Multi-criteria assessment to screen climate smart rice establishment techniques in coastal rice production system of India

Introduction

Conventional rice production techniques are less economical and more vulnerable to sustainable utilization of farm resources as well as significantly contributed GHGs to atmosphere.

Methods

In order to assess the best rice production system for coastal areas, six rice production techniques were evaluated, including SRI-AWD (system of rice intensification with alternate wetting and drying (AWD)), DSR-CF (direct seeded rice with continuous flooding (CF)), DSR-AWD (direct seeded rice with AWD), TPR-CF (transplanted rice with CF), TPR-AWD (transplanted rice with AWD), and FPR-CF (farmer practice with CF). The performance of these technologies was assessed using indicators such as rice productivity, energy balance, GWP (global warming potential), soil health indicators, and profitability. Finally, using these indicators, a climate smartness index (CSI) was calculated.

Results and discussion

Rice grown with SRI-AWD method had 54.8 % higher CSI over FPR-CF, and also give 24.5 to 28.3% higher CSI for DSR and TPR as well. There evaluations based on the climate smartness index can provide cleaner and more sustainable rice production and can be used as guiding principle for policy makers.

Mitigating greenhouse gas emissions from irrigated rice cultivation through improved fertilizer and water management

Greenhouse gas (GHG) emissions from agriculture sector play an important role for global warming and climate change. Thus, it is necessary to find out GHG emissions mitigation strategies from rice cultivation. The efficient management of nitrogen fertilizer using urea deep placement (UDP) and the use of the water-saving alternate wetting and drying (AWD) irrigation could mitigate greenhouse gas (GHG) emissions and reduce environmental pollution. However, there is a dearth of studies on the impacts of UDP and the integrated plant nutrient system (IPNS) which combines poultry manure and prilled urea (PU) with different irrigation regimes on GHG emissions, nitrogen use efficiency (NUE) and rice yields. We conducted field experiments during the dry seasons of 2018, 2019, and 2020 to compare the effects of four fertilizer treatments including control (no N), PU, UDP, and IPNS in combination with two irrigation systems- (AWD and continuous flooding, CF) on GHG emissions, NUE and rice yield. Fertilizer treatments had significant (p < 0.05) interaction effects with irrigation regimes on methane (CH₄) and nitrous oxide (N₂O) emissions. PU reduced CH₄ and N₂O emissions by 6% and 20% compared to IPNS treatment, respectively under AWD irrigation, but produced similar emissions under CF irrigation. Similarly, UDP reduced cumulative CH₄ emissions by 9% and 15% under AWD irrigation, and 9% and 11% under CF condition compared to PU and IPNS treatments, respectively. Across the year and fertilizer treatments, AWD irrigation significantly (p < 0.05) reduced cumulative CH₄ emissions and GHG intensity by 28%, and 26%, respectively without significant yield loss compared to CF condition. Although AWD irrigation increased cumulative N₂O emissions by 73%, it reduced the total global warming potential by 27% compared to CF irrigation. The CH₄ emission factor for AWD was lower (1.67 kg ha^-1 day^-1) compared to CF (2.33 kg ha^-1 day^-1). Across the irrigation regimes, UDP increased rice yield by 21% and N recovery efficiency by 58% compared to PU. These results suggest that both UDP and AWD irrigation might be considered as a carbon-friendly technology.

Farmers’ Participatory Alternate Wetting and Drying Irrigation Method Reduces Greenhouse Gas Emission and Improves Water Productivity and Paddy Yield in Bangladesh

In dry season paddy farming, the alternate wetting and drying (AWD) irrigation has the potential to improve water productivity and paddy production and decrease greenhouse gas (GHG), such as methane (CH4) and nitrous oxide (N2O), emissions when compared to continuous flooding (CF). Participatory on-farm trials were conducted from November 2017 to April 2018 in the Feni and Chattogram districts of Bangladesh. Total 62 farmers at Feni and 43 at Chattogram district, each location has 10 hectares of land involved in this study. We compared irrigation water and cost reductions, paddy yield, and CH4 and N2O emissions from paddy fields irrigated under AWD and CF irrigation methods. The mean results of randomly selected 30 farmers from each location showed that relative to the CF irrigation method, the AWD method reduced seasonal CH4 emissions by 47% per hectare and CH4 emission factor by 88% per hectare per day. Moreover, the AWD decreased the overall global warming potential and the intensity of GHG by 41%. At the same time, no noticeable difference in N2O emission between the two methods was observed. On the other hand, AWD method increased paddy productivity by 3% while reducing irrigation water consumption by 27% and associated costs by 24%. Ultimately it improved water productivity by 32% over the CF method.

Novel QTL Associated with Shoot Branching Identified in Doubled Haploid Rice (Oryza sativa L.) under Low Nitrogen Cultivation

Shoot branching is considered as an important trait for the architecture of plants and contributes to their growth and productivity. In cereal crops, such as rice, shoot branching is controlled by many factors, including phytohormones signaling networks, operating either in synergy or antagonizing each other. In rice, shoot branching indicates the ability to produce more tillers that are essential for achieving high productivity and yield potential. In the present study, we evaluated the growth and development, and yield components of a doubled haploid population derived from a cross between 93-11 (P1, indica) and Milyang352 (P2, japonica), grown under normal nitrogen and low nitrogen cultivation open field conditions. The results of the phenotypic evaluation indicated that parental lines 93-11 (P1, a high tillering indica cultivar) and Milyang352 (P2, a low tillering japonica cultivar) showed distinctive phenotypic responses, also reflected in their derived population. In addition, the linkage mapping and quantitative trait locus (QTL) analysis detected three QTLs associated with tiller number on chromosome 2 (qTNN2-1, 130 cM, logarithm of the odds (LOD) 4.14, PVE 14.5%; and qTNL2-1, 134 cM, LOD: 6.05, PVE: 20.5%) and chromosome 4 (qTN4-1, 134 cM, LOD 3.92, PVE 14.5%), with qTNL2-1 having the highest phenotypic variation explained, and the only QTL associated with tiller number under low nitrogen cultivation conditions, using Kompetitive Allele-Specific PCR (KASP) and Fluidigm markers. The additive effect (1.81) of qTNL2-1 indicates that the allele from 93-11 (P1) contributed to the observed phenotypic variation for tiller number under low nitrogen cultivation. The breakthrough is that the majority of the candidate genes harbored by the QTLs qTNL2-1 and qTNN4-1 (here associated with the control of shoot branching under low and normal nitrogen cultivation, respectively), were also proposed to be involved in plant stress signaling or response mechanisms, with regard to their annotations and previous reports. Therefore, put together, these results would suggest that a possible crosstalk exists between the control of plant growth and development and the stress response in rice.

Effects of water management on greenhouse gas emissions from farmers' rice fields in Bangladesh

Alternate wetting and drying (AWD) irrigation in lowland rice cultivation increases water use efficiency and could reduce greenhouse gas (GHG) emissions compared to the farmers' practice of continuous flooding (CF). However, there is a dearth of studies on the impacts of water management on methane (CH₄) and nitrous oxide (N₂O) emissions in Bangladesh. Multi-location field experiments were conducted during the dry seasons of 2018 and 2019 to determine the baseline emissions of CH₄ and N₂O from rice fields and compare the emissions from AWD irrigation and CF. CH₄ and N₂O emissions were measured using the closed chamber technique and their concentrations were determined using a gas chromatograph. CH₄ and N₂O emissions varied across water management schemes and sites. AWD irrigation significantly (p < 0.05) reduced cumulative CH₄ emissions (37%, average across sites) without affecting grain yields compared to CF. The CH₄ emission factor for AWD was lower (1.39 kg ha^-1 day^-1) compared to CF (2.21 kg ha^-1 day^-1). Although AWD irrigation increased seasonal cumulative N₂O emissions by 46%, it did not offset reduced CH₄ emissions. AWD reduced the total global warming potential (GWP) by 36% compared to CF. Similarly, GHG intensity (GHGI) in AWD was 34% smaller compared to that in CF. Emissions varied across sites and the magnitudes of seasonal cumulative CH₄ and N₂O emissions were higher at the Gazipur site compared to the Mymensingh site. AWD, which saves irrigation water without any yield penalty, could be considered a promising strategy to mitigate GHG emissions from rice fields in Bangladesh.

Effects of straw and plastic film mulching on greenhouse gas emissions in Loess Plateau, China: A field study of 2 consecutive wheat-maize rotation cycles

Mulching practices have long been used to modify the soil temperature and moisture conditions and thus potentially improve crop production in dryland agriculture, but few studies have focused on mulching effects on soil gaseous emissions. We monitored annual greenhouse gas (GHG) emissions under the regime of straw and plastic film mulching using a closed chamber method on a typical winter-wheat (Triticum aestivum L. cv Xiaoyan 22) and summer-maize (Zea mays L. cv Qinlong 11) rotation field over two-year period in the Loess Plateau, northwestern China. The following four field treatments were included: T1 (control, no mulching), T2 (4000kgha^-1 wheat straw mulching, covering 100% of soil surface), T3 (half plastic film mulching, covering 50% of soil surface), and T4 (complete plastic film mulching, covering 100% of soil surface). Compared with the control, straw mulching decreased soil temperature and increased soil moisture, whereas plastic film mulching increased both soil temperature and moisture. Accordingly, straw mulching increased annual crop yields over both cycles, while plastic film mulching significantly enhanced annual crop yield over cycle 2. Compared to the no-mulching treatment, all mulching treatments increased soil CO₂ emission over both cycles, and straw mulching increased soil CH₄ absorption over both cycles, but patterns of soil N₂O emissions under straw or film mulching are not consistent. Overall, compared to T1, annual GHG intensity was significantly decreased by 106%, 24% and 26% under T2, T3 and T4 over cycle 1, respectively; and by 20%, 51% and 29% under T2, T3 and T4 over cycle 2, respectively. Considering the additional cost and environmental issues associated with plastic film mulching, the application of straw mulching might achieve a balance between food security and GHG emissions in the Chinese Loess Plateau. However, further research is required to investigate the perennial influence of different mulching applications.

Inhibition of methane production in microbial fuel cells: operating strategies which select electrogens over methanogens

Methanogenesis may diminish coulombic efficiency of microbial fuel cells (MFCs), although its importance is application dependent; e.g., suppression of methanogenesis may improve MFC sensing accuracy, but may be tolerable in COD removal from wastewaters. Suppression of methanogenesis was investigated in three H-type MFCs, enriched and acclimated with acetate, propionate and butyrate substrates and subsequently operated under open and closed circuit (OC/CC) regimes. Altering the polarisation state of the electrode displaces microorganisms from the anodic biofilm and leads to observable methane inhibition. The planktonic archeal community was compared to the electrode biofilm whilst under the OC/CC regimes. Semi-quantitative DNA analyses indicate a shift in some dominant species, from the electrode to the solution, during OC operation. The effect of prolonged starvation on anodic species was also studied. The results indicate progressive inhibition of methanogenesis from OC/CC operations; and virtual cessation of methanogenesis when an MFC was starved for a significant period.

Peatland geoengineering: an alternative approach to terrestrial carbon sequestration

Terrestrial and oceanic ecosystems contribute almost equally to the sequestration of ca 50 per cent of anthropogenic CO(2) emissions, and already play a role in minimizing our impact on Earth's climate. On land, the majority of the sequestered carbon enters soil carbon stores. Almost one-third of that soil carbon can be found in peatlands, an area covering just 2-3% of the Earth's landmass. Peatlands are thus well established as powerful agents of carbon capture and storage; the preservation of archaeological artefacts, such as ancient bog bodies, further attest to their exceptional preservative properties. Peatlands have higher carbon storage densities per unit ecosystem area than either the oceans or dry terrestrial systems. However, despite attempts over a number of years at enhancing carbon capture in the oceans or in land-based afforestation schemes, no attempt has yet been made to optimize peatland carbon storage capacity or even to harness peatlands to store externally captured carbon. Recent studies suggest that peatland carbon sequestration is due to the inhibitory effects of phenolic compounds that create an 'enzymic latch' on decomposition. Here, we propose to harness that mechanism in a series of peatland geoengineering strategies whereby molecular, biogeochemical, agronomical and afforestation approaches increase carbon capture and long-term sequestration in peat-forming terrestrial ecosystems.