A participatory approach is being taken to examine the interplay of climatic, agronomic and social factors shaping new WA farming systems.
A major farming systems initiative, spanning five years, is underway in the low and medium-rainfall regions of Western Australia. Its aim is to support growers in navigating evolving climatic conditions, enabling them to make informed business and agronomic choices to bolster both on-farm profitability and sustainability.
Complex issues are driving changes in cropping rotations in the low to medium-rainfall regions, says Martin Harries from the Department of Primary Industries and Regional Development (DPIRD), who leads the GRDC-supported project.
“It probably started off with herbicide-resistant weeds in the late 1990s to early 2000s, when growers started managing their weeds for herbicide resistance. As they drove down the presence of herbicide-resistant ryegrass, they found their pastures were not as viable,” Dr Harries says.
“Over the same period, we have also seen massive improvements in cropping technology, with larger machinery and advances with chemicals, crop varieties and agronomy.
“These developments have seen improvements in crop water use efficiency and growers switching to more crop-dominated rotations to push farm profitability.
Now we are starting to see a new driver shaping crop rotations with an increased focus on reducing greenhouse gases to mitigate climate change.
To address these issues GRDC, together with DPIRD, is investing $20 million in the project, which began in 2022. It is focused on the low and medium-rainfall regions, with sites at Northampton (medium-rainfall, north), Merredin (low-rainfall, central) and Lake Grace (medium-rainfall, south).
Consultation and participation
Extensive stakeholder consultation at the commencement of the project established and refined key research themes – targeting early sowing, system break crop or pasture options to increase diversity – that are profitable and reliable and management for profitable lowering of greenhouse gas emissions.
“Feedback from this consultation, together with pre-experimental modelling, is being used to guide the trial program and other focus activities of the WA Farming Systems investment,” Dr Harries says.
To provide ongoing guidance and grower engagement throughout the project’s life, Regional Innovation Groups (RIGs) were established in each target region. The groups’ initial input has been incorporated into 2023 trials and the members will provide ongoing project advocacy.
Two of the three sites are located on growers’ properties and one on DPIRD’s Merredin Research Station. Each covers between four to seven hectares, and is GPS referenced and fully characterised for soil, weed and disease aspects.
Agricultural Production Systems SIMulator (APSIM) modelling was used to look at sowing opportunities, rainfall and temperature history and long-term simulations to determine water-limited yields and nitrogen rates.
“The analysis highlighted regional differences in probability of early sowing opportunities under a range of different sowing rules, differences in risk of high temperatures during the establishment period and yield potential for wheat,” Dr Harries says.
Trial sites will use over 40 treatments to compare different rotations, including wheat/barley, lupins, canola, pasture, vetch, serradella, multi-species mixes and fallow; sowing times (summer/timely or dry versus delayed); and nitrogen rates.
“Satellite sites have been established where the RIGs have expressed interest in a particular facet of the larger farming systems trials. For example in the medium-rainfall area a replicated plot trial was sown investigating time of sowing by crop species was sown at Chapman Valley. In future years this trial will be undertaken in other regions.”
Yield, soil nutrients, water use, weeds and diseases will be monitored and greenhouse gas emissions modelled from the large rotation trials for comparisons. Results will be combined over the four years of the project with whole-farm economic modelling to address key questions.
These questions will include investigation of strategies for reducing financial risks and greenhouse gas emissions, the impact of rotation type on water use and nitrogen use efficiencies, changing timing of sowing and strategies to increase profit across rotations while managing weeds, diseases and soil fertility.
“Ultimately, we are wanting to ensure growers in these rainfall regions have the information required to adopt agronomic and systems innovations to boost their farm profitability while also understanding the greenhouse gas emissions intensity of these new systems.”