“Soil respiration” is when oxygen moves through the soil. It’s the way that soils “breathe.”
Oxygen in the air moves into the soil, filling up the tiny spaces between soil particles. This is important because plants need to take oxygen into their roots. If roots don’t get enough oxygen, the plants can die. Also, most microscopic creatures in the soil (called “microbes”) need oxygen too.
If a soil is very compacted (squished tightly together), that makes it hard for plants and microbes in the soil to get oxygen.
A soil “breathes” when air moves through the tiny gaps between soil particles.