Published July 25, 2026
Why Is Oxygen Less in Soil Air? Why Is CO2 High?
Answering a farmer's direct question about soil gas chemistry, this short paper explains why soil air naturally runs lower in oxygen and higher in CO2 than the atmosphere, and details the three self-reinforcing mechanisms, root retention, surface mulch, and biologically built porosity, that let PQNK sustain a high oxygen diffusion rate without any external management.
Abstract
The paper opens from a farmer's question posed in a WhatsApp learning group: why is soil air lower in oxygen and higher in CO2 than atmospheric air, and how does PQNK maintain the oxygen diffusion rate? The answer starts from basic soil biology: the multitude of microbes, fungi, earthworms, and roots living in soil constantly respire, consuming O2 and releasing CO2, which is why soil air composition naturally differs from the air above it. The critical factor for plant and microbial health, the paper stresses, is not the absolute amount of O2 present but the rate at which it can be replenished from the atmosphere.
PQNK maintains that diffusion rate through in-situ generation of organic matter and structure rather than any imported input. After harvest, root systems are left in place to decompose, releasing organic compounds and, critically, leaving behind a network of stable bio-pores that become direct pathways for air and water to move deep into the soil profile. Above-ground crop residue is never removed or burned, but returned as a permanent surface mulch that protects the soil from forming a hard, gas-blocking crust under rain impact and sun.
This retained organic matter fuels a self-sustaining biology that continuously engineers porosity. Microbes digesting mulch and decaying roots produce sticky substances that bind soil particles into small, water-stable aggregates, creating a crumbly, sponge-like texture; a healthy, undisturbed soil teeming with earthworms gets constant burrowing that creates extensive, deep, durable macropores functioning as 'super-highways' for both oxygen diffusion and water drainage.
The final piece is minimal disturbance: by never uprooting entire plants and avoiding tillage, PQNK protects this delicate, self-made infrastructure of root channels, wormholes, and aggregates, letting the natural ventilation system built by biology persist season after season.
The paper's summary is explicit that PQNK does not actively 'manage' oxygen levels at all. Instead, it establishes a regenerative cycle where retained roots and residues feed soil biology, which in turn builds and maintains a well-structured, porous soil, the fundamental factor that sustains a high, self-sustaining oxygen diffusion rate for the entire soil ecosystem without any external inputs.
Key Takeaways
- Soil air is naturally lower in O2 and higher in CO2 than atmospheric air simply because of constant microbial, fungal, earthworm, and root respiration.
- The critical variable for soil health is the rate of oxygen replenishment (diffusion), not the absolute oxygen concentration at any given moment.
- PQNK never imports compost or manure; organic matter and porosity are generated entirely in-situ from retained roots and returned surface residue.
- Decaying root systems left in place become permanent bio-pore channels; surface mulch prevents the crusting that would otherwise block gas exchange.
- Microbial digestion of mulch produces sticky compounds that bind soil into stable, water-stable aggregates, while earthworm burrows create macropore 'super-highways' for oxygen.
- PQNK's stated position is that it does not actively manage oxygen at all; it builds the conditions for a self-sustaining diffusion cycle and lets biology do the rest.