Cadmium and arsenic accumulation potential of ratoon rice under different water managements

Cadmium (Cd) and arsenic (As) contamination in farmland soils poses a persistent global environmental threat and risks to public health. In rice systems, the synergistic accumulation of Cd and As further complicates pollution control. Ratoon rice, with high biomass and low cost, is a promising material for in-situ remediation of Cd- and As-contaminated soils. A field experiment was conducted using four water regimes, including cyclic intermittent irrigation (CI), moist irrigation (Moist), moist irrigation in main crop with flooding in ratoon crop (MMFR), and flooding irrigation (Flooding) to enhance Cd and As accumulation in ratoon rice (Hybrid rice, Jingliangyouhuazhan). Findings demonstrated that CI achieved the highest Cd accumulation (total 6.46 mg·m⁻²), with main and ratoon crops contributing 2584.35 and 3.887 mg·m⁻² respectively. In the main crop, roots and aboveground parts accumulated 1164.08 and 1.42 mg·m⁻², with average daily accumulation rates of 0.019 and 0.025 mg·day⁻¹ ·m⁻², peaking at main crop maturation. Floodeding irrigation produced the maximum As accumulation (total 153.57 mg·m⁻²), with roots accounting for 86.45% of total accumulation. Although As accumulation decreased during ratoon crop maturation under flooded conditions, it remained the highest among all treatments (roots: 103.20 mg·m⁻²; stems: 6.48 mg·m⁻²; leaves: 3.61 mg·m⁻²). Ratoon rice is a promising phytoremediation material for Cd- and As-contaminated soils. Jingliangyouhuazhan achieved high Cd extraction efficiency with the CI irrigation regime, especially when the ratoon crop growing season was extended. For As-contaminated soils, continuous flooding and prolonged main crop duration are recommended. This study provides an eco-friendly, low-cost and sustainable strategy for remediating co-contaminated paddy soils.