Rice (Oryza sativa. L.), a major food crop widely grown in Myanmar, is the most prominent cause of greenhouse gas (GHG) emissions in agriculture. Moreover, as a result of modification in agricultural management practices (such as soil tillage), the soil organic matter is exposed to more oxidizing conditions, releasing CO2 into the environment, contributing to global warming. Therefore, we studied the effects of both conventional and conservation soil tillage management practices on CO2 fluxes on an experimental rice paddy field in Myanmar. Total CO2 emissions during the night from paddies farmed under conventional practices were significantly higher than those from paddies farmed under conservation practices; however, no net CO2 flux differences were found between practices. Total net CO2 fluxes ranged from −59 to 1614 mg CO2 m−2 h−1 in conventional practices and from −282 to 1082 mg CO2 m−2 h−1 in conservation practices, respectively. Significantly higher rice biomass and grain yields were observed in conventional practices when compared to those in conservation practices, causing a significant rise in both CO2 uptake and emissions during the day and night, respectively. In addition, the results of this study revealed that CO2 emissions in rice fields could be much higher than expected, requiring further study to elucidate key factors driving the dynamics of CO2 in rice paddy systems.

The application of nitrogen fertilizer and the water management practices are important to optimize potential yields in rice cultivation. Moreover, they may affect the emissions patterns of methane (CH4) and carbon dioxide (CO2) emission. Compared to methane, knowledge about the combined effects of different fertilizer rates together with different water management practices on CO2 fluxes are scarce. Therefore, this study aims to assess CO2 fluxes of a selected rice cultivar in response to different fertilizer applications and water management practices. The treatments included two different applications of inorganic fertilizer (recommended rate and farmer’s practice), organic manure application and water management practices; continuous flooding (CF) and alternate wetting and drying (AWD). Mean total CO2 flux in CF was -30.82 g CO2 m-2 d-1 during daytime and 29.64 g CO2 m-2 d-1 during nighttime. Surprisingly, the average net CO2 fluxes were negative under both CF (-49 mg CO2 m-2h-1) and AWD practices (-127 mg CO2 m-2h-1), indicating a net CO2 uptake by the rice plants. Inorganic fertilizer applications led to considerably higher net CO2 emissions compared to the control under both CF and AWD. Conversely, CO2 emission fluxes in the treatment with organic manure showed negative net CO2 fluxes under both water management practices and while revealing the same fresh biomass as observed in other treatments (inorganic fertilizer and control). Taken together, modifications of current cultivation systems toward using organic manure, that emit less CO2, could effectively mitigate CO2 impacts regardless of the selected water management practice.

Small waterbodies like floodplain ponds are considered to be an important component of the global carbon budget. Although they are found in large numbers worldwide and their numbers are increasing every year due to the creation of new ponds, we do not have sufficient data on direct estimates of emission fluxes from these waterbodies yet. Herein, we present results from a set of 24 ponds located in the Morava River floodplain, Czech Republic. The ponds varied in their origin (man-made vs. natural), size, depth, sediment organic matter content, and macrophyte growth. Water chemistry parameters, concentrations, and exchange of CO2 and CH4 with the atmosphere were directly measured during the day and night from spring to summer 2020. The ponds emitted more CO2 and CH4 during nighttime, and both CO2 and, in particular, CH4 emissions tend to increase with the duration of pond inundation. Total diffusive fluxes of CO2 and CH4 into the atmosphere ranged from −37072.9 to 432683.3 μmol m−2 d−1, and −11485.3 to 95,889.6 μmol m−2 day−1, respectively. Generally, all ponds were found to be a net source of CO2 and CH4 to the atmosphere. In average, ponds emitted 7.64 g CO2-equivalent m−2 d−1. Thus, our results indicate that floodplain ponds are an important source of both CO2 and CH4 to the atmosphere and they should not be omitted in a regional carbon budget.