Advice to growers sowing pulses into acidic and dry soils
Author: Sharon Watt | Date: 23 Apr 2019
Grain growers planning to sow pulses into acidic and dry soils this season can greatly improve nodulation by doubling the inoculation rate.
Studies conducted through a Grains Research and Development Corporation (GRDC) investment have shown that increasing the rate of inoculant applied to seed improves nodulation where soil conditions at sowing are suboptimal.
Researchers at the South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA, say an increased inoculation rate also provides a practical way of improving nodulation where legumes are being sown for the first time, especially on hostile soils.
“Our results to date indicate that to optimise nodulation when dry sowing, application of rhizobia in high numbers is required,” says SARDI senior research officer Liz Farquharson. “Increasing the rate of inoculant application always improved nodulation.”
However, Dr Farquharson advises that some growers have experienced seeder blockages when they have increased the inoculation rate, so she recommends testing a small batch of seed first to avoid such problems.
Dr Farquharson and SARDI senior scientist Ross Ballard discuss the latest rhizobial inoculant insights from their studies, which have investment from the GRDC and the South Australian Grain Industry Trust Fund, in a new GRDC YouTube video which can be viewed via https://youtu.be/R8CZ5rLUgig.
Dr Farquharson also features in a new GRDC podcast on increasing the effectiveness of nitrogen fixation in pulse crops, available via http://bit.ly/2uI94zy.
Ahead of the 2019 cropping season, Dr Farquharson encourages growers to take particular care if they intend applying rhizobia to seed along with pesticides, especially when sowing into suboptimal soil conditions.
“Where pesticide application is necessary, granular rhizobial inoculant or a peat slurry in furrow may provide a better option, reducing direct exposure of the rhizobia to the pesticide,” she says.
Dr Farquharson and Mr Ballard have been involved in a decade-long research program with GRDC investment that is working towards development of a new commercial strain of rhizobia to improve the nodulation of bean and lentil in low pH soils.
It is hoped the new strain will have a substantial impact in the southern cropping region where pulse production is expanding into higher rainfall areas with characteristically low pH soils.
“We believe that this new strain has potential to improve the production of pulses on around a hundred thousand hectares of ground so it’s quite significant,” Mr Ballard says.
If data supports the release of the strain of rhizobia with improved acid tolerance, it is likely to be commercially available in 2021.
Meanwhile, the researchers say that improved rhizobia should be seen as an accompaniment, not a replacement, for liming.
“Liming remains important to prevent further acidification and is critical to the longer term sustainability of the farming system,” Mr Ballard says.
“Plant root growth will also likely benefit from the addition of lime and improve overall performance of the pulse crop.”
Dr Farquharson says research into understanding more about how rhizobia survive and nodulate under a range of stressful conditions is continuing so improved inoculation recommendations can be provided to growers.
Overcoming constraints to increased pulse production in the southern cropping region is a priority issue identified by the GRDC’s Southern Regional Cropping Solutions Network (RCSN).
More information on current research efforts and outcomes can be found in the GRDC Grains Research Updates paper, ‘Fixing more N – improving the performance of rhizobial inoculants in suboptimal conditions’, at http://bit.ly/2uI94zy
Other useful resources include:
- Legumes in Acid Soils – Maximising Production Potential publication, https://grdc.com.au/legumes-in-acidic-soils
- GrowNotes™ Tips & Tactics: Legumes and Nitrogen Fixation, https://grdc.com.au/tt-legume-n-fixation
- Inoculating Legumes: A Practical Guide, http://bit.ly/2WHEDFp
- GrowNotes™ Tips & Tactics: Nitrogen Fixation in Field Pea, http://bit.ly/2OJEK0m.
Liz Farquharson, SARDI
08 8429 2243
Ross Ballard, SARDI
08 8429 2217
Sharon Watt, GRDC
GRDC Project code: 9176500
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