The Measurement of Oxygen Diffusion in the Soil with a Platinum Microelectrode

The current obtained in the electrolysis of an electro‐reducible material, as oxygen, at the surface of a platinum electrode can be used to calculate the rate of diffusion of that material to the surface. Measurements made in the soil, based on this principle, give promise of furnishing a new, simple, rapid, and inexpensive method of determining the rate of oxygen supply to an undisturbed environment similar to that in the liquid film surrounding an actively respiring plant root. The method compared favorably with other methods for measuring soil aeration in a greenhouse experiment. Evidence presented indicates that factors controlling the diffusion rate in the gaseous phase of the soil extend into the liquid phase as well. The data show greater oxygen diffusion rates with larger aggregates and greater soil porosity. The rates decreased with increasing depth below the soil surface. At the lower porosities moisture film thickness has a greater effect on oxygen supply than at the higher porosities. Growth of tomatoes correlates well with oxygen diffusion measurements made with the microelectrode, and a critical rate is suggested for their growth.