Renewal of soil air
- Renewal of soil air takes place by two major processes. These processes include diffusion and mass movement.
Diffusion
- Diffusion is important for renewal of air in soil. Diffusion is that random movement of liquid or gases that the net movement of gas occurs when the partial pressure of individual gases in two neighbouring system are different.
- Diffusion of gas is proportional to the square of absolute air temperature.
Mass flow
- Mass flow is viscous movement where the moving force consists of gradient of gradient of total gas pressure. Air exchanges from higher pressure zone to lower pressure zone.
- It is synonymous to convection process. The mass flow results from the penetration of wind in larger soil pores.
- Soil temperature variation, water entry and withdrawal and barometric pressure difference in adjoining soils.