Effects of topdressing silicon fertilizer at key stages on uptake and accumulation of arsenic in rice

The booting stage and filling stage have been considered as the key stages for arsenic (As) uptake in rice. In this study, a field study was conducted to investigate the influence of the topdressing different amounts of silicon (Si) fertilizer at the key stages on rice As uptake and accumulation. The results showed that topdressing of a low amount of Si fertilizer at the booting stage and filling stage could increase rice yield, promote the formation of iron plaque and the retention of As on iron plaque, and reduce inorganic As content in brown rice. Compared with the control, the rice grain yield was increased by 22.60% with the topdressing of 20 kg·hm −2 Si fertilizer at the grain filling stage. As compared with the control, the Fe and As content in iron plaque under the topdressing of 20 kg·hm −2 Si fertilizer at the booting stage and filling stage was significantly ( p < 0.05) increased by 84.34% and 87.78% (Fe content) and 70.96% and 63.80% (As content), respectively. Meanwhile, contents of As in rice roots, stems, and husks at the topdressing of 20 kg·hm −2 Si fertilizer at the booting stage were significantly ( p < 0.05) reduced by 45.10%, 33.34%, and 31.23%, respectively, relative to the control. The lowest inorganic As content (0.21 mg·kg −1 ) in brown rice was obtained at the topdressing of 20 kg·hm −2 Si fertilizer at the booting stage, which was close to the National Food Limit Standard of 0.20 mg·kg −1 (GB 2762–2017). Therefore, topdressing of 20 kg·hm −2 Si fertilizer at the booting stage might be considered as an effective method to reduce inorganic As content in brown rice.