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Greenhouse gas emissions and mitigation in rice agriculture
Abstract
Rice paddies supply half the global population with staple food, but also account for ~48% of greenhouse gas (GHG) emissions from croplands. In this Review, we outline the characteristics of GHG emissions (CH4 and N2O) from paddy soils, focusing on climate change effects and mitigation strategies. Global mean annual area-scaled and yield-scaled GHG emissions are ~7,870 kg CO2e ha−1 and 0.9 kg CO2e kg−1, respectively, with 94% from CH4. However, emissions vary markedly, primarily reflecting the impact of management practices. In particular, organic matter additions and continuous flooding of paddies both stimulate CH4 emissions, whereas fertilizer N application rate is the most important driver of N2O emissions. Although contemporary changes in emissions are uncertain, future elevated [CO2] and warming are projected to increase CH4 emissions by 4–40% and 15–23%, respectively. Yet, integrated agronomic management strategies — including cultivar, organic matter, water, tillage and nitrogen management — offer GHG mitigation potential. In particular, new rice variety selection, non-continuous flooding and straw removal strategies reduce GHG emissions by 24%, 44% and 46% on average, respectively. However, approaches need to be optimized on the basis of seasonal CH4 emission patterns, necessitating improved quantification and reduced uncertainty in regional and global GHG estimates, especially in low latitudes.
... Rice paddies release 24-31 Tg CH 4 into the atmosphere annually (FAO 2023;IPCC 2021), contributing 8%-11% of anthropogenic CH 4 emissions (Yuan et al. 2023). Globally, annual area-scaled and yield-scaled GHG emissions average ~7870 kg CO 2 -eq ha −1 and 0.9 kg CO 2 -eq kg −1 rice grain, respectively, with CH 4 constituting 94% of these emissions (Qian et al. 2023). Even at excessive N application rates, CH 4 emissions are generally far larger than nitrous oxide (N 2 O) emissions from rice paddies (e.g., Chen et al. 2016;Zhong et al. 2016). ...
... In terms of area-scaled and yieldscaled GHG emissions, rice cultivation leads all major food crops (Carlson et al. 2017). CH 4 is produced by methanogens under anaerobic conditions and can be consumed by aerobic methanotrophs in the rhizosphere and topsoil (Qian et al. 2023). Methanogens include acetotrophic and hydrogenotrophic types, while methanotrophs are categorized into Type I and Type II (Conrad 2007). ...
... N fertilization, however, affects both CH 4 production and consumption in rice paddies, through various pathways (Bodelier et al. 2000;Schimel 2000;Shrestha et al. 2010). First, N fertilization generally stimulates plant growth Feng et al. 2023), which increases substrates for CH 4 production (Qian et al. 2023;Schimel 2000), resulting in higher CH 4 emissions. Second, ammonium inhibits CH 4 oxidation due to competition for methane monooxygenase (Qian et al. 2023;Schimel 2000), thereby further increasing CH 4 emissions. ...
Rice paddies account for approximately 9% of human‐induced methane (CH 4 ) emissions. Nitrogen (N) fertilization affects CH 4 emissions from paddy soils through several mechanisms, leading to conflicting results in field experiments. The primary drivers of these N‐related effects remain unclear and the contribution of N fertilization to CH 4 emissions from the rice paddies has not yet been quantified for global area. This uncertainty contributes to significant challenges in projecting global CH 4 emissions and hinders the development of effective local mitigation strategies. Here, we show through a meta‐analysis and experiments that the impact of N fertilization on CH 4 emissions from rice paddies can be largely predicted by soil pH. Specifically, N fertilization stimulates CH 4 emissions most strongly in acidic soils by accelerating organic matter decomposition and increasing the activities of methanogens. Accounting for the interactions between soil pH and N fertilization, we estimate that N fertilization has raised current area‐scaled and yield‐scaled CH 4 emissions across the total global paddy area by 52% and 8.2%, respectively. Our results emphasize the importance of alleviating soil acidification and sound N management practices to mitigate global warming.
... Such a large-scale land use conversion imposes substantial pressure on soil ecological functions, affecting the carbon and nitrogen cycles of regional ecosystems as well as the emission of greenhouse gases like CO 2 and CH 4 [13]. Paddy fields are considered a major source of greenhouse gas emissions, posing a potential threat to global warming [14]. Our previous research indicated that the dryland-to-paddy conversion leads to corresponding changes in microbial structural functions and co-occurrence network [12,15]. ...
... We observed a significant short-term reduction in carbon emission efficiency post-conversion-approximately 30%-despite an increase in grain yield. The heightened microbial activity, triggered by the rise in organic matter secreted by the rice root system, collectively contributes to a surge in CO 2 emissions [14]. Furthermore, due to soil disturbance resulting from flooding-which disrupts the original soil structure-a "priming effect" occurs in the short term following the conversion from dryland to paddy cultivation. ...
To amplify grain production capacity, a global trend is emerging in which many regions are transitioning from dependence on rainfall to irrigated agriculture. An illustrative example of this form of land consolidation is the conversion from dryland to paddy fields, which has changed the ecological environment of farmlands, resulting in significant effects on carbon fixation and emissions. However, there currently exists a deficiency in essential understanding regarding the short-term effects of dryland-to-paddy conversion on ecological processes tied to soil carbon-fixation bacteria and carbon emission efficiency (CEE). Therefore, field monitoring and high-throughput sequencing were carried out to monitor the changes in soil carbon emission efficiency and carbon-fixation bacteria before and after the conversion. Our results indicate that while conversion from dryland to paddy fields can boost grain yield, it also results in an increase in soil carbon emissions and a consequent decrease of 25.78% in carbon emission efficiency. This transition has resulted in an increased soil carbon-fixing bacterial alpha diversity index and enhanced network complexity. The structural equation model indicates that changes in soil environmental factors, especially soil moisture, soil organic carbon (SOC), readily oxidizable carbon (ROC), and carbon-fixing bacteria, are the primary drivers of CEE variation (p < 0.05). Given the critical role that the soil carbon cycle plays in global climate change, there is a pressing need for increased global attention towards the carbon emissions triggered by the transition from rainfed to irrigated agriculture.
... At present, one of the important causes of the greenhouse effect is the excessive emission of CO 2 as a result of human life and production activities [1][2][3]. Carbon capture and storage technology is an efficient means for reducing CO 2 emissions [4,5]. Among the traditional methods of CO 2 capture, organic amine solutions, such as monoethanolamine [6], diethanolamine [7], diisopropanolamine [8], and N-methyldiethanolamine [9], are effective for chemical absorption. ...
... Researchers have reported two Yttrium metal-organic frameworks (MOFs), SNNU-324 and SNNU-325, which were designed using a topology-guided strategy with 1,3,5-tris(4carboxyphenyl) benzene (BTB) and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (TATB) as tritopic linkers and [Y 3 (OH) 2 8 ] clusters as secondary building units (SBUs), respectively [29]. SNNU-324 exhibited a good CO 2 /C2 hydrocarbon performance in CH 4 separation, with a high specific surface area of 1395 m 2 ·g −1 and a good CO 2 uptake of 53 cm 3 ·g −1 . ...
Different types of porous materials have been developed for the efficient separation of CO2 from mixtures of gases. Nevertheless, the most porous materials cannot be used for extensive industrial applications due to their non-negligible disadvantages, such as complex synthesis routes, expensive monomers, and/or costly catalysts. Therefore, a strategy for fabricating a series of polyhedral oligomeric silsesquioxane (POSS)-based porous organic polymer materials (PBPOPs) was developed through the simple condensation reaction of octaphenylsilsesquioxane and different bromine-containing monomers. It was found that PBPOP-2 exhibits the best CO2 adsorption amount of 41 cm3·g−1 at 273 K and 760 mmHg based on the accessible specific surface area, large pore volumes, and accessible pore sizes. Furthermore, PBPOP-2 exhibits efficient CO2/N2 selectivity and complete regeneration under mild conditions, which demonstrates the potential for the selective separation of CO2 from gas mixtures. This work provides a new route to developing POSS-based POPs for CO2-capture applications.
... In regions with single rice cropping, rice emissions typically persist for five to six months, peaking in July-August over East Asia (northern China, Japan, Korea) and in September-November over South and Southeast Asia (western India, eastern Thailand). Subtropical and tropical regions more commonly practice double or triple cropping, where rice emissions can occur over eight months or longer, with diverse seasonality depending on local management practices (mid-season drainage, intermittent irrigation; Qian et al., 2023). Fig. 6 compares our GRPI for 2022 to previous inventories. ...
... Directly returning straw to paddy fields as a nutrient supply accelerates methane emissions, but applying strawderived biochar (biomass charcoal) instead reduces emissions and increases yields (Dong et al., 2013;Sriphirom et al., 2021;Wang et al., 2023). More generally, countries can achieve low methane intensities with high-yield cultivars, upland rice agriculture, water management, and organic matter management (Qian et al., 2023). ...
Rice agriculture is a major source of atmospheric methane, but current emission inventories are highly uncertain, mostly due to poor rice-specific inundation data. Inversions of atmospheric methane observations can help to better quantify rice emissions but require high-resolution prior information on the location and timing of emissions. Here we use Landsat satellite data at 30 m resolution to identify flooded vegetation and combine this information with a 30 m global cropland database, rice-specific data, and a recent global dataset of emission factors (EFs) per unit of rice paddy area. The resulting Global Rice Paddy Inventory (GRPI) provides methane emission estimates at 0.1o× 0.1o (~10 km ×10 km) spatial resolution and monthly resolution. Evaluation of GRPI with independent rice area data and FLUXNET-CH4 eddy flux measurements shows good agreement. Our global emission of 39.3 ± 4.7 Tg a-1 for 2022 (best estimate and error standard deviation) is higher than previous inventories that use outdated rice maps and IPCC-recommended EFs now considered too low. GRPI shows the largest discrepancy from previous inventories in South Asia, where rice agriculture has rapidly developed but outdated rice maps fail to represent it. China is the largest rice emitter in GRPI (8.2 ± 1.0 Tg a-1), followed by India (6.5 ± 1.0 Tg a-1), Bangladesh (5.7 ± 1.2 Tg a-1), Vietnam (5.7 ± 1.0 Tg a-1), and Thailand (4.4 ± 0.9 Tg a-1). These five countries together account for 78% of global total rice emissions. The seasonality of emissions varies between countries depending on local climate and cultivation practices. We define a rice methane intensity (methane emission per unit of rice produced) to assess the potential of mitigating methane without compromising food security. We find national methane intensities ranging from 10 to 120 kg methane per ton of rice produced (global mean 51) for major rice-growing countries. Countries can achieve low intensities with high-yield cultivars, upland rice agriculture, water management, and organic matter management.
... Lower MOP and pmoA were not associated with higher CH 4 emissions because of their contradictory impacts on CH 4 production compared to CH 4 oxidation (Shrestha et al., 2010), albeit higher CH 4 emissions were observed in BDE-fertilized fields (Huang et al., 2014;Minamikawa et al., 2021). On the other hand, the CH 4 emission rate results from the interaction between active methanotrophs and methanogens in rice paddy ecosystems (Qian et al., 2023). Consistent with this hypothesis, Win et al. (2016) reported that the application of biogas slurry to paddy fields increased CH 4 emissions; however, the number The numbers in parentheses indicate the dilution of soil from which the isolates were obtained. ...
... -. An increased carbon source is a preferred environment for methanogens, resulting in higher CH 4 production (Qian et al., 2023), which also benefits type-II methanotrophs (Shrestha et al., 2010;Vishwakarma et al., 2010;Sakoda et al., 2022;Yang et al., 2022), thereby explaining the present results. ...
Biogas digestive effluent (BDE) has been applied to rice fields in the Vietnamese Mekong Delta (VMD). However, limited information is available on the community composition and isolation of methanotrophs in these fields. Therefore, the present study aimed (i) to clarify the responses of the methanotrophic community in paddy fields fertilized with BDE or synthetic fertilizer (SF) and (ii) to isolate methanotrophs from these fields. Methanotrophic communities were detected in rhizospheric soil at the rice ripening stage throughout 2 cropping seasons, winter-spring (dry) and summer-autumn (wet). Methanotrophs were isolated from dry-season soil samples. Although the continued application of BDE markedly reduced net methane oxidation potential and the copy number of pmoA genes, a dissimilarity ordination analysis revealed no significant difference in the methanotrophic community between BDE and SF fields (P=0.167). Eleven methanotrophic genera were identified in the methanotrophic community, and Methylosinus and Methylomicrobium were the most abundant, accounting for 32.3–36.7 and 45.7–47.3%, respectively. Type-I methanotrophs (69.4–73.7%) were more abundant than type-II methanotrophs (26.3–30.6%). Six methanotrophic strains belonging to 3 genera were successfully isolated, which included type I (Methylococcus sp. strain BE1 and Methylococcus sp. strain SF3) and type II (Methylocystis sp. strain BE2, Methylosinus sp. strain SF1, Methylosinus sp. strain SF2, and Methylosinus sp. strain SF4). This is the first study to examine the methanotrophic community structure in and isolate several methanotrophic strains from BDE-fertilized fields in VMD.
... On the other hand, the extensive use of nitrogen-based fertilizers in monoculture is a significant source of nitrous oxide (N 2 O) emissions [41]. N 2 O, a potent GHG with a global warming potential nearly 300 times that of CO 2 , is emitted through nitrification and denitrification processes in soils [42,43]. Additionally, livestock production, rice cultivation, soil management, land use change, and energy consumption in agriculture are all significant contributors to GHG emissions [42][43][44][45]. ...
... N 2 O, a potent GHG with a global warming potential nearly 300 times that of CO 2 , is emitted through nitrification and denitrification processes in soils [42,43]. Additionally, livestock production, rice cultivation, soil management, land use change, and energy consumption in agriculture are all significant contributors to GHG emissions [42][43][44][45]. ...
Crop rotation and diversification (CRD) are crucial strategies in sustainable agriculture, offering multiple benefits to both farmers and the environment. By alternating crops or introducing diverse plant species, CRD practices improve soil fertility, reduce pest populations, and enhance nutrient availability. For example, legume-based rotations increase soil nitrogen levels through biological nitrogen fixation, reducing the need for synthetic fertilizers. Moreover, these practices promote more efficient water and nutrient use, reducing the reliance on synthetic fertilizers and minimizing the risk of pests and diseases. This review synthesizes findings from recent research on the role of CRD in enhancing sustainable agriculture and resilience, highlighting the potential contributions of these practices towards climate change mitigation and adaptation. Specific crop rotation systems, such as the cereal–legume rotation in temperate regions and the intercropping of maize with beans in tropical environments, are reviewed to provide a comprehensive understanding of their applicability in different agroecological contexts. The review also addresses the challenges related to implementing CRD practices, such as market demand and knowledge transfer, and suggests potential solutions to encourage broader adoption. Lastly, the potential environmental benefits, including carbon sequestration and reduced greenhouse gas emissions, are discussed, highlighting the role of CRD in building resilient agricultural systems. Collectively, this review paper emphasizes the importance of CRD methods as sustainable agricultural practices and provides key insights for researchers and farmers to effectively integrate these practices into farming systems.
... Transplanting rice in irrigated conditions uses 24-30% of global freshwater, with each kilogram of rice production requiring approximately 2500 liters of water [6,7]. It also accounts for around 48% of greenhouse gas (GHGs) emissions from agricultural land [8]. The doubling in drought-affected areas from the 1970s to the 2000s poses a significant concern for crop production. ...
Seed germination is crucial for plant survival, crop stand establishment, and achieving optimal grain yield. The main objective of this review is to explore the physiological and molecular mechanisms governing rice seed germination under aerobic (water stress) and anaerobic (hypoxic) conditions in direct-seeded rice (DSR) systems. Moreover, it discusses the recent genomic advancements and innovations to improve rice seed germination. Here, we discuss how coleoptile and mesocotyl elongation plays a vital role in anaerobic germination (AG) and the function of raised antioxidants, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in maintaining Reactive Oxygen Species (ROS), and malondialdehyde (MDA) homeostasis for stabilizing seed germination in water-scarce conditions. This study comprehensively highlights the functions and dynamics of phytohormones—GA (gibberellic acid) and ABA (abscisic acid)—key regulatory genes, transcription factors (TFs), key proteins, and regulatory metabolic pathways, including glycolysis, the pentose phosphate pathway (PPP), and the tricarboxylic acid cycle (TCA), in regulating seed germination under both conditions. Conventional agronomic and cultural practices, such as seed selection, seed priming, seed coating, and hardening, have proven to improve seed germination. Moreover, the utilization of molecular and novel approaches—such as clustered regularly interspaced short palindromic repeat (CRISPR-Cas9) mediated genome editing, marker-assisted selection (MAS), genome-wide associations studies (GWAS), single nucleotide polymorphisms (SNPs), multi-omics, RNA sequencing—combined with beneficial quantitative trait loci (QTLs) has expanded knowledge of crop genomics and inheritance. These advancements aid the development of specific traits for enhancing seed germination in DSR.
... Considerable CH 4 was produced under strictly anaerobic conditions in the flooded soils (Sander et al., 2014;Sanchis et al., 2012), whereas soils were aerobic environment conditions with very low methanogenic activity in drylands (Lagomarsino et al., 2016;Zhang et al., 2023), resulting in low CH 4 formation. The net CH 4 emission from the soil is a balance of methanogenic and methanotrophic processes, which are strongly influenced by soil organic substrates and soil redox conditions (Qian et al., 2023). Hence, straw amendment and water regime represent the two primary factors in regulating CH 4 emissions from paddy fields (Yan et al., 2005). ...
... Atmospheric CH 4 concentration has nearly tripled since the pre-industrial period (Rosentreter et al., 2021), which is attributed to both human and natural sources. The anthropogenic CH 4 emission during human activities such as urbanization, rice cultivation, and fossil fuel production and natural CH 4 emissions from different ecosystems such as rivers, streams, lakes, and reservoirs, have been studied in different studies (Atkins et al., 2015;Bourn et al., 2019;Chen et al., 2023b;Qian et al., 2023;Que et al., 2023;Rocher-Ros et al., 2023;Wang et al., 2023b). Aquatic ecosystems are an important natural CH 4 source to the atmosphere, contributing to nearly half of the recent atmospheric CH 4 increase (Rosentreter et al., 2021). ...
Methane (CH4), the second largest non-vapor greenhouse gas, has larger global warming threat than carbon dioxide (CO2). Atmospheric CH4 levels have spiked since the industrial revolution, with rivers identified as significant CH4 contributors. However, understanding the sources and dynamics of dissolved CH4 in rivers remains a challenge. Our study focuses on the Pearl River Basin (PRB) in China, examining CH4 dynamics across two distinct hydrologic seasons. Dissolved CH4 concentrations in the PRB varied widely, from 4 to 15126 nM, with higher levels during the wet season (681±1508 nM) compared to the dry season (349±328 nM). At the basin scale, dissolved CH4 was under the co-control of thermogenic source as background input (35%) and biogenic source as the high-concentration source (65%). The Pearl River network is a CH4 source and annually, 25.96±32.64 Gg C of CH4 evades into the atmosphere via diffusion. The total CH4 emissions (diffusion + ebullition) account to more than 50% warming potential of CO2 emission from the PRB. Without considering CH4 consumption by oxidation at the sediment-water interface and river water column, the hyporheic zone contributes 286% and 414% of CH4 emission to the atmosphere in the dry and wet seasons, respectively. The hyporheic zone is a “hotspot” for biogenic CH4 production, but our results underlines that the hyporheic zone may also be a conduit medium for the transportation of groundwater derived CH4 into rivers. Furthermore, dissolved CH4 evades from the hyporheic zone into river channels at greater rates in larger rivers. These findings underscore the critical role of rivers in atmospheric CH4 levels and highlight the need for a deeper understanding of CH4 dynamics in the hyporheic zone. This knowledge is essential to complete the regional and global carbon cycle puzzle and address the urgent environmental challenges posed by greenhouse gases.
... Different fertilization methods can alter the growth status of rice and the abundance of CH 4 -metabolizing microorganisms, thereby affecting CH 4 emissions from rice fields [47]. Previous studies have shown that the application of nitrogen fertilizer and organic manure can promote microbial activity, thereby increasing CH 4 emissions from rice fields [48,49]. Our findings are in line with this, as we observed higher cumulative CH 4 emissions from the CF and CM treatments in both early-season and late-season rice. ...
Paddy fields are the main agricultural source of greenhouse gas methane (CH4) emissions. To enhance rice yield, various fertilization practices have been employed in rice paddies. However, the key microbial and abiotic factors driving CH4 emissions under different fertilization practices in paddy fields remain largely uncharted. This study conducted field experiments in a traditional double-cropping rice area in South China, utilizing five different fertilization practices to investigate the key factors influencing CH4 emissions. High-throughput sequencing and PICRUSt2 functional prediction were employed to investigate the contributions of soil physicochemical properties, CH4-metabolizing microorganisms (methanogens and methanotrophs), and key genes (mcrA and pmoA) on CH4 emissions. The results showed that CH4 emission fluxes exhibited seasonal variations, with consistent patterns of change observed across all treatments for both early- and late-season rice. Compared to the no-fertilization (NF) treatment, cumulative CH4 emissions were lower in early-season rice with green manure (GM) and straw returning (SR) treatments, as well as in late-season rice with GM treatment, while rice yields were maintained at higher levels. High-throughput sequencing analysis revealed that potential methanogens were primarily distributed among four orders: Methanobacteriales, Methanocellales, Methanomicrobiales, and Methanosarcinales. Furthermore, there was a significant positive correlation between the relative abundance of the CH4-related key gene mcrA and these microorganisms. Functional analysis indicated that these potential methanogens primarily produce methane through the acetoclastic and hydrogenotrophic pathways. Aerobic CH4-oxidizing bacteria, predominantly from the genus Methylocystis, were detected in all the treatments, while the CH4 anaerobic-oxidizing archaea ANME-1b was only detected in chemical fertilization (CF) and cow manure (CM) treatments. Our random forest analysis revealed that the relative abundance of two methanogens (Methanocellales and Methanosarcinales) and two environmental factors (pH and DOC) had significant impacts on the cumulative CH4 emissions. The variance decomposition analysis highlighted the CH4-metabolizing microorganisms explained 50% of the variance in the cumulative CH4 emissions, suggesting that they are the key microbial factors driving CH4 emissions. These findings provide guidance for the development of rational measures to reduce CH4 emissions in paddy fields.
... In the context of rapid ongoing climate change, adopting AWD practices offers benefits beyond alleviating water scarcity, including the widely concerned reduction of methane emissions 29 . As rice cultivation in major rice-producing countries (for example, Philippines, Vietnam, Bangladesh, Indonesia) contributes up to 40% of their food-system methane emissions 30 , smart AWD application is particularly appealing. ...
Rice is the staple food for half of the world’s population but also has the largest water footprint among cereal crops. Alternate wetting and drying (AWD) is a promising irrigation strategy to improve paddy rice’s water productivity—defined as the ratio of rice yield to irrigation water use. However, its global adoption has been limited due to concerns about potential yield losses and uncertainties regarding water productivity improvements. Here, using 1,187 paired field observations of rice yield under AWD and continuous flooding to quantify AWD effects (ΔY), we found that variation in ΔY is predominantly explained by the lowest soil water potential during the drying period. We estimate that implementing a soil water potential-based AWD scheme could increase water productivity across 37% of the global irrigated rice area, particularly in India, Bangladesh and central China. These findings highlight the potential of AWD to promote more sustainable rice production systems and provide a pathway toward the sustainable intensification of rice cultivation worldwide.
... Rice agroecosystem is not very efficient in terms of NUE-as only limited portion of total N-input harvested as product, due to losses by NH 3 volatilisation, leaching, surface runoffs and denitrification (Galloway et al. 2008;Li et al. 2018). The NUE of rice is estimated to be around 35% of total N applied and~50% to 70% of which is lost by various means (Zhu and Chen 2002;Coskun et al. 2017;Li et al. 2018) which in turn damages the environment as it majorly contributes to NOx production (Qian et al. 2023;Rajbonshi, Mitra, and Bhattacharyya 2024). ...
Nitric oxide (NO) is one of the byproducts of nitrogen metabolism. Excess amount of NO is scavenged by phytoglobins. The role of phytoglobin mediated NO homoeostasis in modulation of nitrate transporters was investigated using NO scavenger cPTIO, phytoglobin overexpressing rice and Arabidopsis. Growing plants under low nitrate leads to generation of reduced levels of NO accompanied by elevated expression of high affinity transporters (HATs) such as NRT2.1, NRT2.3 and NRT2.4 . Scavenging of NO by cPTIO under optimal nitrate caused enhanced HATs expression. Phytoglobin overexpressing Arabidopsis showed improved growth and enhanced expression of HATs under low nitrogen in comparison to WT. Pretreatment of optimal nitrate grown plants with NO scavenger cPTIO enhanced HATs expression and shifting of these primed plants from optimal to low nitrate leads to further elevation of HATs expression accompanied by enhanced nitrogen uptake and its accumulation with positive effect on growth. Phytoglobin overexpression in rice leads to enhanced HATs expression, improved growth, nitrogen accumulation under low nitrate. Pgb OE lines showed enhanced accumulation of amino acids. Taken together our results suggest an important role of phytoglobins in nitrogen uptake and assimilation.
... Rice serves as the primary staple food globally, sustaining more than half of the world's population and accounting for 11% of global cropland [1][2][3] . However, with the growth of the world population, the global food security situation is still grim, as it suffers from the superimposed impact of extreme climate change 4 , resource degradation 5,6 , yield stagnation 7 , water stress 8,9 , and limited room for cropland expansion 10 . ...
Rice serves as a vital staple food, but its accumulation of cadmium (Cd) has sparked widespread concerns regarding food safety and ecosystem security. Here, we conducted a seven-year systematic field experiment in the Xiangjiang River Basin of China, where an integrated governance framework (IGF) was established to ensure rice safety. The IGF, tailored to geographical zoning and pollution gradation, includes targeted soil treatments, crop management strategies, and stakeholder engagement. The quality of both the soil and the crop was improved, with a reduction in soil Cd availability of 36%, and a decrease in Cd in rice grain of 57-78%. This framework not only addresses multiple challenges but also supports sustainable development goals (SDGs 2, 3, 6, 9) by fostering comprehensive synergies among science, policy, and local community participation. Our findings provide empirical guidance for safe rice production in Cd-contaminated areas and provide solid scientific-driven decision support globally.
... Paddy soils are the largest anthropogenic wetlands on Earth and contribute greatly to global N 2 O emissions (25,26). These soils are rich in DNRA drivers due to the reducing conditions caused by waterlogging during rice cultivation (27). ...
Dissimilatory nitrate reduction to ammonium (DNRA), driven by nitrate-ammonifying bacteria, is an increasingly appreciated nitrogen-cycling pathway in terrestrial ecosystems. This process reportedly generates nitrous oxide (N2O), a strong greenhouse gas with ozone-depleting effects. However, it remains poorly understood how N2O is produced by environmental nitrate-ammonifiers and how to identify DNRA-derived N2O. In this study, we characterize two novel enzymatic pathways responsible for N2O production in Geobacteraceae strains, which are predominant nitrate-ammonifying bacteria in paddy soils. The first pathway involves a membrane-bound nitrate reductase (Nar) and a hybrid cluster protein complex (Hcp–Hcr) that catalyzes the conversion of NO2⁻ to NO and subsequently to N2O. The second pathway is observed in Nar-deficient bacteria, where the nitrite reductase (NrfA) generates NO, which is then reduced to N2O by Hcp–Hcr. These enzyme combinations are prevalent across the domain Bacteria. Moreover, we observe distinctive isotopocule signatures of DNRA-derived N2O from other established N2O production pathways, especially through the highest ¹⁵ N-site preference (SP) values (43.0‰–49.9‰) reported so far, indicating a robust means for N2O source partitioning. Our findings demonstrate two novel N2O production pathways in DNRA that can be isotopically distinguished from other pathways.
IMPORTANCE
Stimulation of DNRA is a promising strategy to improve fertilizer efficiency and reduce N2O emission in agriculture soils. This process converts water-leachable NO3⁻ and NO2⁻ into soil-adsorbable NH4⁺ , thereby alleviating nitrogen loss and N2O emission resulting from denitrification. However, several studies have noted that DNRA can also be a source of N2O, contributing to global warming. This contribution is often masked by other N2O generation processes, leading to a limited understanding of DNRA as an N2O source. Our study reveals two widespread yet overlooked N2O production pathways in Geobacteraceae , the predominant DNRA bacteria in paddy soils, along with their distinctive isotopocule signatures. These findings offer novel insights into the role of the DNRA bacteria in N2O production and underscore the significance of N2O isotopocule signatures in microbial N2O source tracking.
... First, this study calculates the carbon emissions generated by the production and use of three kinds of agricultural materials, including chemical fertilizers, pesticides and plastic films 40 , with corresponding coefficients referring to the studies [41][42][43] . Second, considering the distinction between early, medium, and late rice and the differences in hydrothermal conditions across different provinces, carbon emissions from rice cultivation were calculated, which account for both the cycle and the province [44][45][46] . Third, considering the development of China's livestock industry, calculating the carbon emissions from livestock farming of pigs, sheep, mules, donkeys, horses, cows, and beef cattle, the number of livestock and poultry is combined with the difference between the year-end stock and the feeding cycle to calculate the average annual feeding quantity 47 , with the relevant carbon emission coefficients taken from the IPCC. ...
Digital empowerment is a dynamic process of complementary digital technology and production factors and plays a critical role in achieving the dual carbon objectives of the carbon peak by 2030 and carbon neutrality by 2060. Here, we use the input-output method, employing panel data on environmental and social factors from 30 provincial-level regions in China from 2012 to 2021. We explore the impact of digital empowerment development on agricultural carbon dioxide emissions and underlying mechanisms. We found that the relationship between digital empowerment and carbon dioxide emissions is nonlinear and follows an inverted U-curve. The carbon dioxide emissions increase as digital empowerment increases and decrease when digital empowerment crosses the inflection point of 0.0862. Digital empowerment reduces agricultural carbon emissions by optimizing carbon-intensive factor inputs such as fertilizers and improving factor allocation efficiency. Our research provides evidence for policymakers to enable the promotion of digital empowerment of farmers across Chinese provinces.
... Trying to answer to the first research question (1) Which are the most important aspects that the RE influences in order to promote a sustainable development and environment?, here are the main aspects that the RE influences in order to promote a sustainable development and environment: a) Reduced Greenhouse Gas Emissions: The generation of energy from fossil fuels represents a significant source of greenhouse gas emissions (GGE), contributing very much to climate change (CC). Renewable energy sources, such as solar, wind, hydro, and geothermal power, produce electricity with minimal or zero emissions, helping mitigate the impact of CC (Qian et al. 2023;Gopi et al., 2023). b) Climate Change Mitigation: The use of renewable energy contributes directly to the reduction of carbon dioxide (CO2) and other GGE. ...
Sustainable development (SD) represents a growth approach that tries to maintain a social, economic and environmental balance. SD aims to meet the needs of the present without compromising the needs of future generations. For a sustainable development, a key element is represented by renewable energy (RE). The use of RE on an increasingly large scale brings with it a series of advantages and positively influences aspects such as resource conservation, air and water quality improvement, climate change, greenhouse gas emissions, etc. Realization of RE through different ways such as wind energy, solar power, hydropower, etc. and by combining them, European citizens can take an important step in realizing a more sustainable and renewable energy future. The article presents a data mining analysis on the use of RE in EU countries, taking into account the share of industry use such as heating and cooling, transport and electricity. The results of the analysis aim to identify countries that show a similar behavior from the point of view of the use of RE. Based on them, policies and strategies at the EU level can be founded. Keywords: renewable energy, sustainable development, European Union, data mining
... Over the past two decades, much of the research has focused on identifying agricultural management practices that reduce GHG emissions from rice production while ensuring high yields. In the recent review, Qian et al. 1 , summarized the potential agricultural management strategies to mitigate GHG emissions while ensuring yield sustainability. These are: (i) water management, which includes single and multiple drainage [alternate wetting and drying (AWD)], maintaining soil water potential at -10 to -20 kPa and water table below soil surface (10-25 cm), drainage during high CH 4 emission phase and maintaining non-flooded soil conditions during fallow (non-cropping) period, (ii) organic matter management, which includes the addition of compost and straw in the fallow period and the addition of green manure with low C:N ratio to low soil organic carbon (SOC) soils and the removal or return of straw in the fallow period to high SOC soils, (iii) mineral N management, such as optimal N application rate at which maximum yield is achieved, sub-surface (below 10 cm soil depth) N application, and application of enhanced efficiency N fertilizers or ammonium sulfate, (iv) tillage and crop establishment such as no tillage in rice cropping season if transplanting equipment and technology are available, conventional tillage during the fallow season, and direct seeding if directseeding equipment and technology are available, (v) lime application on acidic (pH < 5.5) soils, and (vi) the selection of rice cultivars based on local high yielding and low GHG emitting cultivars (Table 1). ...
... 메탄이 발생하기에 적합한 혐기성 조건이 갖춰진 벼 재배지는 밀 재배지보다 두 배나 많은 메탄을 배출한다 [4,6]. 담수된 논 토양은 산소 공급을 제한하고 혐기성 조건을 유발하여 토양 유기물의 혐기성 발효를 일으켜 메탄을 대기로 방출한다 [7]. ...
... On the other hand, soybeans, with their nitrogen-fixing ability, do not need external nitrogen fertilizer, thus reducing greenhouse gas emissions [69]. Moreover, the duration of the growth cycle of economic crops influences their greenhouse gas emissions, with crops having longer growth cycles generally emitting higher levels [17]. Maize has a longer growth cycle than soybeans and requires more nutrients and pesticides, leading to increased greenhouse gas emissions [70]. ...
This review paper synthesizes the current understanding of greenhouse gas (GHG) emissions from field cropping systems. It examines the key factors influencing GHG emissions, including crop type, management practices, and soil conditions. The review highlights the variability in GHG emissions across different cropping systems. Conventional tillage systems generally emit higher levels of carbon dioxide (CO2) and nitrous oxide (N2O) than no-till or reduced tillage systems. Crop rotation, cover cropping, and residue management can significantly reduce GHG emissions by improving soil carbon sequestration and reducing nitrogen fertilizer requirements. The paper also discusses the challenges and opportunities for mitigating GHG emissions in field cropping systems. Precision agriculture techniques, such as variable rate application of fertilizers and water, can optimize crop production while minimizing environmental impacts. Agroforestry systems, which integrate trees and crops, offer the potential for carbon sequestration and reducing N2O emissions. This review provides insights into the latest research on GHG emissions from field cropping systems and identifies areas for further study. It emphasizes the importance of adopting sustainable management practices to reduce GHG emissions and enhance the environmental sustainability of agricultural systems.
... By implementing practices such as straw returning and protective tillage, farmers can effectively contribute to carbon sequestration and reduce farmland carbon emissions [75,79]. Additionally, enhancing grain yields through the selection of high-yielding, low-carbon varieties and optimizing planting patterns can increase crop production while mitigating carbon emissions from agricultural activities [80]. As the agricultural industry scale continues to expand in the NCP, the emission reduction pressure on grain production will intensify. ...
The North China Plain (NCP) serves as a critical grain-producing region in China, playing a pivotal role in ensuring the nation’s food security. A comprehensive analysis of the carbon footprint (CF) related to the cultivation of major grain crops within this region and the proposal of strategies to reduce emissions through low-carbon production methods are crucial for advancing sustainable agricultural practices in China. This study employed the lifecycle assessment (LCA) method to estimate the CF of wheat, maize, and rice crops over a period from 2013 to 2022, based on statistical data collected from five key provinces and cities in the NCP: Beijing, Tianjin, Hebei, Shandong, and Henan. Additionally, the Logarithmic Mean Divisia Index (LMDI) model was utilized to analyze the influencing factors. The results indicated that the carbon footprints per unit area (CFA) of maize, wheat, and rice increased between 2013 and 2022. Rice had the highest carbon footprint per unit yield (CFY), averaging 1.1 kg CO2-eq kg−1, with significant fluctuations over time. In contrast, the CFY of wheat and maize remained relatively stable from 2013 to 2022. Fertilizers contributed the most to CF composition, accounting for 48.8%, 48.0%, and 25.9% of the total carbon inputs for wheat, maize, and rice, respectively. The electricity used for irrigation in rice production was 31.8%, which was much higher than that of wheat (6.8%) and maize (7.1%). The LMDI model showed that the labor effect was a common suppressing factor for the carbon emissions of maize, wheat, and rice in the NCP, while the agricultural structure effect and the economic development effect were common driving factors. By improving the efficiency of fertilizer and pesticide utilization, cultivating new varieties, increasing the mechanical operation efficiency, the irrigation efficiency, and policy support, the CF of grain crop production in the NCP can be effectively reduced. These efforts will contribute to the sustainable development of agricultural practices in the NCP and support China’s efforts to achieve its “double carbon” target.
... Atmospheric temperature and seasonal flooding conditions are known to influence the composition of CH 4 -cycling microbial communities in soil. However, the nature and extent of these influences may be driven by an intricate interplay of environmental factors [30,69,72]. Several studies have investigated the role of CH 4 -related microbial communities in Amazonian floodplains and upland soils [2,5,25,57,82]. ...
Seasonal floodplains in the Amazon basin are important sources of methane (CH 4), while upland forests are known for their sink capacity. Climate change effects, including shifts in rainfall patterns and rising temperatures, may alter the functionality of soil microbial communities, leading to uncertain changes in CH 4 cycling dynamics. To investigate the microbial feedback under climate change scenarios, we performed a microcosm experiment using soils from two floodplains (i.e., Amazonas and Tapajós rivers) and one upland forest. We employed a two-factorial experimental design comprising flooding (with non-flooded control) and temperature (at 27 °C and 30 °C, representing a 3 °C increase) as variables. We assessed prokaryotic community dynamics over 30 days using 16S rRNA gene sequencing and qPCR. These data were integrated with chemical properties, CH 4 fluxes, and isotopic values and signatures. In the floodplains, temperature changes did not significantly affect the overall microbial composition and CH 4 fluxes. CH 4 emissions and uptake in response to flooding and non-flooding conditions, respectively, were observed in the floodplain soils. By contrast, in the upland forest, the higher temperature caused a sink-to-source shift under flooding conditions and reduced CH 4 sink capability under dry conditions. The upland soil microbial communities also changed in response to increased temperature, with a higher percentage of specialist microbes observed. Floodplains showed higher total and relative abundances of methanogenic and methanotrophic microbes compared to forest soils. Isotopic data from some flooded samples from the Amazonas river floodplain indicated CH 4 oxidation metabolism. This floodplain also showed a high relative abundance of aerobic and anaerobic CH 4 oxidizing Bacteria and Archaea. Taken together, our data indicate that CH 4 cycle dynamics and microbial communities in Amazonian floodplain and upland forest soils may respond differently to climate change effects. We also highlight the potential role of CH 4 oxidation pathways in mitigating CH 4 emissions in Amazonian floodplains.
... CO 2 , CH 4 and N 2 O) emissions generated by microorganisms, thereby exacerbating climate change . Given that croplands are significant contributors to greenhouse gas emissions (Davidson, 2009;Qian et al., 2023), it is crucial to assess the influence of soil moisture on virus-bacteria interactions and their potential effects on soil nutrient cycling in agroecosystems (Bonetti et al., 2021;Braga et al., 2020;Du Toit, 2023;Tong et al., 2023;Wei et al., 2021;Wu Wan, et al., 2022;Wu, Zhang, et al., 2022). In addition, future investigations should consider employing more advanced analytical methods to obtain more specific information on virusbacteria collaboration. ...
Genomic evidence suggests that lysogenic viruses significantly influence the evolution of their host communities and soil microbial ecology and functional-ity. However, the response of soil viral reproductive strategies (VRS) to environmental factors, in particular soil water stress, remains poorly understood. We investigated this by employing a laboratory microcosm incubation system with different soil moisture levels (30%, 60% and 90% field capacity). Our study focused on soil biochemical properties, bacterial and viral populations, lyso-genic fractions and virus/bacteria ratio (VBR). The results showed that soil moisture significantly affected bacterial and viral counts, lysogenic fractions and VBR (p < 0.01), with bacterial counts increasing and viral counts decreasing with increasing soil moisture. The lysogenic fraction peaked at low moisture , suggesting a shift in viral strategy under hydration stress, which may affect virus-bacteria interactions and nutrient dynamics, enhancing host adaptability. Analyses using correlation, random forest and structural equation modelling identified soil moisture as the dominant factor shaping VRS by altering nutrient availability and host population. These findings provide a new insight into microbial regulation of feedback to environmental change from the life history strategies of soil viruses.
Nitrogen fertilizer plays a vital role in rice cultivation, yet its excessive application significantly intensifies methane emissions from rice paddies. Therefore, the urgent adoption of effective agronomic interventions is crucial to mitigate methane emissions resulting from nitrogen fertilizer application.
Rice cultivation constitutes a significant anthropogenic methane (CH4) source and a crucial target for CH4 mitigation. However, global and regional emissions remain poorly constrained. In this study, we validated a global-process-based methane model for rice paddies (CH4MOD), analyzed the sensitivity of major emission drivers, and simulated management scenarios involving four water regimes and three organic matter amendments. CH4MOD simulations achieved a correlation coefficient of 0.76 across 986 CH4 flux observations globally, demonstrating its capability under different environmental conditions and management practices. The sensitivity analysis revealed water regime as the primary driver, followed by organic matter amendment and temperature. Under different crop management, CH4 emissions varied significantly from 8 to 78 Tg CH4/yr. This wide range of emissions demonstrates the need to use and improve rice-specific emission models and spatiotemporal data on rice distribution, water, and residue management for accurately assessing local to global emissions and their climate mitigation potential.
The homogeneous and heterogeneous catalyst systems applied in N -formylation reaction of amines and CO 2 reaction from both homogeneous and heterogeneous systems are summarized.
Rice paddies contribute substantially to atmospheric methane (CH 4 ) and these emissions are expected to increase as the need to feed the human population grows. Here, we show that two independent rice genotypes overexpressing genes for PLANT PEPTIDES CONTAINING SULFATED TYROSINE ( PSY ) reduced cumulative CH 4 emissions by 38% (PSY1) and 58% (PSY2) over the growth period compared with controls. Genome-resolved metatranscriptomic data from rhizosphere soils reveal lower ratios of gene activities for CH 4 production versus consumption, decrease in activity of H 2 -producing genes, and increase in bacterial H 2 oxidation pathways in the PSY genotypes. Metabolic modeling using metagenomic and metabolomic data predicts elevated levels of H 2 oxidation and suppressed H 2 production in the PSY rhizosphere. The H 2 -oxidizing bacteria have more genes for utilization of gluconeogenic acids than H 2 -producing counterparts, and their activities were likely stimulated by the observed enrichment of gluconeogenic acids (mostly amino acids) in PSY root exudates. Together these results suggest that decreased CH 4 emission is due to the reduction of H 2 available for hydrogenotrophic methanogenesis. The combination of rice phenotypic characterization, microbiome multi-omic analysis, and metabolic modeling described here provides a powerful strategy to discover the mechanisms by which specific plant genotypes can alter biogeochemical cycles to reduce CH 4 emissions.
Agriculture (e.g., rice paddies) emissions have been considered one of the main sources contributing to the revived atmospheric methane (CH4) increase since 2007 while it remains debated. In this study, we synthesized available paddy field CH4 emissions from publications in a representative region of China. The results showed that CH4 emissions exhibited strong variation among the 416 samples. Compared to the period 2000–2009, CH4 emissions significantly (p < 0.01) increased during 2010–2018 and the average (252.17 kg ha-1) was 1.52 times higher than that in 2000–2009 (146.02 kg ha-1), which was consistent with the trend of atmospheric CH4 concentrations. CH4 emissions were significantly affected by both air temperature and water saving practices, however, this was not likely the reason for the increase after 2009. This study provides a quantitative estimate of regional CH4 emissions based on available data, although the connection with the revived atmospheric CH4 increase since 2007 remains uncertain.
Introduction
More than half of the world’s population consumes rice as their primary food. The majority of rice production is concentrated in Asia, with the top 10 rice-growing countries accounting for 84% of the world’s total rice cultivation. However, rice production is also strongly linked to environmental changes. Among all the global sources of greenhouse gas (GHG) emissions, paddy cultivation stands out as a significant contributor to global methane (CH4) and nitrous oxide (N2O) emissions. This contribution is expected to increase further with the projected increase of 28% in global rice output by 2050. Hence, modifications to rice management practices are necessary both to increase yield and mitigate GHG emissions.
Methods
We investigated the effect of seedling treatment, soil application, and foliar application of a methane-derived microbial biostimulant on grain yield and GHG emissions from rice fields over three seasons under 100% fertilizer conditions. Further, microbial biostimulant was also tested under 75% nitrogen (N) levels to demonstrate its effect on grain yield. To understand the mechanism of action of microbial biostimulant on crop physiology and yield, a series of physiological, transcript, and metabolite analyses were also performed.
Results
Our three-season open-field studies demonstrated a significant enhancement of grain yield, up to 39%, with a simultaneous reduction in CH4 (31%–60%) and N2O (34%–50%) emissions with the use of methane-derived microbial biostimulant. Under 75% N levels, a 34% increase in grain yield was observed with microbial biostimulant application. Based on the physiological, transcript, and metabolite analyses data, we were further able to outline the potential mechanisms for the diverse synergistic effects of methane-derived microbial biostimulant on paddy, including indole-3-acetic acid production, modulation of photosynthesis, tillering, and panicle development, ultimately translating to superior yield.
Conclusion
The reduction in GHG emission and enhanced yield observed under both recommended and reduced N conditions demonstrated that the methane-derived biostimulant can play a unique and necessary role in the paddy ecosystem. The consistent improvements seen across different field trials established that the methane-derived microbial biostimulant could be a scalable solution to intensify rice productivity with a lower GHG footprint, thus creating a win–win–win solution for farmers, customers, and the environment.
Soil organic carbon (SOC) plays a vital role in the global carbon cycle and is a potential sink for carbon dioxide. Agricultural management practices can support carbon sequestration and, therefore, offer potential removal strategies whilst also improving overall soil quality. Meta-analysis allows one to summarize results from primary articles by calculating an overall effect size and to reveal the source of variation across studies. The number of meta-analyses published in the field of agriculture is continuously rising. At the same time, more and more articles refer to their synthesis work as a meta-analysis, despite applying less than rigorous methodologies. As a result, poor-quality meta-analyses are published and may lead to questionable conclusions and recommendations to scientists, policymakers, and farmers.
This study aims at quantitatively analyzing 31 meta-analyses, published between the years of 2005 and 2020, studying the effects of different management practices on SOC. We compiled a set of quality criteria suitable for soil and agricultural sciences by adapting existing meta-analytical guidelines from other disciplines. The set is supported by a scoring scheme that allows for a quantitative analysis. The retrieved meta-analyses were structured according to 11 management categories, such as tillage, cover crops, crop residue management, and biochar application, which allowed us to assess the state of knowledge on these categories. Major deficiencies were found in the use of standard metrics for effect size calculation, independence of effect sizes, standard deviation extraction for each study, and study weighting by the inverse of variance. Only 1 out of 31 SOC meta-analyses, which studied the effects of no tillage/reduced tillage compared with conventional tillage, was found to be of high quality. Therefore, improved meta-analyses on the effects of organic agriculture, biochar, fertilization, or crop diversification on SOC are urgently needed.
We conclude that, despite efforts over the last 15 years, the quality of meta-analyses on SOC research is still low. Thus, in order for the scientific community to provide high-quality synthesis work and to make advancements in the sustainable management of agricultural soils, we need to adapt rigorous methodologies of meta-analysis as quickly as possible.
Agricultural food production is a main driver of global greenhouse gas emissions, with unclear pathways towards carbon neutrality. Here, through a comprehensive life-cycle assessment using data from China, we show that an integrated biomass pyrolysis and electricity generation system coupled with commonly applied methane and nitrogen mitigation measures can help reduce staple crops’ life-cycle greenhouse gas emissions from the current 666.5 to −37.9 Tg CO2-equivalent yr⁻¹. Emission reductions would be achieved primarily through carbon sequestration from biochar application to the soil, and fossil fuel displacement by bio-energy produced from pyrolysis. We estimate that this integrated system can increase crop yield by 8.3%, decrease reactive nitrogen losses by 25.5%, lower air pollutant emissions by 125–2,483 Gg yr⁻¹ and enhance net environmental and economic benefits by 36.2%. These results indicate that integrated biochar solutions could contribute to China’s 2060 carbon neutrality objective while enhancing food security and environmental sustainability.
Nitrous oxide (N 2 O) emissions from agricultural soils are the main source of atmospheric N 2 O, a potent greenhouse gas, and key ozone-depleting substance. Several agricultural practices with potential to mitigate N 2 O emissions have been tested worldwide. However, to guide policymaking for reducing N 2 O emissions from agricultural soils, it is necessary to better understand the overall performance and variability of mitigation practices and identify those requiring further investigation. We performed a systematic review and a second-order meta-analysis to assess the abatement efficiency of N 2 O mitigation practices from agricultural soils. We used 27 meta-analyses including 41 effect sizes based on 1119 primary studies. Technology-driven solutions (e.g., enhanced-efficiency fertilizers, drip irrigation, and biochar) and optimization of fertilizer rate have considerable mitigation potential. Agroecological mitigation practices (e.g., organic fertilizer and reduced tillage), while potentially contributing to soil quality and carbon storage, may enhance N 2 O emissions and only lead to reductions under certain pedoclimatic and farming conditions. Other mitigation practices (e.g., lime amendment or crop residue removal) led to marginal N2O decreases. Despite the variable mitigation potential, evidencing the context-dependency of N 2 O reductions and tradeoffs, several mitigation practices may maintain or increase crop production, representing relevant alternatives for policymaking to reduce greenhouse gas emissions and safeguard food security.
Cascade rice flood distribution (CASC), the predominate method used for rice irrigation in the lower Mississippi River basin (LMRB), is inherently water intensive owing to the need to overfill rice paddies to move irrigation water from one paddy to the next. The objectives of this research were to devise practices that make CASC more water efficient, assessing how early cascade rice irrigation shutoff (ECIS) impacts applied irrigation, run-off, and flood depth under LMRB rainfall conditions. This research used a conservation-of-mass model to show that using flood depth in the penultimate rice paddy to trigger irrigation shutoff in a 16-ha simulated rice field results in nominal irrigation water savings of 23% relative to CASC. This savings was reduced to 15% when supplemental irrigation was added to the last paddy at two critical stages of rice production. Field run-off estimates for ECIS were reduced by up to 78% relative to a CASC for both clay and silt loam soils, demonstrating how with ECIS the last paddy of a rice field acts as a ‘catch basin’ for excess up-field irrigation and uncaptured rainfall. Flood depth estimates for the last paddy resulting from ECIS resembled those of alternate wetting and drying flood management (AWD), suggesting that the agronomics developed for AWD could be used to help address production issues arising in the catch basin from ECIS. Success in coupling ECIS with irrigation automation technologies could reduce aquifer withdrawals across the rice producing areas of the LMRB.
Extreme temperatures are predicted to become increasingly common due to climate change, threatening the sustainability and profitability of global rice production. Manure amendment is a common agricultural practice to improve soil fertility and increase crop yields, but whether this practice modulates the effect of extreme temperatures on crop yield is unclear. Here we show through a series of experiments and meta-analysis that long-term manure amendment reduces losses of rice yield due to extreme temperatures. We propose that by increasing soil fertility, manure amendment increased net photosynthetic rate and plant physiological resistance to extreme temperatures. Without considering the impact of other global change factors, we estimate that manure amendment could potentially reduce global losses of rice yield due to extreme temperatures from 33.6 to 25.1%. Thus, our findings indicate that manure amendment may play a key role in improving food security in a changing climate. Heat resilience and tolerance of rice crops is enhanced by manure amendment and could improve yield stability under projected climate change, suggest a meta-analysis and long term manure amendment experiments.
Inhibitors are widely considered an efficient tool for reducing nitrogen (N) loss and improving N use efficiency, but their effectiveness is highly variable across agroecosystems. In this study, we synthesized 182 studies (222 sites) worldwide to evaluate the impacts of inhibitors (urease inhibitors [UI], nitrification inhibitors [NI] and combined inhibitors) on crop yields and gaseous N loss (ammonia [NH3 ] and nitrous oxide [N2 O] emissions) and explored their responses to different management and environmental factors including inhibitor application timing, fertilization regime, cropping system, water management, soil properties and climatic conditions using subgroup meta-analysis, meta-regression and multivariate analyses. The UI were most effective in enhancing crop yields (by 5%) and reducing NH3 volatilization (by 51%), whereas NI were most effective at reducing N2 O emissions (by 49%). The application of UI mitigates NH3 loss and increases crop yields especially in high NH3 -N loss scenarios, whereas NI application would minimize the net N2 O emissions and the resultant environmental impacts especially in low NH3 -N loss scenarios. Alternatively, the combined application of UI and NI enables producers to balance crop production and environmental conservation goals without pollution tradeoffs. The inhibitor efficacy for decreasing gaseous N loss was dependent upon soil and climatic conditions and management practices. Notably, both meta-regression and multivariate analyses suggest that inhibitors provide a greater opportunity for reducing fertilizer N inputs in high-N-surplus systems and presumably favor crop yield enhancement under soil N deficiency situations. The pursuit of an improved understanding of the interactions between plant-soil-climate-management systems and different types of inhibitors should continue to optimize the effectiveness of inhibitors for reducing environmental losses while increasing productivity.
Aims
To assess 1) the effect of the combination of flooding (winter flooding vs. non-winter flooding; WFL vs NWF) and timing of straw incorporation (early vs late straw incorporation; ESI vs LSI) in the post-harvest of paddy agrosystem, on a year-round global balance of greenhouse gases (GHG) exchanges, i.e. methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O); 2) the impact on the net ecosystem carbon balance (NECB) and 3) the resulting net global warming potential (GWP).
Methods
A field experiment was conducted with fortnightly samplings of main GHG emissions. Effect of the studied factors on GHG emissions was seasonally assessed. The net GWP is estimated from the balance between GHG (CH4 and N2O) and NECB.
Results
NWF-LSI reduced net GWP by 206% compared to conventional post-harvest management (WFL-ESI). NECB was similar in all treatments. Avoiding winter flooding reduced CH4 emissions significantly in the post-harvest and next growing seasons, while delay straw incorporation prevented CH4 and CO2 emissions during post-harvest. None of the treatments increased N2O emission. Environmental implications of post-harvest management options are discussed.
Conclusions
Post-harvest management affects net GWP of the paddy rice cultivation by modifying GHG emissions in post-harvest and next growing season without compromise sequestration C budget. The combination of non-winter flooding and late straw incorporation strategies were more effective in reducing both CH4 and CO2 emissions, due to avoiding higher temperatures at the time of the straw incorporation during post-harvest and increasing soil Eh conditions at the following growing season.
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.
Future rice systems must produce more grain while minimizing the negative environmental impacts. A key question is how to orient agricultural research & development (R&D) programs at national to global scales to maximize the return on investment. Here we assess yield gap and resource-use efficiency (including water, pesticides, nitrogen, labor, energy, and associated global warming potential) across 32 rice cropping systems covering half of global rice harvested area. We show that achieving high yields and high resource-use efficiencies are not conflicting goals. Most cropping systems have room for increasing yield, resource-use efficiency, or both. In aggregate, current total rice production could be increased by 32%, and excess nitrogen almost eliminated, by focusing on a relatively small number of cropping systems with either large yield gaps or poor resource-use efficiencies. This study provides essential strategic insight on yield gap and resource-use efficiency for prioritizing national and global agricultural R&D investments to ensure adequate rice supply while minimizing negative environmental impact in coming decades.
The inevitable rise of atmospheric CO2 concentration plays an important role in regulating the carbon (C) and nitrogen (N) cycling in the rice-cropping system. Elucidating the effects of elevated CO2 concentration (ECO2) on CH4 and N2O emissions from paddy fields is essential for evaluating agricultural production in response to global climate change. In this study, we conducted a global meta-analysis to assess the overall effect of ECO2 on CH4 and N2O emissions from paddy fields, aiming at providing a guideline for sustainable C and N management in paddy fields under future climate conditions. The results showed that, overall, ECO2 significantly increased CH4 emissions from rice fields by 23% (P<0.05), but reduced N2O emissions by 22% (P<0.05). With a long duration (>10 yr) of ECO2, ECO2 significantly reduced CH4 and N2O emissions from paddy fields by 27% and 53%, respectively (P<0.05). Along with the increasing levels of ECO2, the stimulating effect of ECO2 on CH4 emissions showed a trend of “weakening firstly and then strengthening”, while its effect on N2O emissions changed from stimulation to inhibition. Agronomy managements (e.g., N application rates, straw incorporations, water regimes, and rice cultivars) affected the effects of ECO2 on CH4 and N2O emissions from paddy fields. With no or half amount of straw incorporation, ECO2 increased CH4 emissions by 27% or 49% (P<0.05) from paddy fields, respectively, while non-significant effects on CH4 emissions from paddy fields were observed under full straw incorporation. With the increasing amount of straw incorporation, the reductions in N2O emissions from paddy fields were enhanced by ECO2. Compared with a continuous flooding regime, intermittent irrigation weakened the promoted effect on CH4 emissions but stimulated the inhibited effect on N2O emissions from paddy fields under ECO2. Therefore, under the future condition of ECO2, it is recommended to adopt the appropriate agricultural management measures, such as combining straw incorporation and intermittent irrigation, and optimizing N application and using rice cultivars of high-yield with lower emissions. In addition, it is necessary to conduct comprehensive studies at multi-scale, with multi-factor, and by multi-method to effectively reduce the uncertainty of quantifying the response of CH4 and N2O emissions from paddy fields to future ECO2.
Potential climate-related impacts on future crop yield are a major societal concern. Previous projections of the Agricultural Model Intercomparison and Improvement Project’s Global Gridded Crop Model Intercomparison based on the Coupled Model Intercomparison Project Phase 5 identified substantial climate impacts on all major crops, but associated uncertainties were substantial. Here we report new twenty-first-century projections using ensembles of latest-generation crop and climate models. Results suggest markedly more pessimistic yield responses for maize, soybean and rice compared to the original ensemble. Mean end-of-century maize productivity is shifted from +5% to −6% (SSP126) and from +1% to −24% (SSP585)—explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9% shifted to +18%, SSP585), linked to higher CO2 concentrations and expanded high-latitude gains. The ‘emergence’ of climate impacts consistently occurs earlier in the new projections—before 2040 for several main producing regions. While future yield estimates remain uncertain, these results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated. Climate change affects agricultural productivity. New systematic global agricultural yield projections of the major crops were conducted using ensembles of the latest generation of crop and climate models. Substantial shifts in global crop productivity due to climate change will occur within the next 20 years—several decades sooner than previous projections—highlighting the need for targeted food system adaptation and risk management in the coming decades.
The amount of soil organic matter (SOM) is considered a key indicator of soil properties associated with higher fertility. Despite the ubiquity of assumptions surrounding SOM's contributions to soil functioning, we lack quantitative relationships between SOM and yield outcomes on working farms. We quantified the relationship between SOM and yields of corn (Zea mays L.) and silage for a dataset of 170 fields arrayed across 49 farms in a network of growers based in Wisconsin and Minnesota, USA. As SOM concentrations increase so do yields, though gains start to level off around 4% SOM. When examining the relationship between yield and soil health indicators representative of biologically active C pools, we found that mineralizable C has a stronger relationship with yield than permanganate oxidizable C. Mineral fertilizer, manure, and SOM had relationships of similar magnitude with yield, highlighting that SOM in combination with exogenous inputs likely plays an important role in driving agricultural productivity in this region. An interaction between SOM and crop rotation indicated that the impact of SOM on crop yields varied depending on rotation (continuous corn vs. corn in rotation). That is, continuous corn had lower yields than corn in rotation despite higher SOM concentrations. Our findings provide insight into the relationship between indicators of soil health, farm management, and crop yields for a set of working farms and lend support to the goals of soil health initiatives that rest on building SOM in agricultural soils to improve agricultural outcomes.
Mitigating soil nitrous oxide (N2O) emissions is essential for staying below a 2 °C warming threshold. However, accurate assessments of mitigation potential are limited by uncertainty and variability in direct emission factors (EFs). To assess where and why EFs differ, we created high-resolution maps of crop-specific EFs based on 1,507 georeferenced field observations. Here, using a data-driven approach, we show that EFs vary by two orders of magnitude over space. At global and regional scales, such variation is primarily driven by climatic and edaphic factors rather than the well-recognized management practices. Combining spatially explicit EFs with N surplus information, we conclude that global mitigation potential without compromising crop production is 30% (95% confidence interval, 17–53%) of direct soil emissions of N2O, equivalent to the entire direct soil emissions of China and the United States combined. Two-thirds (65%) of the mitigation potential could be achieved on one-fifth of the global harvested area, mainly located in humid subtropical climates and across gleysols and acrisols. These findings highlight the value of a targeted policy approach on global hotspots that could deliver large N2O mitigation as well as environmental and food co-benefits.
Rice paddies account for ~9% or the world’s cropland area and are characterized by environmental conditions promoting soil organic carbon storage, methane emissions and to a lesser extent nitrous oxide emissions. Here, we synthesize data from 612 sites across 51 countries to estimate global carbon stocks in paddy soils and determine the main factors affecting paddy soil carbon storage. Paddy soils (0–100 cm) contain 18 Pg carbon worldwide. Paddy soil carbon stocks decrease with increasing mean annual temperature and soil pH, whereas mean annual precipitation and clay content had minor impacts. Meta-analysis shows that paddy soil carbon stocks can be increased through several management practices. However, greenhouse gas mitigation through paddy soil carbon storage is generally outweighed by increases in methane and nitrous oxide emissions. Our results emphasize the key role of paddies in the global carbon cycle, and the importance of paddy management in minimizing anthropogenic greenhouse gas emissions.
Background and aimsIn China and several other rice growing countries, lime application is a common practice to alleviate soil acidification in rice paddies. Liming may also reduce the concentration of the common toxin Cadmium (Cd) in rice plants. We evaluated to what extent lime application affects rice yield and grain Cd concentration.Methods
We conducted a meta-analysis to quantify the effect of liming on rice yield and grain Cd concentration, synthesizing data from 35 studies.ResultsAveraged across our dataset, lime application significantly increased rice yield (+ 12.9%) and soil pH (+ 0.85 units), and reduced grain Cd concentrations (-48%). Overall, grain Cd uptake and soil available Cd were reduced by 48% and 44% under liming, respectively. Liming increased rice yield more strongly 1) in soils with initial pH < 4.5 than in soils with pH ≥ 4.5, and 2) at lime rates ≥ 3.0 t ha−1 than at lime rates < 3.0 t ha−1. Liming-induced reductions in grain Cd concentration, grain Cd uptake and soil available Cd all increased with lime application rates. Lime application rates exceeding 1.0 and 6.0 t ha−1 reduced average grain Cd concentrations to meet food safety standards set by the FAO/WHO and China, respectively.Conclusions
Lime application is effective in both enhancing grain yield and reducing grain Cd concentrations in acidic rice paddies.
Irrigated transplanted flooded rice is a major source of methane (CH 4) emission. We carried out experiments for 2 years in irrigated flooded rice to study if interventions like methane-utilizing bacteria, Blue-green algae (BGA), and Azolla could mitigate the emission of CH 4 and nitrous oxide (N 2 O) and lower the yield-scaled global warming potential (GWP). The experiment included nine treatments: T 1 (120 kg N ha −1 urea), T 2 (90 kg N ha −1 urea + 30 kg N ha −1 fresh Azolla), T 3 (90 kg N ha −1 urea + 30 kg N ha −1 Blue-green algae (BGA), T 4 (60 kg N ha −1 urea + 30 kg N ha −1 BGA + 30 kg N ha −1 Azolla, T 5 (120 kg N ha −1 urea + Hyphomicrobium facile MaAL69), T 6 (120 kg N ha −1 by urea + Burkholderia vietnamiensis AAAr40), T 7 (120 kg N ha −1 by urea + Methylobacteruim oryzae MNL7), T 8 (120 kg N ha −1 urea + combination of Burkholderia AAAr40, Hyphomicrobium facile MaAL69, Methylobacteruim oryzae MNL7), and T 9 (no N fertilizer). Maximum decrease in cumulative CH 4 emission was observed with the application of Methylobacteruim oryzae MNL7 in T 7 (19.9%), followed by Azolla + BGA in T 4 (13.2%) as compared to T 1 control. N 2 O emissions were not significantly affected by the application of CH 4-oxidizing bacteria. However, significantly lower (P<0.01) cumulative N 2 O emissions was observed in T 4 (40.7%) among the fertilized treatments. Highest yields were observed in Azolla treatment T 2 with 25% less urea N application. The reduction in yield-scaled GWP was at par in T 4 (Azolla and BGA) and T 7 (Methylobacteruim oryzae MNL7) treatments and reduced by 27.4% and 15.2% in T 4 and T 7 , respectively, as compared to the T 1 (control). K-means clustering analysis showed that the application of Methylobacteruim oryzae MNL7, Azolla, and Azolla + BGA can be an effective mitigation option to reduce the global warming potential while increasing the yield.
Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO2) emitted by human activities each year¹, yet the persistence of this carbon sink depends partly on how plant biomass and soil organic carbon (SOC) stocks respond to future increases in atmospheric CO2 (refs. 2,3). Although plant biomass often increases in elevated CO2 (eCO2) experiments4,5,6, SOC has been observed to increase, remain unchanged or even decline⁷. The mechanisms that drive this variation across experiments remain poorly understood, creating uncertainty in climate projections8,9. Here we synthesized data from 108 eCO2 experiments and found that the effect of eCO2 on SOC stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO2, SOC storage declines; conversely, when biomass is weakly stimulated, SOC storage increases. This trade-off appears to be related to plant nutrient acquisition, in which plants increase their biomass by mining the soil for nutrients, which decreases SOC storage. We found that, overall, SOC stocks increase with eCO2 in grasslands (8 ± 2 per cent) but not in forests (0 ± 2 per cent), even though plant biomass in grasslands increase less (9 ± 3 per cent) than in forests (23 ± 2 per cent). Ecosystem models do not reproduce this trade-off, which implies that projections of SOC may need to be revised.
Improved irrigation management is identified as a potential mitigation option for methane (CH4) emissions from rice (Oryza sativa). Furrow-irrigated rice (FR), an alternative method to grow rice, is increasingly adopted in the Mid-South U.S. However, FR may provide a potential risk to yield performance and higher emissions of nitrous oxide (N2O). This study quantified the grain yields, CH4 and N2O emissions from three different water management practices in rice: multiple-inlet rice irrigation (MIRI), FR, and FR with cereal rye (Secale cereale) and barley (Hordeum vulgare) as preceding winter cover crops (FRCC). CH4 and N2O fluxes were measured from May to September 2019 using a static chamber technique. Grain yield from FR (11.8 Mg ha−1) and MIRI (12.0 Mg ha−1) was similar, and significantly higher than FRCC (8.5 Mg ha−1). FR and FRCC drastically reduced CH4 emissions compared to MIRI. Total seasonal CH4 emissions decreased in the order of 44 > 11 > 3 kg CH4-C ha−1 from MIRI, FR, and FRCC, respectively. Cumulative seasonal N2O emissions were low from MIRI (0.1 kg N2O-N ha−1) but significantly higher from FR (4.4 kg N2O-N ha−1) and FRCC (3.0 kg N2O-N ha−1). However, there was no net difference in global warming potential among FR, FRCC and MIRI. These results suggest that the increased N2O flux from furrow-irrigated rice may not greatly detract from the potential benefits that furrow-irrigation offers rice producers.
The Working Group I contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the physical science basis of climate change. It considers in situ and remote observations; paleoclimate information; understanding of climate drivers and physical, chemical, and biological processes and feedbacks; global and regional climate modelling; advances in methods of analyses; and insights from climate services. It assesses the current state of the climate; human influence on climate in all regions; future climate change including sea level rise; global warming effects including extremes; climate information for risk assessment and regional adaptation; limiting climate change by reaching net zero carbon dioxide emissions and reducing other greenhouse gas emissions; and benefits for air quality. The report serves policymakers, decision makers, stakeholders, and all interested parties with the latest policy-relevant information on climate change. Available as Open Access on Cambridge Core.
The subsurface application (SA) of nitrogenous fertilizers is a potential solution to mitigate climate change and improve food security. However, the impacts of SA technology on greenhouse gas (GHG) emissions and agronomic yield are usually evaluated separately and their results are inconsistent. To address this gap, we conducted a meta-analysis synthesizing 40 peer-reviewed studies on the effects of SA technology on GHG and ammonia (NH3) emissions, nitrogen uptake (NU), crop yield, and soil residual NO3-N in rice paddies and upland cropping system. Compared to the surface application of N, SA technology significantly increased rice yields by 32 % and crop yield in upland systems by 62 %. The largest SA-induced increases in crop yield were found at low N input rates (<100 kg Nha-1) in rice paddies and medium N input rates (100-200 kg Nha-1) in upland systems, suggesting that soil moisture is a key factor determining the efficiency of SA technology. SA treatments increased yields by more at reduced fertilizer rates (~30 % less N), a shallow depth (<10 cm), and with urea in both cropping systems than at the full (recommended) N rate, a deeper depth (10-20 cm), and with ammonical fertilizer. SA treatments significantly increased NU in rice paddies (34 %) and upland systems (18 %), and NO3-N (40 %) in paddyland; however, NO3-N decreased (28 %) in upland conditions. Ammonia mitigation was greater in paddyland than in upland conditions. SA technology decreased the carbon footprint (CF) in paddyland by 29 % and upland systems by 36 %, and overall by 33 %. Compared with broadcasting, SA significantly reduced CH4 emissions by 16 %, N2O emissions by 30 %, and global warming potential (GWP) by 10 % in paddy cultivation. Given SA increased grain yield and NU while reducing NH3, CF, and GWP, this practice provides dual benefits - mitigating climate change and ensuring food security.
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 yr-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 yr-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.
Energy equivalent yield Energy use efficiency Net ecosystem economic benefit Resource use efficiency A B S T R A C T Resource scarcity, large environmental footprint and low economic profits are great challenges faced by global crop production. Development of feasible cropping systems that can coordinate productivity and sustainability is critical for addressing these challenges. Here, field experiments were conducted from 2017 to 2020 to compare the energy equivalent yield, energy use efficiency, labor and water productivity, carbon footprint, and net ecosystem economic benefits of the six rice-based crop rotation systems in central China, including rice-wheat (RW), rice-rapeseed (RRs), double-season rice (DR), ratoon rice (RR), maize-rice (MR), and rice-fallow systems (RF). The results demonstrated that MR had the highest energy equivalent yield of 20.3 Mg ha − 1 among all the tested rotation systems, which was significantly increased by 28.0%, 32.8%, 18.9%, 26.9%, and 99.5% compared with that of RW, RRs, DR, RR, and RF, respectively. MR and RR achieved higher energy use efficiency than RW, RRs and DR due to their higher total energy output and lower total energy input, respectively. Meanwhile, MR and RR also exhibited the highest water and labor productivity among these rotation systems, respectively. Furthermore, their carbon footprint per area and per energy output were comparable to those of RW and RRs, but significantly lower than those of DR. Overall, MR and RR increased the net ecosystem economic benefits by 12.6-76.8% and 25.1-188.3% relative to other four traditional systems (RRs, RW, DR and RF), respectively. These results suggest that MR and RR are the recommended feasible rice-based crop rotation systems to coordinate high productivity, resource use efficiency, and economic benefit with lower carbon footprint in central China.
Acidic soils cover about 30% of the world’s land. Liming is a management practice applied worldwide to reduce the negative effects of acidification on soil fertility and plant growth. Liming also affects the biotic and abiotic soil properties controlling the production and consumption of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Although our understanding of how liming regulates net GHG emissions is increasing, the impact of liming on soil biological drivers of GHG emissions has not been quantitatively synthesized. Here we conducted a global meta-analysis using 1474 paired observations from 124 studies to explore the responses of GHG emissions to liming, with a focus on soil biological factors. We show that the N2O mitigation capacity of liming could be linked to (i) increases in bacterial abundance of N2O reductase genes (NosZ) and decreases in fungi:bacteria ratio, both contributing to a lower N2O:N2 product ratio of denitrification; and (ii) reductions in soil mineral nitrogen (N) via stimulation of plant N uptake. The limited evidence available indicates that liming reduced CH4 emissions and the abundance of methanogens, but it had no effect on CH4 uptake and abundance of methanotrophs. Liming-induced increases in soil CO2 emissions can be explained by higher heterotrophic and/or autotrophic respiration. The strong coupling between liming effects on GHG emissions and on soil microbial communities involved in GHG production and consumption can be used to identify strategies to reduce GHGs in response to liming, and to improve process-based models for better predictions of soil GHG emissions.
Rice cultivation is a major source of methane (CH4) emissions. Intermittent irrigation systems in rice cultivation, such as the mid-season drainage (MSD), are effective strategies to mitigate CH4 emissions during the growing season, though the reduction rates are variable and dependent on the crop context. Aeration periods induce alteration of soil CH4 dynamics that can be prolonged after flooding recovery. However, whether these changes persist beyond the growing season remains underexplored. A field experiment was conducted in Spain to study the effect of MSD implemented during the rice growing season on greenhouse gas (GHG) emissions in relation to the standard permanently flooded water management (PFL). Specifically, the study aimed at (1) assessing the CH4 mitigation capacity of MSD in the studied area and (2) testing the hypothesis that the mitigating effect of MSD can be extended into the following winter flooded fallow season. Year-round GHG sampling was conducted, seasonal and annual cumulative emissions of CH4 and N2O as well as the global warming potential were calculated, and grain yield was measured. MSD reduced growing season CH4 emissions by ca. 80% without yield penalties. During the flooded fallow season, MSD reduced CH4 emissions by ca. 60%, despite both fields being permanently flooded. The novelty of our observations lies in the amplified mitigation capacity of MSD by extending the CH4 mitigation effect to the following flooded winter fallow season. This finding becomes especially relevant in rice systems with flooded winter fallow season given the large contribution of this season to the annual CH4 emissions.
Appropriate crop rotation in rice field is an important measure to maintain soil fertility and rice productivity. However, the effects of different rice rotation systems on methane (CH4) emission and the underlying mechanisms, as well as rice grain yields have not been well assessed. Here, a 2-year field study involving three rice rotation systems (Wh-PR: wheat-flooded rice rotation, Ra-PR: rapeseed-flooded rice rotation, Ra-UR: rapeseed-aerobic rice rotation) was conducted. CH4 emissions, methanogenic and methanotrophic communities and rice grain yields were measured during rice growing seasons to determine which rice rotation pattern can reduce CH4 emissions and improve rice grain yields. The average cumulative CH4 emission was 136.19 kg C ha-1 in Ra-PR system, which was significantly higher than that in Wh-PR and Ra-UR systems by 60.6 % and 14.6-fold, respectively. These results were mainly attributed to the low soil dissolved organic carbon in Wh-PR system and the well aerated soil condition in Ra-UR system, as compared with Ra-PR system. Rice grain yields exhibited no significant differences among the three rotation systems in 2019 and 2020. The abundances of methanogens in Ra-PR system were obviously higher than those in Wh-PR and Ra-UR systems. While the abundances of methanotrophs were comparable between Ra-PR and Wh-PR systems, which exhibited significantly lower abundances than that in Ra-UR system. CH4 fluxes showed markedly positive relations to methanogen abundances, while exhibited no relationship with methanotroph abundances. Both methanogenic and methanotrophic communities differed considerably in Wh-PR and Ra-UR systems in comparison with Ra-PR system. Specifically, the relatively low abundance of Methanothrix and Type I methanotrophs occurred in Wh-PR and Ra-UR systems, whereas Methanosarcina, Methanocella, Methanomassiliicoccus and type II methanotrophs (Methylocystis and Methylosinus) were found in higher relative abundance in Wh-PR and Ra-UR systems. Overall, changing preceding upland crop types or introducing aerobic rice to substitute flooded rice in rice-based rotation systems could diminish CH4 emissions, mainly by regulating soil properties and eventually changing soil methanogenic and methanotrophic communities.
Rice paddy fields are major sources of atmospheric methane (CH4) and nitrous oxide (N2O). Rice variety is an important factor affecting CH4 and N2O emissions. However, the interactive effects of rice metabolites and microorganisms on CH4 and N2O emissions in paddy fields are not clearly understood. In this study, a high greenhouse gas-emitting cultivar (YL 6) and a low greenhouse gas-emitting cultivar (YY 1540) were used as experimental materials. Metabolomics was used to examine the roots, root exudates, and bulk soil metabolites. High-throughput sequencing was used to determine the microbial community composition. YY 1540 had more secondary metabolites (flavonoids and isoflavonoids) in root exudates than YL 6. It was enriched with the uncultured members of the families Gemmatimonadanceae and Rhizobiales_Incertae_Sedis in bulk soil, and genera Burkholderia-Caballeronia-Paraburkholderia, Magnetospirillum, Aeromonas, and Anaeromyxobacter in roots, contributing to increased expression of pmoA and nosZ genes and reducing CH4 and N2O emissions. YL 6 roots and root exudates contained higher contents of carbohydrates [e.g., 6-O- acetylarbutin and 2-(3- hydroxyphenyl) ethanol 1′-glucoside] than those of YY 1540. They were enriched with genera RBG-16-58-14 in bulk soil and Exiguobacterium, and uncultured member of the Kineosporiaceae family in roots, which contributed to increased expression of mcrA, ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nirS, and nirK genes and greenhouse gas emissions. In general, these results established a link between metabolites, microorganisms, microbial functional genes, and greenhouse gas emissions. The metabolites of root exudates and roots regulated CH4 and N2O emissions by influencing the microbial community composition in bulk soil and roots.
Our previous pot experiments showed that using Azolla either or both as dual and green manure with rice increases its yield or significantly reduces either or both methane (CH4) and nitrous oxide (N2O) emissions. To confirm these findings in an actual field, Azolla was either grown as a dual crop (herein Cover) or incorporated as green manure plus dual cropping (herein AGM + Cover) at the beginning of the experiment along with rice. Compared with the control (chemical fertilizer; herein NPK), NPK + Cover and AGM + Cover treatments did not influence cumulative CH4 emissions throughout the rice growth period. However, AGM + Cover treatment affected significant CH4 emissions at early, middle, and later rice growth stages by 140.6%, 24.6%, and 33.1%, respectively, compared with NPK + Cover treatment. These emissions were attributed to the readily available carbon substrate for methanogens following the incorporation of Azolla as green manure. Compared with NPK, NPK + Cover and AGM + Cover significantly increased N2O emissions by 645.9% and 816.2%, respectively, during the middle rice growth stage. No significant N2O emission differences were observed in the three treatments in the early or later rice growth stages. The higher N2O emissions from the middle rice growth stage were ascribed to high substrate availability from the dead Azolla by higher summer air temperature in the 2019 season. AGM + Cover significantly decreased rice yield by 37.5% (NPK) and 35.3% (NPK + Cover), with no significant differences between NPK and NPK + Cover. This reduction was attributed to nitrogen immobilization from the incorporated Azolla during the early stage. Therefore, to ascertain the potential of Azolla in paddy fields to address environmental safety while sustaining yield, emphasis on the interaction of different application methods with various management practices is necessary.
The responses of grain yield and greenhouse gas (GHG) emissions to climate warming in rice paddies are serious concerns for both global food security and climate change mitigation. However, the impact of free-air temperature increase (FATI) on grain yield and methane (CH4) and nitrous oxide (N2O) emissions remains unclear for one of the most globally significant rice production practices: the double rice cropping system. Here, we conducted a two-year field experiment to examine the effect of FATI by infrared heaters on grain yield and CH4 and N2O emissions in a double rice field in subtropical China. FATI increased rice canopy temperature by 2.0 °C and soil temperature by 1.2 °C on average but had no effect on either early or late rice yield production. FATI did not affect CH4 emissions, but significantly increased N2O emissions in both the early and late rice seasons. Averaged across two years, N2O emissions increased by 0.3 kg ha⁻¹ and 0.7 kg ha⁻¹ in the warmed plots for the early and late rice seasons, respectively. Consequently, FATI enhanced the global warming potential (GWP) and GHG intensity (i.e., yield scaled GWP) in the double rice cropping system. In addition, warming increased the abundance of ammonia-oxidising bacteria, ammonia-oxidising archaea, and a nitrite reductase gene (nirS), but decreased that of a nitrous oxide reductase gene (nosZ). Our results indicate that warming by FATI does not affect grain yield and CH4 emissions but stimulates N2O emissions in the double rice cropping system and therefore promotes a potential positive feedback with future climate warming.
Non‐continuous flooding is an effective practice for reducing greenhouse gas emissions (GHGs) and irrigation water use (IRR) in rice fields. However, advancing global implementation is hampered by the lack of comprehensive understanding of GHGs and IRR reduction benefits without compromising rice yield. Here, we present the largest observational data set for such effects as of yet. By using Random Forest regression models based on 636 field trials at 105 globally georeferenced sites, we identified the key drivers of effects of non‐continuous flooding practices and mapped maximum GHGs or IRR reduction benefits under optimal non‐continuous flooding strategies. The results show that variation in effects of non‐continuous flooding practices are primarily explained by the UnFlooded days Ratio (UFR, that is the ratio of the number of days without standing water in the field to total days of the growing period). Non‐continuous flooding practices could be feasible to be adopted in 76% of global rice harvested areas. This would reduce the global warming potential (GWP) of CH4 and N2O combined from rice production by 47% or the total GWP by 7% and alleviate irrigation water use by 25%, while maintaining yield levels. The identified UFR targets far exceed currently observed levels particularly in South and Southeast Asia, suggesting large opportunities for climate mitigation and water use conservation, associated with the rigorous implementation of non‐continuous flooding practices in global rice cultivation.
Atmospheric CO2 concentrations and water management practices both affect greenhouse gas (GHG) emissions from rice paddies, but interactive effects between these two factors are still unknown. Here, we show the first study to compare the impact of elevated atmospheric CO2 (eCO2) on GHG emissions under continuously flooded irrigation (CF) and under intermittently flooded (IF) conditions. Elevated CO2 stimulated CH4 emissions under CF by 50% in a field experiment and by 46% in a pot experiment, but it had no effect under IF in both experiments. Elevated CO2 had no effect on N2O emissions in either the field or pot experiment. Rice root biomass, aboveground biomass and grain yield increased with eCO2, but were not affected by water management. Elevated CO2 only stimulated the abundance of methanogens under CF, suggesting that increased soil O2 availability with IF limited methanogenic activity under eCO2. Our findings suggest that estimates of CH4 emissions from global rice agriculture with eCO2 need to account for recent changes in water management.
Climate warming increases the emissions of soil greenhouse gases (GHGs) by stimulating carbon (C) and nitrogen (N) processes in terrestrial ecosystems, contributing to climate change. However, the responses of soil GHG fluxes to warming from global agricultural ecosystems remain unknown. Here, we evaluate the effects of warming on soil GHG fluxes from global croplands under different agro-ecosystems, cropping systems, crop species, and N fertilizer levels, and determine the potential mechanisms through a meta-analysis of field observations. The results showed that warming (+2.0 °C on average) significantly enhanced soil carbon dioxide (CO2) emissions (i.e., soil respiration) by 14.7% and nitrous oxide (N2O) fluxes by 12.6% across croplands and increased soil methane (CH4) uptake by 21.8% in uplands and CH4 release by 23.4% in paddy fields. The responses of C gas fluxes to warming were regulated by initial C substrates, initial wetness, and changes in temperature in croplands. The responses of N2O fluxes to warming were mainly associated with changed NH4⁺-N and NO3⁻-N as well as initial wetness and N fertilizer in croplands. The responses of soil GHG fluxes to warming were generally comparable among different crop species and N fertilizer levels, respectively. However, the responses of CO2 emissions and CH4 release to warming were significantly higher in upland-paddy fields than in uplands and paddy fields; the warming-induced changes in CH4 release was significantly greater in rotation cropping systems than in single- and double-cropping systems. This synthesis highlights the important role of climate warming in increasing soil GHG fluxes from croplands, underscoring the critical need for agricultural practice adjustment to mitigate climate change in the future.
