High concentration of arsenic (As) in rice is a serious problem worldwide. Pot experiments were conducted to assess the potential dietary toxicity of arsenic and effect of various soil amendments on arsenic accumulation in rice grains. Two basmati rice genotypes were used to conduct pot experiments using various levels of arsenic (10, 25, 50 and 100 mg kg-1 soil). In addition, plants were exposed to soil collected from a well documented arsenic contaminated site. Contrasting results for growth, yield and grain arsenic concentration were obtained for basmati-385 (Bas-385), exhibiting tolerance (56% yield improvement at 10 mg As kg-1), while genotype BR-1 showed 18% yield decline under same conditions. Furthermore, application of soil amendments such as iron (Fe), phosphate (PO4) and farmyard manure (FYM) at 50 mg kg-1, 80 kg ha-1 and 10 t ha-1, respectively improved the plant height and biomass in both genotypes. Accumulation of arsenic in rice grain followed a linear trend in BR-1 whereas a parabolic relationship was observed in Bas-385. Both genotypes exhibited a positive response to iron sulfate amendment with significant reduction in grain arsenic concentrations. Regression analysis gave soil arsenic threshold values of 12 mg kg-1 in Bas-385 and 10 mg kg-1 in BR-1 for potential dietary toxicity. This study suggests that genotype Bas-385 can be used for safe rice production in areas with soil arsenic contamination up to 12 mg kg-1 and that appropriate dose of iron sulfate for soil amendment can be used effectively to reduce translocation of arsenic to rice grain.
Keywords: Arsenic; Iron sulfate; Potential dietary toxicity; Rice; Soil amendments; Soil arsenic thresholds.
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