T. Honma, H. Ohba & A. Kaneko (Kadokura) Niigata Agricultural Research Institute, Nagaoka, Japan

T. Makino & K. Nakamura National Institute for Agro-Environmental Sciences, Tsukuba, Japan

ABSTRACT: Arsenic and cadmium contents in rice grains are of public concern for human health. We carried out field experiments to investigate the effects of water management and soil amendments applied into paddy on arsenic and cadmium uptake by rice. We also investigate the effects of those factors on arsenic speciation in rice grain. Prolonged ponding water management (3 weeks before and after heading) led to increase the arsenic concentration in soil solution and in rice grain. Ponding water release management which is non-irrigation to harvest after midseason drainage led to increase cadmium concentration in soil solution and in rice grain. Arsenic uptake by rice decreased with application of short-range-order iron hydroxide. On the other hand, cadmium uptake decreased with converter furnace slag. Additionally, the main arsenic species in rice grain was As(III), and there was no difference in the ratio of several species among water management and soil amendments.