Wimmera farmers have been adapting farm management practices in response to climate change. In the 30 years from 1989 to 2018, the Wimmera has experienced a 9% decrease in annual rainfall, more frosts occurring later in the growing season and more hot days (>38°C).⁽⁵⁾ In response, farmers are using new technologies such as soil moisture probes, precision agriculture, minimum tillage and stubble retention to better inform land management practices that boost productivity and conserve soil and soil moisture.

Social research indicates that over 50% of Wimmera farmers are well-versed in management practices such as grazing and cropping strategies to manage ground cover and minimise soil erosion. Close to 50% of farmers reported sound knowledge in the use of stock containment areas, and the benefits of retaining native vegetation on properties.⁽⁴⁾ This is substantiated by the 2019 Wimmera Land Use and Land Management Transect Surveys, where 15% of paddocks were recorded with exposed soil vulnerable to erosion, compared to 38% of paddocks in 1996.⁽²⁶⁾ This is a positive trend that requires continued support to ensure it is maintained.

Social research has also indicated that farmers are concerned about the impact of drought and changing rainfall patterns on property viability.⁽⁴⁾ Climate modelling predicts that the Wimmera will continue to experience a reduction in rainfall, as well as an increase in the number of hot days.⁽²⁷⁾ These climate predictions present both challenges and opportunities.

Reduced growing season rainfall and rising temperatures will likely make agricultural productivity and profitability challenging. Management of soils must involve innovative strategies to improve soil health and resilience to climatic change. This challenge can be met by farmers, industry partners and researchers working together.

There is general understanding and continued practice of maintaining ground cover to reduce wind and water erosion amongst farmers.⁽²⁾ This enables the retention and enhancement of healthy, productive soils and increases the amount of water available to plants to produce crops and pastures. These principles also apply to public land.

Established minimum tillage and stubble retention practices, maintenance of perennial pastures and ground cover, combined with climatic changes has likely led to a reduction in soil disturbance and erosion (Figure 12). The annual Wimmera Land Management and Land Use Transect Survey reports have tracked changes in land management trends since 1996. Over this time a 30% increase in the number of paddocks retaining stubble has been recorded in the northern Wimmera. There has also been a dramatic decline in large erosion events such as the 1983 dust storm that engulfed Melbourne. Such events cause highly valuable topsoil from the Wimmera and Mallee to be lost, which takes decades, if not centuries to renew.⁽²⁸⁾

Figure 12: Annual percentage of exposed soil in the Wimmera over time⁽²⁹⁾

There is a positive and increasing trend towards minimum tillage cropping practices, and an increase in retaining adequate ground cover across the farming landscape. There are also some seasons where decreases in this positive trajectory are observed.⁽²⁶⁾ This is largely due to seasonal challenges. Increased prevalence of pests such as mice, snails and slugs or increases in stubble biomass and stubble lodging, which makes inter row sowing of crops difficult are some examples. These seasonal challenges are often tackled using historical management practices, particularly stubble burning, leaving bare soil susceptible to erosion, moisture loss and a reduction in organic matter. Further work needs to be undertaken to promote innovation, technology and new approaches to address these seasonal challenges.

Bare ground leaves soil vulnerable to wind and water erosion. National ground cover thresholds have been developed for controlling erosion on agricultural land. The thresholds are 50% cover to control wind erosion and 70% cover to control water erosion.⁽³⁰⁾ Land management practices are consistently providing ground cover above the required thresholds across most of the catchment.⁽³¹⁾ However, satellite mapping has demonstrated that ground cover percentage levels decline in dry years, particularly from November to April when crops have been harvested and over-grazing is more likely to occur. It is likely that predicted climate variability will impact ground cover levels, particularly during droughts and low rainfall occurrences. Ground cover management will be particularly important during these times.

Lack of ground cover can also leave non-agricultural land, including national parks and public reserves, vulnerable to erosion. Bare ground vulnerable to wind and water erosion can result from fire, herbivores such as rabbits, deer and goats, and motorbikes and four wheel drives entering areas and removing vegetation.

The south west Wimmera has a long agricultural history of pastures and grazing. There has been a shift in recent years to also incorporate crops into farming enterprise mixes,  which now appears to be stabilising.⁽²⁵⁾ Data from the 2019 Wimmera Land Use and Land Management Transect Surveys indicates an increase in stubble burning and cultivated fallow practices, which leaves soil vulnerable to erosion.⁽²⁶⁾

Use of perennial pastures has continued in the Upper Catchment and can be an effective way of maintaining ground cover and reducing soil erosion. Pasture research will need to continue to reflect the changing needs and challenges faced by farmers. Soil health gains can still be made by increasing the percentage of land with adequate ground cover. Practices such as the use of perennial pastures, fencing waterways, off-stream water points, stubble retention, stock containment areas and rotational grazing are all being used to retain ground cover.

The use of regenerative agricultural practices have been observed in the Wimmera. Regenerative agriculture intends to improve soil health and function, which in turn enhances water quality, vegetation and land productivity. Regenerative farm practices include multi species cover cropping, increased use of organic fertilisers and amendments, as  well as a reduction in the use of herbicides, insecticides and fungicides. Research is required to understand the potential benefits and challenges of regenerative farming principles and practices in the Wimmera, given lower rainfall and the need to retain soil moisture.

Some Wimmera soils are naturally acidic. Intensive farm practices, such as the use of nitrogen-based fertilisers, growing legumes in crop rotations and hay production accelerate soil acidification, which can lead to productivity decline. Modelling estimates indicate that the upper catchment, south-west Wimmera and parts of the north-west Wimmera are moderate to high-risk areas for soil acidification, accounting for 53% of Wimmera grazing areas.⁽³²⁾ Anecdotally, there is widespread use of lime to mitigate the impact of soil acidification. Soil pH monitoring has not been completed in Victoria since 1994. Comprehensive testing would be required to assess the current trend in acid soils within the Wimmera.

Sodic soils are naturally widespread in Wimmera subsoils. Dispersion of sodium in the subsoil can cause compaction and water logging, negatively impacting productivity and causing erosion. Testing and treating soils as required can limit decline in productivity and soil structure. Anecdotally, there is widespread use of gypsum to mitigate the impact of soil sodicity. Comprehensive testing would be required to assess the current trend in sodic soils within the Wimmera.

Salt has accumulated naturally in Wimmera subsoils over the last few million years and can remobilise due to rising groundwater levels bringing salt to the surface. Anecdotally dryland salinity appears to have stabilised across the catchment, most likely due to land management measures and the Millennium Drought where subsequent dry years resulted in groundwater levels falling. Waterlogging following drought years may increase the risk of dryland salinity, as groundwater systems recharge. Almost 22,000 hectares, or just over 1% of the region, is visibly affected to some degree by salinity. This includes almost 6,000 hectares of severely impacted land.⁽³³⁾