Tuesday 29 November 2011
Concurrent Session 7 – Field Applications III
1600 - 1720
Authors: Amanda Bonython 1,2 , Ross Ballard 1,2 , Nigel Charman 1,2 & Andrew Craig 1,2
1 South Australian Research and Development Institute, GPO Box 397, Adelaide, SA,
5001, Australia.
2 Cooperative Research Centre for Future Farm Industries. Crawley, WA, 6009.
Presentation Title: Improved nodulation of regenerating messina plants
Presentation Time: 1640 – 1700
Messina (Melilotus siculus syn. M. messanensis) is a promising annual pasture legume for areas affected by
dryland salinity. Sinorhizobium medicae strain, WSM1115, was used during initial species evaluation. Prompt
nodulation occurred in year of sowing but nodulation failure was commonplace in regenerating pastures. Strain
WSM1115 failed to persist in the saline soils over summer. Alternative strains of rhizobia and agronomic
practices were evaluated to improve nodulation.
Six agronomic treatments and two inoculation treatments were applied in a factorial design. Messina seed was
inoculated with either a mixture of experimental strains (SRDI554, WSM4118 and WSM4194) or WSM1115.
Agronomic treatments were applied to modify the soil micro-environment and improve rhizobial persistence.
They comprised sowing a perennial companion species, either Cichorium intybus or Puccinellia ciliata;
incorporating soil additives at sowing, gypsum (2.5 t/ha) or clay (75t/ha); applying an organic mulch over the
summer months, or applying a soil containing medic rhizobia prior to regeneration. Plots were sown in 2008 at
two trial sites near Keith, South Australia. The soils were alkaline sands with summer soil surface salinity levels
of 14.6 ECe dS/m (Site 1) and 5.3 ECe dS/m (Site 2). The sites were free of medic rhizobia prior to sowing.
In 2008, all treatments had >97% plants nodulated. In 2009, ten regenerating plants from each plot were
sampled and percentage nodulation and nodule score per plant determined (Score 0=0 nodules; 1=1-4 nodules;
2=5-9 nodules; 3=10-14 nodules, 4=15-19 nodules, 5=20-29 nodules, 6=30+ nodules). At Site 1 (more saline)
plant nodulation and nodule score increased from 35% and 0.6 (WSM1115 treatment) to 95% and 3.0 (strain
mixture treatment). At Site 2, most regenerating plants in the WSM1115 treatment were nodulated (80%), but
had few nodules (score 1.6). Nodule score increased to 3.9 in the strain mixture treatment. At both sites, the
application of soil containing medic rhizobia resulted in levels of nodulation approaching the strain mixture
treatment. Other agronomic treatments were less effective.
The mixture of rhizobia strains improved the nodulation of regenerating messina plants compared to WSM1115.
Strain of rhizobia influenced messina nodulation more than the agronomic treatments.
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2011