Water and air: the invisible half

The liquid component of soil is mainly water. Soil water fills part of the pore space between particles and acts as a transport system, carrying dissolved nutrients and organic compounds to plant roots and soil organisms. However, not all soil water is equally available.

The gas component of soil is the air found in the remaining pores. Soil air differs from above-ground air: oxygen concentrations are usually lower, while carbon dioxide concentrations are higher because plant roots and (micro)organisms are constantly respiring. In poorly aerated or waterlogged soils, microbes switch to alternative metabolic pathways.

For example, in flooded soils such as wetlands or rice paddies, certain microorganisms produce methane. Other microbes release nitrous oxide during nitrogen transformations. Both gases are powerful greenhouse gases.

Optional: Watch this short (25-second) VR video that takes you into the surface litter layer, pore space, and water film in soil.