DR SUSAN ORGILL, CHIEF SCIENTIST
As scientists, we’re trained to reduce complex systems into clear, measurable questions: it’s how we understand problems, test assumptions, and design solutions. But when you take scientific findings beyond the lab and into the paddock, things get more interesting! Agriculture doesn’t operate in isolation. Soils, seasons, crops, livestock and human decisions all interact dynamically.
That’s where applied science comes in. Throughout my career, I’ve worked alongside farmers and researchers, not just on papers, but in paddocks, observing how change really happens. My take home after 20 years? The most effective soil management decisions are evidence-based, grounded in observation, and informed by a systems view of the landscape.
SOIL AS AN ASSET CLASS.
There’s growing recognition that soil is more than just the ground beneath our feet. It’s a living, breathing asset. Soil delivers nutrients, water, and air to plants. It stores carbon, regulates climate, filters water, and supports biodiversity. It’s the foundation of healthy food systems – and healthy people.
Unsurprising, really, that it’s also incredibly complex. Soil is made up of mineral particles (sand, silt, and clay), organic matter, microbes, air, and water. Its texture – the ratio of sand, silt and clay – is largely fixed, inherited from its parent material. But soil structure can be improved by good management practices.
By promoting biological activity, we build the “organic glues” and static charges that help particles stick together and create stable aggregates. These structures form the pore spaces needed for aeration, water infiltration and root exploration.
When we look at a soil sample, we can see structure in action. The energy a seed would need to push through, the ability of water to infiltrate a hard setting soil; these are practical indicators of how well the soil is functioning. Because a soil can be technically “wet” after rain, but still thirsty if that water runs off rather than soaking in. Think about it as effective rainfall – how much rain did you actually get in the soil for plants to grow?
We can also take lessons from the shape and stability of aggregates, the depth and direction of root growth, and visible signs of biological activity – like earthworm and root channels, which act like superhighways for air, water and microbes. We might also see signs of bioturbation – the natural mixing of soil by macrofauna like worms, dung beetles or other invertebrates. These organisms are nature’s little tractors, constantly working the soil to improve structure, aeration and nutrient distribution.
This isn’t just fascinating biology. It’s a visible sign of healthy function below the surface.
SAMPLING MATTERS – BUT IT’S ONLY PART OF THE PICTURE.
A soil test, like a blood test, gives us useful indicators: pH, nutrient balance, salinity, organic carbon. But just as a doctor won’t prescribe treatment without asking about our diet, sleep, exercise, and family history, soil test results only make sense in context.
That means looking especially at paddock history and management practices. Has it been rested? What’s been grown or grazed? I’m not suggesting soil tests don’t matter! They’re a vital tool to understand the soil physicochemical environment and diagnose soil constraints. But it’s the system around them that tells the full story, and leads to more meaningful recommendations than the test alone can provide.
SOIL CARBON: THE CENTRAL INDICATOR.
Soil organic carbon is the most widely recognised indicator of soil health, playing a central role in nutrient cycling, microbial function, and water dynamics. And its impact can be quite significant. A 1% increase in soil organic carbon in the top 10 cm of a loamy soil can deliver:
- ~1080 kg more nitrogen
- ~228 kg more phosphorus
- ~168 kg more sulphur.
It can also boost cation exchange capacity by up to 90% in some soils, improving the soil’s ability to hold and supply calcium, magnesium and potassium. And it enhances water-holding capacity by 20–30%, depending on soil type.
THE GOOD NEWS?
Soil carbon can be built over time. Maintaining ground cover is essential, along with increasing the diversity of organic matter inputs through biodiverse pastures, including legumes. Time-controlled grazing, crop and pasture rotations, targeted nutrition, organic amendments, addressing soil constraints, and minimising disturbance all contribute to building soil carbon – and unlocking the benefits that come with it.
GROWING MORE THAN YIELD
Healthy soils don’t just grow better crops and pastures. They increase the effective farming area, reduce reliance on synthetic inputs, expand species options, and buffer against climate volatility.
If we left it to nature, growing soil would take centuries. But with targeted, evidence-based management, we can build soil from the top down – deepening fertility, improving function, and unlocking productivity within the constraints of today’s farming systems.
At Impact Ag Australia, I’m proud to be part of a team that takes science beyond the trial plot – applying it through systems thinking, practical insight and genuine collaboration with land managers. Because that’s where soil science matters most.
Dr Susan Orgill is Chief Scientist at Impact Ag Australia and a leading soil scientist with 20+ years’ experience. She specialises in soil health, carbon farming, and regenerative agriculture, delivering science-based strategies that improve farm resilience, natural capital, and climate outcomes across research, policy, and sustainability initiatives.
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