Leading soil scientist to oversee stubble research project
Text by JACQUELINE WILSON
AUSTRALIA’S leading authority on stubble management, Dr Clive Kirkby, will head up a research project at the new Hamilton Branch Southern Farming Systems trial site.
With funding from the National Landcare Programme (NLP), the project will investigate how different retained stubble systems influence the movement of nutrients, as well as the impact of each stubble system on soil organic matter levels.
Dr Kirkby, who has been at the forefront of groundbreaking research undertaken by CSIRO into the management of stubbles for two decades, will have a real hands-on role in the project and will be at the site in August for collection of up to 180 soil samples for analysis of total carbon, nitrogen, phosphorus and sulphur levels.
“Stubble management in high rainfall areas is becoming more of a problem because cropping in these areas produces stubble loads far in excess of the three tonne/ha Australian average for wheat,” Dr Kirkby said.
“Trials like these often need to carry on for several seasons and farmer enthusiasm is critical if they are to be maintained. Members of the Hamilton Branch have done an amazing job in getting the trial up and running and I’m sure we have some exciting times ahead as we get stuck into repeated sampling and impose our regular stubble treatments.”
The project results from local farmers’ concerns that subsoils saturated early in the growing period are losing nutrients to levels well below the root zone.
Despite receiving rainfall of up to 700mm in the cropping districts surrounding Hamilton, farmers seem unable to break through the five tonne/ha average yield ceiling.
And it’s not only yield performance that is affected as fertiliser inputs could also be leaked through the subsoil to unreachable levels. There is also a danger of these nutrients leaching into waterways, thereby reducing water quality for the wider community.
The project will be undertaken on a 4ha section of the new Hamilton Branch site near Dunkeld with four replicates of each stubble treatment. Trial plots are 12 metres wide and 286 metres long.
Treatments will include stubble incorporation, surface retention (standing) and a common practice plot as a control. The control treatment will be dependent on seasonal conditions and the following crop, but could include burning, low harvesting or slash, bale and remove.
One plot of each stubble system will also be treated with phosphorus and sulphur to enhance the formation of stabilised organic matter that is much more resistant to leaching.
“Soil organic matter is much more than just carbon – it is a complex mixture of carbon, nitrogen, phosphorus and sulphur,” Dr Kirkby said.
“Most stubbles are quite low in phosphorus and sulphur, as are many Australian soils. Results from other trials have suggested that a deficiency of phosphorus and sulphur in the soil can limit the formation of stabilised organic matter as the fresh stubble decomposes and leads to the formation of decomposition products that are quite high in nitrogen, but are also quite unstable allowing the nitrogen-rich material to be leached below the root zone and possibly into waterways.”
Run-off collection points will be established to collect water samples throughout the season, which will be tested for dissolved nitrogen, phosphorus and carbon.
Additional soil samples will be collected every three months to analyse plant available nitrogen levels, while bi-annual sampling and analysis of soil microbes will also be completed.
Site inspections and field days will be held throughout the season to keep local farmers abreast of trial results.
The project received funding from the Australian Government throughout the National Landcare Programme (NLP) Community Support Component following submission of a funding application by Hamilton Branch SFS in February. The project was selected from an original pool of almost 300 applications from across Australia.
Enquiries, information and comments to:
Michelle McClure
Hamilton Branch Coordinator
Southern Farming Systems
P: 03 5572 3426
M: 0417 228 233
E: mmclure@sfs.org.au
Information current at July 2007
