Soil phosphorus (P) pool composition and availability are strongly influenced by nitrogen (N) inputs, as N fertilization can alter soil microbial community composition and functional profiles that regulate P cycling in soil ecosystems. However, the relationships among the soil microbial community composition, P-cycling functional gene, and soil P pool composition and availability under long-term N input remains poorly understood. In the present study, variations in soil P pool composition, bacterial community structure, and microbial P-cycling functional profiles were examined in a long-term agricultural experiment subjected to different N input intensities (N0, N200, N400, N600). N fertilization significantly decreased soil total P, primarily due to reductions in inorganic P (Pi), whereas soil organic P (Po) increased significantly with N fertilization. However, soil labile P remained at similar levels among treatments, and N fertilization significantly increased moderately labile P. N treatments significantly altered the soil bacterial community and decreased the relative abundance of the genes involved in the P starvation response, while increasing the relative abundance of genes involved in P mobilization (Pi dissolution and Po mineralization). N treatments also enriched Pi-dissolving bacteria and increased soil alkaline phosphatase activity. Soil P pool composition and P availability were more closely associated with soil bacterial community composition and alkaline phosphatase activity than with P-cycling functional gene profiles. These results demonstrate that N fertilization promotes the transformation of Pi to Po and of non-bioavailable P to bioavailable P by enriching P-mobilizing microorganisms and enhancing phosphatase activity, and indicate that soil microbial community composition and enzyme activity are more sensitive indicators of soil P pool variation than microbial functional gene profiles.

To more precisely reconstruct the long-term evolutionary processes of coastal wetlands in the past using microbial deposition records, it is essential to differentiate various types of coastal wetlands along sea-land gradients based on their community and diversity characteristics, and to identify the primary factors influencing them. In this study, based on high-throughput sequencing technology, we revealed the microbial community composition and diversity characteristics of four major coastal wetlands in Bohai Bay, including Lagoon & Estuary (L&E), Suaeda (SU), Freshwater-Phragmites (F-P), and Freshwater-Weeds (F-W), and discussed their relationship with environmental factors. The results showed that dominant microbial communities had clear indicative significance for corresponding wetlands. In the L&E wetlands, the microbial communities are characterized by dominant taxa spanning multiple taxonomic ranks: Desulfobacterota, Gammaproteobacteria, and Desulfuromonadia. In SU wetlands, the indicator taxa comprised Flavobacteriales, Balneolales, and Planococcaceae. In F-P wetlands, the differentially abundant taxa included Acidobacteriota, Myxococcota, Gemmatimonadota, and Planctomycetota. Salinity and vegetation cover were the most important factors affecting soil microbial composition in Bohai Bay coastal wetlands. F-P wetlands had the highest richness and evenness of microbial species, followed by L&E, F-W, and SU wetlands. Na+ and Cr contents were negatively correlated with microbial diversity, while vegetation cover, TOC and P contents were positively correlated with microbial diversity. Our study emphasized the significance of understanding the relationship between microbial community composition and environmental factors in different wetlands in Bohai Bay, and lay a foundation for wetland biodiversity conservation and reconstruction of past ecosystem succession processes.

Composting is the most common approach for animal manure disposal, converting it into valuable organic fertilizer. Supplementary forced aeration has been proved can accelerating composting process. However, improper aeration from the bottom of composting biomass may lead to the inhomogeneous distribution of moisture and oxygen content, also blow ammonia (NH3) and greenhouse gas to the atmosphere. Here, stratified continuous and alternate aeration strategies were applied to investigate the potential effect of optimized aeration method on composting efficiency, NH3 and greenhouse gas emissions. Traditional aeration from bottom with the same total flowrate was set up for comparison. Both stratified continuous and alternate aeration could significantly increase the temperature and oxygen content in composting biomass in the upper layer that increased the degradation rate of organic matter by 74.4 % and 92.1 %, respectively. The seed germination index of the upper materials in the treatments with stratified continuous and alternate aeration were increased by 15.3 % and 33.4 %, respectively, comparing with traditional bottom aeration. Stratified continuous aeration strategy performed obviously benefit on NH3 and nitrous oxide (N2O) mitigation which were 30.6 % and 27.7 % less than gaseous emitted from traditional bottom aeration. These findings indicate that stratified gas supply technology can accelerate the composting process and reduce NH3 and N2O emissions, making it a promising practical composting technique.

Straw incorporation and nitrogen amendment in agricultural soils have been shown to increase the diversity of bacterial communities and antibiotic resistance genes (ARGs). However, the effects of straw types and nitrogen amendment levels on ARG dissemination potential lack genetic evidence. Here, we conducted a metagenomic analysis of 24 agricultural soils amended with wheat or maize straw under a nitrogen fertilization gradient (0, 200, 400, and 600 kya). Our results showed that the incorporation of wheat straw in soils significantly increased the abundance of ARGs and mobile genetic elements (MGEs) compared with maize straw. Moreover, genetic evidence of the coexistence of ARGs and MGEs (distance < 5 000 bp) demonstrated that the dissemination potential of ARGs was significantly greater in wheat than in maize straw-returning soils. Glycopeptide, fluoroquinolone and diaminopyrimidine resistance were the dominant ARGs and were assigned to Pseudomonadota, Actinobacteria and Firmicutes, which were also the predominant bacteria harboring ARG-MGE. Compared with the absence of nitrogen amendment or at 600 kya, nitrogen amendment at 200 and 400 kya increased the ARG dissemination potential in wheat straw-returning soils. The different correlation patterns between the dominant ARGs and the carbon and nitrogen metabolism genes implied that bacteria involved in degrading organic substrates and nitrogen metabolism may have antibiotic resistance ability. This study suggested that wheat straw incorporation and nitrogen fertilization contribute to the spread of ARGs in agricultural soils and should not be neglected.

Recycling manure compost as organic fertilizer closes nutrients loops in crop-livestock system but spreads antibiotic resistance genes (ARGs) in soils, threatening food sanitation and environmental health. Heavy metals (HMs) in manure further complicate ARGs reduction in compost due to co-resistance and cross-resistance. Here, we conducted an in-depth investigation into the relationship between bioavailable HMs and ARGs using sequential extraction for HMs and high-throughput quantitative gene analysis. High-throughput qPCR revealed a 4.9-49.3 % increase in the relative abundance of ARGs and mobile genetic elements (MGEs) under HMs pressure. Additionally, the effectiveness of a supplementary DC electric field (5 V) in regulating HMs speciation and reducing ARGs during chicken manure composting was evaluated. The electric field decreased the bioavailability of Cu, Cr, and As by 18.9-37.4 % and reduced the relative abundance of ARGs and MGEs by 24.6 %. Network analysis, mantel test, and variation partitioning analysis indicated that the reduction of ARGs was primarily attributed to the alleviated co-selection pressure of HMs under the electric field. In conclusion, applying an electric field represents a practical and efficient method to facilitate ARGs reduction in composting systems, thereby offering important insights into the environmental risk assessment and control of agricultural ARGs.

Global patterns in soil microbiomes are driven by non-linear environmental thresholds. Fertilization is known to shape the soil microbiome of terrestrial ecosystems worldwide. Yet, whether fertilization influences global thresholds in soil microbiomes remains virtually unknown. Here, utilizing optimized machine learning models with Shapley additive explanations on a dataset of 10,907 soil samples from 24 countries, we discovered that the microbial community response to fertilization is highly dependent on environmental contexts. Furthermore, the interactions among nitrogen (N) addition, pH, and mean annual temperature contribute to non-linear patterns in soil bacterial diversity. Specifically, we observed positive responses within a soil pH range of 5.2-6.6, with the influence of higher temperature (>15°C) on bacterial diversity being positive within this pH range but reversed in more acidic or alkaline soils. Additionally, we revealed the threshold effect of soil organic carbon and total nitrogen, demonstrating how temperature and N addition amount interacted with microbial communities within specific edaphic concentration ranges. Our findings underscore how complex environmental interactions control soil bacterial diversity under fertilization.

1,1,1-Trichloroethane (1,1,1-TCA) is a typical organochloride solvent in groundwater that poses threats to human health and the environment due to its carcinogenesis and bioaccumulation. In this study, a novel composite with nanoscale zero-valent iron (nZVI) supported by polycaprolac-tone (PCL)-modified biochar (nZVI@PBC) was synthesized via solution intercalation and liquid-phase reduction to address the 1,1,1-TCA pollution problem in groundwater. The synergy effect and improvement mechanism of 1,1,1-TCA removal from simulated groundwater in the presence of nZVI@PBC coupling with Shewanella putrefaciens CN32 were investigated. The results were as follows: (1) The composite surface was rough and porous, and PCL and nZVI were loaded uniformly onto the biochar surface as micro-particles and nanoparticles, respectively; (2) the optimal mass ratio of PCL, biochar, and nZVI was 1:7:2, and the optimal composite dosage was 1.0% (w/v); (3) under the optimal conditions, nZVI@PBC + CN32 exhibited excellent removal performance for 1,1,1-TCA, with a removal rate of 82.98% within 360 h, while the maximum removal rate was only 41.44% in the nZVI + CN32 treatment; (4) the abundance of CN32 and the concentration of adsorbed Fe(II) in the nZVI@PBC + CN32 treatment were significantly higher than that in control treatments, while the total organic carbon (TOC) concentration first increased and then decreased during the culture process; (5) the major improvement mechanisms include the nZVI-mediated chemical reductive dechlorination and the CN32-mediated microbial dissimilatory iron reduction. In conclusion, the nZVI@PBC composite coupling with CN32 can be a potential technique to apply for 1,1,1-TCA removal in groundwater.

Long-term excessive application of nitrogen fertilizer under diverse land uses has caused serious environmental problems on the North China Plain. Current studies focus on denitrifiers and bacterial communities in topsoil under diverse land-use types; however, few studies have studied denitrifiers and microbial communities in subsoils. The variations in soil bacterial communities and denitrifiers with soil profiles (0–300 cm) under crop, apple orchard, and vegetable fields were investigated through high-throughput sequencing and quantitative PCR technologies. NO3−-N largely accumulated in the deeper soil layers (100–300 cm) in the apple orchard, resulting in a higher risk of NO3−-N leaching. The soil bacterial community structure at the 0–100 cm soil depth had a marketable difference from that at 100–300 cm under these three land-use types, and the C:N ratio was the main driving factor for their vertical distribution. The bacterial α-diversity decreased with soil depth; the crop field had the highest α-diversity across all horizons except 100–200 cm, and total carbon was the most important factor driving α-diversity. In addition, the absolute abundance of the nirK, nirS, and nosZ genes decreased with soil depth and varied with land-use type, which was deeply affected by multiple soil properties, such as soil organic matter and total nitrogen. Our findings highlighted that potentially important and unique functions remain to be revealed in subsoils, which may provide new insights into mitigating nitrate leaching in various land-use types.

Taipu River is an important transboundary river and drinking water source in the Yangtze River Delta, China. This study collected 15 topsoil samples along the Taipu River banks and subsequently determined the polycyclic aromatic hydrocarbons (PAHs) concentrations, sources, and ecological and health risks. The sum of toxic 15 PAHs concentrations ranged from 83.13 to 28342.53 ng/g, with a mean of 2828.69 ng/g. High molecular weight (HMW) PAHs were the dominant components and Indene (1,2,3, -cd) benzopyrene (InP) accounted for the highest proportion in individuals. The average PAH concentration in residential land was the highest, followed by those in industrial and agricultural land. The PAH concentration was positively related to contents of total carbon, total nitrogen, ammonium nitrogen, and aminopeptidase activity in soils. The mixed combustion of biomass, coal, and petroleum and traffic emissions could be the primary PAH contributors. The total PAHs at over half of sampling points had relatively high risk quotients and incremental lifetime cancer risk (ILCR) values, posing potential or great ecological threats and health risks.

Nitrous oxide (N2O) pulse emissions are detected in soils subjected to freeze–thaw cycles in both laboratory and field experiments. However, the mechanisms underlying this phenomenon are poorly understood. In this study, a laboratory incubation experiment that included freeze–thaw cycles (FTC), freezing (F) and control (CK) treatments was performed on three typical Chinese upland soils, namely, fluvo-aquic soil (FS), black soil (BS) and loess soil (LS). A higher similarity in soil properties and bacterial community structure was discovered between FS and LS than between FS and BS or LS and BS, and the bacterial diversity of FS and LS was higher than that of BS. FTC significantly increased the denitrification potential and the proportion of N2O in the denitrification gas products in FS and LS but decreased the denitrification potential in BS. Accordingly, with the increasing number of freeze–thaw cycles, the bacterial community composition in the FTC treatments in FS and LS diverged from that in CK but changed little in BS. Taxa that responded to FTC or correlated with denitrification potential were identified. Taken together, our results demonstrated that the effects of FTC on N2O emissions are soil-type-dependent and that the shift in the microbial community structure may contribute to the elevated N2O emissions.

Manure is a potential substitute for chemical phosphate fertilizer, especially in intensive agriculture, such as greenhouse farming, but the associations between soil phosphorus (P) availability and the soil microbial community under manure application instead of chemical phosphate fertilizers are still rarely addressed. In this study, a field experiment in greenhouse farming with manure application instead of chemical phosphate fertilizers was established, including five treatments: a control with conventional fertilization and chemical phosphate fertilizer substitution treatments using manure as the sole P resource at 25% (0.25 Po), 50% (0.50 Po), 75% (0.75 Po), and 100% (1.00 Po) of the control. Except for 1.00 Po, all the treatments applied with manure harbored similar levels of available P (AP) as the control. Most of the bacterial taxa involved in P transformation were enriched in manure treatments. Treatments of 0.25 Po and 0.50 Po significantly enhanced bacterial inorganic P (Pi) dissolution capacity, while 0.25 Po decreased bacterial organic P (Po) mineralization capacity. In contrast, the 0.75 Po and 1.00 Po treatments significantly decreased the bacterial Pi dissolution capacity and increased the Po mineralization capacity. Further analysis revealed that the changes in the bacterial community were significantly correlated with soil pH, total carbon (TC), total nitrogen (TN), and AP. These results revealed the dosage effect of the impact of manure on soil P availability and microbial P transformation capacity and emphasized that an appropriate dosage of organic manure is important in practical production.

Livestock manure, as a major source of antibiotic resistance genes (ARGs), could further transfer ARGs from soil to vegetables when it's used as fertilizer in field and then pose threat to human health. Meanwhile, manure inputs and vegetable planting also affect soil bacterial communities, but these effects on the transmission of ARGs from soil to vegetable is still lacking. Here, lettuce and endive were cultivated in manure-amended soils using pot experiment. The distribution of bacterial community, ARGs and intI1 gene were studied in manure-amended soil and vegetable roots and leaves at harvest. High-throughput sequencing analysis demonstrated that planting vegetables exerted significant effect on soil bacterial communities, which partly explained the decrease of certain ARGs and the intI1 gene in planted soil than in control soil. ARGs in vegetable and soil were interconnected. The bacterial community compositions among root endophyte, leaf endophyte, and phyllosphere were varied by Hierarchical clustering analysis. Higher abundance of shared bacterial taxa was found between root endophytes and soil microbes, which could lead to a relative higher detection frequency of ARGs in root endophyte. Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes were dominant in the plant endophyte and phyllosphere microbes and had intensive correlations with ARGs. Taken together, our findings provided valuable insights into the role of bacterial community structure in the dissemination of ARGs from manure-amended soil to vegetables.

本文通过对养殖场猪粪和鸡粪堆放地0～100 cm土壤样品的采集和分析,研究了长期堆放畜禽粪便对土壤中抗生素抗性基因(简称"抗性基因")和细菌群落结构垂直分布的影响.定量PCR结果表明,与对照土壤相比,猪粪和鸡粪堆放增加了0～100 cm土壤中四环素类抗性基因(tetC、tetG、tetL、tetW)、磺胺类抗性基因(sulI、sulII)以及整合酶基因(intI1)的检出率和检出丰度,说明粪肥堆放造成堆放地土壤中抗性基因污染.聚类分析结果表明,抗性基因和intI1基因的丰度随土壤深度呈递减趋势,且主要集中在0～30 cm土层,表明堆放地土壤中抗性基因存在向下层土壤迁移的风险.相关性分析表明,intI1基因分别与抗性基因呈显著正相关,说明intI1基因可能在抗性基因传播中起着重要作用.同时高通量测序结果表明,与对照土壤相比,猪粪和鸡粪堆放显著降低了0～10 cm和10～30 cm土层细菌群落结构的多样性,0～30 cm土层中,猪粪和鸡粪堆放地土壤中细菌群落结构与对照土壤的差异要高于深层土壤.此外,方差分解分析结果表明,土壤化学性质和细菌群落结构均影响了土壤中抗性基因的垂直分布,且细菌群落结构的变化是其主要的影响因素.本研究可为控制畜禽粪便堆放地土壤中抗性基因污染提供科学依据.

The shortage of phosphorus (P) as a resource represents a major challenge for the sustainable development of agriculture. Manure has a high P content and is a potential substitute for mineral P fertilizers. However, little is known about the effects on soil P availability and soil microbial P transformation of substituting manure for mineral P fertilizers. In this study, variations in soil P availability and bacterial P mobilization were evaluated under treatment with manure as compared to mineral P fertilizers. In the greenhouse fruit and vegetable production system that provided the setting for the study, substitution of manure for mineral P (PoR treatment) resulted in a similar level of soil total P and a similar fruit and vegetable yield as compared to traditional fertilization, but a significantly increased level of soil available P. In addition, PoR treatment enhanced bacterial organic P mineralization potential and decreased inorganic P dissolution potential. These results demonstrate that manure application increases the availability of soil P primarily by enhancing soil microbial Po mineralization, indicating the potential feasibility of applying manure instead of mineral P fertilizers in greenhouse farming.

华北平原农田由于长期过量施用氮肥,造成了土壤硝酸盐累积,导致地下水硝酸盐污染日趋严重.微生物的反硝化作用可将土壤中累积的硝酸盐或亚硝酸盐还原为气态产物,是消减厚包气带土壤累积的硝酸盐的重要途径.因此筛选高效反硝化微生物资源,对人工强化厚包气带土壤反硝化脱氮,阻控地下水硝酸盐污染具有重要作用.基于此,本研究采集位于华北平原的中国科学院栾城农业生态系统试验站长期施氮[施氮量为600 kg(N)·hm?2·a?1]定位试验0～150 m农田厚包气带及含水层土壤样品,从中筛选到62株细菌.16S rRNA基因序列分析表明这62株菌株与变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)中的9个属具有较高的同源性.根据系统发育树的结果,挑选7株亲缘关系较远的菌株进行反硝化潜势试验,结果表明,菌株L71、L13和L103具备反硝化产气能力.电镜观察结果表明,这3株菌均为无鞭毛的杆状细菌,其长度分别为1.0μm、1.5μm和1.5μm,只有L103具有运动能力.此外,菌株L103具有完全反硝化能力,且脱氮能力受到pH的影响,在本试验条件下,菌株L103的反硝化速率高达1.62～2.36 g(KNO3)·d?1·L?1,具备实际应用潜力.本研究表明华北平原厚包气带土壤中存在完全反硝化微生物,并可为人工强化治理厚包气带土壤硝酸盐污染提供菌种资源和理论依据.

突破厚包气带农田根层氮磷淋溶与地下水污染复杂定量关系和阻控机理是国际研究难点.本文系统梳理了重点研发专项"农田氮磷淋溶损失污染与防控机制"项目取得的主要进展,项目包括以下4方面研究内容:1)北方主要农区农田根层氮磷淋溶时空规律;2)根层—深层包气带氮磷淋溶机制和主控因子;3)黑土、潮土和褐土氮磷淋溶阻控机制及其效果;4)典型农区氮磷淋溶风险与区域消减途径.主要科学发现包括:1)受土地利用类型、地下水埋深、包气带岩性、水文地质条件等综合因素的影响,黑土区、潮土区和褐土区根层氮磷淋溶规律与地下水硝酸盐超标率体现出空间不一致和较大差异性.黑土区虽然根层淋溶较小,然而受地形地貌影响,地下水水质对淋溶响应更强烈,应该进一步研究黑土区地下水水质对淋溶的响应机制.华北潮土区和褐土区厚包气带具有明显氮阻控能力,应该进一步加强厚包气带对氮磷淋溶减排机理与途径研究.2)基于长期施肥定位试验和12 m深观测井对包气带农田土壤氮盈余累积特征和淋失规律的研究发现,华北平原区的环境安全施氮量约为200 kg(N)·hm?2·a?1,超过环境安全阈值的多投入氮肥中有51％淋失到1 m根层以下,不合理灌溉、强降水、大孔隙和裂隙是造成土壤硝酸盐淋溶的主要因素,对包气带累积硝态氮的淋失作用可影响至6 m以下土层.3)利用深层取样和生物学方法结合,对厚包气带0～10.5 m原位土壤微生物的反硝化活性和微生物区系组成的研究结果表明,表层土壤是微生物进行反硝化的主要场所,深层土壤中反硝化作用显著减弱,"碳饥饿"是限制底层土壤反硝化微生物丰度与活性的关键因素;室内培养试验证实添加碳源可有效激活土壤微生物的反硝化活性,为"根层截氮包气带脱氮"的淋溶阻控机理找到了突破口.4)利用黑土、潮土和褐土区氮磷淋溶阻控试验、全国农业面源污染国控监测网、北方农区地下水硝酸盐监测网和NUFER(NUtrient flows in Food chains,Environment and Resources use)模型,提出了养分损失脆弱区区划和区域氮磷污染削减草案,可为农业绿色发展和面源污染阻控提供科学依据.

The excessive use of nitrogen (N) fertilizer in intensive agriculture has increased nitrate leaching into groundwater, but its impacts on N transformation processes and the associated microbial communities in the deep vadose zone remain unclear. Soil samples from 0–1050 cm depth were collected from a 20-year field experiment with two N fertilization treatments: 0 (N0) and 600 kg N ha−1 year−1 (N600). Amplicon sequencing and quantitative PCR analyses were performed to profile the vertical distribution of soil microbial communities and denitrification genes. The soil microbial community structure and diversity were strongly influenced by soil depth and N fertilization. The 250 cm depth was identified as a threshold depth, as dramatically different microbial communities were found below and above this depth. Quantitative PCR results showed that the absolute abundance of denitrification genes decreased with increasing soil depth. This study elucidated the profound effects of long-term N input on the composition and diversity of the microbial communities and the abundance of denitrifiers in the deep vadose zone. Our results provide basic information for use in mitigating nitrate leaching by enhancing microbial denitrification in deep vadose zones in intensive agricultural areas.

Since the introduction of antibiotics into clinical practices in the 1940s, antibiotics have become an integral part of animal production to meet the increasing human demand for animal-derived foods. As a result, industrial-scale animal production has emerged as a hotspot for the evolution and dissemination of antibiotic resistance genes (ARGs), thereby potentially contributing to a looming public health crisis. The knowledge of ARGs in livestock systems has been greatly expanded with the recent development of rapid molecular tools. However, comprehensive reviews on ARGs in the animal industry and possible mitigation solutions are still lacking from a One Health perspective. Here we provide this review focusing on human health risks associated with the antimicrobial (antibiotic and metal) usages, ARGs in livestock animals and aquaculture systems in a One Health perspective to untangle the complexities of ARGs across animals, environments and humans. Specifically, this review covers (1) antimicrobials usages in the animal industry, (2) ARGs in animals affected by selective agents, (3) animal-to-human direct/indirect ARG transmission pathways, and (4) mitigation approaches. We highlighted the burden of using antimicrobials in animals for public and environmental health, and also the urgent needs for mitigating the spread of antibiotic resistance from the livestock and aquaculture industries.

Excessive nitrogen (N) fertilization in agricultural ecosystems strongly affects microbial N-cycling processes in soil. However, a comprehensive understanding of how microorganisms involved in each N transformation process respond to long-term N input is lacking. Here, using metagenomic sequencing combined with the direct assembly of N-cycling genes, we found that long-term N fertilization elevated the abundance of the microorganisms involved in most N-transforming processes but decreased that of N-fixing assemblages. The composition of the microbial groups involved in each N-transforming process was altered by fertilization, even though the abundance of several functional genes was not significantly changed. The relative abundance of microbial genera participating in the same step of N-cycling processes correlated with different soil properties, suggesting niche separation of these N-cycling taxa. Our results also indicated that the different responses to N fertilization exhibited by the taxa within the same functional group may be important for sustaining microbial nitrogen cycling in complex and dynamic environments.