Soil: A Journey Through Time and Space

Abstract

Soil is the life support system of our planet. It helps make our air breathable, cleans the water we drink and supports production of the food we eat. This life support system relies upon processes that operate at spatial scales from less than a micron to over hundreds of metres or more, and over timescales from seconds to millennia. The smallest soil particles are nanometres across. It is at this scale that we find the engine room of the soil where chemical compounds are transformed between gas and liquid phases and where material containing carbon is digested by microorganisms, who then release carbon dioxide. Just like animals and plants living on the soil surface, most microorganisms need air and water to survive. At the nanometre scale the soil atmosphere has a carbon dioxide concentration that is much greater than the air we breathe, and where soil pores are filled with water there may be little oxygen. In this anaerobic world we find microorganisms that are specially adapted, relying on other compounds for respiration. Processes occur quickly here - microbial life cycles may take a matter of minutes and in that time they perform many vital biochemical processes for the soil.