Alternate wetting and drying irrigation (AWD) is widely adopted to save water in crop production, yet it may enhance nitrogen (N) leaching and deep migration in alluvial soil with high water percolation, posing risks to groundwater quality and N use efficiency. A 3-yr field experiment was conducted to elucidate the dual role of biochar in reducing N leaching and reshaping 0-200 cm soil N migration in AWD-managed alluvial soil paddies with three treatments in total, including continuous flooding irrigation (CF) without biochar, AWD without biochar, and AWD with 20 t ha(-1) maize straw biochar. The shift from CF to AWD significantly reduced water percolation by 29 % but increased NO3--N leaching and inorganic N deep migration (100-200 cm) in most cases. AWD combined with biochar lowered water percolation by 36 % over CF alone and reduced inorganic N leaching by 24 % over AWD alone. In addition, AWD combined with biochar increased topsoil (0-40 cm) inorganic N and total N accumulation by 151-280 % while reducing their deep migration (150-2350 %) compared to AWD alone. The reduction in inorganic N deep migration stemmed from the decreased soil solution NO3--N at 120-200 cm, and the enhanced surface soil NH4+-N and inorganic N at 40-100 cm. This study highlights the potential of biochar as a valuable soil amendment that effectively decouples the trade-off between water-saving irrigation and environmental degradation, offering a sustainable strategy for N management in high-percolation cropping systems.

Co-applying biochar with phosphate-solubilizing bacteria (PSB) holds promise for ameliorating severely degraded ecosystem productivity due to low phosphorus (P) bioavailability in saline-alkaline soils. However, their interaction on how biochar reshapes microbial metabolism function remains poorly understood. Here, low/high-temperature biochar (BC300 and BC700) were utilized to explore the possible mechanism on biochar derived carbon-driven cell's metabolic characteristics in terms of P-solubilization optimization. Specifically, BC300 at 15,000 mg/L was prominent in P-solubilization level over 37.0% of the control rather than BC700 (decreased by 21.4%). Consistent with this divergence, BC300 exhibited significantly higher DOC (108.9 vs. 21.5 mg/L) and SUVA254 values (4.3 vs. 0.9) than BC700. Metabolic-transcriptomic revealed up-regulated the PhoR/PhoB two-component system, enhancement of aromatic amino acid metabolism alongside suppressed ribosome biosynthesis and citrate cycle in BC300. Further detection on targeted LC-MS confirmed a 12.8-fold increase in extracellular maleic acid (28,571.2 ng/mL). Meanwhile, BC300 also improved stress defense supported by increase in extracellular polymeric substances and superoxide dismutase activity. Collectively, these findings suggest the pivotal role of low-temperature biochar in modulating microbial metabolic response to phosphorus deficiency under saltine-alkaline stress, which is possibly associated with aromatic-rich DOC that drives organic acid overflow and stress defense, thereby sustaining efficient P-solubilization.

We propose an innovative dipole magnet vacuum chamber design to minimize eddy currents based on a thin-wall stainless steel outer envelope supported by a titanium alloy ring structure. The internal surface of the chamber is coated with a thin layer of Ti-Zr-V non-evaporable getter (NEG) film to decrease the pressure gradient. The present study characterizes the ultimate pressure, the pumping speed, and the adsorption capacity of Ti-Zr-V both at room temperature and at liquid nitrogen temperature (LN2), and likewise for Ti film. Monte Carlo draws were used to obtain an accurate getter film sticking probability, and the results indicate that in the NEGcoated chamber saw a significant decrease in pressure from 5.8 x 10- 9 Pa at 295 K to 9.28 x 10- 10 Pa at 80 K. Furthermore, the maximum sticking probabilities of H2 for Ti-Zr-V film at 295 K and 80 K were 0.002 and 0.006, respectively. Thus, the Ti-Zr-V film has a measurable adsorption capacity at low temperature. The initial pumping rate of the Ti film for H2 at 80 K was higher than that of the Ti-Zr-V film, but the Ti film saturated faster. Finally, the average calculated static pressure in the arc section of the HIAF-BRing vacuum system with an NEGcoated titanium alloy-lined thin-wall chamber was found to be less than 3.2 x 10- 10 Pa at low temperature.

As an organic soil amendment, biochar can effectively increase the contents of soil nutrients such as nitrogen (N), phosphorus (P), and potassium (K). However, few studies have focused on the effects of biochar on K fractions and contents in maize rhizosphere soil. To investigate the effects of biochar on different K fractions in maize rhizosphere soil and on maize growth, four treatments were established in this experiment: B0K0 (control, no biochar and no K fertilizer), B0K1 (no biochar, K fertilizer at 60 kg ha-1 yr-1), B1K0 (biochar at 2.625 t ha-1 yr-1, no K fertilizer), and B1K1 (biochar at 2.625 t ha-1 yr-1 combined with K fertilizer at 60 kg ha-1 yr-1). Results indicate that biochar significantly increased microbial biomass carbon (MBC), cation exchange capacity (CEC), and electrical conductivity (EC) in the rhizosphere soil, while also improving rhizosphere soil pH. Compared with the treatment without biochar, biochar application significantly increased the content of water-soluble potassium (WSK), exchangeable potassium (EK), and non-exchangeable potassium (NEK) in the rhizosphere soil by 18.57% (2021) and 11.18% (2022), 13.49% (2021) and 11.43% (2022), 14.65% (2021) and 17.06% (2022), respectively. However, the increases in different K fractions were not accompanied by significant changes in total K (TK) content across the two years. In addition, biochar application significantly improved maize root development, plant height, stem diameter, and leaf area index. Meanwhile, aboveground dry weight and K uptake increased significantly by 13.87% (2021) and 12.04% (2022), and 41.84% (2021) and 43.87% (2022), respectively. Compared with B0K0, the B1K1 treatment-which combined biochar with K fertilizer-exhibited the highest K content in all forms within the rhizosphere soil, along with the greatest maize aboveground dry weight and K uptake. This study demonstrates biochar's potential in meeting crop root K demands, laying the foundation for its application in enhancing soil K fertility.

A magnetic mass spectrograph has been developed for measuring the ion composition of pulsed vacuum arc ion sources at 60 kV extraction voltage. The mass spectrograph is comprised of an ion beam collimator, an einzel lens, a 114 degrees dipole magnet, and a 416-channel Faraday-strip array detector. The main advantages of this mass spectrograph are its high simultaneous mass-to-charge ratio detection range and gapless Faraday-strip array detector. This paper introduces the design of the mass spectrograph and evaluates its performance in terms of resolving power and simultaneous detection range.

Phosphorus (P) is a key macronutrient for plants. Nevertheless, its low efficiency and overuse in paddy soil were addressing important agricultural and environmental issues. Biochar has been generally accepted as an effective and environmentally friendly material for improving soil fertility, but its role in soil P cycling and related microbial processes has not been adequately understood. In this study, a field microcosm experiment was carried out to assess the impact of three biochar types (rice husk biochar, BC; low-phosphorus biochar, LP; high-phosphorus biochar, HP) at two rates (0.5% and 2%, w: w) on soil P fractions, arbuscular mycorrhizal (AM) fungal colonization, microbial community structure, and rice growth. Biochar addition significantly increased soil pH, total carbon content, and total nitrogen content, and also significantly affected soil P fractions by increasing P availability. HP addition significantly increased soil total P, available P, and phosphatase activity by 3%, 158%, and 76%, respectively. Compared with all other treatments, the 0.5% HP treatment significantly increased rice shoot dry weight by 11% and 40% P accumulation in shoot and 29% in root, together with a higher AM fungal colonization rate. In contrast, grain yield was not significantly different among treatments, indicating that biochar addition mainly improved soil fertility and nutrient uptake ability rather than grain yield under the experimental conditions. Metagenomic analysis further showed that HP addition increased microbial richness and diversity and changed microbial community structure by reducing the relative abundance of Acidobacteria and Chloroflexi, increasing genes involved in fructose metabolism, and increasing the abundance of AM fungi and beneficial bacteria. In general, these findings showed that biochar, especially 0.5% HP, improved soil P cycling and microbial functional potential, and thus improved paddy soil P cycling and rice P uptake. This study emphasizes the importance of targeted biochar application as a sustainable approach for optimizing P management in paddy soils.

Antibiotic residues threaten agricultural ecosystems, yet the differential phytotoxicity of typical antibiotics and the antibiotic-specific remediation mechanisms of zero-valent iron biochar (ZVI/BC) in soil-rice systems remain unclear, particularly regarding the integrated analysis of soil properties, rice growth, and key regulatory factors. This study investigated tetracycline (TC), and sulfamethoxazole (SMX) stress on rice and remediation by ZVI/BC via pot experiments. SMX exhibited stronger toxicity than TC, causing 72.39% reduced plant height, complete tiller inhibition, 95.61% lower total dry matter, and impaired root morphology/antioxidant systems, while TC only slightly inhibited panicle weight (28.96%). ZVI/BC effectively remediated TC-polluted rice (7.55% increased dry matter, reduced antioxidant enzyme activity) but had limited effects on SMX pollution (122.73% higher plant height, 7.85-fold dry matter accumulation, yet unrecovered tillering/roots). It improved soil physicochemical properties (e.g., 49.74% higher electrical conductivity, 37.37%-49.18% increased total K/C) and available nutrients, reducing soil TC (83.53%) and SMX (73.57%) residues via adsorption-degradation synergy, and inhibiting antibiotic enrichment in rice (root > stem > leaf > panicle). Random forest modeling identified soil physicochemical factors (CEC, total K) as dominant regulators under TC pollution, and root development/available P as key limiting factors under SMX pollution. This study demonstrates ZVI/BC's potential for agricultural antibiotic remediation, but material optimization for highly toxic antibiotics and field-scale collaborative mechanisms require further exploration to support antibiotic control.

IntroductionStraw biochar can significantly increase the content of available potassium (K) in soil, whereas its regulatory effect on soil K supply capacity remains unclear and lacks long-term field verification. To clarify the response mechanism of soil K supply capacity to long-term straw biochar amendment, a 9-year continuous field experiment was carried out to explore the improvement effect of straw biochar on soil K supply characteristics and K uptake by maize.MethodsThis study was conducted based on a long-term field experiment in Shenyang Agricultural University under a humid and sub-humid monsoon climate, with Haplic Luvisols as the tested soil. After 9 consecutive maize growing seasons, soil samples at the 0–20 cm depth were collected. A two-factor randomized block design was set up with four treatments, including B0K0 (no biochar and no K fertilizer), B0K1 (K fertilizer only), B1K0 (biochar only), and B1K1 (biochar with K fertilizer).Results9 consecutive years of straw biochar application significantly increased illite content. Compared to B0K0, the illite proportion in B1K0 and B1K1 increased by 16.15% and 19.84%, respectively. The soil K quantity/intensity (Q/I) curve and K release kinetic curves showed that biochar significantly improved soil K supply pool (−ΔK0) and K supply intensity (ARe) by 60.76% and 36.06%. In addition, biochar reduced the content of exclusively adsorbed K (Kx) and the free exchange energy of K (−ΔG), and effectively increased the cumulative release of soil K.DiscussionThese variations induced by biochar application effectively alleviated the negative K balance of farmland soil, comprehensively improved soil K supply capacity, and facilitated K uptake and utilization of maize, which further promoted the accumulation of plant dry matter. This long-term field study confirms that the combined application of straw biochar and K fertilizer is an effective measure to improve soil K availability, which provides reliable scientific basis for K nutrient regulation in farmland soil.

Iron-modified biochar shows high efficiency in Cr(VI) removal; however, its long-term stability and aging mechanisms remain inadequately understood. In this study, iron-modified biochar was synthesized through co-pyrolysis (FeBC1) and impregnation-precipitation (FeBC2) methods, followed by oxidative aging with H2O2. Characterization techniques (SEM-EDS, BET, XPS, etc.) confirmed the successful incorporation of Fe3O4 nano-particles and enhanced surface functional groups. Electrochemical analysis (CV, Tafel) revealed a distinct Fe(II) oxidation peak at 0.36 V and the highest corrosion potential (0.22 V) for FeBC1, indicating superior reducibility and interfacial stability. The maximum adsorption capacity of FeBC1 for Cr(VI) reached 38.95 mg g-1, which is 3.9 times that of pristine biochar. Kinetic analysis suggested that Cr(VI) removal follows a synergistic mechanism involving adsorption, reduction, and immobilization. Oxidative aging selectively etched the amorphous carbon domains, resulting in decreased Fe(II) content, a negative shift in corrosion potential, and weakened reducibility. Concurrently, the increased oxygen-containing functional groups and decreased zeta potential diminished electrostatic attraction, ultimately reducing the adsorption capacities of FeBC1 and FeBC2 by 11.99 % and 8.52 %, respectively. Despite the performance decline, the oxidatively aged biochar retained relatively high removal efficiency and exhibited excellent environmental stability, with Cr(VI) leaching below 5.19 % across a broad pH range (2-14) and active iron release below 3.21 %. This study confirms that although oxidative aging reduces the reducibility of iron-modified biochar, it maintains excellent structural stability, providing crucial scientific support for its long-term and safe application in Cr(VI) remediation.

The dynamic vacuum effect is the primary constraint on beam intensity in high-intensity heavy-ion syn chrotrons. The dynamic vacuum effect induced by the charge exchange beam loss significantly limits the ion intensity and beam lifetime in the booster ring (BRing) of the HIAF. The collimator is a critical and indis pensable component for mitigating the dynamic vacuum effect in high-intensity heavy-ion circular accelerators. A dedicated collimation system was designed for BRing to decrease ion-induced gas desorption and suppress the dynamic vacuum effect. Nevertheless, this intercepting structure may introduce longitudinal and transverse beam coupling impedances in BRing. In this study, comprehensive investigations were conducted to charac terize the beam-coupling impedance of a movable collimator. Furthermore, we systematically describe the results of the single- and two-wire bench transmission measurements and numerical simulations. Satisfactory agreement was obtained between the numerical simulations and wire transmission bench measurements. The heat deposition power on each part of the collimator due to the longitudinal impedance was evaluated. The 24 movable collimators were processed and entered the online installation stage of the Booster Ring.

To investigate the effects of long-term biochar application on different forms of potassium (K) content in maize rhizosphere soil and maize growth, two biochar application rates (B0: 0 t ha⁻¹ yr⁻¹, B1: 2.625 t ha⁻¹ yr⁻¹) and two K fertilizer application rates (K0: 0 kg ha⁻¹ yr⁻¹, K1: 60 kg ha⁻¹ yr⁻¹) to create four treatments (B0K0, B0K1, B1K0, B1K1). In this long-term field trial, we investigated various forms of K in the maize rhizosphere soil, together with soil physicochemical properties and maize growth indicators. Results indicate that biochar significantly increased microbial biomass carbon (MBC), cation exchange capacity (CEC), and electrical conductivity (EC) in the rhizosphere soil, while also improving rhizosphere soil pH. Compared with the treatment without biochar, biochar application significantly increased the content of water-soluble potassium (WSK), exchangeable potassium (EK), and non-exchangeable potassium (NEK) in the rhizosphere soil by 18.57% (2021) and 11.18% (2022), 13.49% (2021), and 11.43% (2022), 14.65% (2021), and 17.06% (2022), respectively. Maize roots were more developed, and plant height, stem diameter, and leaf area index were significantly increased. With above-ground dry weight and K uptake significantly increasing by 13.87% (2021) and 12.04% (2022), and 41.84% (2021) and 43.87% (2022), respectively. Compared with B0K0, the B1K1 treatment—which combined biochar with K fertilizer—exhibited the highest K content in all forms within the rhizosphere soil, along with the greatest maize aboveground dry weight and K uptake. This study demonstrates biochar’s potential in meeting crop root K demands, laying the foundation for its application in enhancing soil K fertility.

Biochar and stover incorporation are common ways to achieve long-term increases in soil organic carbon (SOC) storage. However, the effects of biochar and stover application on the dissolved organic carbon (DOC) molecular chemodiversity and origin of SOC still remain unclear. We explored the DOC molecular chemodiversity, plant derived carbon and microbial necromass carbon by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), lignin phenols and amino sugars by using a 10-year maize field experiment receiving three treatments (control, biochar application at a rate of 2.63 t ha−1 annually, hereafter termed BC, stover application at a rate of 7.5 t ha−1 annually, hereafter termed SR). Both biochar and stover incorporation increased SOC contents significantly (P < 0.05), with no significant difference in the topsoil between BC and SR treatments (0–20 cm, BC: + 49.70

Undissolved biochar (UBC) plays a key role in persistently affecting bacterial characteristics after loss of dissolved biochar. However, its potential role as electron shuttle mediating tetracycline (TC) removal by bacteria is less understood. Result demonstrated UBC (700°C) coupled strain MSM2304 resulted in 72.19 % of TC biodegradation (37.76 % in free cells). UBC improved nutrients usage of TOC and TN to enhance cells proliferation, and facilitated biofilms formation and secretion of redox-active-related extracellular polymeric substances (EPS) including protein (40 % higher) and humus (30 % higher). Moreover, UBC optimized cells oxidative stress indicators including reactive oxygen species (40 % lower), total antioxidant capacity (30 % higher), superoxide dismutase (35 % higher), and catalase (30 % higher) during TC exposure. Importantly, UBC not only accelerated electron transfer from intracellular into extracellular by stimulating cytochrome C reductase activity and cytochrome C development, also decreased extracellular electron transfer resistance between MSM2304 and TC from 231.7 to 109.5 Ω, proved by cyclic voltammetry and electrochemical impedance spectra of EPS, and helped quinone moieties formation on UBC through CO and CC or CO production determined by FTIR and XPS. These findings indicate UBC could be as electron shuttle and contribute to provide a better understanding of interactions between biochar and microorganism.

The biochar standard could exert profound influences on the sustainable and sound production and application of biochar to address the agriculture and environment problems. Therefore, the feedstock and quality requirements of biochar were summarized and compared based on six standards of International Biochar Initiative (IBI) Biochar Standards in USA, European Biochar Certificate (EBC) in Europe, Biochar Quality Mandate (BQM) in UK, Code of Practice by Australia New Zealand Biochar Initiative (ANZBI) Inc., Biochar of agricultural industry standard in China (CNAIS) and Singapore Standard (SGS). The comparison mainly focuses on the feedstock of biochar, properties requirements, proposed limits for heavy metals and organic pollutants, and packaging requirements set by biochar standards. Based on the published studies, the basic properties, heavy metals and polycyclic aromatic hydrocarbons of biochar are summarized and compared with biochar standards. The proposed recommendations on biochar for soil application will help to further promote the long-term and sustainable benefits of biochar management.

Application of zero valent iron biochar (ZVI-BC) activated persulfate (PS) oxidation in various antibiotics treatments has been universally confirmed. Full utilization of biomass waste characteristics to reduce usage of toxic reagents in the preparation of ZVI-BC is an environmental optimization strategy. Herein, tetracycline (TC) degradation based on PS-oxidation activated by a novel ZVI-BC (ZVI-Fe3O4-BC) was assessed, in which blueberry pomace extraction substitutes part of sodium borohydride and red mud substitutes iron salt. The ZVI-Fe3O4-BC was a magnetic material loading ZVI on its surface by characterization detection. ZVI-Fe3O4-BC/PS degradation system resulted in over 95.6 % of TC removal following to conditions optimization and ·OH, SO4-·, ·O2- radicals contributed 27.8 %, 29.4 % and 20.8 %, respectively. Although TC ultimately degraded into H2O and CO2, the presence of toxic intermediates during the reaction emphasizes the importance of the sufficiency of reaction. This study highlights the potential of natural waste as substitutes for toxic reagents in environmental remediation.

The accumulation of soil organic carbon (SOC) is critical for maintaining soil fertility and mitigating climate change. The incorporation of organic amendments is a common practice for improving SOC, but the SOC dynamics affected by biochar and straw in rice cultivation still remain unclear. This study focused on paddy ecosystems in cold regions of Northeast China. Through a two-year field experiment (with three treatments: conventional fertilization (CK), biochar application (BC), and straw incorporation (SR)), combined with amino sugars and lignin phenols as biomarkers, the differential soil organic carbon dynamics were revealed. The results revealed that biochar and straw incorporation significantly increased the soil organic carbon content by 10.4 % and 3.4 %, respectively (P< 0.05), among which straw incorporation increased the accumulation of plant-derived carbon by 2.6 % and microbial necromass carbon by 4.8 %, and the contribution rate of bacterial necromass carbon reached 12.8 %. The SR and BC treatments increased the proportion of macroaggregates by 6.1 % and 10.1 %, respectively. Biochar treatment significantly changed the origin of SOC, reducing the proportion of plant-derived carbon by 2.9 % while increasing the fungal/bacterial necromass carbon ratio (F/B) to 3.2. These results demonstrate that straw incorporation enhances carbon conversion efficiency by synergistically increasing plant-derived and microbial necromass carbon, whereas biochar enhances carbon pool stability by promoting plant-derived carbon conversion and reconstructing the proportion of the carbon fraction dominated by fungal necromass carbon. Overall, this study highlights the different carbon sequestration pathways between biochar and straw incorporation and reveals the function of carbon sequestration in biochar application.

Methane (CH4), a significant greenhouse gas, plays a critical role in the global emission dynamics, with agricultural soils exerting dual action on its atmospheric levels. While the efficacy of biochar and stover incorporation in mitigating CH4 emissions in flooded soils is well-documented, their impact in upland systems, particularly within maize monocropping systems, has not been fully elucidated. This study presents a comprehensive analysis of the effects of biochar and stover incorporation on CH4 fluxes and the associated methanogenic and methanotrophic microbial communities in a maize monocropping system in Northeast China, over a fiveyear period. The field study was established with three treatments: untreated control (CK), maize stover incorporation at 7.5 t ha-1 yr-1 (MS), and biochar application at 2.63 t ha-1 yr-1 (MB). Soil CH4 fluxes, physical and chemical properties, and abundances of mcrA and pmoA genes were measured. Our findings indicated that MB and MS treatments effectively enhanced total CH4 uptakes during the study period compared to CK by 55.3 % and 84.4 %, respectively. Both MS and MB treatments significantly increased soil organic C (SOC), easily oxidizable C (EOC), and dissolved organic C (DOC) contents, with MS demonstrating a more pronounced boost. A shift in the microbial community, favoring methanotrophy, was indicated by a reduced mcrA/pmoA ratio and altered gene abundances of mcrA and pmoA in the MB and MS relative to the CK. Pearson's correlation analysis did not find a significant relationship between DOC and soil water content (SWC) with CH4 emissions. The random forest (RF) model identified that pmoA, mcrA/pmoA, SOC, and mcrA were the top four determinants of CH4 emissions. This study underscores the potential of biochar and stover return as effective strategies for reducing agricultural CH4 emissions and emphasizes the necessity of elucidating the microbial underpinnings involved. Further research is warranted to refine these practices for diverse agricultural contexts and to evaluate their long-term environmental efficacy.

Biochar is a promising strategy for improving crop yield and mitigating greenhouse gas emissions. However, the impacts of acid modified biochar on CH4 emissions and yield in rice fields are not comprehensively understood, especially under alternate wetting and drying irrigation (IAWD). Here, we conducted a 3-yr (2019-2021) field experiment with two irrigation regimes (ICF: continuous flooding irrigation, IAWD) and three biochar treatments (B0: no biochar; B20: 20 t ha-1 rice straw biochar; and B20A: 20 t ha-1 acid modified rice straw biochar). Results showed IAWD reduced CH4 emissions by 63-80 % and water consumption by 10-12 % but threatened the rice soil fertility. B20 and B20A increased soil cation exchange capacity by 13-36 %, soil organic carbon by 24-44 % and C/N by 17-36 % over the three years. However, compared to B0, B20 tended to increase CH4 emissions and factor (CH4EF), reduced grain yield by 6 % in 2019, but B20A suppressed CH4 emissions by 19 % while maintaining a stable grain yield. B20 and B20A enhanced yield by 5 % and 8 %, 11 % and 12 % and decreased CH4 emissions by 22 % and 38 %, 38 % and 40 % in 2020 and 2021, respectively. B20A alleviated its initial negative impact on CH4 emissions and yield in 2019 due to acid modified biochar enhancing more acidic and oxygenated functional groups. IAWDB20A decreased CH4 emissions by 75-89 % and greenhouse gas emission intensity (GHGI) by 75-90 % compared to ICFB0 over the three years. Consequently, B20A coupled with IAWD achieves sustainable use of water resources, improves soil degradation and mitigates climate change.

Given the worsening global climate change that drives drought frequency and irrigation water shortages, implementing water-conserving practices like alternate wetting and drying (AWD) is now critically urgent. Biochar is widely used for soil carbon sequestration. However, there is limited information on the effects of biochar on soil organic carbon (SOC) and its labile fractions in paddy fields, especially under AWD. A two-year field experiment was conducted with two irrigation regimes (CF: continuous flooding irrigation; AWD) as the main plots and 0 (B0) and 20 t ha−1 (B1) biochar as sub-plots. AWD had no effect on the SOC and particulate organic carbon (POC) content, but increased the dissolved organic carbon (DOC), microbial biomass carbon (MBC), easily oxidizable organic carbon (EOC), light fraction organic carbon (LFOC), and carbon pool management index (CPMI) at 0–10 cm depths, by 24.4–56.4%, 12.6–17.7%, 9.2–16.8%, 25.6–28.1%, and 11.3–18.6%, respectively. Biochar increased SOC while also increasing DOC, MBC, EOC, LFOC, POC, and CPMI at 0–20 cm depths, by 18.4–53.3%, 14.7–70.2%, 17.4–22.3%, 10.2–27.6%, 95.2–188.3%, 46.6–224%, and 5.6–27.2, respectively, making SOC more labile under AWD. Our results highlight that biochar still holds great potential for improving soil quality and carbon sequestration under AWD, and the combination of biochar and AWD can achieve the synergistic optimization of the food–water–carbon sequestration trade-off, which is beneficial to sustainable agricultural production.