Relationship between soil solution electrochemical changes and methane and nitrous oxide emissions in different rice irrigation management systems.

ABSTRACT

Rice (Oryza sativa L.) intermittent irrigation is a potential strategy to mitigate methane (CH4) and nitrous oxide (N2O) emissions, but the effects of dry-wetting intervals on soil electrochemical changes and plant characteristics should be considered. This study was conducted in a greenhouse evaluating CH4 and N2O fluxes in rice under five different irrigation management practices (continuous irrigation (CI), intermittent irrigation with flooding resumption in saturated soil condition (SSI) and soil moisture at field capacity (FCI), saturated soil and irrigation resumption with soil moisture bellow field capacity (FCS), and soil at field capacity (FCD)) and its relation to plant development and global warming potential (GWP). Soil electrochemical conditions and CH4 and N2O emissions were expressively affected by irrigation management. The CI system presented the greatest CH4 flux (20.14 g m-2) and GWP (462.7 g m-2 eq. CO2), whereas intermittent irrigation expressively reduced CH4 emissions. Overall, the N2O flux was low (bellow 20 µg m-2 h-1) even with N application, with greater emissions occurring at the FCD treatment at the beginning of the rice season. Soil moisture at field capacity had no CH4 flux but presented greater GWP (271 g m-2 eq. CO2) than intermittent irrigation systems due to N2O flux while compromising rice plant development. The best soil moisture condition to initiate a flooding cycle during intermittent irrigation is at saturated soil conditions.