Soil and Plant Analysis

Measurement of soil aeration

Oxygen Diffusion Rate (ODR) - the rate at which O2 in soil air is replenished. ODR decreases with soil depth.
Measurement of ODR in soil
Lemon and Erickson (1952) devised a method for measuring oxygen diffusion in the soil system with the help of platinum micro electrode

Principle
When a certain potential is applied across the platinum electrode and a reference electrode inserted in the soil, oxygen is reduced at the platinum surface. The electric current flowing between two electrodes is proportional to the rate of oxygen reduction. The later, in turn, is related to the rate of oxygen diffusion to the electrode. The oxygen diffusion rate is calculated from the measured electric current with the following equation

ODR = Mi/ήFA

Where M is molecular wt of O2, n is the number of electrons involved in the reduction of one molecule of oxygen, F is Faraday constant, i is current in amperes and A is the exposed surface (m2) of the electrode.