Oxygen Diffusion Rate ODR

Upon application of a certain potential across the platinum electrode and a reference electrode inserted in the soil, oxygen is reduced at the platinum surface. The electric current flowing between the electrodes is proportional to the rate of oxygen reduction which in turn is related to the rate of oxygen diffusion to the electrode. The oxygen diffusion rate (ODR) is calculated from the measured electric current according to the following equation. 

A milli-ampere meter to measure the output current. 

Output current Electrode length Electrode radius Surface area of electrode Molecular weight of oxygen Faraday constant 

Number of electrons required for reduction of one molecule of oxygen = n = 4 

Note ODR value of 20 x 10 g cm s or more suggests STifficient oxygen supply for root growth. 

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Fig. 2.14. Schematic diagram of oxygen diffusion rate (ODR) measurement.

FIGURE 6.11 Oxygen diffusion rates (ODRs) and oxidation-reduction potential in North Yorkshire valley hog peat. (Redrawn from Armstrong, 1967.)... 

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