CHANGES IN THE NETWORK PROPERTY OF PORES DUE TO SOIL AGGREGATE FORMATION
Keywords:
Soil aggregates, Pore-network, Percolation probability, Percolation threshold, Water retentionAbstract
Soil aggregates are clumps of soil particles bound to each other through organic matter. Soil with aggregates has favorable features for crop cultivation, such as adequate water retention and filtration. This feature was clarified from the perspective of the network formed by pores. The connectivity of pore networks in soil was investigated in this study using virtually generated porous media with and without aggregates. The connectivity for drainability was evaluated using the percolation probability (PP), which is represented as a curve of the ratio of the largest subnetwork formed by pores that are larger than a certain value as the value decreases from the maximum to the minimum pore size. Compared with the PP of porous media without aggregates, PP with aggregates has a smaller percolation threshold, which is the point at which PP rises sharply, indicating that soil with aggregates has high drainability. Furthermore, PP without aggregates asymptotically approached the diagonal, whereas PP with aggregates left the diagonal halfway and approached again. This demonstrates that the aggregates contain loosely isolated subnetworks and that the water retained in the aggregates is difficult to drain once the aggregates are filled with water. These findings enhanced our understanding of the water retention property of soils with aggregates.