This month on Wheatbelt NRM in the Field, host Aimee Mouritz sat down with Dr. Mehran Rashti from Griffith University to explore soil resilience at a time when farmers and land managers are facing unprecedented pressure from rising fuel costs, fertiliser shortages and increasingly variable seasons.

Their discussion dove into how soils function under stress, what helps them bounce back, and why these insights matter for growers across the Wheatbelt.

The focus of the episode was Dr Rashti’s recently completed Soil CRC project ‘Evaluating the role of ecosystem processes in enhancement of soil carbon stocks and functional resilience,’ as well as insights from Ms Mouritz’s own experience as a Sustainable Agricultural Facilitator and her work on the National Soils Monitoring Program.

To first gain an understanding of soil resilience, Dr Rashti explained that “Soil resistance is considered the ability of the soil to basically keep its optimal function during stressful conditions (e.g. drought, flood, compaction). And then soil resilience is how fast the system can bounce back to its original condition after that stressor is removed from the system.”

Many farming systems achieve good yields in good years, but this doesn’t guarantee stability in challenging years. Management that boosts peak yield isn’t always the management that keeps yield from crashing during drought, compaction, acidity, or nutrient shortages.

Why is soil resilience suddenly so important?

Fertiliser shortages and pricing are forcing growers to rethink inputs, something that was highlighted during the podcast:

“A lot of people are looking at reducing their fertiliser inputs because they can’t access them.” Said Ms Mouritz.

Connecting this to how soils process nutrients, Dr. Rashti explained that many soils have become dependent on fertiliser inputs and microbial activity has declined over time. While the fertilisers are replacing the microbial activity, the microbial community need carbon as well. In resilient soils, microbes help buffer nutrient shortages, while in degraded soils, the system collapses quickly.

“If our soil health has declined so badly… then without these fertilisers, it may take many years for these soils to go back to their original condition.”

This is particularly important in a year when fuel costs make every pass expensive, and fertiliser is harder to obtain.

Depth matters more than surface practices

During the conversation, Ms Mouritz asked whether retaining stubble would help during limited fertiliser access and Mehran agreed, but with a key nuance.

“Definitely it can contribute to that, but we need to keep in mind that the resilience is not something that generates over months.”

He explained that surface carbon is quickly consumed in wet years, meaning surface practices help short-term biology but don’t always build long-term resilience.

If there’s one key takeaway from the conversation, it was Dr. Rashti’s advice that if you want to have a good microbial community and good resilient soil, investing in understanding the whole soil profile is as important as the surface soil. The reasoning is that soil below 10 centimetres has a significant influence on yield potential. Subsoil carbon can create stable reservoirs for roots and microbes, giving crops access to nutrients for years rather than weeks.

Dr Rashti adds, “What you see at the soil surface can change really significantly… but the story at 20 to 30 centimetres would be really different.”

This further enhances the point that topsoil reflects management in the last season or two, while subsoil reflects the last decade.

Can Wheatbelt farms really build soil carbon?

The answer was encouraging, Dr Rashti explaining, “Each soil has a limitation… But if you want to improve compared to where you are at now, there is always possibilities to do that.”

This Soil CRC project showed that cover cropping, and minimum tillage improved microbial resilience and enzyme stability, enhancing soil health and nutrient cycling. Surface residues break down rapidly providing a feed source for microbes and supporting nutrient cycling, so deeper root systems and subsoil organic matter has the potential to create more permanent gains in stable carbon pools.

The podcast episode highlighted the simple reality that fuel costs and fertiliser shortages will expose the true condition of our soils. Resilient soils maintain function when conditions tighten. Dr. Rashti’s research is building a path forward for growers seeking long-term stability increasing during unpredictable seasons.

To listen to the full conversation, view all our podcasts here.

To learn more about Mehran’s research, check out the following article and webinars:

Article - Understanding soil microbial functional resistance and resilience to drought – Soil CRC

Webinars - Evaluating soil resilience to drought and compaction and 15 Evaluating Soil Functional Resilience to Compaction and Drought

This episode has been supported by the Cooperative Research Centre for High Performance Soils (Soil CRC).