Optimizing biochar, vermicompost, and duckweed amendments to mitigate arsenic uptake and accumulation in rice (Oryza sativa L.) cultivated on arsenic-contaminated soil.

The accumulation of arsenic (As) in rice (Oryza sativa L.) grain poses a significant health concern in Bangladesh. To address this, we investigated the efficacy of various organic amendments and phytoremediation techniques in reducing As buildup in O. sativa. We evaluated the impact of five doses of biochar (BC; BC_0.1: 0.1%, BC_0.28: 0.28%, BC_0.55: 0.55%, BC_0.82: 0.82% and BC_1.0: 1.0%, w/w), vermicompost (VC; VC_1.0: 1.0%, VC_1.8: 1.8%, VC_3.0: 3.0%, VC_4.2: 4.2% and VC_5.0: 5.0%, w/w), and floating duckweed (DW; DW₁₀₀: 100, DW₁₆₀: 160, DW₂₅₀: 250, DW₃₄₀: 340 and DW₄₀₀: 400 g m^{− 2}) on O. sativa cultivated in As-contaminated soil. Employing a three-factor five-level central composite design and response surface methodology (RSM), we optimized the application rates of BC-VC-DW. Our findings revealed that As contamination in the soil negatively impacted O. sativa growth. However, the addition of BC, VC, and DW significantly enhanced plant morphological parameters, SPAD value, and grain yield per pot. Notably, a combination of moderate BC-DW and high VC (BC_0.55VC₅DW₂₅₀) increased grain yield by 44.4% compared to the control (BC₀VC₀DW₀). As contamination increased root, straw, and grain As levels, and oxidative stress in O. sativa leaves. However, treatment BC_0.82VC_4.2DW₃₄₀ significantly reduced grain As (G-As) by 56%, leaf hydrogen peroxide by 71%, and malondialdehyde by 50% compared to the control. Lower doses of BC-VC-DW (BC_0.28VC_1.8DW₁₆₀) increased antioxidant enzyme activities, while moderate to high doses resulted in a decline in these activities. Bioconcentration and translocation factors below 1 indicated limited As uptake and translocation in plant tissues. Through RSM optimization, we determined that optimal doses of BC (0.76%), VC (4.62%), and DW (290.0 g m^{− 2}) could maximize grain yield (32.96 g pot^{− 1}, 44% higher than control) and minimize G-As content (0.189 mg kg^{− 1}, 54% lower than control). These findings underscore effective strategies for enhancing yield and reducing As accumulation in grains from contaminated areas, thereby ensuring agricultural productivity, human health, and long-term sustainability. Overall, our study contributes to safer food production and improved public health in As-affected regions. [ABSTRACT FROM AUTHOR]