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Minimising the yield impacts of soil constraints

Agriculture Victoria scientist Roger Armstrong led a project to identify cost-effective soil amelioration practices in the southern region.
Photo: Agriculture Victoria

The challenge

Large areas of Victoria have multiple soil constraints that limit crop productivity. Despite research showing productivity benefits from soil amelioration, grower adoption has been limited.

To increase adoption, a need was identified for a shift from high-cost single constraint management strategies to those that address multiple soil constraints spatially applied at scale across a paddock.

Investments made through the Victorian Grain Innovation Partnership (VGIP) assessed the potential to integrate multiple detection methods to map multiple soil constraints. Trials were also designed to assess the yield response when soil treatments are targeted to where they are needed.

The project was led by Dr Roger Armstrong of Agriculture Victoria.

The response

Between 2019 and 2022, the project developed a new method to map soil constraints in three dimensions by integrating current best-practice soil sampling techniques with rapid soil-sensing technology.

These maps were overlayed with crop growth rates estimated from ground-based and satellite images for three consecutive growing seasons.

The power of the approach was further boosted by the use of machine learning algorithms to better process the mapping and crop growth data and discover the important relationships.

Simulation modelling and long-term climate data were then used to understand relationships between soil constraints and yield under different seasonal conditions.

Finally, field experiments were undertaken to test the impacts of targeting soil amelioration strategies to mapped soil constraints. Data was gathered to validate the yield response and the findings extended to growers and advisers.

The impact

Field experiments demonstrated that better-targeted soil amelioration strategies can markedly increase the yield response. Yield increases of 10 to 15 per cent were found to be achievable where major soil constraints exist.

The average cost of soil amelioration with organic components was $56 per hectare per year over 884,568 hectares. Increasing organic matter including stubble, chicken manure and other carbon sources can help to reduce nitrogen losses in higher-rainfall areas by 10 per cent. This translates to a $4/ha gross margin increase over a benefit period of 13 years.

In the process, the positive yield response validated the new technique for identifying soil constraints at the 3D level. The new techniques can also reduce the high upfront costs of outdated techniques, leading to greater opportunities for grower adoption.

The spatially targeted soil management strategy was also found to reduce the impact of biotic and abiotic constraints on crop water use efficiency.

Overall, this investment developed new, more readily adoptable soil mapping techniques that can help bridge the yield gap and reduce management costs. Once adopted, impacts include increased grower profitability and reduced enterprise risk.

The present value of investment in this project was just under $6 million. The present value of benefits it generated was estimated at $72 million. This amounts to a benefit cost ratio of 12.18.

While the approach was focused on managing soil constraints for crop productivity, other areas of potential application of the new mapping technology include frost and disease management.

More information: view the Delivering impact case studies.

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