Microplastics pollution constitutes a global environmental challenge. Although degradable microplastics can alter soil organic carbon (SOC) mineralization through the priming effect, the key drivers governing this process remain poorly understood, especially in the subsoil (> 30 cm). Combining a meta-analysis, an incubation experiment, and a random forest model, we found that dissolved organic carbon (DOC) from microplastics decomposition affected the priming effect by regulating microbial growth. Specifically, the highly biodegradable polyhydroxyalkanoate promoted microbial growth by increasing the DOC released from microplastics decomposition, thereby enhancing SOC mineralization via a positive priming effect (462 to 1198 mg CO2-C kg-1 soil). Polylactic acid with low biodegradability reduced carbon availability through the sorptive protection of soil DOC, consequently decreasing SOC mineralization by 149 to 268 mg CO2-C kg-1 soil. In the subsoil, fungi primarily used the microplastics-derived DOC as carbon and energy source through enzyme-mediated nutrient mining, which represents the main driving mechanism for the strong positive priming effect. In the topsoil, the preferential absorption and assimilation of microplastics-derived DOC by bacteria promoted the microbial necromass accumulation, thus attenuating the priming effect through microbial and mineral carbon pumps. These findings highlight the role of carbon availability (particularly DOC) in topsoil and subsoil on the microplastics-induced priming effect, and underscore the necessity of incorporating soil carbon status into assessments of microplastics pollution impacts on global carbon budgets and soil health.

Tillage and crop rotation systems are known to influence soil nematode community structure, but their effects on community assembly processes remain unclear. We conducted a two-year field experiment in the black soil of northeast China to assess how tillage practices— no-tillage (NT), reduced tillage (RT), and conventional tillage (CT)—combined with cropping systems—continuous corn (CC) and corn-soybean rotation (CS)—affect nematode community structure, assembly processes, and associated environmental drivers. A semi-quantitative approach that combined nematode extraction with high-throughput sequencing of 18S rDNA was employed. Tillage, rotation, and their interaction significantly affected nematode alpha diversity and abundance. Compared to CT-CC, RT-CC treatment significantly enhanced nematode Richness and Chao1, while CT-CS treatment increased nematode total abundance. Community composition also varied with tillage, with Acrobeloides (bacterivore) dominating across treatments and Aphelenchoides (fungivore) being particularly enriched under CT. Assembly analyses revealed that CT intensified environmental filtering and deterministic processes, leading to community homogenization-particularly in the CC system, where Aphelenchoides was strongly linked to deterministic assembly. In contrast, NT and RT improved microhabitat heterogeneity, enhancing the role of stochastic processes under both cropping systems. Environmental factors, particularly dissolved organic nitrogen (DON) and ammonium nitrogen (NH4+-N), emerged as key drivers of nematode community structure and assembly, respectively. These findings highlight that aligning nitrogen management with rational tillage–rotation strategies is essential for promoting nematode functional diversity and sustaining soil ecosystem functioning in black soil regions.

Streptomyces, a well-known plant growth-promoting rhizobacterium (PGPR), often shows inconsistent efficacy in soil due to poorly understood interactions with native microbes and soil fauna. This study used factorial pot experiments to investigate how microbial competition and nematode predation influence the growth-promoting effect of Streptomyces on Arabidopsis thaliana (A. thaliana), through co-inoculation with indigenous soil microbes or/and nematodes. Compared to inoculation with Streptomyces alone, co-inoculation with either indigenous microbes or nematodes significantly reduced the aboveground dry biomass of A. thaliana, and Streptomyces relative abundance declined by 61.29 % and 79.68 %, respectively. Sequencing showed that Streptomyces introduction altered the indigenous resident community and significantly increased the abundance of functional genes for nutrient competition and antibiotic synthesis, resulting in strong competitive exclusion that impaired its growth-promoting effect. Nematode identification and feeding assays revealed that over 90 % of the nematode community were bacterivores grazing on Streptomyces spores, thereby preventing population recovery and growth-promoting function. However, when Streptomyces, microbes, and nematodes coexisted, the plant growth promotion was restored. This recovery was primarily driven by nematodes selectively grazing on competing taxa, reshaping the resident community and alleviating competitive constraints on Streptomyces, thereby sustaining its plant growth-promoting effect. These findings highlight trophic buffering as a key mechanism maintaining PGPR function in complex soils, which informs future strategies that design and apply PGPR inoculants around multitrophic interactions to achieve more stable field performance.

The soil micro-food web is a hidden engine driving nutrient cycling in agricultural ecosystems, with bacterivorous nematodes as key regulators. However, the effects of nematode predation on microbial-mediated nitrogen (N) transformations at the transcriptional level remain unclear. Here, we conducted a microcosm experiment using a fluvo-aquic soil with long-term N fertilization, inoculating Mesorhabditis (colonizer–persister 1 (c–p1)), Acrobeloides (c–p2), and their mixture, followed by metatranscriptomic sequencing. Mesorhabditis inoculation decreased copiotrophic Pseudomonadota and Actinomycetota, enriched oligotrophic Acidobacteriota, and concurrently increased positive co-occurrence associations. K01501 (nitrilase) and the KO00460 pathway were downregulated, coinciding with reduced Actinomycetota abundance. Multiple bacterial groups upregulated glutamine synthetase. Asparagine synthetase and asparaginase were coordinately upregulated, suggesting a potential pathway for N mobilization. The denitrification genes (napA, narG, nirK, nirS, norB, and nosZ) were upregulated, with multiple taxa contributing to distinct steps. This study provides transcriptional evidence that Mesorhabditis inoculation influences microbial N metabolism, establishing a metatranscriptomic framework for nematode-driven N dynamics in the North China Plain.

Soil microbial network complexity and stability are fundamental to ecosystem functioning, yet their interdependence across agricultural practices remains poorly understood. This study investigates long-term (>10 years) tillage (no-tillage [NT] vs. conventional tillage [CT]) and cropping systems (maize (Zea mays L.)-soybean (Glycine max Merr.) rotation [MS] vs. continuous maize [MM]) effects on bacterial network complexity and stability across soil layers (0-5 cm and 5-20 cm) in the black soils of northeastern China. High-throughput sequencing and cohesion-based network analysis were used to assess microbial interactions, complexity as the sum of absolute cohesion values, and stability as the ratio of negative to positive cohesion. Results revealed depth-dependent trade-offs between bacterial network complexity and stability. Compared to CT, NT increased complexity at 0-5 cm (2.13%) but reduced it at 5-20 cm (-2.69%), where stability improved (2.20%). Compared to MM, MS decreased complexity at both depths (0-5 cm: -2.11%; 5-20 cm: -3.94%) and improved stability at 5-20 cm (1.84%). Maximum complexity occurred under NTMM (no-tillage with continuous maize cropping) (0-5 cm) and CTMM (conventional tillage with continuous maize cropping) (5-20 cm), whereas stability was greatest under NTMS (no-tillage with maize-soybean rotation) (5-20 cm). A significant negative correlation between complexity and stability was detected at both depths (r = -0.38 at 0-5 cm; r = -0.75 at 5-20 cm), supporting the "complexity-stability paradox" in soil ecosystems. These findings underscore that trade-offs between microbial network complexity and stability are shaped by the interaction of agricultural practices and soil depth. Tailoring tillage and crop rotation strategies to influence specific soil depth zones is crucial for enhancing microbial resilience and sustaining long-term soil health.

Freeze-thaw events contribute substantially to annual soil greenhouse gas (GHG) emissions. However, it remains unclear how soil properties and microbial characteristics, altered by long-term agricultural management, individually or interactively regulate GHG emissions. To address this gap, we quantified CO2, CH4, and N2O fluxes through field monitoring during seasonal freeze-thaw periods in Mollisol farmland of Northeast China. Results demonstrated that CO2 and CH4 emissions were higher during the thawing period than the freezing period, with CH4 emission increasing by 266%; overall emissions of both GHGs were greater in high-fertility soils. While N2O exclusively peaked during the thawing period, with its mean peak flux 1.68 times higher in high-fertility soils than in low-fertility soils. These emission patterns were further amplified under maize monoculture compared to maize-soybean and maize-fallow rotation systems. During the freeze-thaw process, GHG fluxes were primarily driven by variations in soil temperature, moisture, and aggregate stability. The alleviation of resource-microbe carbon:nitrogen (C:N) imbalance during the thawing period likely stimulated pulses of CO2, CH4, and N2O emissions. This effect was more pronounced in soils with initial properties characterized by lower C:N ratio, greater available C and N, and stronger microbial stress tolerance (indicated by higher fungal: bacterial and gram-positive: gram-negative ratios). These mechanisms underpin the greater cumulative GHG emissions observed in high-fertility soils and continuous monocropping systems. Collectively, our findings suggest that long-term fertilization and maize monoculture amplify freeze-thaw-induced GHG emissions via specific edaphic-microbial properties, providing field evidence for mitigating non-growing season climate impacts through optimized management.

Soil salinization and alkalization have caused substantial ecosystem degradation worldwide. Previous studies have predominantly examined soil physicochemical properties and species diversity in saline-alkaline conditions, but the internal biotic interactions within these ecosystems remain poorly understood. This study investigated the dynamics of nematode functional group networks across a saline-alkaline gradient categorized into non-, weakly, moderately, and highly saline-alkaline soils. Nematodes were classified into functional groups based on their feeding behaviors and life-history strategies (r-strategy: cp1-2; K-strategy: cp3-5). Their interactions were categorized as nontrophic interactions within and across trophic levels, and predator-prey interactions. The results showed that the number of classified taxa of K-strategist omnivores-predators (OP-4) declined sharply, whereas the number of r-strategist bacterivores (Ba-1) remained stable, with a significant increase in their relative abundance with increasing saline-alkaline stress. Different types of interactions exhibited distinct patterns of changes along the saline-alkaline gradient. The number and strength of nontrophic interactions within trophic levels decreased with increasing salinity-alkalinity. In contrast, the strength of nontrophic interactions across trophic levels and predator-prey interactions increased gradually, while their numbers initially increased but then decreased sharply in highly saline-alkaline soils. In non-and weakly saline-alkaline soils, no single dominant environmental factor was identified as influencing nematode functional group interactions. In moderately and highly saline-alkaline soils, Na+ emerged as the primary driver. This study revealed non-linear changes in nematode functional group interactions along the saline-alkaline gradient and identified Na+ as a key environmental driver of these interaction patterns.

Soil food webs regulate microbial biomass and necromass production and are therefore critical for carbon sequestration. The mechanisms by which top predators regulate microbial necromass formation across multitrophic levels in the real-world soil food web remain nearly unknown. This study investigates how top-down forces-from omnivorous-predaceous nematodes to microbivorous nematodes and microbes-affect the formation of microbial necromass within tritrophic food webs under contrasting tillage regimes (tillage (till) vs. no-tillage (no-till)) on black soils (Mollisols), using a 1-year 13C-labeled straw in situ tracing experiment integrated with a long-term (> 5 years) tillage trial. The fungal-to-bacterial necromass ratio increased strongly in the no-till soil compared to the till soil, with omnivores-predators being the key factor for these changes. In the no-till soil, abundant and diverse omnivores-predators (46% and 67% higher in abundance and richness than in the till soil) created a typical predator-prey relationship with fungivores. This relationship was characterized by heavy predation on fungivores (51% of omnivore-predator diet) and opposite 1-year dynamics of 13C content between omnivores-predators and fungivores. Such a predator-prey relationship substantially reduced fungivore activity (73% and 90% decrease in 13C content and enrichment rate), while accompanied by increased fungal activity (64% and 50% increase in 13C content and enrichment rate) in the no-till soil compared to the till soil. This predator-driven cascade down the food chain amplified the fungal contribution to the fungal-to-bacterial necromass ratio. Conversely, these interactions, disrupted by continuous tillage, weakened fungal functions by interrupting the trophic cascade. In conclusion, these tiny yet ubiquitous omnivorous-predaceous nematodes exert a disproportionate impact on necromass formation by boosting fungal biomass and activity. Further manipulative experiments targeting multi-trophic interactions are essential to disentangle the mechanisms of microbial necromass formation, given the inherent complexity of soil food webs and the observational nature of this study.

The biogeochemical cycling of carbon (C) and its associated enzyme activities are vital for maintaining crop productivity and play a crucial role in soil C sequestration. However, distinguishing the specific effects on the rhizosphere and bulk soils soil organic C (SOC), labile organic C (LOC) and enzyme activities presents a significant knowledge gap that needs to be addressed. The objective of this study is to explore the effects of various tillage management practices on soil C fractions and enzyme activities, while examining their interrelationships in both the rhizosphere and bulk soil. We measured SOC and LOC fractions, including microbial biomass C (MBC), dissolved organic C (DOC), particulate organic C (POC), easily oxidizable C (EOC) and light-fraction organic C (LFOC), as well as soil enzyme activities, including cellobiohydrolase (CBH), beta-glucosidase (BG) and xylosidase (BXYL) after 10 years of different tillage management practice. The tillage management included no-tillage with straw return (NTS), mouldboard ploughing with straw incorporated into the 0-20 cm soil layer (MPS) and conventional tillage practice (CT). The results demonstrated that NTS and MPS significantly increased both rhizosphere and bulk SOC contents, LOC fractions and enzyme activities compared to the CT treatment. Moreover, the rhizosphere exhibited higher SOC, LOC and enzyme activity levels than the bulk soil. Redundancy (RDA) analysis unveiled that tillage practices boost soil enzyme activities through the modulation of SOC and LOC levels. RDA analysis also indicated significant impacts of tillage management techniques and soil type on SOC, LOC components (including MBC, DOC, POC, EOC, LFOC) and C-cycle enzyme activities (CBH, BG, BXYL). Notably, soil CBH activity exhibited positive associations with MBC, DOC and LFOC, while no significant correlations were observed between CBH and SOC, POC or EOC. Furthermore, it highlights the differential responses of SOC, LOC and enzyme activity to tillage management in both the rhizosphere and bulk soil. These findings contribute to a deeper understanding of the interactions between the rhizosphere and tillage management, offering valuable implications for assessing the ecological dynamics of rhizosphere soil. Such insights can guide the development of plant-focused strategies aimed at enhancing productivity and promoting sustainability within agroecosystems.

Ammonia oxidation, the first and rate-limiting step of nitrification, is essential for converting ammonium (NH4+) to nitrite (NO2-) in soil, and is a key process in nitrogen (N) cycling that supports crop growth in agroecosystems. Previous research has focused on the impacts of ammonia-oxidizing microbes on soil nitrification under agricultural management, but the influence of the interaction between microfauna, particularly nematodes, and ammonia-oxidizing microbes on soil nitrification remains unclear. In this study, we selected four rates of N applied to lime concretion black soil and fluvo-aquic soil and tested the effect of the interplay of nematodes with ammonia-oxidizing archaea (AOA) and bacteria (AOB) on the potential nitrification rate (PNR). The results demonstrated that the application of N to the fluvo-aquic soil led to an increase in the PNR, as well as a significant enhancement in the abundance of copies of the AOA and AOB amoA genes. However, no consistent outcomes were observed in the lime concretion black soil. The application of N increased the relative abundance of bacterivorous nematodes, particularly Chiloplacus, in the fluvo-aquic soil, but it decreased their relative abundance in the lime concretion black soil. A co-occurrence network analysis indicated that the AOB nodes accounted for a higher proportion in the network and had more potential associations with bacterivorous nematodes in the fluvo-aquic soil. The partial least-squares path model suggests that bacterivorous nematodes positively regulated the AOB and further influenced the PNR in the fluvo-aquic soil. These results provide novel insights into our understanding of the processes of soil nitrification, as well as the interactions between soil microorganisms and nematodes.

Nematodes play critical roles in mountain ecosystems, but their distribution patterns and community assembly remain poorly understood. This study aimed to clarify the distribution patterns and community assembly processes of soil nematode communities and their trophic groups along the elevation gradient on Changbai Mountain in northeast China, both for the whole mountain and for the north- and west-facing slopes. A total of 108 soil samples were collected from nine elevations (600–2,200 m a.s.l) for the north- and west-facing slopes of Changbai Mountain. We investigated the community similarity and assembly of whole nematode communities and within trophic groups, and assessed the relative contribution of elevation, environmental, and geographical distances to their spatial variations and community assembly processes. Species turnover primarily accounted for the changes in nematode community composition along the elevation gradient, with communities shifting from plant-parasites dominating at lower elevations (600–1,000 m) to fungivores at mid-elevations (1,200–1,600 m) and omnivores-predators at higher elevations (1,800–2,200 m). Stochastic processes dominated the community assembly of whole nematode communities and within trophic groups across the whole mountain and on both north- and west-facing slopes, primarily as an undominated scenario where the influences of dispersal and selection were weak. Geographical distance emerged as the primary factor affecting both the community composition and assembly processes of whole nematode communities. However, the relative contribution of elevation, environmental and geographical distances exhibited different impacts on the community composition and assembly processes of each trophic group. Overall, our findings underscore the importance of species turnover and stochastic processes in shaping and maintaining the composition of soil whole nematode communities and within trophic groups along the elevation gradient in Changbai Mountain.

Elevation patterns and assembly processes of soil microbial community structures are essential for understanding biogeochemical processes in mountain systems. Differences in soil properties caused by elevation gradients can regulate the spatial distribution and network complexity of the community structure. To explore the variations in soil microbial community structures and their assembly mechanisms across different elevations of the Changbai Mountains, as well as their responses to environmental factors, we collected microbial samples along an elevational gradient (seven elevations containing four vegetation zones) on the western slope of the Changbai Mountains using the method of metagenomic sequencing. The results showed a significant difference (P < 0.05) for the Chao1 index across different elevations, but no significant difference was observed for the Shannon and Simpson indices. With increasing elevation, the number of nodes and links in the microbial network gradually decreased. Acidobacteria were highly connected to many nodes. The microbial communities indicated a significant distance-decay relationship (P < 0.001) and were affected more by stochastic processes along the elevation gradient. The results of the Structural Equation Model (SEM) showed that elevation had direct significant effect on carbon (C, P < 0.01), nitrogen (N, P < 0.01), and phosphorus (P, P < 0.05) and weak negative effect on their ecological stoichiometry. Elevation was one of the major variables contributing to microbial network topology. The contribution of C and N to microbial network complexity was higher than that of P. Our study provides valuable insights into the responses of soil microbial communities to elevation variations.

Exploring the dynamics of soil carbon (C) response to multi -faceted global climate change plays a vital role in facilitating the estimation of carbon -climate feedback. However, the direction and extent of the warming effect on soil carbon pool within different soil fractions considered simultaneously in increased precipitation and decreased precipitation system are not well understood. Here we established a 2 -year field manipulation experiment based on open top chamber (OTC) to assess the effects of warming and altering precipitation regimes (40 % reduction, normal, and 40 % increment) on soil physical fractions formation and distribution. Our results showed that in the precipitation increment, warming significantly increased particulate organic carbon (POC) and mineral -associated carbon (MAOC) by an average of 48.10 % and 21.28 % in the 0-5 cm soil layer. And the formation mechanism of POC and MAOC were different. POC was directly affected by the coupling between plant input and C -degradation fungal functional genes adjusted by dissolved organic carbon (DOC) and total nitrogen (TN); and MAOC was affected by increasing labile carbon inputs (such as DOC) of maize residue and belowground biomass. However, precipitation reduction neutralized the beneficial effects of warming, mainly through reducing plant inputs and residue decomposition, thereby suppressing C -degradation fungal functional genes and labile carbon supply. Overall, our results provide new insights into the potential mechanisms through which interaction of warming and altered precipitation controls soil C dynamics.

Effective application of biochar is critical to improving soil health, but its intricate biological impact on the soil micro-food web remains poorly understood. To address this, a field experiment with four treatments - inorganic fertilization (IF), organic fertilization (OF), inorganic fertilization with biochar addition (B + IF), and organic fertilization with biochar addition (B + OF) - was conducted within a wheat cropping system on a sandy loam soil. The study aimed to elucidate the role of biochar-induced changes in abiotic factors and plant root inputs in shaping the soil micro-food web. Results showed that the effects of biochar on the soil micro-food web varied depending on the fertilization context. Under inorganic fertilizer, biochar strongly increased the abundance of total microbes and total nematodes, but reduced the biomass of omnivores-predators. However, biochar combined with organic fertilizer had a positive effect on the abundance and biomass of total microbes as well as the biomass of total nematodes and omnivores-predators. In addition, biochar with inorganic fertilizer affected the abundance of microbes and nematodes through direct pathways and indirectly affected microbial biomass and abundance mediated by reducing NH4+-N and DOC content. In contrast, in organic fertilization, the improvement of root biomass and soil pH were the most direct drivers of variation in microbial abundance. These findings highlight the potential of biochar as a strategic amendment to optimize soil micro-food web dynamics, with fertilizer type playing a critical role in determining its effectiveness. The combination of biochar with organic fertilizer provides a basis for improving soil health and supporting sustainable agricultural practices on sandy loam soils.

Conservation tillage, particularly the implementation of no-tillage and straw retention (NTS), has been proposed as an effective practice to enhance soil structure and improve soil quality in Northeast China. However, the impact of NTS on maize ( Zea mays L.) root growth morphology and the influence of tillage practices on maize root morphology through soil physical properties and structure in Northeast China remain understudied. To address this knowledge gap, a continuous ten-year experiment was conducted to assess the effects of NTS on soil physical properties, aggregate structure, maize root morphology, and their interconnections. Our findings demonstrate that the NTS treatment significantly increased soil water content and soil bulk density at depths of 0-5 cm (1.6%) and 5-10 cm (2.2%), while decreasing soil porosity at depths of 0-5 cm (1.4%) and 5-10 cm (2.0%) compared to conventional tillage (CT). Additionally, NTS resulted in a higher content of soil macro- aggregates (> 0.25 mm) and improved soil aggregate stability compared to CT. Notably, root length, root surface area, root volume, and root biomass in the NTS treatment were 6.04%, 22.15%, 10.04%, and 9.29% higher than those in CT, respectively. However, there was no significant difference in root diameter between the two tillage practices. These results reveal that NTS induces alterations in soil physical properties, aggregate size distribution and aggregate stability, thereby affecting maize root growth morphology.

The soil organic carbon (SOC) cycle is dynamic and exhibits both addition of new carbon and consumption of existing SOC; carbon inventory in the soil is the net result of these two opposing processes. Quantifying the residue-derived carbon (RDC) under different tillage systems via 13C tracing technique provides an objective appraisal of the contribution of returned residue to soil carbon sequestration in bulk soil and different fractions. We used 13C-labelled maize residue to monitor the fate of RDC stock (RDCstock) in different soil fractions under no-tillage (NT) and mouldboard ploughing (MP). Accumulation of RDC increased in the surface layer under NT while it decreased in all layers under MP over time. After two years, both NT and MP stored an equivalent amount of RDCstock with a RDCconversion rate of 16.8-17.0 %. Tillage had no effect on the RDC concentration (RDCcon) in microaggregate (Mic), silt-clay (Si-Cl), labile organic carbon (LP-C) and recalcitrant carbon (RP-C), but affected the RDCconin macroaggregate (Mac) and particulate organic carbon (POC). NT generated more RDCstock in Mac than MP, which was induced by the higher RDCstock in coarse particulate organic matter (cPOM) and occluded silt-clay (O-Si-Cl). The percentage of RDCstock in mineral-associated organic carbon (MAOC) contributed more to total RDCstock than POC in both NT and MP, but RDCstock in POC was higher in NT (47 %) than MP (18 %). Most (70 %-75 %) of RDCstock existed as LP-C in both tillage practices. Our results showed that although the total RDCstock reached the same status in both NT and MP, the distribution in soil fractions varied, especially in physical fractions. RDC reached 10-20 cm in NT through leaching and was stored in MAOC, and NT provided strong protection for newly derived carbon via macroaggregates. It also inferred that tillage practices strongly affected the way that newly derived carbon was stored.

This paper examines the development of ecological indices for soil nematodes from the perspective of functional traits. It emphasizes the increasing significance of integrating multiple functional traits to achieve a more accurate assessment of soil health. Ecological indices based on life history strategies, feeding habits, and body size provide useful tools for assessing soil health. However, these indices do not fully capture the dynamics of energy flow across multiple-trophic levels in the soil food web, which is critical for a deeper understanding of the intrinsic properties of soil health. By combining functional traits such as functional group, body size, feeding preference and metabolic rate, nematode energy flow analyses provide a more comprehensive perspective. This approach establishes a direct correlation between changes in the morphology, physiology, and metabolism of soil organisms and alterations in their habitat environment. We conducted comparative analyses of the sensitivity of nematode metabolic footprints and energy flow to latitudinal variation using a nematode dataset from the northeastern black soil region in China. The findings suggest that energy flow analyses are more sensitive to latitude and have greater potential to reveal soil health and ecosystem function. Therefore, future research should prioritize the development of automated and efficient methods for analyzing nematode traits. This will enhance the application of energy flow analyses in nematode food webs and support the development of sustainable soil management and agricultural practices.

CONTEXT: Conservation tillage plays a positive role in restoring degraded cropland in terms of increasing carbon sequestration, improving soil aggregation, and maintaining crop productivity. Assessing the key indicators of environment, energy, and economy under different tillage practices could provide a comprehensive scientific basis to implement low-carbon emission, clean and sustainable agricultural management, especially in the longterm experiment field. OBJECTIVE: Our objectives were: 1) to compare crop production under different long-term tillage practices, 2) to evaluate the carbon footprint (CF), energy budget, and net ecosystem economic benefit (NEEB) of spring maize production under different long-term tillage practices. METHODS: Three tillage practices consisting of conventional tillage with complete removal of residue (CT), moldboard plowing with residue return (MP) and no-tillage with residue return (NT), had been conducted for eight years. Greenhouse gas (GHG) emissions from the soil were measured, and the inputs of raw materials and outputs of crop production were also recorded. CF, energy budget, and NEEB were evaluated for two consecutive growing seasons based on the life cycle assessment (LCA) approach. RESULTS AND CONCLUSIONS: Compared with CT, NT could reduce N2O emissions and absorb more CH4, whereas MP significantly increased CO2 emissions from soil. However, there was no significant difference in maize yield among all treatments. Moreover, NT led to both the lowest GHG emissions from soil (GWPGHG) and agricultural inputs (AIGHG), thus NT decreased CF by approximately 40% compared to CT for maize production. Furthermore, MP and NT decreased 8.4% and 35.7% of the energy inputs owing to lower diesel fuel consumption in comparison with CT, yet there was no significant difference in energy output among different tillage practices. The same was true in NEEB, although MP and NT showed lower investments during maize production. These results indicated NT required the lowest energy and financial investment for the same maize yield. In conclusion, NT could minimize CF and energy inputs while insuring maize production from a long-term perspective. Longterm NT can be implemented in Northeast China and similar agro-eco-regions around the world. SIGNIFICANCE: The findings of our study provide scientific data on the performance of different long-term tillage practices in the environment, energy budget and economic benefits. Meanwhile, it also helps to clarify the role of agricultural systems in achieving carbon neutrality and saving energy.

Conservation tillage as an effective alternative to mitigate soil degradation has attracted worldwide attention, but the influences of conservation tillage on soil microbial community and especially function remain unclear. Shotgun metagenomics sequencing was performed to examine the taxonomic and functional community variations of black soils under three tillage regimes, namely no-tillage with residue (maize straw) return (NTS), moldboard plow with residue return (MPS), and moldboard plow without residue return (MPN) in Northeast China. The results revealed: 1) Soil bacterial and archaeal communities differed significantly under different tillage regimes in contrast to soil fungal community. 2) The overlay of less tillage and residues return under NTS led to unique soil microbial community composition and functional composition. Specifically, in contrast to other treatments, NTS increased the relative abundances of some taxa such as Bradyrhizobium, Candidatus Solibacter, and Reyranella, along with the relative abundances of some taxa such as Sphingomonas, Unclassified Chloroflexi and Nitrososphaera decreased; NTS had a unique advantage of increasing the relative abundances of genes involved in 'ATP-binding cassette (ABC) transporters' and 'quorum sensing (QS)' pathways, while MPN favored the genes involved in 'flagellar assembly' pathway and some metabolic pathways such as 'carbon' and 'glyoxylate and dicarboxylate' and 'selenocompound' metabolisms. 3) Significantly different soil bacterial phyla (Acidobacteria, Gemmatimonadetes, and Chloroflexi) and metabolic pathways existed between MPN and another two treatments (NTS and MPS), while did not exist between NTS and MPS. 4) Dissolved organic carbon (DOC) and soil bulk density were significantly affected (P < 0.05) by tillage and accounted for the variance both in microbial (bacterial) community structure and functional composition. These results indicated that a change in tillage regime from conventional to conservation tillage results in a shift of microbial community and functional genes, and we inferred that residue return played a more prominent role than less tillage in functional shifts in the microbial community of black soils.