GRAINGROWERS sowing pulses into acidic and dry soils this season are advised there is greatly improved nodulation when the inoculation rate is doubled.
GRDC-funded studies show that increasing the rate of inoculant applied to seed improves nodulation where soil conditions at sowing are suboptimal.
SARDI researchers 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.
"Results indicate that to optimise nodulation when dry sowing, application of rhizobia in high numbers is required," SARDI senior research officer Liz Farquharson said. "Increasing the rate of inoculant application always improved nodulation."
But 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 this problem.
She also recommends particular care be taken when 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 said.
Increasing the rate of inoculant application always improved nodulation.
Dr Farquharson and SARDI senior scientist Ross Ballard have been developing 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 the new strain has potential to improve pulse production on about 100,000 hectares, so it's quite significant," Mr Ballard said.
If data supports the new strain of rhizobia with improved acid tolerance, it could be commercially available by 2021.
But the researchers stress 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 long-term sustainability of the farming system," Mr Ballard said.
"Plant root growth will also likely benefit from the addition of lime and improve overall crop performance."
- Details: grdc.com.au