Increasing the effectiveness of N fixation through extension and communication of improved inoculation and crop management practices in the southern region

As well as generating useful income, pulses provide significant benefits to following crops, including nitrogen (N) fixation boosting N supplies to following crops. Pulses are estimated to fix about 120kg N/ha, or more than 220,000 tonnes N across Australia, worth about $220 million each year.

However, not all pulses are well nodulated and fix N to their potential, especially on acidic soils and it was recently estimated that N fixation could be increased by 25%. Several past and present GRDC funded projects have been designed to help reach this target, and their outputs require further extension and communication.

This GRDC project investment aims to improve N fixation of winter pulse crops and to promote their wider adaptation and adoption by promoting best management inoculation and pulse management practices, raising awareness and knowledge around pulse nodulation and N fixation as well as the impact of soil acidity, especially subsoil acidity.

A number of groups across the GRDC southern region are involved in the project including: Mallee Sustainable Farming (lead organisation), AgCommunicators, Bates Ag, Rural Directions, Southern Farming Systems, Birchip Cropping Group, Ryder Ryan Research Pty Ltd, Moodie Agronomy, Riverine Plains Inc, Southern Pulse Extension, SARDI and Tregove Consulting.

2019 GRDC Nitrogen fixation demonstrations in the Riverine Plains region

Through the project, demonstration trials were sown at Bungeet and St James  in June 2019 as part of the Riverine Plains region trials investigating the effectiveness of nitrogen fixation in pulse crops, with a number of paddock walks held at the sites during 2019. Table 1 shows the treatments established.

Table 1 GRDC Nitrogen fixation demonstration site and treatment details

*pH_{Ca Cl} 0-10cm

When plants were sufficiently advanced, samples were dug up and nodulation scored (1-5), with results shown in Figure 1.  A score of 5 was given when nodules/plant  were greater than 20 and when evenly distributed throughout the rootzone.

The chickpea site had nil background rhizobia and at this site, inoculation resulted in more nodules per plant that the untreated control, regardless of inoculation type. The highest nodulation score was in the double rate treatment.

Figure 1 Nodulation scores from the GRDC nitrogen fixation demonstrations at Bungeet and St James.

The lentil site had low levels of background rhizobia.  The acid tolerant rhizobia treatments (969 and 970) appeared to give the best results, however soil type variability across the treatment plots may have  affected results.

The faba bean site had soil pH of 6 with good  background rhizobia levels.  Both the nil inoculant and inoculant treatments were well nodulated, suggesting that inoculum was not required at this site.

 These demonstrations will be taken through to harvest to see if there is a yield difference between treatments.

To learn more about this project, please contact Kate Coffey, Riverine Plains Inc on 5744 1713 or email kate@riverineplains.org.au