Effect of Groundwater Level on Cadmium Uptake and Yield of Soybean from Cadmium Polluted Soils

抄録

Human uptake of Cadmium (Cd), a toxic heavy metal that can cause kidney damage and other physiological disorder, takes place mainly through food. In some regions of Japan, the agricultural land area was polluted with heavy metals especially Cd. Management of groundwater level can be effective method for minimization of Cd uptake in plant at large scale agricultural field. In this greenhouse experiment, we investigated two constant groundwater levels; 10cm groundwater level model (M-10) and 40cm groundwater level model (M-40) on Cd uptake in Soybean plant in Cd polluted soils (3.39 mgkg^-1). The redox potential of soil layer was measured from seed sowing to harvesting. Thickness of gravel layer, non-polluted soil and polluted soil was 14, 15 and 25cm respectively. The soil layer (10-40 cm) of M-10 was always measured in reduction condition and 0-40cm layer of M-40 was always in oxidation condition. Cd concentration of Soybean seed was significantly lower in M-10 (0.92 ± 0.1 mgkg^-1) than that of M-40 (1.31 ± 0.2 mgkg^-1). Cd concentration of stem was also found significantly lower in M-10 (0.82 ± 0.1 mgkg^-1) than that of M-40 (2.34 ± 0.2 mgkg^-1). In the other hand, main stem height of soybean plant of M-40 (111.6 ± 5.1 cm) was significantly higher than that of M-10 (100.5 ± 3.6 cm). In vegetative stage (first 50 days) the SPAD-value was observed higher in M-40 (about 46.5) and lower in M-10 (about 31.3). Branch number, 100 seed weight and seed yield were also found significantly higher in M-40 than those of M-10. The result revealed that, reduction condition was effective for minimization of Cd uptake in Soybean plant whereas, oxidation condition was favorable for seed yield.