| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 107 === The accumulation of arsenic (As) in rice grain had posed a threat to food safety and human health via the daily intake of rice by Asian people, because of the high bioavailability of arsenite (iAsIII) in paddy soils, thus caused higher accumulation of As in rice grain rather than other cereal crops. Previous studies indicated that increasing concentration of silicic acid (Si) in soil solutions may alleviate the negative impacts of As on rice plants. In contrast, some studies also found that Si application can lead to an increase in As uptake by rice via competitive adsorption between iAsIII and Si on the soil surface. However, field experiment for investigating the dynamic of Si and As in soil-paddy rice system is still scarce. To evaluate the feasibility of Si application on reducing As accumulation in rice grains, four rice (Oryza sativa L.) cultivars including TK9, TN11 (japonica) and TCS10, TCSW2 (indica) commonly planted in Taiwan were used in this study, which were grown in two As-contaminated paddy fields located at Minsyong (Ms) and Guandu Plain (Gd), Taiwan, respectively. Based on recommended application rate of Si (750 kg SiO2 ha-1), there are four calcium silicate application rates (0, 750, 1500, and 3000 kg SiO2 ha-1) used in this study. The results show that Si application could decrease the concentrations of As in straw and brown rice in Ms fields, and no negative effects on plant growth was observed. For Gd soils, the As concentrations in rice plants could be reduced by Si application, but the growth inhibition were also observed. In addition, it found that iAsIII is the predominant As species in brown rice (75-92 %), and the concentrations of inorganic As in brown rice were lower than the permission level (0.35 mg kg-1) under Si treatments. Based on the above results, it suggests the Si application can reduce inorganic As accumulation in brown rice, and the extents of decrease were controlled by the Si application rate, soil properties, and rice cultivars. Therefore, it needs to consider these factors when Si fertilizer is applied to As-contaminated paddy soils.
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