Abstract
Leaching of several components from soils with percolating water was measured by a column experiment during 150 days of incubation under controlled conditions. In this experiment, four kinds of agricultural soils in Japan (Andosol, Brown Forest soil, Gray Lowland soil, and Dark Red soil) and two kinds of composts (sewage sludge compost and city refuse compost) were examined. The results are as follows ; 1) pH values of percolating water measured during incubated periods from soils applied with city refuse compost were high compared with those applied with sewage sludge compost and the control. Percolating water high compared with those applied with sewage sludge compost and the control. Percolating water from Dark Red soil applied with city refuse compost and sewage sludge compost showed a pH of about 8 during the whole period of incubation. On Andosol, Brown Forest soil, and Gray Lowland soil with compost applied, pH percolating water was depressed at an early stage of incubation. 2) Electrical conductivity (EC) of percolating water during incubation showed the order : city refuse compost > sewage sludge compost > control. EC of percolating water from soils applied with city refuse compost showed maximum values during 20-30 days of incubation due to leaching of cations. In the case of soils with sewage sludge compost, the maximum values of EC were shown during 30-50 days of incubation by leaching of nitrate nitrogen. 3) Concentration on nitrate nitrogen in percolating water from soils applied with sewage sludge compost and the control were markedly high compared with city refuse compost ; however, on soil with city refuse compost applied, concentration of nitrate nitrogen was high. 4) Concentration of cations and anions in percolating water differed according to soils and composts. From these discrepancies in ion balance it was estimated that the leaching of anions such as phosphoric, carbonic, and organic acid had occurred. 5) It was concluded that leaching of several components from soils applied with city refuse compost occurred at an early stage of incubation whereas that from soils applied with sewage sludge compost continued to occur throughout the period of incubation.
