Studies of soil oxygen diffusion into and through the soil profile were conducted to determine the oxygen status of soil under varying soil moisture conditions. It was found that soil oxygen diffusivity was related to soil air-space porosity even at high soil moisture levels such that the relationship could be described by a single function. In this manner different soil layers within the profile were found to have distinct diffusivity-porosity relationships. Significantly, soil oxygen diffusivities were found to be an order of magnitude lower than published values for disturbed soil samples showing that it is necessary to determine diffusivity on undisturbed soil core samples if field conditions of soil oxygen transfer systems are to be studied. (Author)