Analysis of 57 elements in Japanese soils, with special reference to soil group and agricultural use

The concentrations of 57 elements in 514 soil samples collected from 78 sampling sites throughout Japan were determined, and the elemental composition of Japanese soils were discussed, with special reference to differences among soil groups and the influence of agricultural activity. Close relationships between the element concentration and rock type were found. Typically, levels of Si, K, Rb, Ba, Tl, Th, and U increased as rock type shifted from mafic toward felsic, whereas levels of Mg, Sc, Ti, V, Fe, Co, and Cu decreased. The concentration of some elements in soils was strongly dependent on the soil group. For example, Andosols had relatively higher contents of mafic elements, which might be reflected by the composition of parent rock type, and Acrisols had lower concentrations of many other elements, especially Na, Mg, Ca, and Sr, possibly because of the their heavily weathered nature. Cultivated top soil showed higher content of P, Cr, Ni, Cu, and U than subsoil due to agricultural activities. For example, in the long-term experimental field on applications of fertilizers, the concentrations of P, Cd, and U in topsoil were obviously elevated, probably because of the successive application of phosphate fertilizer. The accumulation of U of anthropogenic origin could be evaluated more clearly by examining the U/Th ratio rather than the U content alone.