Plant traits influencing greenhouse gas emission potential and assessment of technical options for emission screening with large number of rice varieties

Methane (CH4) is a major greenhouse gas (GHG), which accounts for 16% of the global GHG effect. In the agriculture sector, rice cultivation substantially contributes 10% of all anthropogenic CH4 emissions, thus the importance of determining the variables that influence and/or control CH4 production in rice fields. Over the last decades, various studies reported differences in the emission potential of CH4 of different rice cultivars. However, physiological plant traits responsible for such differences are still unknown. A literature review was therefore conducted to collect relevant studies, which examined the differences in CH4 emission potential of different rice cultivars. While GHG emission studies from rice are typically done through ‘closed chamber’ measurements, the assessment and sampling of CH4 emissions from large numbers of rice cultivars (>100) pose a challenge in terms of management of sampling and experimental design. Therefore, this study has developed recommendations for screening a large number of rice varieties to identify cultivars with low CH4 emission potential. A new concept and two practical approaches are presented

How does burning of rice straw affect CH4 and N2O emissions? A comparative experiment of different on-field straw management practices

Open-burning of rice straw residues pollutes the air and contributes to global warming through emissions of greenhouse gases (GHGs). Although burning of straw residues emits large amounts of CO2, this component of the smoke is not considered as net GHG emissions and only concludes the annual carbon cycle that has started with photosynthesis. Hence, we focused on emissions of CH4 and N2O from open-field burning against a baseline of straw incorporation. The experimental approach combined a newly designed combustion chamber for the collection of smoke followed by chemical analysis (Exp. A) as well as field observations of soil-borne emissions for different straw treatments (Exp. B). At constant straw moisture of 10%, the mass-scaled Emission Factors (EFm) were 4.51 g CH4 and 0.069 g N2O per kg dry weight (kg−1dw) of straw. In Exp. B, we conducted field trials over two seasons with the following straw management practices: SRt − straw retained including stubbles and incorporated, PSRm − partial straw removal only stubbles incorporated, CSRm − complete straw removal including removal of stubbles, and SB − straw burned followed by incorporation of ash and unburned residues. Soil-borne emissions were recorded with a closed chamber approach whereas straw burning was computed indirectly using the EF from Exp. A. As metrics for comparison, we have used the GWP contributions of CH4 and N2O for the different straw management practices over two cropping seasons in the field. On an annual basis, SRt had the highest total GWP (8023 kg CO2eq ha−1). SB entailed a GWP of 4913 kg CO2eq ha−1 that was almost identical to the GWP of PSRm (4531 kg CO2eq ha−1). CSRm had the lowest GWP (3470 kg CO2eq ha−1) that was significantly lower than that of SRt. However, full GHG accounting of straw removed from the field will depend on the ensuing utilization of straw and the off-field emissions involved − which was outside of the boundaries of this study. The quantification of open field burning in this study can be instrumental for diverse purposes by providing data of an important component in emission inventories and carbon footprint analysis of rice

An assessment of irrigated rice production energy efficiency and environmental footprint with in-field and off-field rice straw management practices

The research provided scientific evidences for improved rice straw management. Rice cultivation with in-field burning of rice straw is the worst option with the lowest energy efficiency and highest air pollution emission. This article comprises a comparative assessment of energy efficiency and the environmental footprint of rice production using four different rice straw management scenarios, namely, straw retained, straw burned, partial straw removal, and complete straw removal. Paddy yield, grain quality, and energy balance were assessed for two seasons while greenhouse gas emissions (GHGE) were measured weekly starting from land preparation through to the cropping and fallow period. Despite the added energy requirements in straw collection and transport, the use of collected rice straw for mushroom production can increase the net energy obtained from rice production systems by 10–15% compared to burning straw in the field. Partial and complete removal of rice straw reduces GHGE by 30% and 40% compared to complete straw retention, respectively