GROWERS and advisers have access to a new tool that can help them assess the long-term profitability of methods to control brome grass – one of Australia’s most-costly cropping weeds.
The Brome RIM tool is hands-on, user-friendly decision-support software that has been adapted from the well-known RIM (Ryegrass Integrated Management) model for annual ryegrass (Lolium rigidum).
The original RIM model, that was developed by the Australian Herbicide Resistance Initiative (AHRI), was modified by CSIRO – with Grains Research and Development Corporation (GRDC) investment as part of the GRDC Stubble Initiative to include brome grass.
The University of Adelaide and Mallee Sustainable Farming also helped in the development and testing of the new tool.
CSIRO farming systems scientist Rick Llewellyn, who led the development of Brome RIM with colleague Marta Monjardino, said brome grass – comprising two main problem species Bromus diandrus and B. rigidus – was an annual grass weed that was widely distributed across cropping areas of southern Australia.
“It is very competitive against crops and is the major grass weed in many districts, with a lack of herbicide options making it difficult to control in cereals,” Mr Llewellyn said.
“Changes in brome grass populations mean its germination is now often more staggered and occurs later in the season, allowing it to evade early season control.”
Dr Llewellyn said brome grass was becoming an increasing problem in some cropping areas due to a higher intensity of cropping in rotations, reduced tillage and limited effective herbicides for its control in cereals.
“It has long been an issue for growers in lower rainfall areas, especially on sandy soils, but increasingly it is also becoming a problem in medium rainfall areas as well,” he said.
Dr Llewellyn said the nature of brome grass meant the use of an integrated weed management (IWM) strategy, combining several tactics to drive down the weed seed bank over several years, was particularly important as there were few individual practices that offered consistent high efficacy.
“The Brome RIM tool is well suited to testing brome grass strategies, as it allows users to look at long-term management scenarios, weed number outcomes and the profitability of a range of combinations of control strategies,” he said.
“The tool integrates biological, agronomic and economic considerations in a dynamic and user-friendly framework, at paddock scale and over the short and long-term.
“It tracks changes through time – on a five or 10-year crop rotation cycle – for brome grass seed germination, seed production and competition with the crop.
Financial returns are estimated annually and as a five or 10-year average.”
Dr Llewellyn said years of consolidated scientific data – as well as grower and adviser knowledge – were built into the Brome RIM model which allowed users to then generate individually-focused weed control solutions based on that information.
“The beauty of Brome RIM is that it allows growers to test different measures before taking the leap to make financial investments or practice changes on-farm,” he said.
“Measures that growers can consider to manage brome grass include harvest weed seed control (HWSC) tactics; changes to crop rotations; changes to herbicide use patterns; inclusion of pasture breaks; and increasing crop competition.”
Dr Llewellyn said Brome RIM had been tested with growers and advisers at many workshops, and feedback was that it was an easy-to-use and practical tool that stimulated a lot of thinking about what a sustainable strategy for brome grass would look like.
He said the Brome RIM tool was highly valuable when used in small groups where a number of growers were dealing with the same issues, or by advisers doing planning work with individual growers.
