Greenhouse gas emissions from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta

Abstract

The Mekong Delta produces 21 Mt of rough rice (Oryza sativa L.) and an estimated 24 Mt of straw (dry weight) annually. Approximately one fourth of the straw is burned on the field, which is a common practice in intensive rice cultivation systems in this region because there is limited time to prepare the field for the next crop. The spread of intensive rice production in the Delta may increase the total biomass of burning crop residues, significantly impacting greenhouse gas (GHG) emissions in Vietnam. In this study, GHG emissions from the major uses of straw (burning and mushroom beds) were monitored in a triple rice cropping system located in the central Mekong Delta. Between September 2011 and November 2012, both wind tunnel and closed chamber methods were used to measure the emissions of major GHGs from straw-burning and straw-mushroom cultivation systems, respectively. The global warming potential (GWP) was then determined. Methane (CH 4 ) and non-methane volatile organic carbon emissions (NMVOC) increased with lower modified combustion efficiency [MCE: emissions ratio of Carbon composing carbon dioxide (CO 2 -C) and carbon monooxide (CO-C) (CO 2 -C/(CO-C + CO 2 -C))]. Furthermore, higher moisture straw stacks generated lower nitrous oxide (N 2 O) emissions. Small straw stacks (5 or 10 kg dry straw) with higher moisture content emitted more carbon monoxide (CO), CH 4 and NMVOC. These results suggest that factors that increase the straw moisture content, such as rainfall, can cause smoldering combustion in small straw stacks or when straw is scattered on the ground, thereby inhibiting N 2 O emissions but enhancing CO, CH 4 and NMVOC. The measured N 2 O emissions contributed negligible amounts to the GWP compared with measured CO and CH 4 , which are relatively intense GHG emissions; this was likely a result of the slow and inefficient burning that was observed from the smaller straw stacks with higher moisture content. In this study, rice straw burning threatened to generate more GHGs than straw-mushroom (Volvariella volvacea (Bul. ex Fr.) Singer) cultivation under the studied agroecosystems.

Enhancing Carbon Sequestration Using Organic Amendments and Agricultural Practices

“…of rice straw annually. The spread of these crop residues in this area can increase CS and SOM, significantly reducing GHG emissions [66]. Crop residue decomposition acceleration can enhance the SOM [67].…”

Methane emission from rice cultivation in different agro-ecological zones of the Mekong river delta: seasonal patterns and emission factors for baseline water management

“…There is only one published study available on methane emissions in the MRD, but that focuses on straw burning and mushroom production (Arai et al 2015), so the reported values cannot be taken as a reference for our study. Moreover, there are few studies from other deltas of Vietnam available such as the Red River Delta in North Vietnam (Pandey Nguyen et al 2014;Nguyen et al 2016;Vu et al 2015;Tariq et al 2017) and the Vu Gia/Thu Bon delta in Central Vietnam (Tirol-Padre et al 2017) which reported values ranging from 104 to 696 kg CH 4 ha −1 per season.…”

“…The deltaic rice production systems are characterized by very specific hydrological conditions as compared to other rice-growing environments (Wassmann et al 2009), so that the application of default emission factors may be erroneous. However, there are only few studies published on methane emissions of rice grown in such environments (Pandey Nguyen et al 2014;Arai et al 2015;Vu et al 2015;Nguyen et al 2016;Tariq et al 2017;Tirol-Padre et al 2017).…”

Impacts of alternate wetting and drying on greenhouse gas emission from paddy field in Central Vietnam

“…The alluvial soils of the MRD also have similar fertility characteristics of alluvial soil in the RRD; however, the texture is heavier (Le and Pham 2015). Although several field experiments for paddy CH 4 emission have been conducted in the RRD, Northern Vietnam (Vu et al 2015;Pandey et al 2014) and the MRD, Southern Vietnam (Arai et al 2015), the existing dataset is still scarce for Central Vietnam (e.g., Tirol-Padre et al 2017).…”