The effect of particle size on the nutrient leaching of soil was examined experimentally. Theexperimental results agreed well with the theoretical normal distribution curves for sand although the curves of effluents from aggregates were skew and did not fit the theoretical curves. Mean displacement velocity could be obtained from the maximum concentration point of effluent curve of sand, but could not in case of aggregates. The cause of the skewness was assumed to, be a wider velocity distribution ranging from small pores in aggregates to large pores surrounded by aggregates. These aspects, together with the unsaturated condition, will require further theoretical development.