Abstract
To evaluate representative elemental composition of agricultural soils in Japan and to investigate the relationship between the elemental composition of agricultural soils and the soil type, land use, and region in Japan, 180 soil samples were collected from the surface layer of paddy or upland fields in Japan and their total contents of 20 elements were determined. Total concentrations of aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), titanium (Ti), phosphorus (P), manganese (Mn), barium (Ba), vanadium (V), strontium (Sr), zinc (Zn), copper (Cu), and nickel (Ni) were determined by ICP-AES and those of potassium (K) and sodium (Na) by atomic absorption spectrophotometry after wet digestion of the finely ground samples with nitric acid (HNO_3), hydrofluoric acid (HF), and perchloric acid (HClO_4). The total concentration of selenium (Se) was determined by high-performance liquid chromatography after treatment of the wet digest (HNO_3, HF, and HClO_4) solution with 2,3-diaminonaphthalene and extraction with cyclohexane. Total concentrations of carbon (C) and nitrogen (N) were determined by the dry combustion method, and those of silicon (Si) and oxygen (O) were determined by calculation. The medians of the total concentrations of the 10 major elements were 504 g-O kg^<-1>, 291 g-Si kg^<-1>, 76.6 g-Al kg^<-1>, 36.8 g-Fe kg^<-1>, 24.8 g-C kg^<-1>, 15.0 g-K kg^<-1>, 14.3 g-Na kg^<-1>, 11.9 g-Ca kg^<-1>, 8.78 g-Mg kg^<-1> and 3.82 g-Ti kg^<-1>, which accounted for 98.7% of the total dry weight of samples. The medians of the other elements were 2.15 g-N kg^<-1>, 1.43 g-P kg^<-1>, 705 mg-Mn kg^<-1>, 394 mg-Ba kg^<-1>, 140 mg-V kg^<-1>, 125 mg-Sr kg^<-1>, 90.5 mg-Zn kg^<-1>, 24.5 mg-Cu kg^<-1>, 14.3 mg-Ni kg^<-1> and 0.42 mg-Se kg^<-1>. By soil type, volcanic soils had relatively high Al, Fe, C, N, and P contents and alluvial soils had relatively high Si, K, and Ba contents, whereas red yellow soils had extremely low Ca, Mg, and Na contents. By land use, upland soils had significantly higher Al, Fe, C, Ca, Mg, Ti, N, P, Mn, V, and Se contents and lower Si, K, and Ba contents than paddy soils. Cluster analysis of the elemental composition of agricultural soils grouped the regions in Japan into three groups: (1) Okinawa region, (2) Hokkaido, Tohoku, Kanto, Chugoku, and Kyushu regions, and (3) Hokuriku-Chubu, Kinki, and Shikoku regions. These groups reflect differences in the relative abundance of soil types. In conclusion, these data can be used as basic information to support the development of sustainable agriculture and promotion of environmental conservation.
