Restricting cadmium uptake in lowland rice [Oryza sativa] by flooding in the latter growth stage and soil improvement
2008
Inahara, M.(Toyama-ken. Agricultural Research Center (Japan)) | Ogawa, Y. | Azuma, H. | Yamada, M.
In Japan, a double standard relating to the cadmium (Cd) concentration of brown rice is valid. One is 1.0mg/kg based on the laws for foods sanitation and arable soil pollution. The other, based on an announcement by the Minister of Agriculture, Forestry and Fisheries in 1971, is 0.4mg/kg, and it functions as the standard for brown rice distributed by the government. Based on these standards, Cd contaminated paddy fields in the Jinzu River basin are restored by soil dressing. Conversely, in 2006, the CODEX Alimentarius Commission of the United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO) set 0.4mg/kg as the international standard of Cd concentration in polished rice. This standard is almost equal to the standard of brown rice distributed by the government. The effects of flooding management and inorganic soil amendments to restricting Cd uptake were investigated in the past. But those effects were unstable as the investigations were carried out in heavily polluted fields. Thus, the effects of those techniques are not clear under a slightly polluted condition. Against this background, this study was conducted to evaluate the effects of flooding management and alkalinity application under a slightly polluted condition with Cd where the Cd content in brown rice was around 0.4mg/kg. And we proposed an urgent need for an effective cultivation method against Cd contamination in brown rice with consideration of the traffic ability of a harvester. Moreover, we evaluated the effects of the chemical washing method with ferric chloride as a lasting countermeasure of slightly polluted soils with Cd.
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