Greenhouse gas mitigation in agriculture

Vertical distribution of Candidatus Methylomirabilis and Methanoperedens in agricultural soils

Candidatus Methylomirabilis-related bacteria conduct anaerobic oxidation of methane (AOM) coupling with NO2- reduction, and Candidatus Methanoperedens-related archaea perform AOM coupling with reduction of diverse electron acceptors, including NO3-, Fe (III), Mn (IV) and SO42-. Application of nitrogen fertilization favors the growth of these methanotrophs in agricultural fields. Here, we explored the vertical variations in community structure and abundance of the two groups of methanotrophs in a nitrogen-rich vegetable field via using illumina MiSeq sequencing and quantitative PCR. The retrieved Methylomirabilis-related sequences had 91.12%-97.32% identity to the genomes of known Methylomirabilis species, and Methanoperedens-related sequences showed 85.49%-97.48% identity to the genomes of known Methanoperedens species which are capable of conducting AOM coupling with reduction of NO3- or Fe (III). The Methanoperedens-related archaeal diversity was significantly higher than Methylomirabilis-related bacteria, with totally 74 and 16 operational taxonomic units, respectively. In contrast, no significant difference in abundance between the bacteria (9.19 × 103-3.83 × 105 copies g-1 dry soil) and the archaea (1.55 × 104-3.24 × 105 copies g-1 dry soil) was observed. Furthermore, the abundance of both groups of methanotrophs exhibited a strong vertical variation, which peaked at 30-40 and 20-30 cm layers, respectively. Soil water content and pH were the key factors influencing Methylomirabilis-related bacterial diversity and abundance, respectively. For the Methanoperedens-related archaea, both soil pH and ammonium content contributed significantly to the changes of these archaeal diversity and abundance. Overall, we provide the first insights into the vertical distribution and regulation of Methylomirabilis-related bacteria and Methanoperedens-related archaea in vegetable soils. KEY POINTS: • The archaeal diversity was significantly higher than bacterial. • There was no significant difference in the abundance between bacteria and archaea. • The abundance of bacteria and archaea peaked at 30-40 and 20-30 cm, respectively.

Insights into CO2 and N2O emissions driven by applying biochar and nitrogen fertilizers in upland soil

Biochar and soil carbon sequestration hold promise in mitigating global warming by storing carbon in the soil. However, the interaction between biochar properties, soil carbon-nitrogen cycling, and nitrogen fertilizer application's impact on soil carbon-nitrogen balance remained unclear. Herein, we conducted batch experiments to study the effects and mechanisms of rice straw biochar application (produced at 300, 500, and 700 °C) on net greenhouse gas emissions (CO2, N2O, CH4) in upland soils under different forms of nitrogen fertilizers. The findings revealed that (NH4)2SO4 and urea significantly elevated soil carbon dioxide equivalent emissions, ranging from 28 to 61.7 kg CO2e/ha and 8.2 to 37.7 kg CO2e/ha, respectively. Conversely, KNO3 reduced soil CO2e emissions, ranging from 2.2 to 13.6 kg CO2e/ha. However, none of these three nitrogen forms exhibited a significant effect on CH4 emissions. The pyrolysis temperature of biochar was found negatively correlated with soil CO2 and N2O emissions. The alkaline substances presented in biochar pyrolyzed at 500-700 °C raised soil pH, increased the ratio of Gram-negative to Gram-positive bacteria, and enhanced the relative abundance of Sphingomonadaceae. Moreover, the co-application of KNO3 based nitrogen fertilizer and biochar increased the total carbon/inorganic nitrogen ratio and reduces the relative abundance of Nitrospirae. This series of reactions led to a significant increase in soil DOC content, meanwhile reduced soil CO2 emissions, and inhibited the nitrification process and decreased the emission of soil N2O. This study provided a scientific basis for the rational application of biochar in soil.

Emerging bio-capture strategies for greenhouse gas reduction: Navigating challenges towards carbon neutrality

Greenhouse gas emissions are significantly contributing to climate change, posing one of the serious threats to our planet. Addressing these emissions urgently is imperative to prevent irreversible planetary changes. One effective long-term mitigation strategy is achieving carbon neutrality. Although numerous countries aim for carbon neutrality by 2050, only a few are on track to realize this ambition. Existing technological solutions, including chemical absorption, cryogenic separation, and membrane separation, are available but tend to be costly and time intensive. Bio-capture methods present a promising opportunity in greenhouse gas mitigation research. Recent developments in biotechnology for capturing greenhouse gases have demonstrated both effectiveness and long-term benefits. This review emphasizes the recent advancements in bio-capture techniques, showcasing them as dependable and economical solutions for carbon neutrality. The article briefly outlines various bio-capture methods and underscores their potential for industrial application. Moreover, it investigates into the challenges faced when integrating bio-capture with carbon capture and storage technology. The study concludes by exploring the recent trends and prospective enhancements in ecosystem revitalization and industrial decarbonization through green conversion techniques, reinforcing the path towards carbon neutrality.

Global systematical and comprehensive overview of mountainous flood risk under climate change and human activities

Snow-covered mountainous regions are crucial for the hydrologic cycle. Any changes in the cryosphere are critical and directly impact the hydrologic cycle and socio-environment of the downstream. It is likely to occur more extreme events of precipitations, raising the risk of flooding worldwide. Glacier melting is increasing, thus the formation of the moraine-dammed lake called glacial lake, whose outburst may be a catastrophic disaster. Due to steep topography, flash floods with high energy can sweep away infrastructure, electric power stations, property, and livelihood and even change the channel morphology, hence the whole environment. In this article, we present the causes of flooding in mountainous regions and historical trends of mountainous flooding and its management policies. Carbon emission is a driver to increase the temperature of the globe and which is triggering the flash floods in mountainous regions is illustrated using data from different sources. The discussion section includes how technology helps to achieve a climate-resilient environment. Understanding river morphology, mapping and monitoring risks, and simulating essential natural processes are necessary for reducing the cascading hazards in the mountains. There is still a gap in modern data collection techniques in mountainous regions. More advanced technology for regional and global collaborations, climate change adaption, and public awareness can build the climate resilience cryosphere.

Synergistic advantages of volcanic ash weathering in saline soils: CO2 sequestration and enhancement of plant growth

Carbon dioxide (CO2) is a primary greenhouse gas that has experienced a surge in atmospheric concentration due to human activities and lifestyles. It is imperative to curtail atmospheric CO2 levels promptly to alleviate the multifaceted impacts of climate warming. The soil serves as a natural reservoir for CO2 sequestration. The scientific premise of this study is that CO2 sequestration in agriculturally relevant, organically-deficient saline soil can be achieved by incorporating alkaline earth silicates. Volcanic ash (VA) was used as a soil amendment for CO2 removal from saline soil by leveraging enhanced silicate rock weathering (ERW). The study pursued two primary objectives: first, we aimed to evaluate the impact of various doses of VA, employed as an amendment for organically-deficient soil, on the growth performance of key cultivated crops (sorghum and mung bean) in inland saline-alkaline agricultural regions of northeastern China. Second, we aimed to assess alterations in the physical properties of the amended soil through mineralogical examinations, utilizing X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) analyses, quantifying the increase in inorganic carbon content within the soil. In the potting tests, mung bean plant height exhibited a noteworthy increase of approximately 41 % with the addition of 10 % VA. Sorghum plant height and aboveground and belowground biomass dry weights increased with VA application across all tested doses. At the optimal VA application rate (20 %), the sorghum achieved a CO2 sequestration rate of 0.14 kg CO2·m-2·month-1. XRD and SEM-EDS analyses confirmed that the augmented inorganic carbon in the VA-amended soils stemmed primarily from calcite accumulation. These findings contribute to elucidating the mechanism underlying VA as an amendment for organically-deficient soils and provide an effective approach for enhancing the carbon sink capacity of saline soils.

Enhancing the Performance of Hemihydrate Phosphogypsum by the Collaborative Effects of Calcium Hydroxide and Carbonation

Normally, the acidic impurities in hemihydrate phosphogypsum (HPG) must be neutralized when HPG is utilized, and a little amount of calcium hydroxide (CH) is the best choice. In this paper, the effects of excessive CH (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.% of HPG) for carbonation curing on the performance of hardened HPG paste were studied. According to the results of macro tests and microanalyses of XRD, TG, SEM-EDS, MIP and N2 physisorption, it could be verified that CaF2, Ca3(PO4)2 and a large amount of nanoscale CaCO3 crystals were produced as a result of neutralization and carbonation, and the compressive strength and the water resistance of carbonated HPG + CH paste were significantly improved due to the effects of nanoscale CaCO3 crystals on pore refinement and the coverage on the surfaces of gypsum crystals of the hardened paste. Therefore, this study suggests a feasible and green method for recycling HPG/PG, with the collaborative effects of neutralization, performance enhancement and reductions in CO2 emissions.

Conservation Agriculture Impacts on Economic Profitability and Environmental Performance of Agroecosystems

The rationale of this study originates from the primary sector's multiple roles in the global warming issue. Agriculture is reported among the main causes of anthropogenic global warming. At the same time, it is profoundly impacted by climate change and concurrently holds potential as a solution through the sequestration of soil organic carbon (SOC) facilitated by Conservation Agriculture (CA). However, the findings in the literature are controversial on the SOC sequestration capacity and the profitability of CA implementation. Considering the new and old objectives of the sector, this paper tackles the assessment of the actual capabilities of CA to be a viable strategy to pursue the social good of climate change mitigation and concurrently be profitable for farmers. The economic profitability and environmental performance of CA are assessed analysing data from a field experiment in Northern Italy (European temperate area) and identifying the best management practice by means of a data envelopment analysis.

Earthworms and plants can decrease soil greenhouse gas emissions by modulating soil moisture fluctuations and soil macroporosity in a mesocosm experiment

Earthworms can stimulate microbial activity and hence greenhouse gas (GHG) emissions from soils. However, the extent of this effect in the presence of plants and soil moisture fluctuations, which are influenced by earthworm burrowing activity, remains uncertain. Here, we report the effects of earthworms (without, anecic, endogeic, both) and plants (with, without) on GHG (CO2, N2O) emissions in a 3-month greenhouse mesocosm experiment simulating a simplified agricultural context. The mesocosms allowed for water drainage at the bottom to account for the earthworm engineering effect on water flow during two drying-wetting cycles. N2O cumulative emissions were 34.6% and 44.8% lower when both earthworm species and only endogeic species were present, respectively, and 19.8% lower in the presence of plants. The presence of the endogeic species alone or in combination with the anecic species slightly reduced CO2 emissions by 5.9% and 11.4%, respectively, and the presence of plants increased emissions by 6%. Earthworms, plants and soil water content interactively affected weekly N2O emissions, an effect controlled by increased soil dryness due to drainage via earthworm burrows and mesocosm evapotranspiration. Soil macroporosity (measured by X-ray tomography) was affected by earthworm species-specific burrowing activity. Both GHG emissions decreased with topsoil macropore volume, presumably due to reduced moisture and microbial activity. N2O emissions decreased with macropore volume in the deepest layer, likely due to the presence of fewer anaerobic microsites. Our results indicate that, under experimental conditions allowing for plant and earthworm engineering effects on soil moisture, earthworms do not increase GHG emissions, and endogeic earthworms may even reduce N2O emissions.

Incentive mechanisms of carbon farming contracts: A systematic mapping study

Despite increasing interest, a lack of comprehensive knowledge regarding the efficient design and implementation of carbon farming schemes remains. These schemes must efficiently achieve higher carbon sequestration, incentivize farmers, and increase farmers' participation in global carbon markets. Our study systematically reviews, describes, and maps available evidence related to carbon farming contracts to assess different incentive mechanisms for carbon farming. We conduct a systematic mapping review of articles extracted from various databases employing the Collaboration for Environmental Evidence method. We shortlist 52 articles and analyze about 40 global case studies, identifying three main incentive mechanisms of carbon farming contracts, namely, result-based, action-based, and hybrid payments. We examine how these incentive mechanisms are designed, in addition to associated payment types, monitoring approaches, and barriers to implementation. Result-based payments include stringent monitoring and can be implemented through auctions, carbon credits, product labels or certificates. Action-based payments are found to be simpler, with lower monitoring requirements for farmers and can be paid upfront or after contract implementation. Hybrid payments combine both techniques, offering low-risk and guaranteed payments for farmers and definite environmental mitigation impacts. Result-based and hybrid payments motivate farmers to innovate to meet environmental objectives while also connecting them to carbon markets. The major challenges to developing a successful carbon farming project include lack of permanence, non-additionality, and the absence of stringent monitoring, reporting, and verification standards, all of which affect farmers' incentives. This study determines that carbon farming contract design and efficiency can be improved by analyzing the lessons learned from previous experiences. By examining and improving the attributes that define different incentive mechanisms, farmers can be better motivated to enroll in carbon farming schemes and benefit from increased access to carbon markets to potentially transform agriculture into a viable tool for climate action.

Land capability assessment of Sali watershed for agricultural suitability using a multi-criteria-based decision-making approach

The assessment of land's agricultural potential, through a land capability evaluation, delves into its innate limitations, crop suitability, and responses to soil management. In regions where agriculture reigns supreme, socio-economic development is inexorably linked to the agricultural sector, making the optimal utilization of land resources an imperative pursuit. The pursuit of this objective is underpinned by the selection of new agricultural areas and the determination of which crops thrive in specific locations, for which the multi-criteria decision-making (MCDM) method emerges as an ideal choice. This comprehensive research endeavour revolves around the intricate interplay of climatic, edaphic, fertility, topographical, and socioeconomic determinants. Within this intricate web, a total of 15 determinants play a pivotal role, including precipitation, potential evapotranspiration (PET), soil texture, drainage, soil organic-carbon, nitrogen content, pH, clay content, river proximity, land use/land cover (LULC), slope, temperature, social suitability, irrigation density, and elevation. To weigh these determinants, the Analytical Hierarchy Process (AHP) comes into play, ultimately revealing that the dominant influences on land capability stem from the realms of climate and soil. The watershed's terrain analysis revealed a distinct suitability contrast: 168 km2 highly suitable, 181.3 km2 moderate, and 429 km2 low. The eastern and northeastern sectors were notably promising. Rigorous validation, using the ROC curve, confirmed the reliability and precision. The process yielded an impressive 83.2% AUC, unequivocally confirming the assessment's remarkable accuracy and dependability.

Spatiotemporal analysis of national carbon emission and regional carbon simulation in China

Land use and land cover (LULC) will cause large flows of carbon sources and sinks. As the world's largest carbon emitter with a complicated LULC, China's carbon emissions have profound implications for its ecological environment and future development. In this paper, we account for the land-use changes and carbon emissions of 30 Chinese provinces and cities in China from 2000 to 2020. Furthermore, the spatial correlation of carbon emissions among the study areas is explored. Four typical regions with spatial association (Beijing, Hebei, Sichuan, and Anhui) are selected, and their land-use change trends in 2025 and 2030 are simulated to predict the total carbon emissions in the future. The results show that the distribution of land-use in China is mainly cultivated and woodland, but the growth of urban built-up (UBL) land area indirectly leads to the continuous increase of carbon emissions. Total carbon emissions have increased over the past two decades, albeit at a slower growth rate, with some provinces experiencing no further growth. In the typical regional carbon emission simulation, it is found that the carbon emissions of the four provinces would show a downward trend in the future. The main reason is the reduction in indirect carbon emissions from fossil energy in UBL, while the other part is the influx of carbon sinks due to grassland, woodland, etc. We recommended that future carbon reduction measures should focus and prioritize controlling fossil energy and mitigating carbon emissions from UBL. Simultaneously, the significant contribution of forests and other land types as carbon sinks should be acknowledged to better implement China's carbon neutral commitment.

Energy-use efficiency of organic and conventional plant production systems in Germany

Sustainable and efficient energy use in agriculture helps tackle climate change by reducing fossil energy use. We evaluated German farming systems by analysing energy input and output. Data from 30 organic and 30 conventional farms (12 arable, 18 dairy farms each) between 2009 and 2011 was used. Energy input, output, and the influence of farm type, farm structure, and management intensity on energy-use efficiency (EUE) were analysed for crop production using the farm management system REPRO. Conventional farms (CF) always had higher energy input. The energy input for organic farms (OF) was 7.2 GJ ha-1 and for CF 14.0 GJ ha-1. The energy output of CF was also higher. Reductions were higher in energy input than in energy output. In 73.3% of the farm pairs, OF were more energy efficient than CF. The EUE was comparable with CF on 10% of OF and for 16.7% of CF the EUE was higher suggesting better fossil energy utilization. EUE can be increased when reducing fossil energy inputs through more efficient machinery, reduction of agrochemicals, precision farming, the use of renewable energy or energy retention, and by increasing yields. A reduction of inputs is urgently required to lower the (political) dependence on fossil energy.

Spatial prediction of winter wheat yield gap: agro-climatic model and machine learning approaches

This study aimed to identify the most influential soil and environmental factors for predicting wheat yield (WY) in a part of irrigated croplands in southwest Iran, using the FAO-Agro-Climate method and machine learning algorithms (MLAs). A total of 60 soil samples and wheat grain (1 m × 1 m) in 1200 ha of Pasargad plain were collected and analyzed in the laboratory. Attainable WY was assessed using the FAO method for the area. Pearson correlation analysis was used to select the best set of soil properties for modeling. Topographic attributes and vegetation indices were used as proxies of landscape components and cover crop to map actual WY in the study area. Two well-known MLAs, random forest (RF) and artificial neural networks (ANNs), were utilized to prepare an actual continuous WY map. The k-fold method was used to determine the uncertainty of WY prediction and quantify the quality of prediction accuracy. Results showed that soil organic carbon (SOC) and total nitrogen (TN) had a positive and significant correlation with WY. The SOC, TN, normalized different vegetation index (NDVI), and channel network base level (CHN) were recognized as the most important predictors and justifying more than 50% of actual WY. The ANNs outperformed the RF algorithm with an R 2 of 0.75, RMSE of 400 (kg ha-1), and RPD of 2.79, according to statistical indices. The uncertainty analysis showed that the maximum uncertainty of the prediction map [400 (kg ha-1)] was very low compared to the mean value [4937 (kg ha-1)] of WY map. Calculation yield gap using the FAO-agro-climatic model showed that the average yield gap of the region was about 50% of actual yield. The findings of this study demonstrated that integrating simulated attainable crop growth using crop model and a set of soil and environmental covariates with the ANNs algorithm can effectively predict WY gaps in large areas with acceptable and reasonable accuracy. The study emphasizes that the implementation of efficient management practices has the potential to enhance agricultural production in the study area and similar regions. These results represent a significant advancement of sustainable agriculture and provide valuable insights for ensuring global food security.

Isolation, Quantification, and Visualization of Extracellular Membrane Vesicles in Rhizobia Under Free-Living Conditions

Rhizobia are a group of soil proteobacteria that are able to establish a symbiotic interaction with legumes. These bacteria are capable to fix atmospheric nitrogen into ammonia within specific plant root organs called nodules. The rhizobia-legume interaction is established by a complex molecular dialogue that starts with flavonoids exudated by the plant roots. In response, signaling molecules known as Nod factors (NFs) are secreted by the bacteria. These factors are sensed by specific plant receptors that trigger a downstream signaling cascade leading to rhizobium-specific intracellular colonization of the root hair via the formation of infection threads and the eventual development of nodules on roots. In these organs, rhizobia can fix nitrogen from the atmosphere for the plant in exchange for photosynthates and the appropriate environment for nitrogen fixation. Recently, it has been demonstrated that extracellular membrane vesicles (EMVs) produced by some rhizobia carry NFs. EMVs are proteolipidic structures that are secreted to the milieu from the bacterial membranes and are involved in several important biological processes, including intercellular communication. Thus far, little is known about rhizobia vesicles, and further studies are needed to understand their functions, including their role as transporting vessels of signaling molecules during the process of symbiosis. Here, we present a detailed protocol to isolate high-purity EMVs from free-living cultured rhizobia, test their integrity, and quantify their abundance.

Decarbonization of Agriculture: The Greenhouse Gas Impacts and Economics of Existing and Emerging Climate-Smart Practices

The worldwide emphasis on reducing greenhouse gas (GHG) emissions has increased focus on the potential to mitigate emissions through climate-smart agricultural practices, including regenerative, digital, and controlled environment farming systems. The effectiveness of these solutions largely depends on their ability to address environmental concerns, generate economic returns, and meet supply chain needs. In this Review, we summarize the state of knowledge on the GHG impacts and profitability of these three existing and emerging farming systems. Although we find potential for CO2 mitigation in all three approaches (depending on site-specific and climatic factors), we point to the greater level of research covering the efficacy of regenerative and digital agriculture in tackling non-CO2 emissions (i.e., N2O and CH4), which account for the majority of agriculture's GHG footprint. Despite this greater research coverage, we still find significant methodological and data limitations in accounting for the major GHG fluxes of these practices, especially the lifetime CH4 footprint of more nascent climate-smart regenerative agriculture practices. Across the approaches explored, uncertainties remain about the overall efficacy and persistence of mitigation-particularly with respect to the offsetting of soil carbon sequestration gains by N2O emissions and the lifecycle emissions of controlled environment agriculture systems compared to traditional systems. We find that the economic feasibility of these practices is also system-specific, although regenerative agriculture is generally the most accessible climate-smart approach. Robust incentives (including carbon credit considerations), investments, and policy changes would make these practices more financially accessible to farmers.

The impact of organic fertilizer replacement on greenhouse gas emissions and its influencing factors

Although organic fertilizers played an important role in enhancing crop yield and soil quality, the effects of organic fertilizers replacing chemical fertilizers on greenhouse gas (GHG) emissions remained inconsistent, and further impeding the widespread adoption of organic fertilizers. Therefore, a global meta-analysis used 568 comparisons from 137 publications was conducted to evaluate the responses of GHG emissions to organic fertilizers replacing chemical fertilizers. The results indicated that organic fertilizers replacing chemical fertilizers significantly decreased N2O emissions, but increasing global warming potential (GWP) by enhancing CH4 and CO2 emissions. When replacing chemical fertilizers with organic fertilizers, a variety of factors such as climate conditions, soil conditions, crop types and agricultural practices influenced the GHG emissions and GWP. Among these factors, fertilizer organic C and available N level were the main factors affecting GHG and GWP. However, considering the feasibility and ease of optimizing these factors, fertilizer organic C, C/N and N substitution rate showed a more favorable choice for GWP reduction, and their interactions significantly affecting GWP. Moreover, considering the distinct GHG emissions patterns in dryland and paddy field, the analysis of optimizing GWP based on fertilizer organic C, C/N and N substitution rate was separately conducted. According to the simulation optimization, the optimal combination of fertilizer organic C (137.2-228.8 g·kg-1), C/N (6.9-52.0) and N substitution rate (20.0-22.5 %) effectively suppressed the extent of increase in GWP in paddy field compared with chemical fertilizers. In dryland, optimizing fertilizer organic C (100-278 g·kg-1), C/N (70.7-76.6) and N substitution rate (10.2-16.0 %) led to a reduction in GWP compared with chemical fertilizers, indicating that dryland are more suitable for promoting organic fertilizer application. In conclusion, this meta-analysis study quantitatively assessed the GHG emissions when organic fertilizers replacing chemical fertilizers, and also provided a scientific basis for the mitigation of GHG emissions by organic fertilizers management.

DNA methylome analysis provides insights into gene regulatory mechanism for better performance of rice under fluctuating environmental conditions: epigenomics of adaptive plasticity

MAIN CONCLUSION

Roots play an important role in adaptive plasticity of rice under dry/direct-sown conditions. However, hypomethylation of genes in leaves (resulting in up-regulated expression) complements the adaptive plasticity of Nagina-22 under DSR conditions. Rice is generally cultivated by transplanting which requires plenty of water for irrigation. Such a practice makes rice cultivation a challenging task under global climate change and reducing water availability. However, dry-seeded/direct-sown rice (DSR) has emerged as a resource-saving alternative to transplanted rice (TPR). Though some of the well-adapted local cultivars are used for DSR, only limited success has been achieved in developing DSR varieties mainly because of a limited knowledge of adaptability of rice under fluctuating environmental conditions. Based on better morpho-physiological and agronomic performance of Nagina-22 (N-22) under DSR conditions, N-22 and IR-64 were grown by transplanting and direct-sowing and used for whole genome methylome analysis to unravel the epigenetic basis of adaptive plasticity of rice. Comparative methylome and transcriptome analyses indicated a large number (4078) of genes regulated through DNA methylation/demethylation in N-22 under DSR conditions. Gene × environment interactions play important roles in adaptive plasticity of rice under direct-sown conditions. While genes for pectinesterase, LRK10, C2H2 zinc-finger protein, splicing factor, transposable elements, and some of the unannotated proteins were hypermethylated, the genes for regulation of transcription, protein phosphorylation, etc. were hypomethylated in CG context in the root of N-22, which played important roles in providing adaptive plasticity to N-22 under DSR conditions. Hypomethylation leading to up-regulation of gene expression in the leaf complements the adaptive plasticity of N-22 under DSR conditions. Moreover, differential post-translational modification of proteins and chromatin assembly/disassembly through DNA methylation in CHG context modulate adaptive plasticity of N-22. These findings would help developing DSR cultivars for increased water-productivity and ecological efficiency.

Greenhouse gas emissions from soils in corn-based cropping systems

Crop rotation is a management practice with high greenhouse gas (GHG) mitigating potential that is often neglected due to economic influences. Three long-term rotation studies in Wisconsin were selected to assess the potential opportunities for mitigating GHG emissions by comparing the temporal and spatial variability of N2 O, CO2 , and CH4 emissions in continuous corn (CC) (Zea mays L.), corn-soybean (CS) [Glycine max (L.) Merr.], and corn-soybean-wheat (CSW) (Triticum aestivum L.) using a static chamber method. GHG emissions were influenced by weather conditions and following nitrogen (N) application during a 3-year measurement period. In high N input environments at Arlington and Lancaster, N2 O emissions in CC were 5.80 and 4.40 kg N ha-1 , respectively, which was much higher than the emissions in CS and CSW rotations that ranged from 1.52 to 3.33 kg N ha-1 . In the low N input environment at Marshfield, N2 O emissions were not statistically different among CC, CS, and CSW rotations (1.20-1.66 kg N ha-1 ). Yield-scaled N2 O emissions were not different among crop rotations. When pooled over locations, CO2 emissions were highest in CC (4.16 Mg C ha-1 ) and were similar in CS and CSW (3.71 and 3.50 Mg C ha-1 , respectively). Soils either emitted or absorbed small and inconsistent amounts of CH4 . These results provide important insights as to how weather conditions and differences among management practices affect GHG emissions and show that application of either 2-year CS or 3-year CSW rotation can be equally effective in reducing N2 O emissions compared to CC, especially with high N applications.

Soil carbon sequestration in global working lands as a gateway for negative emission technologies

The ongoing climate crisis merits an urgent need to devise management approaches and new technologies to reduce atmospheric greenhouse gas concentrations (GHG) in the near term. However, each year that GHG concentrations continue to rise, pressure mounts to develop and deploy atmospheric CO2 removal pathways as a complement to, and not replacement for, emissions reductions. Soil carbon sequestration (SCS) practices in working lands provide a low-tech and cost-effective means for removing CO2 from the atmosphere while also delivering co-benefits to people and ecosystems. Our model estimates suggest that, assuming additive effects, the technical potential of combined SCS practices can provide 30%-70% of the carbon removal required by the Paris Climate Agreement if applied to 25%-50% of the available global land area, respectively. Atmospheric CO2 drawdown via SCS has the potential to last decades to centuries, although more research is needed to determine the long-term viability at scale and the durability of the carbon stored. Regardless of these research needs, we argue that SCS can at least serve as a bridging technology, reducing atmospheric CO2 in the short term while energy and transportation systems adapt to a low-C economy. Soil C sequestration in working lands holds promise as a climate change mitigation tool, but the current rate of implementation remains too slow to make significant progress toward global emissions goals by 2050. Outreach and education, methodology development for C offset registries, improved access to materials and supplies, and improved research networks are needed to accelerate the rate of SCS practice implementation. Herein, we present an argument for the immediate adoption of SCS practices in working lands and recommendations for improved implementation.

Rumen Lachnospiraceae isolate NK3A20 exhibits metabolic flexibility in response to substrate and coculture with a methanogen

Hydrogen (H2) is the primary electron donor for methane formation in ruminants, but the H2-producing organisms involved are largely uncharacterized. This work integrated studies of microbial physiology and genomics to characterize rumen bacterial isolate NK3A20 of the family Lachnospiraceae. Isolate NK3A20 was the first recognized isolate of the NK3A20 group, which is among the ten most abundant bacterial genera in 16S rRNA gene surveys of rumen microbiota. NK3A20 produced acetate, butyrate, H2, and formate from glucose. The end product ratios varied when grown with different substrates and at different H2 partial pressures. NK3A20 produced butyrate as a major product using glucose or under high H2 partial pressures and switched to mainly acetate in the presence of galacturonic acid (an oxidized sugar) or in coculture with a methanogen. Growth with galacturonic acid was faster at elevated H2 concentrations, while elevated H2 slowed growth with glucose. Genome analyses revealed the presence of multiple hydrogenases including a membrane-bound Ech hydrogenase, an electron bifurcating butyryl-CoA dehydrogenase (Bcd-Etf), and an Rnf complex that may be involved in modulating the observed metabolic pathway changes, providing insight into H2 formation in the rumen. IMPORTANCE The genus-level NK3A20 group is one of the ten most abundant genera of rumen bacteria. Like most of the rumen bacteria that produce the hydrogen that is converted to methane in the rumen, it is understudied, without any previously characterized isolates. We investigated isolate NK3A20, a cultured member of this genus, and showed that it modulates hydrogen production in response to its growth substrates and the hydrogen concentration in its environment. Low-hydrogen concentrations stimulated hydrogen formation, while high concentrations inhibited its formation and shifted the fermentation to more reduced organic acid products. We found that growth on uronic acids, components of certain plant polymers, resulted in low hydrogen yields compared to glucose, which could aid in the selection of low-methane feeds. A better understanding of the major genera that produce hydrogen in the rumen is part of developing strategies to mitigate biogenic methane emitted by livestock agriculture.

Proposed solutions to anthropogenic climate change: A systematic literature review and a new way forward

Humanity is now facing what may be the biggest challenge to its existence: irreversible climate change brought about by human activity. Our planet is in a state of emergency, and we only have a short window of time (7-8 years) to enact meaningful change. The goal of this systematic literature review is to summarize the peer-reviewed literature on proposed solutions to climate change in the last 20 years (2002-2022), and to propose a framework for a unified approach to solving this climate change crisis. Solutions reviewed include a transition toward use of renewable energy resources, reduced energy consumption, rethinking the global transport sector, and nature-based solutions. This review highlights one of the most important but overlooked pieces in the puzzle of solving the climate change problem - the gradual shift to a plant-based diet and global phaseout of factory (industrialized animal) farming, the most damaging and prolific form of animal agriculture. The gradual global phaseout of industrialized animal farming can be achieved by increasingly replacing animal meat and other animal products with plant-based products, ending government subsidies for animal-based meat, dairy, and eggs, and initiating taxes on such products. Failure to act will ultimately result in a scenario of irreversible climate change with widespread famine and disease, global devastation, climate refugees, and warfare. We therefore suggest an "All Life" approach, invoking the interconnectedness of all life forms on our planet. The logistics for achieving this include a global standardization of Environmental, Social, and Governance (ESG) or similar measures and the introduction of a regulatory body for verification of such measures. These approaches will help deliver environmental and sustainability benefits for our planet far beyond an immediate reduction in global warming.

Photocatalytic Conversion of Methane: Current State of the Art, Challenges, and Future Perspectives

With 28-34 times the greenhouse effect of CO2 over a 100-year period, methane is regarded as the second largest contributor to global warming. Reducing methane emissions is a necessary measure to limit global warming to below 1.5 °C. Photocatalytic conversion of methane is a promising approach to alleviate the atmospheric methane concentrations due to its low energy consumption and environmentally friendly characteristics. Meanwhile, this conversion process can produce valuable chemicals and liquid fuels such as CH3OH, CH3CH2OH, C2H6, and C2H4, cutting down the dependence of chemical production on crude oil. However, the development of photocatalysts with a high methane conversion efficiency and product selectivity remains challenging. In this review, we overview recent advances in semiconductor-based photocatalysts for methane conversion and present catalyst design strategies, including morphology control, heteroatom doping, facet engineering, and cocatalysts modification. To gain a comprehensive understanding of photocatalytic methane conversion, the conversion pathways and mechanisms in these systems are analyzed in detail. Moreover, the role of electron scavengers in methane conversion performance is briefly discussed. Subsequently, we summarize the anthropogenic methane emission scenarios on earth and discuss the application potential of photocatalytic methane conversion. Finally, challenges and future directions for photocatalytic methane conversion are presented.

Agricultural Methane Emissions in China: Inventories, Driving Forces and Mitigation Strategies

Identification of the spatial distribution, driving forces, and future trends of agricultural methane (AGM) emissions is necessary to develop differentiated emission control pathways and achieve carbon neutrality by 2060 in China, which is the largest emitter of AGM. However, such research is currently lacking. Here, we estimated China's AGM emissions from 2010 to 2020 and then decomposed six factors that affect AGM emissions via the LMDI model. The results indicated that the AGM emissions in China in 2020 were 23.39 Tg, with enteric fermentation being the largest source, accounting for 43.9% of the total emissions. A total of 39.3% of the AGM emissions were from western China. The main driver of AGM emission reduction was emission intensity, accounting for 59% and 33.7% of methane emission reduction in the livestock sector and rice cultivation, respectively. Additionally, higher levels of urbanization contributed to AGM emission reductions, accounting for 31.3% and 43.0% of the livestock sector and rice cultivation emission reductions, respectively. Based on the SSP-RCP scenarios, we found that China's AGM emissions in 2060 were reduced by approximately 90% through a combination of technology measures, behavioral changes, and innovation policies. Our study provides a scientific basis for optimizing existing AGM emission reduction policies not only in China but also potentially in other high AGM-emitting countries, such as India and Brazil.

Are the impacts of food systems on climate change being reported by the media? An Australian media analysis

OBJECTIVE

Food systems are a major contributor to climate change, producing one-third of global greenhouse gas emissions. However, public knowledge of food systems' contributions to climate change is low. One reason for low public awareness may be limited media coverage of the issue. To investigate this, we conducted a media analysis examining coverage of food systems and their contribution to climate change in Australian newspapers.

DESIGN

We analysed climate change articles from twelve Australian newspapers between 2011 and 2021, sourced from Factiva. We explored the volume and frequency of climate change articles that mentioned food systems and their contributions to climate change, as well as the level of focus on food systems.

SETTING

Australia.

PARTICIPANTS

N/A.

RESULTS

Of the 2892 articles included, only 5 % mentioned the contributions of food systems to climate change, with the majority highlighting food production as the main contributor, followed by food consumption. Conversely, 8 % mentioned the impact of climate change on food systems.

CONCLUSIONS

Though newspaper coverage of food systems' effects on climate change is increasing, coverage of the issue remains limited. As newspapers play a key role in increasing public and political awareness of matters, the findings provide valuable insights for advocates wishing to increase engagement on the issue. Increased media coverage may raise public awareness and encourage action by policymakers. Collaboration between public health and environmental stakeholders to increase public knowledge of the relationship between food systems and climate change is recommended.

Climatic responses and variability in bark anatomical traits of 23 Picea species

In woody plants, bark is an important protective tissue which can participate in photosynthesis, manage water loss, and transport assimilates. Studying the bark anatomical traits can provide insight into plant environmental adaptation strategies. However, a systematic understanding of the variability in bark anatomical traits and their drivers is lacking in woody plants. In this study, the bark anatomical traits of 23 Picea species were determined in a common garden experiment. We analyzed interspecific differences and interpreted the patterns in bark anatomical traits in relation to phylogenetic relationships and climatic factors of each species according to its global distribution. The results showed that there were interspecific differences in bark anatomical traits of Picea species. Phloem thickness was positively correlated with parenchyma cell size, possibly related to the roles of parenchyma cells in the radial transport of assimilates. Sieve cell size was negatively correlated with the radial diameter of resin ducts, and differences in sieve cells were possibly related to the formation and expansion of resin ducts. There were no significant phylogenetic signals for any bark anatomical trait, except the tangential diameter of resin ducts. Phloem thickness and parenchyma cell size were affected by temperature-related factors of their native range, while sieve cell size was influenced by precipitation-related factors. Bark anatomical traits were not significantly different under wet and dry climates. This study makes an important contribution to our understanding of variability in bark anatomical traits among Picea species and their ecological adaptations.

Enteric methane emissions in grazing dairy systems

Approximately 80% of agricultural CH₄ comes from livestock systems, with 90% of that derived from enteric CH₄ production by ruminants. Grazing systems are used worldwide to feed dairy cattle. Although quantifying enteric CH₄ emissions in grazing systems has unique challenges, emerging technologies have made gaseous data collection more feasible and less laborious. Nevertheless, robust data sets on enteric CH₄ emissions under various grazing conditions, as well as effective and economic strategies to mitigate CH₄ emissions in grazing dairy cows, are still in high demand because data collection, feeding management, and milk market regulations (e.g., organic certification, grassfed) impose more challenges to grazing than confinement dairy systems. This review will cover management strategies to mitigate enteric CH₄ emissions and applicability to pastoral dairy systems. The effects of enteric CH₄ in the broader context of whole-system assessments will be discussed, which are key to assess the overall environmental impact of grazing dairies.

The Effects of Paddy Cultivation and Microbiota Members on Arsenic Accumulation in Rice Grain

Access to safe food is one of the most important issues. In this context, rice plays a prominent role. Because high levels of arsenic in rice grain are a potential concern for human health, in this study, we determined the amounts of arsenic in water and soil used in the rice development stage, changes in the arsC and mcrA genes using qRT-PCR, and the abundance and diversity (with metabarcoding) of the dominant microbiota. When the rice grain and husk samples were evaluated in terms of arsenic accumulation, the highest values (1.62 ppm) were obtained from areas where groundwater was used as irrigation water, whereas the lowest values (0.21 ppm) occurred in samples from the stream. It was observed that the abundance of the Comamonadaceae family and Limnohabitans genus members was at the highest level in groundwater during grain formation. As rice development progressed, arsenic accumulated in the roots, shoots, and rice grain. Although the highest arsC values were reached in the field where groundwater was used, methane production increased in areas where surface water sources were used. In order to provide arsenic-free rice consumption, the preferred soil, water source, microbiota members, rice type, and anthropogenic inputs for use on agricultural land should be evaluated rigorously.

The potential to increase grassland soil C stocks by extending reseeding intervals is dependent on soil texture and depth

Grasslands account for ∼30% of global terrestrial carbon (C), of which most is stored in soils and provide important ecosystem services including livestock and forage production. Reseeding of temporary grasslands on a 5-year cycle is a common management practice to rejuvenate sward productivity and reduce soil compaction, but is physically disruptive and may reduce soil organic carbon (SOC) stocks. However, research to date is limited, which impacts on the ability to optimise grassland management for climate change mitigation. To determine whether extending the time interval up to 20 years between grassland reseeding can increase stable SOC stocks, a soil survey was conducted across three UK grassland chrono-sequences comprising 24 fields on contrasting soil types. We found that grassland SOC stocks (39.8-114.8 Mg C ha^-1) were higher than co-located fields in arable rotations (29.3-83.2 Mg C ha^-1) and the relationship with grassland age followed a curvilinear relationship with rapid SOC stock accumulation in the year following reseeding (2.69-18.3 Mg C ha^-1 yr^-1) followed by progressively slower SOC accumulation up to 20 years. Contrary to expectation, all grasslands had similar soil bulk densities and sward composition questioning the need for traditional 5-year reseeding cycles. Fractionation of soils into stable mineral associated fractions revealed that coarse textured grassland topsoils (0-15 cm) were near-saturated in C irrespective of grassland age whilst loam soils reached saturation ∼10 years after reseeding. Fine-textured topsoils and subsoils (15-30 cm) of all textures were under saturated and thus appear to hold the most potential to accrue additional stable C. However, the lack of a relationship between C saturation deficit and grassland age in subsoils suggests that more innovative management to promote SOC redistribution to depth, such as a switch to diverse leys or full inversion tillage may be required to maximise subsoil SOC stocks. Taken together our findings suggest that extending the time between grassland reseeding could temporarily increase SOC stocks without compromising sward composition or soil structure. However, detailed monitoring of the trade-offs with grassland productivity are required. Fine textured soils and subsoils (15-30 cm) have the greatest potential to accrue additional stable C due to under saturation of fine mineral pools.

Carbon for soils, not soils for carbon

The role of soil organic carbon (SOC) sequestration as a 'win-win' solution to both climate change and food insecurity receives an increasing promotion. The opportunity may be too good to be missed! Yet the tremendous complexity of the two issues at stake calls for a detailed and nuanced examination of any potential solution, no matter how appealing. Here, we critically re-examine the benefits of global SOC sequestration strategies on both climate change mitigation and food production. While estimated contributions of SOC sequestration to climate change vary, almost none take SOC saturation into account. Here, we show that including saturation in estimations decreases any potential contribution of SOC sequestration to climate change mitigation by 53%-81% towards 2100. In addition, reviewing more than 21 meta-analyses, we found that observed yield effects of increasing SOC are inconsistent, ranging from negative to neutral to positive. We find that the promise of a win-win outcome is confirmed only when specific land management practices are applied under specific conditions. Therefore, we argue that the existing knowledge base does not justify the current trend to set global agendas focusing first and foremost on SOC sequestration. Away from climate-smart soils, we need a shift towards soil-smart agriculture, adaptative and adapted to each local context, and where multiple soil functions are quantified concurrently. Only such comprehensive assessments will allow synergies for land sustainability to be maximised and agronomic requirements for food security to be fulfilled. This implies moving away from global targets for SOC in agricultural soils. SOC sequestration may occur along this pathway and contribute to climate change mitigation and should be regarded as a co-benefit.

The role of rice cultivation in changes in atmospheric methane concentration and the Global Methane Pledge

Resumption of the increase in atmospheric methane (CH₄ ) concentrations since 2007 is of global concern and may partly have resulted from emissions from rice cultivation. Estimates of CH₄ emissions from rice fields and abatement potential are essential to assess the contribution of improved rice management in achieving the targets of the Global Methane Pledge agreed upon by over 100 countries at COP26. However, the contribution of CH₄ emissions from rice fields to the resumed CH₄ growth and the global abatement potential remains unclear. In this study, we estimated the global CH₄ emissions from rice fields to be 27 ± 6 Tg CH₄ year^-1 in the recent decade (2008-2017) based on the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The trend of CH₄ emissions from rice cultivation showed an increase followed by no significant change and then, a stabilization over 1990-2020. Consequently, the contribution of CH₄ emissions from rice fields to the renewed increase in atmospheric CH₄ concentrations since 2007 was minor. We summarized the existing low-cost measures and showed that improved water and straw management could reduce one-third of global CH₄ emissions from rice fields. Straw returned as biochar could reduce CH₄ emissions by 12 Tg CH₄ year^-1 , equivalent to 10% of the total reduction of all anthropogenic emissions. We conclude that other sectors than rice cultivation must have contributed to the renewed increase in atmospheric CH₄ concentrations, and that optimizing multiple mitigation measures in rice fields could contribute significantly to the abatement goal outlined in the Global Methane Pledge.

Variation in methodology obscures clarity of cropland global warming potential estimates

Global warming potential (GWP) estimates from agroecosystems are valuable for understanding management effects on climate regulation services. However, GWP estimates are complex, including attributes with high spatiotemporal variability. Published GWP estimates from cropland were compiled and methodological attributes known to influence GWP were extracted. Results revealed considerable variation in approaches to estimate GWP. Among carbon balance methods, respiration methods were used most frequently (33%), followed by soil carbon stock change over time (30%). Twenty-six percent of studies did not account for carbon change in GWP estimates. Duration of gas flux measurements ranged from 0.5 to 60 months, with weekly and sub-weekly sampling most common (34% and 33%, respectively). Carbon dioxide equivalent conversion factors generally aligned with Intergovernmental Panel on Climate Change recommendations through 2014 but diverged thereafter. This review suggests the need for increased transparency in how GWP estimates are derived and communicated. Presentation of key metadata alongside GWP estimates is recommended.

Sustainable intensification – reaching towards climate resilience livestock production system

An ability to prepare, recover and adapt to frequent climatic variation is called “climate resilience.” Climate change now places additional pressure on the cattle industry, particularly in developing nations, which threatens the livelihood of small farmers. In 2013 “Food and Agriculture Organization” reported that the livestock sector accounts for nearly 1/3rd of agricultural gross production value globally. There are higher possibilities of the effective implications of sustainable intensification in the livestock production systems to determine production pathways that are more sustainable and productive with a minimum negative impact on the environment. The paper discusses the systematic review mingle with qualitative text analysis to explore the interrelation between sustainable intensification and resilient climate practices, specifically towards the livestock production system. The data for systematic review was taken from Scopus, Web of Science, and PubMed databases from 1995 till 2020, with total screened 94 articles in the final selection. The study's results revealed that all approaches involving environment-friendly practices with higher production efficiency, resource use efficiency and reachable to every farmer were considered sustainable intensification. The relevance of this sustainability analysis to climate resilience is illustrated by considering different types of livestock systems with concerned practices. So, the inclusion of appropriate technology in an appropriate system will open the door for sustainable intensification in the face of a climate-resilient livestock production system and finally lead the farming community towards sustainable development.

From hinterland to heartland: Knowledge and market insecurity are barriers to crop farmers using sustainable soil management in Guyana

In Guyana, the coastal plains dominate agricultural production, while the hinterland is an emerging agricultural frontier. The coastal and hinterland regions have differing agro-climatic conditions, but share immediate climate change and environmental degradation pressures, including soil degradation. Even though climate change adaptation is prioritized over greenhouse gas mitigation in Guyana, soil-focused farming, otherwise known as sustainable soil management (SSM), can provide a system that creates synergies between these two facets of climate-smart agriculture and, also, promotes soil security. This article proposes a bottom-up planning process for SSM in Guyana by assessing its underlying psycho-social and physical facilitators and barriers. The main questions addressed are: what are the attitudes of Guyanese farmers to climate change? What are their capabilities for SSM, in terms of education, technology and government support? In answering these questions, inductive-derived thematic analysis of transcripts derived from in-depth telephone interviews with seventeen (17) farmers, from coastal and hinterland regions, provides an initial basis for ground truthing on the local appropriateness of SSM. Results show that hinterland farmers are more emotive and value-driven about their environment, while coastal farmers, instead, prioritize access to markets and gaining favorable prices for their commodities. Additionally, the lack of education and training are identified as severe limitations to the capabilities of farmers to practice SSM. In conclusion, a weak marketing environment is seen as a binding constraint of sustainable intensification as surplus goods attract low prices. Stronger linkages to dynamic markets, as well as increased investment opportunities are needed for sustainable farming to become economically feasible. Therefore, psychosocial capital must be strengthened before any natural capital is improved under Guyana's various agro-environmental policies.

Influence of land use types on the distribution of selected soil properties in tropical soils of the Coastal Savanna zone

Globally, efforts are being made to identify land use types that could potentially improve carbon sequestration to mitigate climate change and global warming and ensure sustainable agriculture. The study was conducted at the University of Cape Coast Teaching and Research Farm to evaluate the influence of different land use types on the distribution of SOC at different soil depths. A stratified random sampling technique was used to collect a total of 180 soil samples at 0-15 cm, 15-30 cm and 30-45 cm depths from arable, fallow, pasture and plantation fields, covering about 24.52 ha. The physico-chemical properties of the soil samples were determined using standard laboratory methods and the data generated was analysed using Minitab 19. The results showed that land use systems significantly (p ≤ 0.05) affected the distribution of the physico-chemical properties of the soil. The SOC content under the different land use types was in the order; of plantation (2.57%) > arable (1.99%) > pasture (1.55%) > fallow (1.14%). The plantation field significantly (p ≤ 0.05) had higher SOC compared to the other land use types and that could be adopted as a better carbon store that can help in mitigating climate change. The mean values of SOC content and most of the other physico-chemical properties determined were generally concentrated in the topsoil (0-15 cm depth) but decreased with depth, so managing these fields properly can equally improve the availability of these nutrients towards sustainable agriculture.

High-yielding nitrate transporter cultivars also mitigate methane and nitrous oxide emissions in paddy

Development of high yield rice varieties is critical to ensuring global food security. However, the emission of greenhouse gases (GHG) such as Methane (CH₄) and Nitrous oxide (N₂O) from paddy fields threatens environmental sustainability. In this study, we selected overexpressed high-affinity nitrate transporters (NRT2.3 along with their partner protein NAR2.1) cultivars, which are effective nitrogen use efficient transgenic lines pOsNAR2.1: OsNAR2.1 (Ox2) and p35S:OsNRT2.3b (O8). We used high (270 kg N/ha) and low (90 kg N/ha) nitrogen (N) fertilizers in paddy fields to evaluate morphophysiological traits, including GHG emission. We found that Ox2 and O8 reduced CH₄ emissions by 40% and 60%, respectively, compared to their wild type (WT). During growth stages, there was no consistent N₂O discharge pattern between WT and transgenics (Ox2, O8) in low and high N application. However, total cumulative N₂O in a cropping season reduced in O8 and increased in Ox2 cultivars, compared to WT. Root aerenchyma formation reduced by 30-60% in transgenic lines. Methanogens like mcrA in low and high N were also reduced by up to 50% from rhizosphere of Ox2 and O8. However, the nitrifying bacterial population such as nosZ reduced in both transgenics significantly, but nirK and nirS did not show a consistent variation. The high yield of transgenic rice with limited aerenchyma mitigates the discharge of CH₄ and N₂O by reducing root exudates that provide substrates for GHG. Our results improve understanding for breeders to serve the purpose of sustainable development.

Nanotechnology - A new frontier of nano-farming in agricultural and food production and its development

The potential of nanotechnology for the development of sustainable agriculture has been promising. The initiatives to meet the rising food needs of the rapidly growing world population are mainly powered by sustainable agriculture. Nanoparticles are used in agriculture due to their distinct physicochemical characteristics. The interaction of nanomaterials with soil components is strongly determined in terms of soil quality and plant growth. Numerous research has been carried out to investigate how nanoparticles affect the growth and development of plants. Nanotechnology has been applied to improve the quality and reduce post-harvest loss of agricultural products by extending their shelf life, particularly for fruits and vegetables. This review assesses the latest literature on nanotechnology, which is used as a nano-biofertilizer as seen in the agricultural field for high productivity and better growth of plants, an important source of balanced nutrition for the crop, seed germination, and quality enrichment. Additionally, post-harvest food processing and packaging can benefit greatly from the use of nanotechnology to cut down on food waste and contamination. It also critically discusses the mechanisms involved in nanoparticle absorption and translocation within the plants and the synthesis of green nanoparticles.

Reduction in soil CO2 efflux through alteration of hydrothermal factor in milk vetch (Astragalus sinicus L.)-rapeseed (Brassica napus L.) intercropping system

INTRODUCTION

Intercropping has a potential to reduce the CO₂ emission from farmlands. Limited information is available on the underlying reasons.

METHODS

This study investigated the effect of milk vetch (Astragalus sinicus L.) (MV), rapeseed (Brassica napus L.) monoculture (RS) and intercropping (Intercrop) on soil CO₂ emissions, moisture and temperature in a bucket experiment during 210 days from October 2015 to May 2016 on Chongqing, China.

RESULTS

The results showed that soil CO₂ efflux of MV, RS and Intercrop was 1.44, 1.55 and 2.08 μmol·m^-2·s^-1 during seedling and stem elongation stages and 3.08, 1.59 and 1.95 μmol·m^-2·s^-1 during flowering and podding stages. At seeding and stem elongation stages Intercrop had 1.4 times higher soil CO₂ efflux than the mean of MV and RS. In contrast, MVhad 1.6 times higher soil CO₂ efflux than Intercrop thereafter, which shows it was inhibited if milk vetch presents as Intercrop only. Decreased sensitivity of soil respiration to temperature in 1.4 times and lower soil moisture by Intercrop were found compared to MV. Intercrop decreased soil moisture, especially at the seedling and stem elongation stages, compared to the monoculture. The fluctuation on soil respiration in RS and Intercrop was slight with changes in soil moisture.

CONCLUSION

Thus, milk vetch-rapeseed system has a potential to decrease CO₂ emission from farmland, however soil moisture should be regulated properly.

The effect of China's leading officials' accountability audit of natural resources policy on provincial agricultural carbon intensities: the mediating role of technological progress

China is one of the largest agricultural countries in the world. In the context of China's efforts to achieve dual carbon goals (carbon peak and carbon neutral), the need for carbon emissions reductions in the agricultural sector cannot be ignored. This study collected 2007 to 2018 data from 30 Chinese provinces and used a difference in differences (DID) model to investigate the relationships between China's leading officials' accountability audit of natural resources policy (LOAANR), agricultural technological progress, and agricultural carbon emissions intensities (CEI). A common trend test, placebo test, PSM-DID, and other test methods were used to verify the reliability of the results. The results show that (1) compared with the non-pilot areas, the policy implementation could significantly reduce CEI; (2) the LOAANR was able to stimulate patented technological progress (ATI) and mechanical technological progress (AMT), but different types of technological progress had different mediation effect sizes; and (3) the policy effects shows obvious regional heterogeneity, manifesting as west > east > central; and the policy effects were more obvious in the non-major grain-producing areas, but had no inhibition effects on the CEI in the major grain-producing areas; compared with low intensity market-based environmental regulation (MER) regions, high-intensity MER regions have stronger LOAANR emission reduction effects. Based on the study findings, policy suggestions are given to reduce agricultural carbon emissions and promote higher quality agricultural development.

Organic carbon sequestration in Chinese croplands under compost application and its contribution to carbon neutrality

Achieving the carbon neutrality in China has great impact on alleviating global warming. Compost application, an important measure to promote soil organic carbon (SOC) sequestration, has been practiced in China since 2015. However, it is still unclear how much carbon can be fixed by cropland soil under compost application in the whole China. China has pledged to strive for the goal of carbon neutrality by 2060, which brought two issues: whether compost application can consistently promote SOC sequestration until 2060, and how much contribution it can make to the carbon neutrality. In the present study, we analyzed the results from 93 literatures to determine the SOC sequestration under compost application in the different agricultural divisions of China. Results showed that there were regional differences in the effect of compost application on SOC sequestration. The annual SOC sequestration in Northern China (NC) and Gansu + Xinjiang (GX) was significantly high than other regions. In addition, the annual SOC sequestration was negatively related to the duration of the experiment, while the accumulative SOC sequestration during the experimental period increased with the increase of the duration. According to our results, the total SOC sequestration in topsoil of Chinese cropland was 85 Tg C year^-1 under compost application, which will make a 4.4% contribution to carbon neutrality during 2021-2060. In conclusion, cropland soil in China can still sequester carbon for more than 35 years under compost application. Thus, abidingly promoting compost application in China is crucial to accomplishing the carbon neutrality goal.

A meta-analysis of the genetic contribution to greenhouse gas emission in sheep

The objective of this study was to use a random-effects model of meta-analysis to merge various heritability estimates of different gas emission traits (methane yield [METY], methane production [METP], carbon dioxide production [CO₂ ], the sum of carbon dioxide and methane production [METP + CO₂ ], METP METP + CO 2 ratio, and oxygen consumption [O₂ ]) and their genetic association with growth and partial efficiency traits in sheep. A total of 53 genetic correlations and 47 heritability estimates from 13 scientific articles were used in the meta-analysis. The included papers were published between 2010 and 2022. To measure heterogeneity, Chi-square (Q) test was performed, and the I² statistic was determined. The average heritability estimates for the studied traits were low to moderate and ranged from 0.137 (for METY) to 0.250 (for METP + CO₂ ). The heterogeneity test of heritability estimates indicated that heritability estimates for METY, O₂ consumption, and METP METP + CO 2 had low Q values and non-significant heterogeneity (p > 0.10). However, the average heritability estimates for other traits experienced significant heterogeneities (p < 0.10). The genetic correlation estimate between METP with O₂ was -0.597 (p < 0.05), but its genetic correlations with other gas traits ranged from 0.593 (with METP + CO₂ ) to 0.653 (CO₂ ; p < 0.05). Also, mean estimates of genetic correlation between METP with live weight (LW), feed intake (FI), and residual feed intake (RFI) were 0.719, 0.598, and 0.408, respectively. The genetic correlations of CO₂ with performance traits varied from 0.641 (with RFI) to 0.833 (with FI; p < 0.05). This meta-analysis showed gas emission traits in sheep are under low-to-moderate genetic control. The average genetic parameter estimates obtained in this study could be considered in the genetic selection programmes for sheep, especially when there is no access to accurate phenotypic records or genetic parameter estimates for gas emission traits.

Straw return and nitrogen fertilization regulate soil greenhouse gas emissions and global warming potential in dual maize cropping system

Abundant nitrogen (N) fertilization is needed for maize (Zea mays L.) production in China because of its huge residual biomass return. However, excessive N fertilization has a negative impact on the soil ecosystem and environment, which contributes to climate change. Soil incorporation of maize residues is a well-known practice for reducing chemical N fertilization without compromising maize yield and soil fertility. Thus, residues incorporation has the capacity to minimize N fertilization uses and hence mitigate soil greenhouse gas emissions by improving plant N uptake and use efficiency. There is still a research gap regarding the effects of maize residues incorporation on maize yield, soil fertility, greenhouse gas emissions, and plant N and carbon (C) contents. Therefore, we conducted a field experiment during spring and autumn involving four different N fertilization rates (N0, N200, N250, and N300 kg N ha^-1), with and without maize residues incorporation, to evaluate grain yield, soil fertility, plant N and C contents, and greenhouse gas emissions (GHGs). Compared to N0, N fertilizer application at 300 kg N ha^-1 with residues incorporation significantly increased area-scaled global warming potential (GWP) compared to other N fertilization rates in both spring and autumn seasons, but soil nutrient contents and plant N and C contents were not statistically different from the N250 treatment. In contrast, the N recovery use efficiency (NRUE), physiological N use efficiency (PNUE), and agronomic N use efficiency (ANUE) were significantly lower in the N300 treatment than in the lower N treatment groups. Nitrous oxide (N₂O) and carbon dioxide (CO₂) fluxes, area-scaled GWP, and greenhouse gas intensity (GHGI) were significantly lower in the N200 treatment with straw incorporation than the N250 and N300 treatments of the traditional planting system. Thus, we concluded that N200 treatment with residues incorporation is optimal for improving grain yield, soil fertility, plant N uptake, and mitigating greenhouse gas emissions.

Drying and rewetting cycles increased soil carbon dioxide rather than nitrous oxide emissions: A meta-analysis

The increased frequency of extreme weather variations worldwide has resulted in dramatic changes in the soil water content via pronounced drying and rewetting cycles (DWCs). A comprehensive exploration of carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions in response to DWCs can help summarize the existing results and better estimate terrestrial greenhouse gas emissions under the intensified drought and precipitation variations. This meta-analysis based on soil emissions of CO₂ (868 observations, 29 studies) and N₂O (52 observations, 19 studies) at the global scale investigated the direction and intensity of the changes in soil CO₂ and N₂O emissions in response to DWCs as controlled by experimental variables including land use type, soil texture, soil nutrients, and frequency and duration of DWCs. The results showed that, compared to the constant soil water content, DWCs led to the increase in CO₂ emissions by 35.7% (95% confidence intervals ranging from 0.300 to 0.415), whereas it had no significant effect on N₂O emissions (-0.2638 to 1.4751). The random-effects model indicated that soil water-filled pore space during wetting, soil clay content, days of drying and wetting, and frequency of DWCs significantly affected CO₂ and N₂O emissions in response to DWCs. Furthermore, potential biotic and abiotic factors affecting soil CO₂ and N₂O emissions under DWCs are also summarized, and it was proposed that mobility and availability of carbon substrate as well as enhanced microbial activity and abundance are the main drivers facilitating soil CO₂ and N₂O emissions in response to DWCs. However, soil gas diffusion or oxygen availability also dominated soil N₂O emissions under DWCs. Overall, this study improves our understanding of soil CO₂ and N₂O emissions in response to various DWC scenarios and facilitates the development of better greenhouse gas mitigation strategies against the background of a rapidly changing climate.

The carbon emission reduction effect of digital agriculture in China

Carbon emission reduction is gaining increasing attention worldwide. This paper focuses on how the development of digital agriculture contributes to agricultural carbon emission reduction. To this end, the spatial characteristics, spillover effects, and driving factors of digital agriculture on agricultural carbon emissions are explored using panel data of 31 regions in China from 2011 to 2019 using a spatial econometric model and STIRPAT model with the extension of an ARDL method that was utilized to demonstrate the linkage amid variables. The results show that digital agriculture development reduces agricultural carbon emissions. Firstly, the results remain robust after estimation using the replacement weight method and the explanatory variable substitution method. Agricultural technological progress, agricultural industry structure, and rural education level all contribute to the reduction of agricultural carbon emissions in a region. Secondly, agricultural carbon emissions in the neighboring regions have a negative relationship with the agricultural industry structure in the region and a positive relationship with rural education level and agricultural technological level. Finally, strengthening the exchange of digital agriculture between regions and leveraging the intermediary effect of digital inclusive finance can effectively enhance the carbon emission reduction effect.

Socio-economic factors influencing the adoption of low carbon technologies under rice production systems in China

BACKGROUND

Rice (Oryza sativa L.) production, such as farmers' livelihood and the soil quality, has been identified to be strong influenced by climate change in China. However, the benefits of low carbon technologies (LCTs) are still debatable in rice production for farmers, which have been identified to tackle agricultural challenges. The choice of potential LCTs relevant to the case study is based on a literature review of previous empirical studies. Thus, the objectives of the study were to (1) investigate the public perception and preferences of LCTs in rice production of China, and (2) analyze the influences of the factors on farmer's decision in adopting LCTs in rice production. There were 555 farmer surveys from eight representative rice production counties in HP province of southern China, both the Poisson estimators and multivariate probit (MVP) approach were applied in the study.

RESULTS

Our results show that water-saving irrigation, integrated pest management techniques and planting green manure crops in winter season were the three major LCTs adapted by farmers in rice production. The intensity and probability of LCTs adoptions were influenced by the main factors including farmers' education level, climate change awareness, machinery ownership, technical support and subsidies. There is a significant correlation among the LCTs, and the adoption of the technologies is interdependent, depicting either complementarities or substitutabilities between the practices.

CONCLUSIONS

This study suggests that policies enhance the integration of LCTs would be central to farmers' knowledge, environmental concerns, technical service and financial support in rice production systems in China.

The climate change mitigation potential of annual grasslands under future climates

Composted manure and green waste amendments have been shown to increase net carbon (C) sequestration in rangeland soils and have been proposed as a means to help lower atmospheric CO₂ concentrations. However, the effect of climate change on soil organic C (SOC) stocks and greenhouse gas emissions in rangelands is not well understood, and the viability of climate change mitigation strategies under future conditions is even less certain. We used a process-based biogeochemical model (DayCent) at a daily time step to explore the long-term effects of potential future climate changes on C and greenhouse gas dynamics in annual grassland ecosystems. We then used the model to explore how the same ecosystems might respond to climate change following compost amendments to soils and determined the long-term viability of net SOC sequestration under changing climates. We simulated net primary productivity (NPP), SOC, and greenhouse gas fluxes across seven California annual grasslands with and without compost amendments. We drove the DayCent simulations with field data and with site-specific daily climate data from two Earth system models (CanESM2 and HadGEM-ES) and two representative concentration pathways (RCP4.5 and RCP8.5) through 2100. NPP and SOC stocks in unamended and amended ecosystems were surprisingly insensitive to projected climate changes. A one-time amendment of compost to rangeland acted as a slow-release organic fertilizer and increased NPP by up to 390-814 kg C ha^-1  year^-1 across sites. The amendment effect on NPP was not sensitive to Earth system model or emissions scenario and endured through the end of the century. Net SOC sequestration amounted to 1.96 ± 0.02 Mg C ha^-1 relative to unamended soils at the maximum amendment effect. Averaged across sites and scenarios, SOC sequestration peaked 22 ± 1 years after amendment and declined but remained positive throughout the century. Though compost stimulated nitrous oxide (N₂ O) emissions, the cumulative net emissions (in CO₂ equivalents) due to compost were far less than the amount of SOC sequestered. Compost amendments resulted in a net climate benefit of 69.6 ± 0.5 Tg CO₂ e 20 ± 1 years after amendment if applied to similar ecosystems across the state, amounting to 39% of California's rangeland. These results suggest that the biogeochemical benefits of a single amendment of compost to rangelands in California are insensitive to climate change and could contribute to decadal-scale climate change mitigation goals alongside emissions reductions.

Alfalfa-grass mixtures reduce greenhouse gas emissions and net global warming potential while maintaining yield advantages over monocultures

Improving forage productivity with lower greenhouse gas (GHG) emissions from limited grassland has been a hotspot of interest in global agricultural production. In this study, we analyzed the effects of grasses (tall fescue, smooth bromegrass), legume (alfalfa), and alfalfa-grass (alfalfa + smooth bromegrass and alfalfa + tall fescue) mixtures on GHG emissions, net global warming potential (Net GWP), yield-based greenhouse gas intensity (GHGI), soil chemical properties and forage productivity in cultivated grassland in northwest China during 2020-2021. Our results demonstrated that alfalfa-grass mixtures significantly improved forage productivity. The highest total dry matter yield (DMY) during 2020 and 2021 was obtained from alfalfa-tall fescue (11,311 and 13,338 kg ha^-1) and alfalfa-smooth bromegrass mixtures (10,781 and 12,467 kg ha^-1). The annual cumulative GHG emissions from mixtures were lower than alfalfa monoculture. Alfalfa-grass mixtures significantly reduced GHGI compared with the grass or alfalfa monocultures. Furthermore, results indicated that grass, alfalfa and alfalfa-grass mixtures differentially affected soil chemical properties. Lower soil pH and C/N ratio were recorded in alfalfa monoculture. Alfalfa and mixtures increased soil organic carbon (SOC) and soil total nitrogen (STN) contents. Importantly, alfalfa-grass mixtures are necessary for improving forage productivity and mitigating the GHG emissions in this region. In conclusion, the alfalfa-tall fescue mixture lowered net GWP and GHGI in cultivated grassland while maintaining high forage productivity. These advanced agricultural practices could contribute to the development of climate-sustainable grassland production in China.

Revisiting sampling duration to estimate N2O emission factors for manure application and cattle excreta deposition for the UK and Ireland

According to the available guidelines, good practices for calculating nitrous oxide (N₂O) emission factors (EFs) for livestock excreta and manure application include that sampling duration should be of at least one year after the nitrogen (N) application or deposition. However, the available experimental data suggest that in many cases most emissions are concentrated in the first months following N application. Therefore resources could be better deployed by measuring more intensively during a shorter period. This study aimed to assess the contribution of the N₂O flux in the period directly after N application to the annual net emission. We used a database of 100 year-long plot experiments from different excreted-N sources (dung, urine, farmyard manure and slurry) used to derive EFs for the UK and Ireland. We explored different shorter potential measurement periods that could be used as proxies for cumulative annual emissions. The analysis showed that the majority of emissions occur in the first months after application, especially in experiments that i) had urine as the N source, ii) had spring N application, iii) were conducted on fine-textured soils, or iv) showed high annual emissions magnitude. Experiments that showed a smaller percentage of emissions in the first months also had a low magnitude of annual net emissions (below 370 gN₂O-N ha^-1 year^-1), so the impact of measuring during a shorter period would not greatly influence the calculated EF. Accurate EF estimations were obtained by measuring for at least 60 days for urine (underestimation: 7.1%), 120 days for dung and slurry (4.7 and 5.1%) and 180 days for FYM (1.4%). At least in temperate climates, these results are promising in terms of being able to estimate annual N₂O fluxes accurately by collecting data for less than 12 months, with significant resource-saving when conducting experiments towards developing country-specific EFs.

Spatiotemporal Dynamics of Carbon Footprint of Main Crop Production in China

As a major agricultural country, the comprehensive accounting of the dynamics and composition of the carbon footprint of major crops in China will provide a decision-making basis for environmental management and agricultural green development in the whole process of the major crop production system in China. To investigate the spatiotemporal dynamics of the carbon footprint for major crops in China, a life cycle-based carbon footprint approach was used to evaluate the carbon footprint per unit area (CF_A) and per unit yield (CF_Y) of eight crops for the period of 1990 to 2019. Our results showed that the CF_A for all major crops showed an increasing trend with time before 2016 but slowly decreased afterward, while the CF_Y decreased by 16-43% over the past 30 years due to the increase in crop yield. The three main grain crops, rice (4871 ± 418 kg CO₂-eq · ha^-1), wheat (2766 ± 552 kg CO₂-eq · ha^-1), and maize (2439 ± 530 kg CO₂-eq · ha^-1), showed the highest carbon footprint and contribution to the total greenhouse gas (GHG) emissions, mainly due to their larger cultivated areas and higher fertilizer application rates. CH₄ emission was the major component of the carbon footprint for rice production, accounting for 66% and 48% of the CF_A and CF_Y, respectively, while fertilizer production and usage were the largest components of carbon footprint for dryland crops, making up to 26-49% of the CF_A and 26-50% of the CF_Y for different crops. The present study also highlighted the spatial and temporal patterns of the carbon footprint for major crops in China, which could serve as references for the development of best management practices for different crop production in China, to mitigate agricultural GHG emission and to pursue low-carbon agriculture.