Can tillage actually increase soil organic matter?
Yes. But there’s a catch.
When soil is tilled, oxygen enters the system and microbial activity increases rapidly. Think of it like blowing oxygen on a fire. Microbes burn carbon for energy and release much of it as CO₂.
This is where the laws of thermodynamics show up in soil systems. Microbes must consume carbon to generate energy. If disturbance accelerates microbial activity, the only way organic matter can increase is if carbon inputs exceed what microbes are consuming.
In other words, you cannot increase organic matter through tillage alone. Organic matter increases only when carbon inputs exceed the energy released through microbial respiration.
Large cover crop biomass in a tilled system often acts more like microbial fuel than long-term carbon storage. The residue feeds microbes, but that same activity can accelerate the breakdown of existing soil organic matter through the priming effect.
Organic matter is fundamentally carbon-based. Simply adding large amounts of salt-based fertilizers does not increase organic matter. These nutrients may increase plant growth and yield, but they contain little to no carbon and do not add to the soil carbon pool.
If building soil organic matter is the goal, the system must increase carbon inputs through roots, crop residues, cover crops, manure, compost, or other organic materials.
No-till systems work differently. By reducing disturbance, they limit oxygen exposure and slow carbon oxidation. They also protect fungal networks that help build soil aggregates and stabilize carbon.
At the end of the day, soil organic matter comes down to a simple equation:
Carbon inputs vs microbial consumption.
If more carbon enters the system than microbes burn, organic matter builds.
If not, the soil eventually gives it back.
What are your thoughts on tillage vs no-till for building organic matter?