Soil air and its dynamics

Abstract

Soil air as a part of the unsaturated zone of soil is a necessary soil constituent for the growth of the majority of plants. Oxidation of assimilates (respiration) is necessary for biomass production, and oxygen is also needed for the respiration of living organisms in soil. The composition of soil air is close to that of the atmosphere because small deficits of oxygen and a surplus of carbon dioxide are quickly equilibrated by air interchanges with an atmosphere. This chapter analyses the convection and diffusion of air in the soil and expresses them quantitatively. It also quantifies oxygen transport to the plant roots to cover respiration by solving the simplified transport equation. The influence of the oxygen diffusion rate on plant canopy growth is also presented.