Riverine Plains Inc research update

GRDC project code: RPI0009

Keywords: soil carbon, nitrogen, stubble, incorporation.

Take home messages

• Riverine Plains Inc conduct a range of research activities to provide local information to members.
• Large farm scale trials provide farmer-relevant information.
• Decisions around stubble management require consideration of the whole system.

Background

Riverine Plains Inc is a progressive farmer group dedicated to improving the productivity of broadacre farming systems in north-east Victoria and southern NSW. The group provides relevant and unbiased research and information to our members and acts as a conduit for information flow from credible research sources to our membership.

During 2014 Riverine Plains Inc contributed to a range of research projects, including two projects managed by Riverine Plains Inc. These projects focus on refining management options under stubble retention (the Stubble Project), and building soil carbon in cropping systems (the Soil Carbon Project).

Results and discussion

The Stubble Project

The Stubble Project, ‘Maintaining profitable farming systems with retained stubble in the Riverine Plains region’ is funded by GRDC as part of a National Initiative (RPI0009) and conducted in partnership with FAR Australia. It is looking at ways to improve and maintain profit and sustainability in stubble retention cropping systems across the region. Four large, commercial scale field trials (‘Focus Farms’) have been established across the region, which are comparing different stubble management practices and plant establishment, growth and yield (Table 1). Smaller trials are also evaluating the importance of timing of nitrogen application, plant growth regulators, row spacing and cultivar selection in optimising production in stubble retained systems.

Table 1. Different stubble management strategies for focus farms as part of the Maintaining profitable farming systems with retained stubble in the Riverine Plains region project. 

Across these sites, the effect of the various treatments on crop yields and protein are as follows:

Coreen:

• No differences in wheat yields (average 3.2 t/ha)
• No differences in protein (average 8.4%)

Yarrawonga:

• No differences in wheat yields (average 4.4 t/ha)
• Protein was greatest with NTSR + 40 kg N/ha at sowing (12%)

Dookie:

• All treatments except the long stubble treatment yielded 5.6 – 5.9 t/ha, the long stubble treatment yielded less (5 t/ha)
• The long stubble treatment had the highest protein (11.6%)

Henty:

• Canola was sown, with the top-work treatment yielding highest (2.5 t/ha).

Although some differences between treatments have been seen within the 2014 season in plant establishment, growth and final yield, of greatest interest is how the various stubble management options perform across a number of seasons with different rainfall patterns. At the conclusion of the project (2018) key findings from this project will be used to develop regional production guidelines and, in conjunction with the National Initiative, will provide new agronomic information on stubble management.

The Soil Carbon Project

The Soil Carbon Project will generate new, regionally relevant information on the potential of cropping soils to build soil carbon. The project ‘Increased soil carbon by accelerated humus formation from crop residues’ is supported by funding from the Australian Government Department of Agriculture - Action on the Ground program. Project partners are Murray Local Land Services, the North East Catchment Management Authority and the Irrigated Cropping Council. This project is evaluating the impact of adding fertiliser to crop residue after harvest, in order to optimise microbial conversion of residues into soil carbon.

Three large field sites were established after the 2012 cropping season to test a range of fertiliser and residue management strategies on soil carbon accumulation (Rutherglen, Culcairn, Tocumwal). The value of such work is that in addition to monitoring soil carbon, the interactions between soil carbon and nitrogen can also be evaluated, and greenhouse gas emissions from the cropping system can be quantified. The 2014 season was the final year of field trials for this project, with all results being consolidated and reported to growers in 2015. The yield results are presented and summarised in respect to stubble management technique.

Rutherglen: No differences in wheat grain yield with respect to stubble management (stubble top-worked, burnt and standing).

Culcairn: Canola yield was greatest when wheat stubble was top-worked, compared to mulched and standing.

Tocumwal: Canola yield was greater when wheat stubble was top-worked or mulched compared to the standing stubble.

No significant differences in soil carbon have been measured with the addition of a range of additional fertiliser applications or with the various stubble management treatments. However, final soil carbon measurements will be conducted in July 2015, after which the final results will be reported.

Conclusion

Within both of these projects the impact of stubble management has differed according to site and season. Therefore, it is important to view these results within the context of the 2014 season; different seasonal conditions may have resulted in a very different story. Therefore, the most productive and profitable approach to stubble management may change according to the season (wet start - dry finish, dry start - wet finish, e.t.c).

Riverine Plains Inc continues to conduct research on behalf of its members into the 2015 year. In order to broaden the delivery of research to members, Riverine Plains Inc also collaborates with other organisations on a range of research projects, from weed-seed management to soil constraints. This supports the ongoing establishment of on-farm trials within the region, ensuring that the results obtained are immediately relevant to local growers.

Contact details

Cassandra Schefe, Extension Officer
Riverine Plains Inc, PO Box 214 Mulwala NSW 2647
(03) 5744 1713
extension@riverineplains.com.au