Link between cereal stubble, subsurface acidity and crown rot
Term
2023-2026
Project Officer
Kate Coffey
WHY THIS PROJECT IS NEEDED
Sampling conducted as part of the Improving soil to optimise water use on-farm project, identified high levels of Fusarium crown rot at sites with high stubble loads and subsurface acidity across the Riverine Plains.
This National Grower Network (NGN) project investment has been made by GRDC to further investigate the potential correlation between stubble management for subsurface acidity and Fusarium crown rot in cereals over multiple seasons.
In short: Consecutive good seasons, along with stubble retention and tight cereal rotations have favoured a build-up of Fusarium crown rot in the Riverine Plains. This project is investigating the potential link between Fusarium crown rot, subsoil acidity and stubble management techniques through demonstrations, surveys and trials to help farmers mitigate yield loss.
Project focus
The project has a focus on demonstration and extension activities to improve grower knowledge on the implications of stubble management and acidic soils on this disease, and how soil testing and management strategies can help reduce yield loss.
As part of the project, paddock surveys are being conducted annually across the Riverine Plains region for soil pH and Predicta®B DNA soil testing. Paddock (crop rotation) history and the stubble loads present is also being recorded.
A demonstration site at Murchison, originally established as part of the Improving soil to optimise water use on farm project, is also being used to show how stubble management strategies can impact Fusarium crown rot pathogen levels over time and according to crop rotation. Predicta B, soil pH and growing season rainfall, as well as yield and quality measurements, are also being collected.
Case studies and strip trials will further demonstrate the effect of stubble management and acidic soils on Fusarium crown rot, providing an extension platform for peer-to-peer learning activities and case studies.
Project full title: NGN Scoping the correlation between stubble management for subsurface acidity and Fusarium crown rot in cereal.
Project Outcomes
Outcomes from the 2024 project demonstration trials at Rand (NSW) and Murchison (Vic) were published in Research for the Riverine Plains, 2025, along with soil testing results from across the region.
Key messages were:
- Two years of break crops (faba bean followed by canola) reduced Fusarium crown rot levels from “high” to “below detection”, demonstrating the benefit of crop rotation in controlling the disease.
- Predicta B testing in 2025 showed that 8 out of 14 paddocks tested as part of this project had a medium to high risk for Fusarium crown rot, indicating that the disease is still present at high levels across the Riverine Plains region.
- Soil acidity is thought to exacerbate Fusarium crown rot severity and soil tests showed 60 percent of paddocks tested as part of this project during 2025 had pH below 5 at a depth of 5–20 cm.
- Even though there were very few whiteheads in paddocks in 2024, Predicta B soil testing and stubble plating analysis showed Fusarium crown rot levels were still “high risk” in 2025. This highlights the importance of testing paddocks before sowing cereal crops as stem browning and whiteheads are not always reliable signs of Fusarium crown rot, with other pathogens causing similar symptoms.
- Unreplicated demonstration trials showed a trend to reduced levels of Fusarium crown rot following barley compared to after wheat, and when a higher seeding rate was used in 2024.
- Using a nitrification inhibitor (eNpower), which can maintain nitrogen in ammonia form for longer, also showed a trend to reduced levels of Fusarium crown rot, compared to urea in one year of unreplicated trials.
Learn more by reading the full report: Understanding the link between cereal stubble, subsurface acidity and crown rot – demonstration trial results.
Detailed results from the project’s 2023 trials were published in Research for the Riverine Plains, 2024.
Key messages were:
- PreDicta B testing across the Riverine Plains during February 2024 showed that 79% of samples collected had medium to high levels of Fusarium crown rot present
- A demonstration site sown to wheat for two years (2021-2022), had high levels of Fusarium crown rot — burning the wheat stubble and planting faba beans in 2023 reduced levels to low within a 12 month period
- Segmented soil tests conducted across Riverine Plains revealed 64% of paddocks tested had pH less than 5 in the 5-10cm layer, with 50 % of the paddocks showing pH below 5 in the 10-15cm layer
- An acid layer, between 5 and 15cm, can affect production of acid-sensitive crops, as well as nodulation by legume species; if an acid layer is present, the recommended target pH(CaCl) for 0-10 cm is 5.8
Learn more about this trial's methods, results and conclusions by reading the full article: Understanding the link between cereal stubble, subsurface acidity and crown rot.
In early 2025, Riverine Plains Senior Project Officer, Kate Coffey, spoke to GRDC about the impact of Fusarium crown rot in the Riverine Plains region - listen to the podcast.
Further reading
Find out more
For further information about the project, please contact Riverine Plains Senior Project Manager, Kate Coffey at kate@riverineplains.org.au
Project investment
This is an investment of the Grains Research and Development Corporation (GRDC).
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