Tillage is a common field practice but it comes with trade-offs, especially when it comes to soil carbon. What happens below the surface when the plow or disk passes through? It turns out, a lot. Understanding the carbon impact of tilling can help you make better decisions for long-term soil health.

Let’s look at what tillage does to the carbon your soil holds and what that means for farmers trying to build it up.

Tillage Exposes Organic Matter to Oxygen

When you break open the soil, you expose buried carbon to air. This wakes up bacteria that feed on that carbon and convert it into carbon dioxide. What used to be stable, stored carbon is now on its way into the atmosphere.

Even shallow tillage can do this. The more surface area is exposed, the more carbon is lost through increased microbial activity.

Soil Structure Breaks Down, Leading to More Loss

Healthy soil has small pockets that protect carbon-rich organic matter. Tillage destroys those pockets. Once they’re gone, the soil becomes loose, and organic particles break apart. These smaller fragments are more likely to erode or break down quickly.

Over time, this makes it harder for soil to hold nutrients, water, or roots and harder to build new carbon.

Roots Stop Growing and So Does New Carbon Input

Living roots add fresh carbon through sugars, root sloughing, and symbiosis with soil organisms. But tillage can destroy shallow root systems or stress plants during early growth.

This means less new carbon is being added to replace what’s being lost. The result is a net loss in total organic matter unless managed carefully.

Increased Risk of Erosion and Runoff

Tilled fields are more likely to shed topsoil during rain events. This top layer is usually where the most carbon is stored. Once it’s gone, it takes years to rebuild.

Without cover or structure, water moves faster across the field, carrying fine particles and the organic matter they contain.

Summary Table