Comparison of Carbon Dioxide (CO2) Fluxes between Conventional and Conserved Irrigated Rice Paddy Fields in Myanmar

Abstract

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.

Effects of Different Water Management and Fertilizer Applications on CO2 Fluxes from a Selected Myanmar Rice (Oryza sativa L.) Cultivar

“…Surprisingly, net CO 2 fluxes were negative under both CF and AWD water management practices, indicating that CO 2 uptake by the rice plants was prevalent during the entire growing period. These results are seemingly in contrast to our previous fields measurements [49] and might be attributed to the different environmental conditions (field versus greenhouse) in the two studies. Number of tiller per plant was 36.5% higher in AWD than CF conditions.…”

“…The increased biomass production is directly linked to the improvement of potential rice yield [67]. Moreover, plants grown under controlled environmental conditions have a tendency to differ in the morphological characters and biomass yields compared with those grown under natural conditions [49,68,69]. In accordance with Thakur et al [70], continuous flooding supported significantly higher root volume (cm 3 ), although, there was found no significant difference among fertilizer treatments.…”

“…6). Generally, mean uptake of net CO 2 flux from AWD (-68 mg CO 2 m -2 h -1 ) treatment was higher than the CF (- 49 ) ( Table 1).…”

“…Declining CO 2 concentrations, hence negative CO 2 fluxes, are most likely caused by photosynthesis-driven carbon-assimilation by the rice plant and algae in overlying water or at the soil surface. During the night, increase in CO 2 concentration and positive fluxes might indicate prevalent respiration of the rice plant together with soil and water biota [49]. Lower CO 2 uptakes with lower photosynthetic activities can be attributed to relatively higher net CO 2 fluxes during an early period of plants (Fig.…”

Water regime and fertilizer‐phosphorus source effects on greenhouse gas emissions from rice

“…However, as hypothesized, every fertilizer‐P source under furrow‐irrigated conditions had earlier peak CO 2 fluxes than under flooded‐soil conditions (Figure 3). Fertilizer‐N application generally increases crop biomass, which subsequentially can enhance CO 2 production and emissions (Min & Rulik, 2020a, 2020b).…”