Soil pore size and geometry as a result of aggregate-size distribution and chemical composition

Soil pore size and pore geometry are important propernes affecting soil hydraulic properties. Using scanning electron micrographs and image analysis, we quantified the actual pore-size distribution and pore shape in undisturbed soil cores. Aggregate-size distribution was also quantified for the same micrographs. For soils with similar texture, we observed a decrease both in the median aggregate size and in the aggregate-size distribution when the sodium content in the soil increased. We hypothesize that the decrease in the aggregate stability is caused by the weakening of the binding capacity of the cementing agents bonding the domains that form the aggregates. An equivalent decrease in the pore-size distribution was found with increasing sodium and pH. There was a significant correlation between median aggregate size and median pore size, but there was not a significant correlation between median pore diameter and soil texture.