Abstract: A numerical solution of the salt diffusion equation for non-stirred bathing solution is presented Theoretical calculations of the salt diffusion from a slab into a non-stirred bathing solution showed that there is no effect of non-stirred bathing solution on the rate of diffusion if the ratio of macro and microprobe volumes (β) is less than unity. Since under field conditions the value of β for aggregated soils is much less than one. Therefore it is suggested that the analytical solution of the diffusion equation for well-stirred bathing solution can be used under field condition where bathing solution is non-stirred.