Dr Nigel Wilhelm

Project Leader

Primary Industries and Regions SA

The challenge

Calcareous soils are widespread across south-eastern Australia, occupying 60% of the cropping soils in the region. They present multiple constraints to crop production, including low phosphorus availability, poor nitrogen cycling, low water-holding capacity, and high levels of rhizoctonia. Crops may also be affected by fertiliser toxicity during germination, extreme pH, sodicity and salinity. These constraints can severely limit early crop growth and overall productivity.

Our research

This collaborative project, which started in 2020, aimed to identify and overcome calcareous soil constraints in order to lift crop production on these difficult soils. Replicated field trials were conducted on the upper Eyre Peninsula (EP) and in the South East (SE) of South Australia (SA) from 2020 to 2023 to investigate impacts of subsoil and topsoil amelioration strategies.

Research findings

  • 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 as well as 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.
  • 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.
  • On very highly calcareous soils, improving the fertility of subsoils has the potential to improve grain yield, but responses only started showing in the third crop after application compared to the control.
  • Correcting severe yellowing in broad beans with multiple applications of iron chelate (EDDHA) resulted in more vigorous growth during winter and large grain yield increases on a highly calcareous soil in the SE region of SA.

Our findings may have direct applicability to other similar regions, despite considerable differences in farming systems and agroclimatic conditions. Addressing multiple constraints in calcareous soils using integrated solutions will ensure an increase in crop productivity and subsequently profitable and sustainable farming systems.

Find out more

Read the project resources on this page to dig deeper.