Water regimes: an approach of mitigation arsenic in summer rice (Oryza sativa L.) under different topo sequences on arsenic-contaminated soils of Bengal delta

Arsenic (As)-contaminated groundwater has been widely used in agricultural purposes especially for summer rice cultivation in South East Asia. Therefore, the present experiments were carried out at low (diara) and medium land topo sequences with the eight water regimes to reduce the As accumulation in summer rice (Oryza sativa L.). Experimental results revealed that the intermittent ponding of 2–4 days after disappearance (DAD) were significantly reduced the As accumulation in root, stem, leaves, flag leaf, husk, and grain (21.86–31.78, 23.55–37.20, 14.83–30.93, 23.53–31.19, 21.33–28.19, and 22.98–25.37 %, respectively), which was followed by aerobic rice (21.34–22.08, 22.49–30.72, 12.21–23.02, 22.06–27.52, 20.14–23.94, and 22.12–22.30 %, respectively), and saturation of top soil (17.43–17.85, 21.91–28.01, 10.76–20.27, 20.59–24.77, 18.96–23.14, and 20.75–21.15 %, respectively) as compared to continuous ponding or farmer practice, where the As accumulation in root: 13.43–17.20 mg/kg; stem: 8.64–10.36 mg/kg; leaves: 2.91–3.44 mg/kg; flag leaf: 0.68–1.09 mg/kg; husk: 1.88–2.11 mg/kg; and grain: 0.52–0.67 mg/kg. However, aerobic rice and saturation of top soil recorded significantly higher grain yield at diara land (7,104–7,141 kg/ha) and only in saturation of top soil at medium land topo sequence (6,654–6,717 kg/ha). The correlation study showed the positive correlation in between grain As and root, straw, husk As, grain Zn, and grain Fe (R ² = 0.893–0.976, p > 0.01), but the negative correlation with the grain P, soil P, soil Fe, and soil Zn (R ² = 0.633–0.841, p > 0.01). About 3.904–6.063 kg/ha of As was added on the surface soil by the contaminated groundwater and most of the added As was accumulated and remained on the top soil (0–30 cm).