Link between cereal stubble, subsurface acidity and crown rot

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

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.

Further reading

• Reducing the risk of cereal yield losses from Fusarium crown rot
• GRDC Investment