Soil Aeration: Definition, Composition and Characterization

After reading this article you will learn about:- 1. Definition of Soil Aeration 2. Composition of Soil Aeration 3. Characterization. 

Definition of Soil Aeration:

Soil aeration may be defined as the exchange of carbon dioxide and oxygen gases between the soil pore space and the aerial atmosphere. So, a well aerated soil is one in which gases are available to growing aerobic organisms in adequate amounts and in proper proportions to encourage optimum rates of the essential metabolic processes of the aerobic organisms.

A well aerated soil must have sufficient space devoid of solids and water and ample opportunity for the ready movement of essential gases into and out of these spaces. There are two types of pores involved in the soil aeration-pores between the crumbs called inter-crumb pores and pores within the crumbs called crumb pores.

Composition of Soil Aeration:

The gaseous constituents of soil atmosphere are as important for crop growth as nutrients and water. Aerobic respiration in roots, micro-organisms and soil fauna involve the continuous consumption of O₂ and the evolution of CO₂. The soil air contains a variety of gases like O₂, N₂, Ar, CO₂ and water vapour etc. The composition of soil air, though quite variable is similar to that of the atmospheric air, but differs in one respect.

The content of CO₂ in soil air may vary from 10-10,000 times. The composition of soil air changes with the soil conditions, locations and the season. Although the composition of atmospheric air also changes with the various locations. Soil air contains a much more CO₂ and less O₂ than the atmospheric air. At the same time, than the atmospheric air.

Characterization of Soil Aeration:

There are various parameters that can be used for characterizing soil aeration.

(i) The volume percentage of soil air or air capacity is that part of the pore space which is filled with air. This is generally determined by applying the tension equivalent to a water column of 50 cm to a saturated soil on a tension table.

(ii) Gaseous composition.

(iii) The oxygen diffusion rate (ODR). It is determined by using the platinum microelectrode technique where the diffusing oxygen is allowed to reduce at the platinum electrode at a given electric potential. The rate of diffusion of oxygen to the platinum electrode is used as an index of the rate of diffusion of oxygen through the water film to the roots.

(iv) Oxidation-reduction potential, indicating the oxidized or reduced condition of the soil.

(v) Composition of the soil for its reduced components.