Alternate wetting and drying in Vietnam affects methane production, nitrogen transformation, and soil elemental dynamics across three consecutive rice cropping seasons.

Alternate wetting and drying (AWD) is increasingly promoted as a sustainable water management practice in rice cultivation; however, its effects on soil biogeochemistry and elemental dynamics remain unclear. This study compared soil chemical properties, methane (CH4) production, nitrogen (N) mineralization, and elemental composition of a three-crop season paddy field between AWD and continuous flooding (CF). AWD significantly increased the soil pH (6.22 vs. 5.68) while decreasing total nitrogen (1.08 vs. 1.32 g kg⁻1) compared with CF. Methane production from 7 weeks of anaerobic incubation under AWD was substantially lower than with CF, particularly after 7 weeks (36.2 vs. 96.5 mg C kg⁻1 soil); NH₄⁺-N accumulation was also lower under AWD (38.3 vs. 62.5 mg N kg⁻1 soil). Among elements, Fe and Mn concentrations were markedly higher under AWD, whereas most macroelements and potentially toxic elements did not differ remarkably. Further, principal component analysis revealed distinct shifts in soil biogeochemical characteristics under AWD management. In conclusion, AWD effectively reduced methane production and altered nitrogen and redox-sensitive elemental dynamics without substantially enhancing the accumulation of potentially toxic elements, supporting its applicability as an environmentally sustainable rice cultivation practice.