[Objective]To elucidate the microbiological mechanisms through which long-term straw return influences the severity of bacterial diseases in paddy fields,thereby providing a theoretical basis for precise disease prevention and control.[Method]Based on a long-term field location experiment in Huizhou,Guangdong Province,this study implemented three treatments:1.3 times the amount of full straw returned(S30,with a seasonal application rate of 8 425 kg·hm-2),full straw returned(CKS,with a seasonal application rate of 6 400 kg·hm-2),and no straw returned(CK).Using metagenomic sequencing,we systematically compared the dynamics of soil bacterial community structure and the relative abundance of key pathogenic species(including Burkholderia glumae,Xanthomonas oryzae,and Dickeya oryzae)under different straw management practices,and examined their relationships with environmental factors through correlation analysis.[Result]Straw returning significantly enhanced the species richness of soil bacterial communities(P<0.05)and altered their structural composition.Among the detected phyla,Proteobacteria,Chloroflexi and Acidobacteria were identified as the dominant taxa,and their relative abundances were significantly influenced by both the amount of returned straw and the growth stages of rice.Redundancy analysis confirmed that soil pH served as a key environmental factor driving shifts in community structure(P=0.024).Straw returning generally reduced the abundance of three pathogenic bacteria during the tillering stage.It also lowered the disease severity indices for bacterial leaf blight,leaf streak,and panicle blight of rice,though not significantly,and even carried a potential risk of increasing foot rot incidence.At the maturity stage,S30 significantly increased the abundance of B.glumae and X.oryzae,while the relative abundance of D.oryzae was markedly reduced.Additionally,S30 significantly promoted the aggravation of bacterial leaf blight and raised the incidence of leaf streak and foot rot.In contrast,CKS showed no significant negative impact on the occurrence of most bacterial diseases.Its disease incidence was only slightly higher than that of CK,and the disease index performance remained relatively moderate.Correlation analysis revealed that at maturity,the abundances of Burkholderia and Xanthomonas were significantly positively correlated with soil pH,while at the tillering stage,Dickeya abundance showed a strong association with soil available phosphorus content.[Conclusion]Long-term straw returning is altering the soil microenvironment,resulting in dual specificity on the type and growth stage of bacterial diseases in rice.At the tillering stage,it reduced the disease indices of bacterial leaf blight,leaf streak,and panicle blight,though not significantly,while even increasing the risk of bacterial foot rot.At maturity,however,straw returning promoted different bacterial diseases depending on the amount applied.Among the treatments,S30 showed the most pronounced effects,providing a scientific basis for ecologically sustainable management of bacterial diseases in rice.

Background Beneficial plant-associated microorganisms are key drivers of sustainable agriculture. However, their discovery and practical application remain insufficiently explored. Here, we present the first comprehensive comparative genomic analysis of a newly identified Sinomonas strain together with all publicly available genomes to assess its agronomic potential Results Our results demonstrate that Sinomonas has an open pangenome and harbors multiple pathways for IAA biosynthesis, including a rare pathway found in only a limited number of bacterial taxa. The genus also contains genes involved in the synthesis of cytokinin analogues. In addition, genomic annotation identified ten genes putatively associated with phosphorus solubilization. A total of sixteen distinct biosynthetic gene clusters were identified, covering pathways for the biosynthesis of stenothricin, dactylocycline, aborycin, reveromycin, michiganin A, ikarugamycin, and peucechelin, all of which are compounds with reported antibacterial activity. In addition, Sinomonas carries multiple genes potentially involved in improving plant stress tolerance, including genes related to the biosynthesis of spermidine, 2,3-butanediol, acetoin, betaine, proline, and trehalose. Conclusion Overall, these findings highlight the functional diversity of the Sinomonas genome and provide preliminary insights into its potential agricultural applications.

Hydrothermal carbonization (HTC) offers a sustainable pathway to convert agricultural wastes into multifunctional hydrochars, yet the stability of hydrochars and the biotoxicity of hydrocharderived dissolved organic matter (DOM) as amendments for contaminated farmland soils remained understudied. Herein, this study investigates feedstock-dependent (straw: HS, swine manure: HSM, and cattle manure: HCM) and time-resolved variations in hydrochar and the derived DOM characteristics for farmland remediation potentials. Feedstock type dominated hydrochars and DOM functionality that manure-based hydrochars exhibited superior metal adsorption capacity (100 % Pb removal by HSM and 51.7-76.2 % by HCM), more biologically suitable C/N ratios (HSM: 15.0-16.5, HCM: 21.4-23.5), and germination index (HSM: 51.1-76.7 %, HCM: 56.2-82.2 %), correlating with the reduced phytotoxicity. The DOM derived from manure-based hydrochar contained more macromolecular fluorescent humus contents and various organic functional groups, while HS released more phytotoxic DOM with 44.3-68.3 % germination inhibition. DOM removal enhanced Pb adsorption capacities by 56.1-97.3 % for lignocellulose-rich HS. With elemental analysis and 2D-FTIR-COS analysis, the prolonged hydrothermal duration enhanced structural stability, reducing DOM release by 19.6-40.5 % through dehydration and decarboxylation. In addition, the stability of hydrochar, alongside the N content and the degree of dehydration and decarboxylation, significantly affected their toxicity to seed germination. In conclusion, the type of feedstock has the most substantial impact on hydrochars and DOM properties that HCM emerged as the most viable candidate due to synergistic benefits, while optimizing hydrothermal time improved performance agricultural remediation.

A novel strain of the genus Sinomonas, designated G460-2 T, was isolated from rice paddy soil. The cells of strain G460-2 T were Gram-positive, aerobic, and non-motile rods. The optimal growth conditions for this strain were observed at 30 °C and a pH of 7.0. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that strain G460-2 T shared the highest sequence similarity (98.41

The prevalence of antibiotic resistance genes (ARGs) in agricultural soils has garnered significant attention. However, the long-term impacts of various nitroge (N)-substitution fertilization regimes on the distribution of soil ARGs and their dominant drivers in a subtropical triple-cropping system remain largely unexplored. This study employed a metagenomic approach to analyze soil ARGs, microbial communities, mobile genetic elements (MGEs), and viruses from a maize-maize-cabbage rotation field experiment with five different fertilization regimes. Soil samples were collected in 2012 and 2021. A total of 615 unique ARG subtypes were identified, with multidrug, bacitracin, and rifamycin resistance genes being the most abundant. Notably, ARG types. the continuous application of fresh chicken manure (CM) over 10 years significantly increased both the count of unique ARG subtypes and the total ARG abundance compared to other fertilization regimes, such as inorganic fertilizer and composted chicken manure. Specifically, the abundance of genes associated with antibiotic target replacement (e.g., sul1 and sul2) in the CM-treated soil rose by 8.83-fold from 2021 to 2012. Our random forest analysis revealed that the abundance of three MGEs (QacEdelta, plasmids, and IstB), two viral families (Myoviridae and Podoviridae), two bacterial phyla (Chloroflexi and Planctomycetes), and two environmental factors (pH and soil organic matter (SOM)) significantly influenced the distribution of ARGs. Furthermore, variance decomposition analysis underscored the critical roles of the three MGEs and the two viral families in the dissemination of ARGs, suggesting that horizontal gene transfer (HGT) may play a key role in ARG spread. These findings enhance our understanding of how different fertilization practices influence ARG dissemination in subtropical triple-cropping agroecosystems over the long term and provide valuable insights for optimizing fertilization management strategies.

An adaptable, low-cost, and easy-to-operate biological treatment system for pollutant abatement in aquaculture water at the field pond scale needs to be developed. In this study, the pollutant removal capacity of a stable bioreactor for aquaculture wastewater was assessed, and the related mechanism was elucidated via an analysis of the microbial community’s characteristics and functions. The average removal efficiencies of chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus were 40%, 86.22%, 38.62%, and 53.74%, respectively. The effluent quality meets the Requirement for Water Discharge from Freshwater Aquaculture Pond, SC/T9101-2007. The results indicate that the fillers under anaerobic conditions could attract Denitratisoma and unclassified_Rhodocyclaceae, promoting the denitrification reaction. This aligns with the characteristic that total nitrogen in aquaculture sewage mainly exists in the form of nitrate nitrogen. An anaerobic atmosphere helps degrade organic contaminants at liquid interfaces and remove nitrogen in the solid phase. The fillers under anaerobic conditions could attract Bacteroidota and promote the production of polysaccharides to form biofilms, which may be associated with phosphorus removal. The results indicate that the anaerobic stage can promote the formation of biofilm on the fillers to remove pollutants, thus achieving higher aquaculture sewage treatment efficiency.

Phage therapy has the potential to alleviate plant bacterial wilt. However, the knowledge gap concerning the phage-agrochemical interaction impedes the broader application of phages in agriculture. This study characterized a phage isolate and investigated its interactions with agrochemicals. A novel species within the Ampunavirus genus was proposed, serving phage LPRS20 as a type phage with a broad lytic range and significant antibacterial activity against Ralstonia solanacearum strains infecting tobacco, chili, or tomato. Sensory evaluation of the morphology of tobacco leaves suggested that phage application resulted in negligible harm to plants. Investigations into phage-agrochemical interactions revealed synergisms when LPRS20 was delivered 4 h before thiodiazole-copper as well as LPRS20 in combination with low-concentration berberine. Overall, our findings reveal that phage LPRS20 represents a novel, effective, and eco-friendly biocontrol agent against tobacco bacterial wilt in vivo and in vitro and contributes to the potential integration of phages and agrochemicals for controlling soil-borne pathogens.

Bacillus velezensis is well known as a plant growth-promoting rhizobacteria (PGPR) and biocontrol agent. Nevertheless, there are very few reports on the study of B. velezensis on tomato early blight, especially the biocontrol effects among different inoculation concentrations. In this study, an IAA-producing strain, Bacillus velezensis YXDHD1-7 was isolated from the tomato rhizosphere soil, which had the strongest inhibitory effect against Alternaria solani. Inoculation with bacterial suspensions of this strain promoted the growth of tomato seedlings effectively. Furthermore, inoculations at 106, 107, and 108 cfu/mL resulted in control efficacies of 100%, 83.15%, and 69.90%, respectively. Genome sequencing showed that it possesses 22 gene clusters associated with the synthesis of antimicrobial metabolites and genes that are involved in the production of IAA. Furthermore, it may be able to produce spermidine and volatile compounds that also enhance plant growth and defense responses. Our results suggest that strain YXDHD1-7 prevents early blight disease by promoting growth and enhancing the defense enzyme activities in tomato plants. This strain is a promising candidate for an excellent microbial inoculant that can be used to enhance tomato production.

Paddy fields are the main agricultural source of greenhouse gas methane (CH4) emissions. To enhance rice yield, various fertilization practices have been employed in rice paddies. However, the key microbial and abiotic factors driving CH4 emissions under different fertilization practices in paddy fields remain largely uncharted. This study conducted field experiments in a traditional double-cropping rice area in South China, utilizing five different fertilization practices to investigate the key factors influencing CH4 emissions. High-throughput sequencing and PICRUSt2 functional prediction were employed to investigate the contributions of soil physicochemical properties, CH4-metabolizing microorganisms (methanogens and methanotrophs), and key genes (mcrA and pmoA) on CH4 emissions. The results showed that CH4 emission fluxes exhibited seasonal variations, with consistent patterns of change observed across all treatments for both early- and late-season rice. Compared to the no-fertilization (NF) treatment, cumulative CH4 emissions were lower in early-season rice with green manure (GM) and straw returning (SR) treatments, as well as in late-season rice with GM treatment, while rice yields were maintained at higher levels. High-throughput sequencing analysis revealed that potential methanogens were primarily distributed among four orders: Methanobacteriales, Methanocellales, Methanomicrobiales, and Methanosarcinales. Furthermore, there was a significant positive correlation between the relative abundance of the CH4-related key gene mcrA and these microorganisms. Functional analysis indicated that these potential methanogens primarily produce methane through the acetoclastic and hydrogenotrophic pathways. Aerobic CH4-oxidizing bacteria, predominantly from the genus Methylocystis, were detected in all the treatments, while the CH4 anaerobic-oxidizing archaea ANME-1b was only detected in chemical fertilization (CF) and cow manure (CM) treatments. Our random forest analysis revealed that the relative abundance of two methanogens (Methanocellales and Methanosarcinales) and two environmental factors (pH and DOC) had significant impacts on the cumulative CH4 emissions. The variance decomposition analysis highlighted the CH4-metabolizing microorganisms explained 50% of the variance in the cumulative CH4 emissions, suggesting that they are the key microbial factors driving CH4 emissions. These findings provide guidance for the development of rational measures to reduce CH4 emissions in paddy fields.

Inadequately managed solid organic waste generation poses a threat to the environment and human health globally. Biotransformation with the black soldier fly larvae (BSFL) is emerging as talent technology for solid waste management. However, there is a lack of understanding of whether BSFL can effectively suppress potential pathogenic microorganisms during management and the underlying mechanisms. In this study, we investigated the temporal variations of microorganisms in two common types of solid waste, i.e., kitchen waste (KW) and pig manure (PM). Natural composting and composting with BSFL under three different pH levels (pH 5, 7, and 9) were established to explore their impact on microbial communities in compost and the gut of BSFL. The results showed that the compost of kitchen waste and pig manure led to an increase in relative abundance of various potentially pathogenic bacteria. Temporal gradient analyses revealed that the most substantial reduction in the relative abundance and diversity of potentially pathogenic microorganisms occurred when the initial pH of both two wastes were adjusted to 7 upon the introduction of BSFL. Through network and pls-pm analysis, it was discovered that the gut microbiota of BSFL occupied an ecological niche in the compost, inhibiting the proliferation of potentially pathogenic microorganisms. This study has revealed the potential of BSFL in reducing public health risks during the solid waste management process, providing robust support for sustainable waste management.

Biochar was popularly used for reducing greenhouse gas (GHG) emissions in vegetable production, but using biochar does not necessarily guarantee a reduction in GHG emissions. Herein, it's meaningful to elucidate the intricate interplay among biochar properties, soil characteristics, and GHG emissions in vegetable production to provide valuable insights for informed and effective mitigation strategies. Therefore, in current research, a meta-analysis of 43 publications was employed to address these issues. The boost-regression analysis results indicated that the performance of biochar in inhibiting N2O emissions was most affected by the N application rate both in high and low N application conditions. Besides, biochar had dual roles and showed well performance in reducing GHG emissions under low N input (≤300 kg N ha-1), while having the opposite effect during high N input (>300 kg N ha-1). Specifically, applying biochar under low N fertilization input could obviously reduce soil N2O emissions, CO2 emissions, and CH4 emissions by 18.7 %, 17.9 %, and 16.9 %, respectively. However, the biochar application under high N fertilization input significantly (P < 0.05) increased soil N2O emissions, CO2 emissions, and CH4 emissions by 39.7 %, 43.0 %, and 27.7 %, respectively. Except for the N application rate, the soil pH, SOC, biochar C/N ratio, biochar pH, and biochar pyrolysis temperature are also the key factors affecting the control of GHG emissions in biochar-amended soils. The findings of this study will contribute to deeper insights into the potential application of biochar in regulating GHG under consideration of N input, offering scientific evidence and guidance for sustainable agriculture management.

Biochar is widely used to maintain crop yields and the sustainability of agroecosystems due to its characteristics. However, its effect on vegetable yield and quality in southern acidic soils has not been fully elucidated. The effects of two kinds of biochar application rates (3 t ha−1 and 12 t ha−1) on the nutrient availability, nutrient absorption, yield, and fruit quality of sandy acid oxide soil in South China were studied in a 2-year field experiment using two varieties of wax gourd (Tiezhu No. 2 and Dadao). The results showed that optimized fertilization (OPT, nitrogen, phosphorus, and potassium were reduced by 20.0%, 20.6%, and 21.1%, respectively) did not reduce the yield of the different varieties of wax gourd compared to FP (farmer practice). On the basis of the OPT treatment, the application of biochar increased the yield of Tiezhu No. 2 and Dadao wax gourd by 16.0–27.3% and 7.7–13.3%, respectively. The increase in yield was attributed to the improvement in soil organic carbon content which increased by 4.5–19.7%, nutrient effectiveness (NO3−-N and Olsen-P content enhanced by 23.7–27.0% and 15.3–23.4% in Tiezhu No. 2), and nutrient uptake (N, P, K, Ca, and Mg accumulation increased significantly by 21.1%, 46.1%, 36.8%, 25.7%, and 31.9%, respectively) by the plant after the biochar application. Different types of biochar also have some differences in these three aspects. Specifically, under the same dosage, rice biochar has a more significant effect on increasing the yield of winter melon, and has a better effect on the improvement of soil physical and chemical properties, while sawdust biochar has a more significant effect on nutrient absorption. In addition, the commercial quality, namely hardness and glossiness, and the nutritional quality, namely soluble sugar, soluble protein, VC content, and sugar–acid ratio of wax gourd fruits, were significantly improved after the biochar application. In summary, biochar application on acidic soils in South China could achieve a win–win situation in terms of increasing soil nutrient effectiveness to improve vegetable yield and quality while reducing chemical fertilizer.

Pseudomonas chengduensis is a new species of Pseudomonas discovered in 2014, and currently, there is a scarcity of research on this bacterium. The P. chengduensis strain WD211 was isolated from a fish pond. This study investigated the purification capability and environmental adaptability of strain WD211 in wastewater and described the basic features and functional genes of its complete genome. According to the results, the sewage treated with strain WD211 showed a decrease in concentration of 18.12% in total nitrogen, 89.39% in NH4+, 62.16% in NO3−, 79.97% in total phosphorus, and 71.41% in COD after 24 h. Strain WD211 is able to survive in a pH range of 6–11. It shows resistance to 7% sodium chloride and different types of antibiotics. Genomic analysis showed that strain WD211 may remove nitrogen and phosphorus through the metabolic pathway of nitrogen assimilation and phosphorus accumulation, and that it can promote organic decomposition through oxygenase. Strain WD211 possesses genes for producing betaine, trehalose, and sodium ion transport, which provide it with salt tolerance. It also has genes for antibiotic efflux and multiple oxidases, which give it antibiotic resistance. This study contributes to the understanding of the sewage treatment ability and potential applications of P. chengduensis.

Tomato cultivars with contrasting resistance to pathogens regulate root exudates differentially in response to Ralstonia solanacearum attacks. However, strategies using innate root exudates against infection remain unknown. This study analyzed the innate root exudates of two tomato cultivars and their functions in regulating R. solanacearum infection. The innate root exudates differed between the two cultivars. Astaxanthin released from resistant plants inhibited colonization by R. solanacearum but promoted motility, while neferine released from susceptible plants suppressed motility and colonization. The secretion of astaxanthin in resistant tomatoes promoted the growth of biocontrol fungi in soil and reduced the abundance of pathogenic fungi. Neferine secreted by the susceptible cultivar inhibited the relative abundance of the bacterial-biocontrol-related Bacillus genus, indirectly reducing the soil's immune capacity. This study revealed contrasting strategies using root exudates in resistant and susceptible tomato cultivars to cope with R. solanacearum infection, providing a basis for breeding disease-resistant cultivars.

Paenibacillus mucilaginosus has widely been reported as a plant growth-promoting rhizobacteria (PGPR). However, the important genomic insights into plant growth promotion in this species remain undescribed. In this study, the genome of P. mucilaginosus G78 was sequenced using Illumina NovaSeq PE150. It contains 8,576,872 bp with a GC content of 58.5%, and was taxonomically characterized. Additionally, a total of 7337 genes with 143 tRNAs, 41 rRNAs, and 5 ncRNAs were identified. This strain can prohibit the growth of the plant pathogen, but also has the capability to form biofilm, solubilize phosphate, and produce IAA. Twenty-six gene clusters encoding secondary metabolites were identified, and the genotypic characterization indirectly proved its resistant ability to ampicillin, bacitracin, polymyxin and chloramphenicol. The putative exopolysaccharide biosynthesis and biofilm formation gene clusters were explored. According to the genetic features, the potential monosaccharides of its exopolysaccharides for P. mucilaginosus G78 may include glucose, mannose, galactose, fucose, that can probably be acetylated and pyruvated. Conservation of the pelADEFG compared with other 40 Paenibacillus species suggests that Pel may be specific biofilm matrix component in P. mucilaginosus. Several genes relevant to plant growth-promoting traits, i.e., IAA production and phosphate solubilization are well conserved compared with other 40 other Paenibacillus strains. The current study can benefit for understanding the plant growth-promoting traits of P. mucilaginosus as well as its potential application in agriculture as PGPR.

[目的]研究长期有机培肥对南方红壤区稻田土壤碳循环功能基因的影响,为南方稻田土壤碳库高效利用和施肥策略提供理论参考.[方法]依托江西省红壤研究所长期定位试验平台,设4个处理:不施肥处理(CK)、单施化肥处理(NPK)、早稻施绿肥紫云英处理(M1)、早稻施绿肥紫云英+晚稻秸秆还田处理(M2).晚稻收获后采集土壤样品,测定土壤基本理化性质,利用实时荧光定量PCR测定土壤碳循环功能基因的绝对定量,分析不同活性碳含量及碳循环相关基因与环境因子的关系.[结果]长期有机培肥处理提高了土壤有机碳组分中活性有机碳含量,其中M2处理易氧化有机碳、热水提取态有机碳、可溶性有机碳含量均显著高于CK(P<0.05,下同);M1处理土壤微生物量碳含量最高(193.98 mg/kg).各处理中,M1和M2处理参与碳水解、碳固定和甲烷代谢过程的相关功能基因表达量均处于较低水平.相关分析结果表明,碳水解过程相关功能基因(除amyX、IsoP、lig和naglu)、碳固定过程相关功能基因(除mcrA)和甲烷代谢(除emGDH)与全钾、微生物量碳和胡富比均呈显著负相关.碳固定过程功能基因和甲烷代谢过程功能基因(除emGDH)与pH和速效钾呈正相关.随机森林分析结果显示,长期有机培肥稻田土壤对碳水解功能基因和环境因子的解释率为89.22%,对碳固定功能基因和环境因子的解释率为90.12%,对甲烷代谢功能基因和环境因子解释率为87.14%;结构方程建模结果表明,长期有机培肥稻田土壤中mnp和apu基因、mct和rbcL基因、emGDH和pmoA基因分别直接影响碳水解、碳固定和甲烷代谢过程,土壤有机碳、胡敏素和胡富比间接影响碳水解和碳固定基因表达量,胡敏酸、有机碳和胡敏素间接影响甲烷代谢过程功能基因表达量.[结论]长期有机培肥有利于增加南方稻田土壤活性有机碳组分含量,降低碳循环功能基因表达量,提高土壤的稳定性,有助于环境变化中保持农田生产力的稳定.

[目的]硝化和反硝化细菌在稻田土壤氮循环中起着十分重要的作用.研究长期有机物料还田条件下红壤区稻田土壤硝化和反硝化细菌群落及功能基因丰度,有助于揭示土壤硝化和反硝化过程中的微生物机制,为红壤区稻田氮高效利用和管理提供参考.[方法]基于 40 年水稻长期施肥定位试验,选择其中的不施肥(CK)、单施化肥(NPK)、早稻施绿肥紫云英(M1)和早稻施绿肥紫云英+晚稻秸秆还田(M2)处理小区采集土壤样品,利用宏基因组测序和荧光定量PCR技术,通过对典型反硝化细菌nirK、nirS和硝化细菌amoA、hao进行基因标记,分析了土壤硝化和反硝化细菌群落结构和多样性.[结果]nirK、nirS型反硝化细菌和AOB(amoA)、hao细菌主要隶属于变形菌门(Proteobacteria).所有处理中nirK型反硝化细菌的优势属为Ardenticatena菌属、硝化螺菌属(Nitrospira)和罗河杆菌属(Rhodanobacter),且M2 处理土壤中罗河杆菌属相对丰度显著高于其他处理(P<0.05).nirS型反硝化细菌中类固醇杆菌属(Steroidobacter)和慢生根瘤菌属(Bradyrhizobium)分别在M2 和NPK处理中占比最高,分别达到 33%和 29%.AOB(amoA)细菌中慢生根瘤菌(Bradyrhizobium)在 CK 和 M1 处理中占比最高,分别为 30%和 32%;变形菌门中的甲基单胞菌属(Methylomonas)在M2 处理中占比最大;硝化螺菌属(Nitrospira)在CK处理中的占比显著高于其他处理.hao细菌中地杆菌属(Geobacter)相对丰度在各处理中占比最高.冗余分析显示,土壤速效氮(P=0.002)、有效磷(P=0.006)和有机碳(P=0.002)是nirK型和nirS型反硝化细菌群落组成变化的主导因子,土壤有机碳(P=0.008)、有效磷(P=0.01)、速效钾(P=0.008)是 hao 细菌群落结构变化的关键因子,速效氮(P=0.004)、有效磷(P=0.004)和全磷(P=0.002)是AOB(amoA)群落结构产生变化的关键因子.Spearman相关性分析表明,土壤有机碳、全氮和铵态氮与功能基因amoA、hao和反硝化功能基因nirK、nirS的丰度都呈现极显著(P<0.01)负相关关系.[结论]土壤有效磷、速效氮和有机碳是影响细菌群落结构的主要环境因子.长期培肥降低了土壤硝化和反硝化功能基因的丰度,减缓了土壤氮素循环的周转,提高了土壤氮素的稳定性.

Objective Effects of straw-returning on phosphorus morphology and microbial phosphorus-cycling genes in paddy soil at rice tillering and maturing stages were investigated. Method In consecutive 7 years on a rice field in southern China under a positioning experiment, spent straws were returned to the acidic soil. The implemented treatments included: (1) chemical fertilizer without straw-returning (CK), (2) chemical fertilizer + 100% straw-returning in same season (CKS), (3) CKS+ straws to replace 10% potassium fertilizer (S10), (4) CKS + straws to replace 20% potassium fertilizer (S20) or (5) CKS + straws to replace 30% potassium fertilizer (S30). At end of the treatments, Guppy soil phosphorus continuous extraction method and metagenomic technology were applied to determine the composition of phosphorus of different forms and microbial phosphorus-cycling genes. Result Straw-returning significantly increased the available NaHCO3-Pi in soil (P＜0.05)—the S10 and S20 treatments resulted in an increase by 5.88%-8.73% over CK. NaOH-Pi was the main form of phosphorus in the acid paddy soil in southern China with a content ranging from 154.03 mg·kg−1 to 202.11 mg·kg−1. By turning the spent straws into the field, the abundance of phosphorus-cycling genes, especially the inorganic phosphorus dissolution gene pqqC under CKS, was significantly affected. The genes, such as phnW, phnO, pqqB, and pqqC, activated the conversion of hydrochloric acid phosphorus and residual phosphorus into available form; those like appA, phnX, and ppx, participated in the formation of stable phosphorus; and NaOH-Pi played a key role in the long-term transformation of the mineral. And the main factors that governed the abundance of the functional genes appeared to be the organic carbon and pH of the soil. Conclusion Through altering the soil physiochemical properties, returning spent straws to the ground significantly enriched the microbial phosphorus-cycling genes that promoted the mineral transformation of the acidic paddy soil in southern China.