Improvement of Soil Aeration
Soil organisms greatly improve soil structure and facilitate aeration. Root decay leaves the soil riddled with channels, and the burrowing of worms and other animals create innumerable passage ways which help in gaseous exchange, i.e., diffusion of oxygen and release of carbon dioxide from the soil. Growing roots often follow such channels on account of better aeration.
Improvement of Aggregate Structure
Bacteria and blue green algae, both of which are abundant in the soil, secrete mucilagenous excretions which cover their cells and colonies. Such muciliagenous materials along with other organic excretions of the cells are very effective in cementing soil grains into larger aggregates. A similar function is performed kthough in an entirely different manner by the soil fungi which bind soil particles together.