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Increasing soil organic carbon (SOC) in agricultural systems is a primary nature-based option for mitigating climate change, improving soil fertility, and ensuring food security. However, the consequences of global warming and increases in carbon inputs on cropland SOC stocks over the last few decades remain largely unknown, particularly in deeper soil layers. Here, by using repeated measurements, we reassess variations in SOC stocks across a 0 to 100 cm soil profile at the same locations in China's upland croplands in 1980 and 2023. We observe an overall net accumulation of 0.74 Pg SOC (7%) with a mean sequestration rate of 13.7 g SOC m -2 y -1 . This accumulation results from 0.86 Pg SOC gains at upper soil depths (0 to 60 cm) induced by carbon inputs, alongside 0.12 Pg SOC losses at deeper soil layers (60 to 100 cm) prompted by warming-enhanced decomposition. While our findings indicate a successful, though lower than expected, increase in overall net SOC stocks, the loss of more recalcitrant deeper SOC warrants further consideration of its effects on enhancing cropland SOC accumulation to achieve carbon neutrality over the long term., Competing Interests: Competing interests statement:The authors declare no competing interest.

Nitrogen (N) deposition is a vital process of N cycling and is consequently important for the evaluation of N budgets. However, the character and quantity of N deposition inside the horticultural greenhouse remain unknown, impeding a deep understanding of N cycling among soil, vegetable and atmosphere. Here, we measured the dry and wet N deposition, and disentangled the relative percentages of ammonia (NH 3 ) and nitrogen oxides (NO X ) gases deposition based on the greenhouse vegetable cultivation experiment. Results found the annual N deposition, was 7.2-17.5 kg N·ha -1 under different chemical/organic N fertilizer managements, consisting of 77.0%-85.5% by dry deposition and 14.5-23% by wet deposition. The proportions of N deposition from NH 3 and NO X emissions ranged within 37.5-83.0% under different N managements. The NH 3 emission was the dominant driving factor of dry N deposition, while soil moisture was the dominant driving factor of wet N deposition. Controlled-release fertilizer combined with organic fertilizer resulted in the lowest N deposition (10.2 kg N·ha -1 ) and NH 3 and NO X emissions (12.5 kg N·ha -1 ), which could be recommended as the mitigation strategy in greenhouse cultivation. This study investigated the dry and wet N deposition characteristics and their influencing factors, as well as the proportion of N deposition attributed to NH 3 and NO X emissions, which provides preliminary understanding of N deposition and the reactive N gas diffusion from greenhouse into the atmosphere., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Using steady-state photosynthesis-intercellular CO 2 concentration (A-C i ) response curves to obtain the maximum rates of ribulose-1,5-bisphosphate carboxylase oxygenase carboxylation (V cmax ) and electron transport (J max ) is time-consuming and labour-intensive. Instead, the rapid A-C i response (RACiR) technique provides a potential, high-efficiency method. However, efficient parameter settings of RACiR technique for evergreen broadleaved species remain unclear. Here, we used Li-COR LI-6800 to obtain the optimum parameter settings of RACiR curves for evergreen broadleaved trees and shrubs. We set 11 groups of CO 2 gradients ([CO 2 ]), i.e. R1 (400-1500 ppm), R2 (400-200-800 ppm), R3 (420-20-620 ppm), R4 (420-20-820 ppm), R5 (420-20-1020 ppm), R6 (420-20-1220 ppm), R7 (420-20-1520 ppm), R8 (420-20-1820 ppm), R9 (450-50-650 ppm), R10 (650-50 ppm) and R11 (650-50-650 ppm), and then compared the differences between steady-state A-C i and RACiR curves. We found that V cmax and J max calculated by steady-state A-C i and RACiR curves overall showed no significant differences across 11 [CO 2 ] gradients (P > 0.05). For the studied evergreens, the efficiency and accuracy of R2, R3, R4, R9 and R10 were higher than the others. Hence, we recommend that the [CO 2 ] gradients of R2, R3, R4, R9 and R10 could be applied preferentially for measurements when using the RACiR technique to obtain V cmax and J max of evergreen broadleaved species., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Estimating ammonia (NH 3 ) emission factors (EFs) for vegetable production can support assessment of potential atmospheric pollution risk and provide information for mitigating NH 3 volatilization. The EFs in greenhouse and open-field systems under different fertilization, irrigation regimes, vegetable types and soil properties in both greenhouse and open-field vegetable production systems in China are poorly understood. An integrated analysis was performed, including 282 field measurements of NH 3 volatilization from 54 field studies, to quantify ammonia EFs under different management practices and soil properties. The results showed that the mean ammonia EF across all measurements was 4.2 % (3.6 %-4.8 %). The EFs of greenhouse and open-field systems were 2.0 % (1.5 %-2.5 %) and 6.3 % (5.4 %-7.2 %), respectively. There was a power function relationship between nitrogen application rate and ammonia EF in greenhouses. No relationship was identified between nitrogen application rate and ammonia EF in the open-field system. The EFs of organic fertilizers were lower than those of both chemical fertilizers and the combination of chemical and organic fertilizers. EFs of leafy vegetables, cabbages, solanaceous vegetables and melons were 2.7 %, 2.9 %, 1.4 % and 1.4 % in the greenhouse system, and 5.2 %, 5.7 %, 7.6 % and 9.7 % in the open-field system, respectively. The EFs of the greenhouse production system increased with increasing soil organic matter. Boosted regression tree analysis showed that N application rate, pH and soil organic matter were the main driving factors of EFs in the greenhouse system. Vegetable type, pH and soil organic matter were the main driving factors in the open-field system. In this study, the EFs were evaluated and distinguished across greenhouse and open-field systems, and the results provided accurate EFs under different management practices and soil properties for vegetable production in both greenhouse and open-field systems., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest to this work. They also declare that they do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Water and fertilizer management practices are considered to have great influence on soil methane (CH 4 ) emissions from paddy fields. However, few studies have conducted a quantitative analysis of the effects of these management practices. Here, we selected 156 observations of water management from 34 articles and 288 observations of fertilizer management from 37 articles and conducted a global meta-analysis of the effects of water and fertilizer management practices on soil CH 4 emissions in paddy fields. In general, compared with traditional irrigation (long-term flooding irrigation), water-saving irrigation significantly decreased soil CH 4 emissions but increased rice yield. Among the different practices, intermittent irrigation had the fewest reductions in CH 4 emissions but the greatest increase in rice yield. In addition, fertilization management practices such as manure, mixed fertilizer (mixture), and straw significantly enhanced CH 4 emissions. Rice yields were increased under fertilization with a mixture, traditional fertilizer, and controlled release fertilizer. Our results highlight that suitable agricultural water and fertilizer management practices are needed to effectively reduce CH 4 emissions while maintaining rice yields. We also put forward some prospects for mitigating soil CH 4 emissions from paddy fields in the context of global warming in the future.

The interaction of warming and soil texture on responsiveness of the key soil processes i.e . organic carbon (C) fractions, soil microbes, extracellular enzymes and CO 2 emissions remains largely unknown. Global warming raises the relevant question of how different soil processes will respond in near future, and what will be the likely regulatory role of texture? To bridge this gap, this work applied the laboratory incubation method to investigate the effects of temperature changes (10-50 °C) on dynamics of labile, recalcitrant and stable C fractions, soil microbes, microbial biomass, activities of extracellular enzymes and CO 2 emissions in sandy and clayey textured soils. The role of texture (sandy and clayey) in the mitigation of temperature effect was also investigated. The results revealed that the temperature sensitivity of C fractions and extracellular enzymes was in the order recalcitrant C fractions > stable C fractions > labile C fractions and oxidative enzymes > hydrolytic enzymes. While temperature sensitivity of soil microbes and biomass was in the order bacteria > actinomycetes > fungi ≈ microbial biomass C (MBC) > microbial biomass N (MBN) > microbial biomass N (MBP). Conversely, the temperature effect and sensitivity of all key soil processes including CO 2 emissions were significantly ( P < 0.05) higher in sandy than clayey textured soil. Results confirmed that under the scenario of global warming and climate change, soils which are sandy in nature are more susceptible to temperature increase and prone to become the CO 2 -C sources. It was revealed that clayey texture played an important role in mitigating and easing off the undue temperature influence, hence, the sensitivity of key soil processes., Competing Interests: The authors declare that they have no competing interests., (© 2022 Hassan et al.)

Ammonia (NH 3 ) volatilization in rice paddies may be affected by elevated atmospheric CO 2 concentration ([CO 2 ]) and temperature due to changes in plant and soil nitrogen (N) metabolism. At present, little is known about the individual and combined effects of CO 2 enrichment and warming on NH 3 volatilization under field conditions. An experiment was conducted in a rice paddy in Central China, after 4 years of warming and CO 2 enrichment using open-top chamber (OTC) devices. Compared with ambient conditions, elevated [CO 2 ] had no significant effects on NH 3 volatilization, although increases in soil pH and urease activity were observed. The stimulation on plant N assimilation under CO 2 enrichment might offset the possible enhancement on NH 3 volatilization, as more soil N was absorbed by plant thus reducing NH 3 loss potential. Elevated temperature increased NH 3 volatilization significantly, which could be attributed to increased soil ammonium nitrogen (NH 4 + -N) concentration, pH, and urease activity. Combination of CO 2 enrichment and warming caused the highest cumulative NH 3 loss, which increased by 26.5% compared with ambient conditions, but the interaction was not significant. Higher plant N uptake, soil NH 4 + -N concentration, pH and urease activity were also observed with co-elevation of [CO 2 ] and temperature, but the combined effects were variable and not synergistic. Our findings confirm that field warming and CO 2 enrichment cause more NH 3 volatilization in rice paddies, among which warming effects are dominant, and suggest that improved N management or field practices are required to reduce NH 3 losses under future climate change., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2020. Published by Elsevier B.V.)

River networks in subtropical agricultural hilly region become an inconvenient greenhouse gas (GHG, methane and nitrous oxide) source because of the influence of human activities, which has caused large uncertainties for refinement of national GHG inventories and their global budget. Based on field monitoring experiments at high temporal resolution, we employed regression tree and importance analysis to identify quantitatively factors that influence the diffusive flux of GHGs to provide a scientific basis for reducing GHG emissions and controlling regional carbon and nitrogen losses. The results indicate that significant spatiotemporal variation of methane (CH 4 ) nitrous oxide (N 2 O) diffusion occurs in all the four reaches (W1, W2, W3 and W4) of Tuojia river networks. Among them, W1 contributed lowest CH 4 (22.55 μg C m -2  h -1 ) and N 2 O (5.00 μg N m -2  h -1 ) diffusive flux than the other three (P < 0.05), while W4 offered highest CH 4 (166.15 μg C m -2  h -1 ) and N 2 O (30.47 μg N m -2  h -1 ) diffusive flux but with no statistically significant difference between W2 and W3 due to homogeneous extraneous nutrition loading into the two reaches. W4 also contributed largest cumulative flux of CH 4 (14.55 kg C ha -1  yr -1 ) and N 2 O (2.69 kg N ha -1  yr -1 ) in Tuojia River networks (P < 0.05). Furthermore, the regression tree and importance analysis indicate that, in the anaerobic environment, dissolved oxygen saturation controlled the production and diffusion for both CH 4 and N 2 O. The findings of this investigation highlighted that decision support tools provide an effective pathway to enhance the GHG mitigation technology research in agroecosystems and simultaneously shed light on the global campaign on refinement of national GHG inventories as well as regional nutrient management., Competing Interests: Declaration of competing interest All the authors have seen and approved the final version of this manuscript, and they are aware of and accept responsibility for the manuscript. Therefore, there is no conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Effectiveness of N might be modified in rice cultivation under future climate change with elevated atmospheric CO 2 concentration ([CO 2 ]). At present, limited information is available to understand how plant N uptake and N use efficiency respond to elevated [CO 2 ] and/or temperature in Chinese double rice cropping systems. A four-year field experiment was therefore conducted using open-top chambers with varying [CO 2 ] (ambient, ambient +60 μmol mol - 1 ) and varying temperature (ambient, ambient +2 °C) in Hubei Province, Central China. Compared with ambient conditions, elevated [CO 2 ] increased plant N uptake and N use efficiency, as measured by fertilizer N recovery efficiency (NRE), N agronomic efficiency (NAE), N physiological efficiency (NPE) and apparent system N use efficiency (NUE sys ), in both early rice and late rice. CO 2 enrichment tended to decrease soil mineral N concentration since more N was assimilated by plants. Elevated temperature led to lower plant N uptake and decreased NRE and NAE in early rice, due to a reduction in grain yield induced by heat injury. In contrast, warming increased plant N uptake and N use efficiency in late rice as no heat stress existed. Warming tended to increase soil mineral N concentration in early rice but had negligible effects in late rice. When elevated [CO 2 ] and temperature were combined, the positive effects of CO 2 enrichment for N utilization were able to compensate for the negative effects of warming in early rice, while the interaction was synergetic in late rice. Hence, co-elevation of [CO 2 ] and temperature led to higher N use efficiency (64.6% for NUE sys across four years) and decreased annual N surplus by 28.6-36.5 kg N ha - 1 compared with ambient conditions. Our findings confirm that CO 2 enrichment and air warming can improve N use efficiency at both crop level and system level in Chinese double rice cultivation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Assessment of indirect emission factors (EF 5r ) of nitrous oxide (N 2 O) from agricultural river networks remains challenging, and results are uncertain due to limited data availability. This study compared two methods of assessing EF 5r using data from long-term observations at high temporal resolution in a typical agricultural catchment in subtropical central China. The concentration method (method 1) and the Intergovernmental Panel on Climate Change (IPCC) 2006 method (method 2) were employed to evaluate the emission factor. EF 5r estimated using method 1 (i.e., EF 5r1 ) was 0.00077 ± 0.00025 (0.00038-0.00097). EF 5r calculated using method 2 (i.e., EF 5r2 ) was lower than EF 5r1 , with a mean value of 0.00004 (0.000015-0.00012). Both EF 5r1 and EF 5r2 were significantly lower than the IPCC 2006 default value of 0.0025, suggesting that N 2 O emissions from China and world river networks may be grossly overestimated. A complex N 2 O production pathway and diffusion mechanism were responsible for the transfer of N 2 O from the sediment to river water and then to the atmosphere. These findings provide essential data for refining national greenhouse gas inventories and contribute evidence for downward revision of indirect emission factors adopted by the IPCC.

In this study, the novel adsorbent PVA-TA-βCD was synthesized via thermal cross-linking between polyvinyl alcohol and β-cyclodextrin. The characterization methods SEM-EDS, FTIR, and XPS were adopted to characterize the adsorbent. The effect of pH, contact time, initial concentrations, and temperature during the adsorption of Pb(II), Cd(II), and Mn(II) onto the PVA-TA-βCD was also investigated. In a single-component system, the data fitted well to pseudo-second-order, and film diffusion and intra-particle diffusion both played important roles in the adsorption process. As for isotherm study, it showed a heterogeneous adsorption capacity of 199.11, 116.52, and 90.28 mg g -1 for the Pb(II), Cd(II), and Mn(II), respectively. Competition between the ions existed in a multi-component system; however, owing to the stronger affinity of the PVA-TA-βCD for Pb(II) relative to Cd(II) and Mn(II), the Pb(II) adsorption onto the PVA-TA-βCD was less affected by the addition of the other metals, which could be effectively explained by the hard and soft acid and base theory (HSAB). Furthermore, PVA-TA-βCD showed good reusability throughout regeneration experiments.

Due to the increasing environmental impact of food production, carbon footprint as an indicator can guide farmland management. This study established a method and estimated the carbon footprint of grain production in China based on life cycle analysis (LCA). The results showed that grain production has a high carbon footprint in 2013, i.e., 4052 kg ce/ha or 0.48 kg ce/kg for maize, 5455 kg ce/ha or 0.75 kg ce/kg for wheat and 11881 kg ce/ha or 1.60 kg ce/kg for rice. These footprints are higher than that of other countries, such as the United States, Canada and India. The most important factors governing carbon emissions were the application of nitrogen fertiliser (8-49%), straw burning (0-70%), energy consumption by machinery (6-40%), energy consumption for irrigation (0-44%) and CH 4 emissions from rice paddies (15-73%). The most important carbon sequestration factors included returning of crop straw (41-90%), chemical nitrogen fertiliser application (10-59%) and no-till farming practices (0-10%). Different factors dominated in different crop systems in different regions. To identity site-specific key factors and take countermeasures could significantly lower carbon footprint, e.g., ban straw burning in northeast and south China, stopping continuous flooding irrigation in wheat and rice production system.

To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5tha(-1) biochar (BC1), application of 10tha(-1) biochar (BC2), application of 10tha(-1) biochar (BC3), rice straw return at 2400kgha(-1)(RS) and inoculated rice straw return at 2400kgha(-1)(RI). The results indicated that biochar amendment significantly decreased methane (CH4) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production (p<0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20tha(-1)) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system., (Copyright © 2016 Elsevier B.V. All rights reserved.)