CHARACTERIZATION OF SOIL AERATION IN SITU WITH AUTOMATED OXYGEN DIFFUSION MEASUREMENTS

Abstract

The measurement of soil oxygen diffusion rate (ODR) with a platinum microelectrode was automated and used to characterize field aeration of a typical compact-layered sandy soil (Varina) under static and dynamic soil water regimes. The yield of millet, grown in the field under wet soil conditions, doubled when the ODR at the 10-cm depth increased from 0.09 to 0.15 μg/cm2/min1 and was related to the ODR, which fluctuated according to the amount of water infiltrating the soil as rainfall and irrigations. After the initial irrigation, the ODR in the A2 layer was below 0.2 μg/cm2/min1, the adopted critical ODR level for sustaining root growth for certain crops. Although the ODR in the B layer was greater than that in the A2, it was usually below the critical level. The ODR measurements were used to determine field soil matric potential (ψ-M) levels critical to aeration of plant roots, and to develop functional relationships between soil ψM and ODR for the A1, A2, and and B horizons. Soil ODR profiles were calculated from measured soil ψM and compared with measured ODR profiles. Automating the ODR measurement procedure permitted frequent measurement of a sensitive and rapidly changing soil variable important to optimal plant growth.