Project background
Calcarosols occupy about 60% of the cropping soils in south-eastern Australia, and more than 1.1mha of SA cropping areas are highly calcareous. These soils challenge crop production with a range of constraints and limits the effectiveness of improved agronomic practices. Current delivery and uptake of synthetic phosphorus is poor and crop production continues to be limited to very low water use efficiency (WUE).
The lack of cost-effective phosphorus sources to increase tissue concentrations to adequate levels makes it challenging to improve crop productivity. The goal of this project is to develop integrated solutions to improve the delivery of phosphorus in challenging calcareous soils. These solutions will be developed in a farming systems context so practical and profitable management options can be provided to farmers and advisers.
Objectives
The aims of the project are to:
- Investigate different sources of conventional phosphorus fertilisers and determine cost-effective rates for a carbon-coated mineral (CCM), which was one of the best performing strategies in previous trials on the Eyre Peninsula (EP)
- Evaluate other commercially available biochars and their effect on crop phosphorus uptake
- Investigate the agronomic and economic thresholds for CCM, through a rate response trial.
Research approach
This project will take a holistic approach to addressing phosphorus delivery and supply to crops by conducting:
- pot experiments under glasshouse conditions to evaluate the different biochar products and conventional fertilisers against CCM, and to investigate the agronomic thresholds for CCM
- replicated field trials on the upper Eyre Peninsula to validate the impact of solutions and strategies developed in the pot experiments on crop performance under conditions typical of commercial crops.
Expected outcomes
Currently, crop production on highly calcareous soils has low WUE at 30-50% and it's feasible that findings from this project could lift that figure to 60-70%. This would improve yields on highly calcareous soils, but only if phosphorus is supplied in cost-effective ways. Improved productivity from cropping also has indirect benefits to the farm business and the environment in general.
Higher levels of production will result in more break crops being viable, which can transform crop sequences and the overall profitability and resilience of the system. Stock-carrying capacity can also increase due to higher stubble loads and more on-farm feed. Higher crop productivity will also help to alleviate natural resource issues, like wind erosion (highly calcareous sandy soils are very vulnerable to wind erosion), vitality of soil microbiology, and risk of dryland salinity.
Key findings from the linked previous project:
- High soil strength is an issue in calcareous soils, however, positive responses to deep ripping are less likely and usually limited by the hostile subsoil.
- Short-term topsoil strategies resulted in better gains in crop biomass and yield when compared to longer-term subsoil strategies.
- A carbon-coated mineral (bespoke biochar) applied in the topsoil improved crop vigour, biomass and grain yield, and provided benefits to the following crop.
- Increasing seeding rates and nutrition at sowing was effective at achieving high plant densities, crop biomass, and grain yield.
Addressing multiple constraints in calcareous soils using integrated solutions will ensure an increase in crop productivity and subsequently profitable and sustainable farming systems.
Collaborators
- AIR EP: Project participant
- SA Discovery Farms: Co-funded project
