Effects of surface water aeration on methane emissions and rice productivity in a paddy soil during cultivation

Rice paddies are a major source of methane (CH 4 ) emissions, necessitating the development of novel mitigation strategies during cultivation.Surface water aeration (SWA) can increase oxygenation in flooded water, potentially reducing CH 4 emissions in paddy systems.However, its efficacy remains unclear.In this pot experiment, different levels of aeration -specifically, none (control, without air supply), low (air supply via a single line) and high (air supply via double lines) -were applied using an air supply device.These treatments were evaluated in the presence (OM) or absence (NOM) of rice straw as an organic amendment to investigate their effects on CH 4 emissions and rice productivity.Dissolved CH 4 and oxygen concentrations in surface water were periodically monitored to decipher the factors influencing CH 4 dynamics.Regardless of organic matter incorporation, SWA partially reduced CH 4 emissions, particularly during the initial period (ca. 3 -4 weeks), resulting in 22 -32% and 5 -7% reductions compared to the control under NOM and OM treatments, respectively.However, SWA did not significantly reduce cumulative CH 4 emissions over the entire cultivation period, likely due to enhanced organic matter decomposition stimulated by increased aeration.Interestingly, dissolved CH 4 concentrations were significantly reduced by aeration in both the OM and NOM treatments, which could be attributed to increased ebullition from the surface water.Furthermore, SWA deteriorated rice productivity.In conclusion, SWA showed negligible effects on overall CH 4 mitigation while reducing rice productivity.This study suggests that SWA is not a feasible strategy for CH 4 mitigation, highlighting the need for alternative approaches that can optimize oxygen levels within the soil profile without hindering plant growth.