Oxygen diffusion rates (ODR) were measured in water/sand/air and PEG solution/sand/air mixtures, spanning a range of liquid/solid/air volume ratios. Replacement of water with PEG solution as the liquid phase was found to reduce the ODR within a given mixture by a factor of approximately two. ODR values were compared with limiting values for plant emergence quoted in another study. It was concluded that PEG solutions could be used to control the osmotic potential of a sandy growth medium without adversely affecting seed germination due to oxygen starvation, providing that the pore volume was less than 70% occupied with liquid.