Soil characteristics and phosphorus accumulation in surface soil in relation to geological and land-use conditions

Abstract

Effects of parent rocks and types of land use on soil physical and chemical properties and the phosphorus (P) accumulation in surface soil were examined in a small watershed. The soil developed from granite with a coarse texture, and felsic chemical and mineralogical compositions showed a coarser texture, lower contents of organic matter, water-soluble cations and anions and a lower cation exchange capacity (CEC) than soil developed from andesite. Farmland soils exhibited higher pH and electrical conductivity values, a lower ignition loss and CEC and a coarser texture compared with forest soils from the same parent rocks. The farmland soils contained greater amounts of total P, water-soluble reactive P, organic P and adsorbed inorganic P, and showed a higher degree of P saturation (DPS) than the forest soils in the following order: upland field > orchards > paddy fields > forest. The DPS of the farmland soils (28.2–93.1%) indicated that the soils showed a high potential to release P in the surface water and that careful management was required to reduce P release for the preservation of surface water quality.