Dispersion behavior of soils from reclaimed lands with poor soil physical properties and their characteristics with special reference to clay mineralogy

Abstract

The characteristics of soils from a reclaimed area with constraints on the cultivation of fruit trees were examined in comparison with a forest soil that was derived from the same parent material. The reduced plant growth in the reclaimed area was attributed to the poor physical properties of the soil owing to low aggregate stability and high dispersibility of clays. To analyze the factors affecting the dispersion and flocculation behavior, the structural stability of the soil samples before and after Na saturation treatment was investigated. After the treatment, some samples showed a much higher dispersibility than untreated ones, presumably due to the displacement of exchangeable Al as the binding agent by Na. Other samples showed a low dispersibility of clays and a high aggregate stability after the same treatment, indicating that hardly exchangeable hydroxy Al may act as the binding agent of fine particles. The differences in the form of Al and clay mineralogy were reflected in the charge characteristics, which may account for the difference in the colloidal behavior. The forest soil, whose zero point of charge was close to pH-H₂O, showed a relatively small amount of variable charges, leading to a weak repulsive force between clays. The surface charge density of the soil from the reclaimed land was large, resulting in the high dispersibility of clays. The importance of organic matter was also indicated.