Soil Carbon Matters: The Hidden Engine of Crop Yield

If you ask a farmer what drives crop yield, you’ll likely hear about rainfall, seed quality, or fertiliser inputs. All important, of course.

But beneath the surface (literally) is something even more fundamental: soil carbon.

Often misunderstood or overlooked, soil organic carbon (SOC) is the engine room of soil health. It supports microbial life, retains moisture, enhances nutrient cycling, and improves structure. And in doing so, it sets the foundation for strong, resilient, productive crops.

In the rush to apply synthetic fertilisers and chase short-term yield gains, we’ve been depleting this resource.

Now, the focus is shifting back.

What Is Soil Carbon, and Why Is It So Important?

Soil organic carbon refers to decomposed plant and animal matter, microbial biomass, and humus stored in the soil. It forms the base of the soil food web and directly affects:

• Nutrient availability
• Water-holding capacity
• Root penetration
• Microbial activity
• Resistance to erosion and compaction

More carbon means:

• Better soil structure
• More efficient fertiliser use
• Improved resilience during drought
• Increased crop productivity

"Healthy soils rich in carbon can store 2–5 tonnes of CO₂ per hectare per year."
— FAO, 2020

Australia’s Soil Carbon Crisis

According to the Australian Department of Climate Change, Energy, the Environment and Water (DCCEEW), large areas of our agricultural land have seen significant SOC decline due to:

• Intensive tillage
• Overgrazing
• Excessive synthetic input use
• Lack of carbon-returning practices

In key cropping regions, soil organic carbon (SOC) levels have dropped by 30–60% compared to pre-agricultural conditions.

This loss is bad for the planet, but worse for farmers.

Why Nitrogen Fertiliser Alone Doesn’t Help

Conventional urea provides nitrogen, but offers no carbon. Worse, over-application can:

• Accelerate soil acidification
• Disrupt microbial balance
• Degrade soil structure
• Trigger nitrous oxide emissions (N₂O)

Over time, this creates a dependency cycle: more fertiliser, for diminishing returns.

How COLDry Fertiliser Supports Soil Carbon Recovery

COLDry Fertiliser, developed under the Zero Quest joint venture, blends urea with lignite, a carbon-rich material derived from Victoria’s brown coal reserves.

This approach delivers nitrogen and carbon in one product.

What the lignite does:

• Adds organic carbon back into the soil
• Improves water retention and soil aeration
• Stimulates microbial activity
• Enhances nutrient retention

What the result is:

• Healthier soil
• Lower fertiliser requirements over time
• Higher and more stable crop yields

And unlike compost or cover crops, COLDry Fertiliser fits seamlessly into existing fertiliser programs; spread it like urea, and let the soil do the work.

The Results Are Clear

Peer-reviewed trials on lignite-urea fertilisers show:

• 21% increase in nitrogen uptake
• 23% yield increase
• Increased SOC and microbial biomass
• Reduced nitrogen loss through leaching and gas emissions

Rebuilding Soils, One Application at a Time

Improving soil carbon used to mean major practice changes, such as cover cropping, rotational grazing, and carbon credits.

Those approaches matter, but they aren’t always accessible.

COLDry Fertiliser offers a carbon-positive solution that:

• Requires no new systems
• Works within current infrastructure
• Delivers immediate agronomic benefits

It’s a regenerative farming solution that doesn’t ask farmers to start from scratch.

Want to Build Better Soil?

If you’re a grower or agronomist interested in how COLDry Fertiliser can boost your soil carbon and your bottom line, get in touch.

Email: [email protected]

It’s time to give back to the soil that gives us everything.

References

• FAO Soil Organic Carbon Guidelines
• DCCEEW State of the Environment: Link