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Despite the increasing impact of atmospheric nitrogen (N) deposition on terrestrial greenhouse gas (GHG) budget, through driving both the net atmospheric CO 2 exchange and the emission or uptake of non-CO 2 GHGs (CH 4 and N 2 O), few studies have assessed the climatic impact of forests and grasslands under N deposition globally based on different bottom-up approaches. Here, we quantify the effects of N deposition on biomass C increment, soil organic C (SOC), CH 4 and N 2 O fluxes and, ultimately, the net ecosystem GHG balance of forests and grasslands using a global comprehensive dataset. We showed that N addition significantly increased plant C uptake (net primary production) in forests and grasslands, to a larger extent for the aboveground C (aboveground net primary production), whereas it only caused a small or insignificant enhancement of SOC pool in both upland systems. Nitrogen addition had no significant effect on soil heterotrophic respiration (R H ) in both forests and grasslands, while a significant N-induced increase in soil CO 2 fluxes (R S , soil respiration) was observed in grasslands. Nitrogen addition significantly stimulated soil N 2 O fluxes in forests (76%), to a larger extent in grasslands (87%), but showed a consistent trend to decrease soil uptake of CH 4 , suggesting a declined sink capacity of forests and grasslands for atmospheric CH 4 under N enrichment. Overall, the net GHG balance estimated by the net ecosystem production-based method (forest, 1.28 Pg CO 2 -eq year -1 vs. grassland, 0.58 Pg CO 2 -eq year -1 ) was greater than those estimated using the SOC-based method (forest, 0.32 Pg CO 2 -eq year -1 vs. grassland, 0.18 Pg CO 2 -eq year -1 ) caused by N addition. Our findings revealed that the enhanced soil C sequestration by N addition in global forests and grasslands could be only marginally offset (1.5%-4.8%) by the combined effects of its stimulation of N 2 O emissions together with the reduced soil uptake of CH 4 ., (© 2023 John Wiley & Sons Ltd.)

Resumption of the increase in atmospheric methane (CH 4 ) concentrations since 2007 is of global concern and may partly have resulted from emissions from rice cultivation. Estimates of CH 4 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 CH 4 emissions from rice fields to the resumed CH 4 growth and the global abatement potential remains unclear. In this study, we estimated the global CH 4 emissions from rice fields to be 27 ± 6 Tg CH 4 year -1 in the recent decade (2008-2017) based on the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The trend of CH 4 emissions from rice cultivation showed an increase followed by no significant change and then, a stabilization over 1990-2020. Consequently, the contribution of CH 4 emissions from rice fields to the renewed increase in atmospheric CH 4 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 CH 4 emissions from rice fields. Straw returned as biochar could reduce CH 4 emissions by 12 Tg CH 4 year -1 , equivalent to 10% of the total reduction of all anthropogenic emissions. We conclude that other sectors than rice cultivation must have contributed to the renewed increase in atmospheric CH 4 concentrations, and that optimizing multiple mitigation measures in rice fields could contribute significantly to the abatement goal outlined in the Global Methane Pledge., (© 2023 John Wiley & Sons Ltd.)

Inland waters (rivers, reservoirs, lakes, ponds, streams) and estuaries are significant emitters of methane (CH 4 ) and nitrous oxide (N 2 O) to the atmosphere, while global estimates of these emissions have been hampered due to the lack of a worldwide comprehensive data set of CH 4 and N 2 O flux components. Here, we synthesize 2997 in-situ flux or concentration measurements of CH 4 and N 2 O from 277 peer-reviewed publications to estimate global CH 4 and N 2 O emissions from inland waters and estuaries. Inland waters including rivers, reservoirs, lakes, and streams together release 95.18 Tg CH 4  year -1 (ebullition plus diffusion) and 1.48 Tg N 2 O year -1 (diffusion) to the atmosphere, yielding an overall CO 2 -equivalent emission total of 3.06 Pg CO 2  year -1 . The estimate of CH 4 and N 2 O emissions represents roughly 60% of CO 2 emissions (5.13 Pg CO 2  year -1 ) from these four inland aquatic systems, among which lakes act as the largest emitter for both CH 4 and N 2 O. Ebullition showed as a dominant flux component of CH 4 , contributing up to 62%-84% of total CH 4 fluxes across all inland waters. Chamber-derived CH 4 emission rates are significantly greater than those determined by diffusion model-based methods for commonly capturing of both diffusive and ebullitive fluxes. Water dissolved oxygen (DO) showed as a dominant factor among all variables to influence both CH 4 (diffusive and ebullitive) and N 2 O fluxes from inland waters. Our study reveals a major oversight in regional and global CH 4 budgets from inland waters, caused by neglecting the dominant role of ebullition pathways in those emissions. The estimated indirect N 2 O EF 5 values suggest that a downward refinement is required in current IPCC default EF 5 values for inland waters and estuaries. Our findings further indicate that a comprehensive understanding of the magnitude and patterns of CH 4 and N 2 O emissions from inland waters and estuaries is essential in defining the way of how these aquatic systems will shape our climate., (© 2022 John Wiley & Sons Ltd.)

Warming can accelerate the decomposition of soil organic matter and stimulate the release of soil greenhouse gases (GHGs), but to what extent soil release of methane (CH 4 ) and nitrous oxide (N 2 O) may contribute to soil C loss for driving climate change under warming remains unresolved. By synthesizing 1,845 measurements from 164 peer-reviewed publications, we show that around 1.5°C (1.16-2.01°C) of experimental warming significantly stimulates soil respiration by 12.9%, N 2 O emissions by 35.2%, CH 4 emissions by 23.4% from rice paddies, and by 37.5% from natural wetlands. Rising temperature increases CH 4 uptake of upland soils by 13.8%. Warming-enhanced emission of soil CH 4 and N 2 O corresponds to an overall source strength of 1.19, 1.84, and 3.12 Pg CO 2 -equivalent/year under 1°C, 1.5°C, and 2°C warming scenarios, respectively, interacting with soil C loss of 1.60 Pg CO 2 /year in terms of contribution to climate change. The warming-induced rise in soil CH 4 and N 2 O emissions (1.84 Pg CO 2 -equivalent/year) could reduce mitigation potential of terrestrial net ecosystem production by 8.3% (NEP, 22.25 Pg CO 2 /year) under warming. Soil respiration and CH 4 release are intensified following the mean warming threshold of 1.5°C scenario, as compared to soil CH 4 uptake and N 2 O release with a reduced and less positive response, respectively. Soil C loss increases to a larger extent under soil warming than under canopy air warming. Warming-raised emission of soil GHG increases with the intensity of temperature rise but decreases with the extension of experimental duration. This synthesis takes the lead to quantify the ecosystem C and N cycling in response to warming and advances our capacity to predict terrestrial feedback to climate change under projected warming scenarios., (© 2020 John Wiley & Sons Ltd.)

Grassland ecosystems are sensitive to invasions by plants from other functional groups which can alter soil greenhouse gas (GHG) fluxes. However, the effects of plant invasion on net GHG exchanges between soils and the atmosphere, plant production, and global warming potential (GWP) of annual grasslands is poorly understood. To evaluate the impacts of perennial forb invasions on GHG budgets of an annual grassland in China, we measured soil carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) fluxes over two years in replicated invaded (dominated by Alternanthera philoxeroides or Solidago canadensis) and non-invaded (dominated by the annual grass Eragrostis pilosa or the annual forb Sesbania cannabina) field sites. On average, soil CO 2 and N 2 O emissions from invaded sites were 30% and 76% higher, respectively, relative to sites dominated by native species. Emissions of N 2 O and CO 2 were especially high in Solidago and Alternanthera dominated sites, respectively. Soil CH 4 emissions did not vary with plant species. On average, total biomass C of invaded sites was higher than that of the native dominated sites but this reflected the high C in Solidago dominated sites. Global warming potential (GWP) was increased by Alternanthera invasions and decreased by Solidago invasions. Plant invasions affected GWP of these annual grasslands through higher emissions of some GHGs but also sometimes higher biomass C. Together, this suggests that perennial forb invasions could change the net source or sink role of annual grasslands for GHG budgets, but the effects on GWP vary among species depending on GHG responses and C storage., (Copyright © 2018. Published by Elsevier B.V.)

The net balance of greenhouse gas (GHG) exchanges between terrestrial ecosystems and the atmosphere under elevated atmospheric carbon dioxide (CO 2 ) remains poorly understood. Here, we synthesise 1655 measurements from 169 published studies to assess GHGs budget of terrestrial ecosystems under elevated CO 2 . We show that elevated CO 2 significantly stimulates plant C pool (NPP) by 20%, soil CO 2 fluxes by 24%, and methane (CH 4 ) fluxes by 34% from rice paddies and by 12% from natural wetlands, while it slightly decreases CH 4 uptake of upland soils by 3.8%. Elevated CO 2 causes insignificant increases in soil nitrous oxide (N 2 O) fluxes (4.6%), soil organic C (4.3%) and N (3.6%) pools. The elevated CO 2 -induced increase in GHG emissions may decline with CO 2 enrichment levels. An elevated CO 2 -induced rise in soil CH 4 and N 2 O emissions (2.76 Pg CO 2 -equivalent year -1 ) could negate soil C enrichment (2.42 Pg CO 2 year -1 ) or reduce mitigation potential of terrestrial net ecosystem production by as much as 69% (NEP, 3.99 Pg CO 2 year -1 ) under elevated CO 2 . Our analysis highlights that the capacity of terrestrial ecosystems to act as a sink to slow climate warming under elevated CO 2 might have been largely offset by its induced increases in soil GHGs source strength., (© 2018 John Wiley & Sons Ltd/CNRS.)

Despite the increasing impact of atmospheric nitrogen (N) deposition on terrestrial greenhouse gas (GHG) budget, through driving both the net atmospheric CO2 exchange and the emission or uptake of non‐CO2 GHGs (CH4 and N2O), few studies have assessed the climatic impact of forests and grasslands under N deposition globally based on different bottom‐up approaches. Here, we quantify the effects of N deposition on biomass C increment, soil organic C (SOC), CH4 and N2O fluxes and, ultimately, the net ecosystem GHG balance of forests and grasslands using a global comprehensive dataset. We showed that N addition significantly increased plant C uptake (net primary production) in forests and grasslands, to a larger extent for the aboveground C (aboveground net primary production), whereas it only caused a small or insignificant enhancement of SOC pool in both upland systems. Nitrogen addition had no significant effect on soil heterotrophic respiration (RH) in both forests and grasslands, while a significant N‐induced increase in soil CO2 fluxes (RS, soil respiration) was observed in grasslands. Nitrogen addition significantly stimulated soil N2O fluxes in forests (76%), to a larger extent in grasslands (87%), but showed a consistent trend to decrease soil uptake of CH4, suggesting a declined sink capacity of forests and grasslands for atmospheric CH4 under N enrichment. Overall, the net GHG balance estimated by the net ecosystem production‐based method (forest, 1.28 Pg CO2‐eq year−1 vs. grassland, 0.58 Pg CO2‐eq year−1) was greater than those estimated using the SOC‐based method (forest, 0.32 Pg CO2‐eq year−1 vs. grassland, 0.18 Pg CO2‐eq year−1) caused by N addition. Our findings revealed that the enhanced soil C sequestration by N addition in global forests and grasslands could be only marginally offset (1.5%–4.8%) by the combined effects of its stimulation of N2O emissions together with the reduced soil uptake of CH4. [ABSTRACT FROM AUTHOR]

Agricultural soils play an important role in the atmospheric methane (CH4) budget, where paddy soils can contribute significant CH4 to atmosphere whereas upland soils may act as a source or sink of atmospheric CH4, dependent on soil water conditions. Biochar amendments have effects on soil CH4 production or oxidation processes in individual experiments, but the causative mechanisms are yet to be fully elucidated. To synthesize the response of soil CH4 release or uptake to biochar amendment, we performed a meta-analysis using data from 61 peer-reviewed papers with 222 updated paired measurements. When averaged across all studies, biochar amendment significantly decreased CH4 release rates by 12% for paddy soils and 72% for upland soils, and CH4 uptake rates by 84% for upland soils. Neither soil CH4 release nor uptake responses to biochar amendment were significant in field soils. Nitrogen (N) fertilizer application would weaken the response of soil CH4 release or uptake to biochar amendment. Biochar-incurred decreases in soil CH4 release and uptake rates were the largest in medium-textured soils or neutral-pH soils. Soil CH4 release or uptake responses to biochar were also significantly altered by biochar characteristics, such as feedstock source, C/N ratio, pH, and pyrolysis temperature. The results of this synthesis suggest that the role of biochar in soil CH4 mitigation potential might have been exaggerated, particularly in fields when biochar is applied in combination with N fertilizer. [ABSTRACT FROM AUTHOR]

Abstract: The net balance of greenhouse gas (GHG) exchanges between terrestrial ecosystems and the atmosphere under elevated atmospheric carbon dioxide (CO2) remains poorly understood. Here, we synthesise 1655 measurements from 169 published studies to assess GHGs budget of terrestrial ecosystems under elevated CO2. We show that elevated CO2 significantly stimulates plant C pool (NPP) by 20%, soil CO2 fluxes by 24%, and methane (CH4) fluxes by 34% from rice paddies and by 12% from natural wetlands, while it slightly decreases CH4 uptake of upland soils by 3.8%. Elevated CO2 causes insignificant increases in soil nitrous oxide (N2O) fluxes (4.6%), soil organic C (4.3%) and N (3.6%) pools. The elevated CO2‐induced increase in GHG emissions may decline with CO2 enrichment levels. An elevated CO2‐induced rise in soil CH4 and N2O emissions (2.76 Pg CO2‐equivalent year−1) could negate soil C enrichment (2.42 Pg CO2 year−1) or reduce mitigation potential of terrestrial net ecosystem production by as much as 69% (NEP, 3.99 Pg CO2 year−1) under elevated CO2. Our analysis highlights that the capacity of terrestrial ecosystems to act as a sink to slow climate warming under elevated CO2 might have been largely offset by its induced increases in soil GHGs source strength. [ABSTRACT FROM AUTHOR]

A full accounting of net greenhouse gas balance ( NGHGB) and greenhouse gas intensity ( GHGI) was examined in an annual coastal reclaimed saline Jerusalem artichoke-fallow cropping system under various soil practices including soil tillage, soil ameliorant, and crop residue amendments. Seasonal fluxes of soil carbon dioxide ( CO2), methane ( CH4), and nitrous oxide (N2O) were measured using static chamber method, and the net ecosystem exchange of CO2 ( NEE) was determined by the difference between soil heterotrophic respiration ( RH) and net primary production ( NPP). Relative to no-tillage, rotary tillage significantly decreased the NPP of Jerusalem artichoke while it had no significant effects on the annual RH. Rotary tillage increased CH4 emissions, while seasonal or annual soil N2O emissions did not statistically differ between the two tillage treatments. Compared with the control plots, soil ameliorant or straw amendment enhanced RH, soil CH4, and N2O emissions under the both tillage regimes. Annual NGHGB was negative for all the field treatments, as a consequence of net ecosystem CO2 sequestration exceeding the CO2-equivalents released as CH4 and N2O emissions, which indicates that Jerusalem artichoke-fallow cropping system served as a net sink of GHGs. The annual net NGHGB and GHGI were estimated to be 11-21% and 4-8% lower in the NT than in RT cropping systems, respectively. Soil ameliorant and straw amendments greatly increased NPP and thus significantly decreased the negative annual net NGHGB. Overall, higher NPP but lower climatic impacts of coastal saline bioenergy production would be simultaneously achieved by Jerusalem artichoke cultivation under no-tillage with improved saline soil conditions in southeast China. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer-induced direct nitrous oxide (N2O) emissions depend on water regimes in paddy fields, such as seasonal continuous flooding (F), flooding–midseason drainage–reflooding (F-D-F), and flooding–midseason drainage–reflooding–moist intermittent irrigation but without water logging (F-D-F-M). In order to estimate the changes in direct N2O emission from paddy fields during the rice-growing season in Mainland of China between the 1950s and the 1990s, the country-specific emission factors of N2O-N under different water regimes combined with rice production data were adopted in the present study. Census statistics on rice production showed that water management and nitrogen input regimes have changed in rice paddies since the 1950s. During the 1950s–1970s, about 20–25% of the rice paddy was continuously waterlogged, and 75–80% under the water regime of F-D-F. Since the 1980s, about 12–16%, 77%, and 7–12% of paddy fields were under the water regimes of F, F-D-F, and F-D-F-M, respectively. Total nitrogen input during the rice-growing season has increased from 87.5 kg N ha−1 in the 1950s to 224.6 kg N ha−1 in the 1990s. The emission factors of N2O-N were estimated to be 0.02%, 0.42%, and 0.73% for rice paddies under the F, F-D-F, and F-D-F-M water regimes, respectively. Seasonal N2O emissions have increased from 9.6 Gg N2O-N each year in the 1950s to 32.3 Gg N2O-N in the 1990s, which is accompanied by the increase in rice yield over the period 1950s–1990s. The uncertainties in N2O estimate were estimated to be 59.8% in the 1950s and 37.5% in the 1990s. In the 1990s, N2O emissions during the rice-growing season accounted for 8–11% of the reported annual total of N2O emissions from croplands in China, suggesting that paddy rice development could have contributed to mitigating agricultural N2O emissions in the past decades. However, seasonal N2O emissions would be increased, given that saving-water irrigation and nitrogen inputs are increasingly adopted in rice paddies in China. [ABSTRACT FROM AUTHOR]

How to achieve high soil organic carbon (SOC) sequestration and low greenhouse gases emissions but without compromising yields is the challenge of rice cultivation in China. This study explored the potential to simultaneously increase SOC stocks and reduce methane (CH 4) emissions by optimizing rice cropping rotation and fertilization based on a 2-year field experiment in southeast China. We tested five optimized N management practices including directly reducing chemical N fertilizer input and replacing chemical N fertilizers with organic and controlled-release fertilizers in double-rice cropping and Chinese milk vetch-rice cropping rotation systems. Results showed higher seasonal rice yields, nitrogen use efficiency (NUE) and SOC stocks for Chinese milk vetch-rice rotation systems (CR) as compared to double-rice cropping systems (DR). Seasonal rice yields were the highest in the 2019 single-rice season (2019-SR), followed by the 2018 late (2018-LR) and early rice seasons (2018-ER). SOC stocks of CR for the treatment receiving organic N fertilizer (OF) were the largest among all rice seasons and fertilization treatments. Seasonal CH 4 emissions were 8–12% greater in the OF than in the chemical N fertilizer treatments across all rice seasons, with the greatest in 2019-SR and lowest in 2018-ER. Fertilization stimulated CH 4 emissions through enhancing mcrA gene activity, but regulated by soil properties, while rice rotation models indirectly influenced CH 4 emissions through direct effects on soil properties. However, yield-scaled CH 4 emissions remained unaffected by N fertilization in the two-year rice rotation systems. The NUE was significantly enhanced in OF than in other fertilizer treatments over all seasons. Seasonal net ecosystem C budget (NECB) was 24–41% greater in OF than in chemical N fertilizer treatments across all rice seasons, with the greatest in 2019-SR and lowest in 2018-LR. The NECB was increased by 46% in CR as compared to DR. Our results revealed that the optimized rice cropping rotation by incorporation of Chinese milk vetch with organic N fertilization is beneficial for enhancing soil C sequestration and maintaining rice yields in southeast China. [Display omitted] • Green manure rotation benefits for the enhancement of paddy soil carbon sinks. • Green manure rotation stimulates CH 4 emissions during the rice growing season. • Yield-scaled CH 4 emissions remain unaffected by N fertilization and crop rotation. • Green manure rotation can reconcile low climatic impacts with high yield of rice. [ABSTRACT FROM AUTHOR]

• CH 4 and N 2 O emissions from rice-aquaculture systems remain poorly constrained. • Rice-crayfish co-culture production is beneficial to reduce CH 4 and N 2 O emissions. • Ditched culture areas release more CH 4 but less N 2 O relative to rice planted areas. • Lower emission factors of N 2 O in rice-crayfish co-culture than monoculture systems. Rice paddies and rice-aquaculture co-culture systems are important sources of methane (CH 4) and nitrous oxide (N 2 O) to the atmosphere. Due to the growing human demand of aquaculture protein and the rapid development of green agriculture, rice-aquaculture co-culture systems have been increasingly developed from rice paddies in southeast China. However, the strength of CH 4 and N 2 O emissions from rice-aquaculture co-culture systems remains poorly quantified, in particular the contribution of these emissions from different functional cultivation areas. Here, a two-year parallel field experiment was conducted to examine the changes in CH 4 and N 2 O fluxes following the conversion from rice paddies to rice-crayfish co-culture systems in southeast China. Over the two-year period, annual CH 4 and N 2 O fluxes from rice-crayfish co-culture systems averaged 4.59 mg m-2 h-1 and 39.50 μg m -2 h -1, amounting to 391.9 kg ha−1 and 3.46 kg ha−1, respectively. The conversion from rice paddies to rice-crayfish co-culture systems significantly reduced CH 4 and N 2 O emissions by 14% and 31%, respectively. The emission factors of N 2 O were estimated to be 1.25–1.61% in the rice-crayfish co-culture system. Relative to rice planted areas, CH 4 and N 2 O fluxes from crayfish ditched culture areas were three times higher and 50% lower, which contributed 26% and 5% to the total CH 4 and N 2 O emissions from rice-crayfish co-culture systems, respectively. Our results highlight that the conversion of paddy rice monoculture to rice-crayfish co-culture systems can benefit low greenhouse gas emissions and high ecosystem economic profits as a potential option to sustain agricultural development and achieve carbon neutrality. [Display omitted] [ABSTRACT FROM AUTHOR]

The potential of biochar for mitigating climatic impacts of coastal saline bioenergy production is not well established. A full accounting of net greenhouse gas balance (NGHGB) and greenhouse gas intensity (GHGI) affected by biochar amendment combined with or without nitrogen (N) fertilizer application was examined in an annual coastal reclaimed Jerusalem artichoke bioenergy cropping system. The net ecosystem exchange of CO 2 (NEE) was determined by the difference between soil heterotrophic respiration ( R H ) and net primary production (NPP) using static chamber method. Biochar amendment raised the seasonal R H but without suppressing the NPP during the Jerusalem artichoke cropping season. Soil CH 4 emissions were 72% and 80% lower in the biochar amended than unamended plots when combined with N fertilizer application during the Jerusalem artichoke cropping and non-cropping seasons, respectively. The biochar-induced soil N 2 O mitigation efficiency was weakened by N fertilizer input over the annual cycle. Annual NGHGB and GHGI were negative for all the field treatments and were significantly lower in biochar amended than in unamended soils, suggesting that Jerusalem artichoke cropping system served as a net sink of GHGs due to net ecosystem CO 2 and biochar-induced C sequestration exceeding CO 2 -equivalents released as CH 4 and N 2 O emissions. On average, biochar amendment significantly enhanced GHGs sink capacity by resulting in almost 4–5 folds decrease in annual NGHGB or GHGI when combined with N fertilizer application or not. Therefore, higher biomass gain as potential alternative source of biofuels but lower climatic impacts of bioenergy production would be reconciled by biochar use in southeast coastal China. [ABSTRACT FROM AUTHOR]

Efforts to advance our knowledge on the potential of bioenergy instead of fossil fuels in terms of mitigating climatic impact are in urgent need. No data is currently available on the use of urease and nitrification inhibitors in costal saline bioenergy cropping systems. An overall accounting of net greenhouse gas balance (NGHGB) and greenhouse gas intensity (GHGI) affected by combined effects of urease inhibitor hydroquinone (HQ) and nitrification inhibitor dicyandiamide (DCD) amendment was examined in a coastal saline Jerusalem artichoke bioenergy cropping system. The net ecosystem exchange of CO 2 (NEE) was determined by the difference between soil heterotrophic respiration ( R H ) and net primary production (NPP) using static chamber method. Urease and nitrification inhibitors amendment increased the NPP but exerted a suppression effect on soil R H over the Jerusalem artichoke cropping system. A trade-off relationship was observed by decreasing soil N 2 O but stimulating soil CH 4 emissions following HQ+DCD amendment. The plots combined urea with HQ+DCD application increased soil CH 4 by 167% while decreased N 2 O by 16% as compared to with urea only in the bioenergy cropping system. On average, the fertilizer N-induced emission factor of N 2 O was estimated to be 0.25% across the fertilized plots. Compared with urea, the plots with urea and HQ+DCD resulted in a further decrease by 37% and 15% in estimated NGHGB and GHGI over the Jerusalem artichoke cropping system, respectively. Overall, Jerusalem artichoke production would achieve higher biomass as source of biofuels but lower climatic impacts, particularly when together with urease and nitrification inhibitors amendment in coastal saline soils. [ABSTRACT FROM AUTHOR]

The optimization of fertilization management has the potential to improve crop yield, reduce greenhouse gas (GHG) emissions and enhance nitrogen agronomy efficiency (NAE). However, less is known about whether these benefits can be simultaneously achieved by optimizing fertilization regimes in Chinese croplands. We carried out a year-round field experiment to measure methane (CH 4) and nitrous oxide (N 2 O) fluxes, crop yield and NAE under different fertilization regimes in a subtropical double-rice cropping system. Relative to the conventional chemical N fertilizer application (F), alternative fertilization strategies significantly decreased N 2 O emissions by 26–78% when averaged across the options of chemical N fertilizer application with reduced rates (RF, 30% off), chemical N fertilizer fully replaced by organic N fertilizer with reduced rates (OF, 30% off) and chemical N fertilizer fully replaced by controlled-release N fertilizer with reduced rates (CF, 30% off), with the largest mitigation potential occurring in OF-treated plots, but comparable extents between the early- and late-rice seasons. Soil CH 4 emissions had no consistent response to alternative fertilization regimes, showing contrasting seasonal patterns between in the early- and late-rice seasons. Alternative fertilization options consistently increased NAE by 7–36% and 30–38% in the early- and late-rice seasons, respectively, and this benefit was maximized in OF-treated plots. Direct emission factors of N fertilizer for N 2 O and the combined greenhouse gas intensity (GHGI) of N 2 O and CH 4 were negatively related to NAE while rice yield was positively related to NAE. Our findings suggest that optimized fertilization strategies especially through the option of chemical N fertilizer fully substituted by organic N fertilizer can reconcile low climatic impact and high NAE, but without compromising yield in double-rice cropping systems. • Soil GHG emissions were linked to NAE in double-rice under different fertilization regimes. • Soil N 2 O emissions showed a significant decrease by 26–78% across optimized fertilization regimes. • Optimized fertilization alternatives consistently increased NAE in double-rice cropping seasons. • Direct EFs of N 2 O and annual combined GHGI of CH 4 and N 2 O were negatively related to NAE. • Organic N substitution stood out to reconcile low SGWP and high NAE of double-rice production. [ABSTRACT FROM AUTHOR]