Calcium (Ca) and selenium (Se) are garnering growing interest because of their capacity to boost crop yields and minimize cadmium (Cd) concentration within edible parts. However, whether Ca and Se can synergistically inhibit Cd accumulation in crops and its mechanism remains poorly understood. A hydroponic experiment was conducted under Cd exposure with the combined supplementation of Ca and Se, specifically focused on Cd accumulation and its mechanism. The results revealed that Ca and Se synergistically enhanced growth and photosynthetic content, whereas they inhibited Cd accumulation in the roots, stems, and leaves of peppers. Ca and Se also synergistically reduced the content of Cd in the cell wall, organelle fraction, and soluble fraction of the roots, as well as in pectin, hemicellulose I, hemicellulose II, and cellulose. Ca and Se supplementation synergistically downregulated the expression levels of CaNramp1, CaNramp5, CaHMA1, and CaHMA2. These results revealed that Ca and Se synergistically reduced Cd accumulation in peppers by modulating targeted gene downregulation involved in Cd absorption and translocation.

Soil cadmium (Cd) pollution is a global environmental issue of significant concern. In southwestern China, soil Cd content is notably influenced by high geochemical background and mining/smelting activities. However, the specific contributions of these Cd sources to Cd enrichment and environmental risks in soils remain poorly understood. Therefore, this study investigated the total and bioavailable Cd and other metals in the topsoil and subsoils surrounding Caohai Lake in northwestern Guizhou Province. This research aimed to identify Cd sources, assess pollution characteristics, and evaluate the potential environmental risks. The results revealed that the carbonate bedrock has average Cd content of 0.66 mg/kg, confirming a naturally high geochemical background of Cd in the study area. Soil Cd content ranged from 0.14 to 6.69 mg/kg, with topsoil exhibiting higher average Cd content (2.29 mg/kg) than subsoil (0.71 mg/kg). Statistical analyses indicated that Cd in subsoil is primarily of geogenic origin. In contrast, approximately 87% of the total Cd in topsoil originates from atmospheric deposition linked to historical artisanal zinc smelting activities. The study found that Cd in topsoil reaches a moderate pollution level and poses a high potential ecological risk. Furthermore, the proportion of bioavailable Cd (DTPA-extractable) was significantly higher in topsoil (26%) than in subsoil (13%). This elevated Cd bioavailability in topsoil is attributed to atmospheric Cd deposition, lower soil pH, and higher organic matter content. These findings provide critical insights for managing Cd risks in soils from regions with high geochemical backgrounds and smelting activities.

Microplastic accumulation in soil ecosystems poses significant environmental concerns, potentially impacting nitrogen cycling processes and ecosystem health. This meta-analysis of 147 studies (1138 data points) assessed the impact of microplastics (MPs) on soil nitrogen-acquisition enzymes. We found that MPs exposure significantly increased soil urease (UE) and leucine aminopeptidase activities by 7.6 % and 8.0 %, respectively, while N-acetyl-beta-D-glucosaminidase activity was not significantly affected. Biodegradable MPs showed more pronounced effects compared to conventional MPs. Enzyme activities were influenced by MPs properties (e.g., polymer type, size, concentration), experimental conditions (e.g., field or laboratory setting, temperature, nitrogen fertilization), and soil properties (e.g., clay content, pH, organic carbon, total nitrogen). For instance, acidic soils enhanced UE activity, while neutral soils reduced it. These findings emphasize the complex interactions between MPs and soil ecosystems, highlighting the need for context-specific environmental management strategies and policy-making approaches to mitigate the impacts of MPs pollution on soil health.

Soil free-living nitrogen fixation (FLNF) represents an eco-friendly and crucial pathway for N input in terrestrial ecosystems. Despite its significance, global variations and regulatory factors of FLNF rates remain poorly understood. In this study, a meta-analysis of 58 published studies encompassing 910 observations was conducted based on the N-15 assimilation method to elucidate global patterns and drivers of FLNF rates. The analysis revealed that the global average FLNF rate was 73.9 mu g N kg(-1) day(-1) across terrestrial ecosystems. Among different ecosystem types, croplands exhibited the highest mean rate of 372 mu g N kg(-1) day(-1), while forests had the lowest mean rate of 54 mu g N kg(-1) day(-1). Globally, FLNF rates were positively correlated with mean annual precipitation (MAP; p < 0.001, slope = 0.39), soil organic carbon (SOC; p < 0.001, slope = 0.14), total nitrogen (TN; p < 0.001, slope = 0.14), soil moisture (p < 0.01, slope = 0.39), total phosphorus (p < 0.05, slope = 0.28), nifH gene abundance (p < 0.05, slope = 0.37), and the carbon:(nitrogen: phosphorus) ratio (p < 0.01; slope = 0.39). In contrast, FLNF rates declined with an increase in sand content and latitude. Random forest analysis further identified MAP as the strongest environmental predictor of global FLNF rates across different ecosystem types. While significant environmental controls on FLNF rates were observed, approximately 60 % of the variance in FLNF rates could be attributed to differences in sampling locations on a global scale, except in forest ecosystems. These findings provide new insights into the environmental regulators of global FLNF rates, underscoring the critical role of precipitation and key soil properties (e.g., SOC, TN and soil moisture). Given the substantial unexplained variance, future research should focus on local-scale biotic interactions, land-use changes, and microbial functional traits to enhance predictions of FLNF responses to global environmental change.

Lanthanum (La) can enhance crop growth while mitigating cadmium (Cd) accumulation in the edible parts of plants. This study determined the optimal timing of La application‒specifically at the rice heading stage‒to maximize yield and suppress Cd accumulation in grains. In pot experiments, La application at the heading stage increased the grain weight by 24.6 % and reduced Cd content in grains by 60.5 %. La treatment at this stage enhanced the transfer index (TFIN2-N1) of Cd by 29.95 % and reduced TFN1-IN1 by 29.86 %. Low-dose La in hydroponics further inhibited Cd accumulation while supporting growth. Additionally, La treatment significantly reduced Cd levels in root cell sap and xylem sap and downregulated the expression of critical Cd transporter genes, including OsNramp5, OsNramp1, OsIRT1, and OsHMA2 in the roots and OsZIP7 in the nodes. These results reveal that La application at the heading stage minimizes Cd accumulation in rice grains by limiting Cd uptake, translocation, and redistribution through targeted gene downregulation, establishing this stage as key for maximizing yield and ensuring safer rice production.

BACKGROUND:Chinese Yellow Earth is a key subtropical agricultural resource in southwestern China; however, its productivity is limited by acidity and poor nutrient retention. This study examined how reduced nitrogen plus organic amendments affect its soil microbial structure and maize yield. METHODS:A field experiment with four treatments evaluated reduced nitrogen fertilization amended with rice husk plus rapeseed cake (RS) or RS with biochar (BC). Soil properties (pH, nitrogen, organic matter) and maize yield were analyzed. Metagenomic analysis (NR database) characterized microbial communities, and correlation analysis with Mantel tests identified key relationships. RESULTS:Combined organic amendments under reduced N significantly increased soil pH, nitrogen components, and organic matter, increasing maize yield by 4.41-8.97%. Metagenomics revealed enriched beneficial genera including Sphingomonas and Bradyrhizobium. Yield positively correlated with nitrate nitrogen and a beneficial microbial cluster containing Lysobacter and Reyranella, whereas Steroidobacter negatively correlated with key fertility indicators. Mantel tests revealed nitrate nitrogen as the primary correlate of functional gene community succession. CONCLUSIONS:This study reveals that reduced nitrogen with organic amendments promotes soil improvement and microbial modulation, demonstrating potential as a sustainable practice to maintain crop productivity in Chinese Yellow Earth. The observed trend toward yield improvement underscores its promise and warrants further validation through additional trials. Overall, the findings highlight the beneficial effects of these amendments on soil health and their role in supporting sustainable subtropical agriculture under reduced nitrogen input.

Reductive soil disinfestation (RSD) is an important tool for sustainable agricultural productivity. However, the differences in soil bacterial communities and their community assembly processes among RSD and other treatment strategies (e.g., biochar and chemical fumigation) are still subject to open questions. In this study, soils subjected to various treatments–un-treated control (CK), chemical soil fumigation with CaCN 2 (CF), 1% biochar (1%B), 3% biochar (3%B), and reductive soil disinfestation (RSD) are investigated. Soil samples were collected, incubated, and then used for growth of tomato plants. The Sloan neutral community model indicates that stochastic processes dominate in bacterial community assembly for both biochar and CF amendments. In contrast, this work shows that RSD treatment can have a strong impact on soil bacterial community composition. The relative abundance of Firmicutes increased during unplanted soil incubation, whereas Proteobacteria and Bacteroidetes dominated in the rhizosphere after planting of tomatoes. Normalized stochasticity ratio reveals that deterministic selection played an important role in the bacterial assembly under RSD amendment. We found that RSD amendment yielded lower biomass than that for other treatments after 28 days of tomato growth. Our results suggest that although RSD treatment has great potential to rebuild soil bacterial ecology by shaping bacterial communities and their assembly processes, it is important to monitor and manage soil conditions (e.g., soil nutrients or physical properties) before planting to ensure plant productivity.

Reducing cadmium (Cd) accumulation in wheat is an effective way to decrease the potential threats of Cd to human health. The application of lanthanum (La) in agricultural fields is eliciting extensive attention due to its beneficial effects on improving yields and inhibiting Cd accumulation in edible parts of crops. However, the potential mechanism of La-restricted Cd accumulation in crop grains is not entirely understood. Here, we investigated the effects of La and Cd accumulation in wheat grains by implementing application at the shooting and heading stages. Some associated mechanisms were explored. Results showed that La application at the shooting and heading stages considerably promoted the thousand-grain weight. La application at the shooting and heading stages increased Cd accumulation in the first node beneath the panicle (N1) but reduced Cd levels in the other tissues. La application at the heading stage exerted greater effects on Cd storage in N1 while reducing Cd concentrations in the other tissues compared with La application at the shooting stage. La addition substantially decreased the translocation of Cd from the lower nodes to the upper internodes, but increased Cd translocation from the lower internodes to the upper nodes. The expression of TaZIP7 in N1 was downregulated by La treatment. These results suggest that the effective reduction in Cd in wheat grains by La application at the heading stage is probably a consequence of the successful promotion of Cd storage in nodes by downregulating the expression of TaZIP7 during the grain-filling stage, thereby hindering the redirection Cd from nodes to grains.

本研究以贵州西北部典型喀斯特地质高背景区土壤剖面为对象,探讨了土壤镉(Cd)含量与形态的纵向分布特征、Cd迁移转化过程及关键影响因素.结果表明,下伏高Cd碳酸盐岩风化成土作用是剖面土壤Cd富集的重要原因,在土壤形成初期,土壤pH较高,地质源Cd淋失较少,土壤Cd含量高;随着土壤发育程度加深,地质源Cd逐渐淋失,Cd含量降低.此外,区域人为源输入可能影响表层土壤Cd的富集.土壤地质源Cd主要以残余态存在,其次为铁锰氧化物结合态,可交换态的占比较低,Cd活性较低.剖面中下层(＞60 cm)土壤Cd的赋存形态变化较小,剖面上层(＜60 cm)土壤可交换态Cd的占比随土壤深度的降低而逐渐增大,地质源Cd被活化.本研究结果可为理解喀斯特地质高背景区土壤Cd的地球化学行为提供科学参考.

: In order to explore the relationship between soil-water and fertilization under different land use types in karst rocky desertification areas, we selected cultivated land, Zanthoxylum forest, dragon fruit plantation, and loquat forest soils in the Huajiang Hot Valley area of Guizhou Province as experimental materials. We measured the soil moisture content, bulk density, maximum water holding capacity, capillary water holding capacity, capillary porosity, total porosity, and soil carbon, nitrogen, and phosphorus in these four types of sites. The results showed that the soil hydrological properties in the dragon fruit plantation were significantly lower than those in the cultivated land, Zanthoxylum forest, and loquat forest (p<0.05), but the bulk density was significantly higher, indicating poorer soil structure. Cultivated land exhibited the best soil properties among the studied land use types. The cultivated land had the highest soil organic carbon (SOC) and total phosphorus (TP) content, while the loquat forest had the highest total nitrogen (TN) content. Nitrogen deficiency was the primary limiting factor for soil in the cultivated land, while phosphorus deficiency was the primary limiting factor for the other three land use types.

为探讨微塑料对蔬菜作物生长及产量的影响,于2022年4-9月采用室内盆栽实验,研究聚乙烯微塑料(PE-MPs)在不同浓度下(0、50、500、2500 mg·kg-1)对辣椒(Capsicum annuum L.)不同生长阶段(幼苗期、开花期与结果期)的生长状况、植株养分、光合色素含量与产量的影响.结果表明:幼苗期,PE-MPs增加了辣椒的根长、鲜质量及植株中碳含量,而对株高有抑制作用,在浓度为50 mg·kg-1时亦抑制了光合色素的合成;开花期,PE-MPs对辣椒的根长与碳含量有促进作用,而减少了其株高、鲜质量及磷含量,在浓度为2500 mg·kg-1时则能促进光合色素的合成;结果期,PE-MPs对辣椒根长、碳含量及叶片类胡萝卜素含量有促进作用,对株高、鲜质量及磷含量有抑制作用;PE-MPs降低了辣椒产量,最多可使每株辣椒减产42.86%.由此可见,PE-MPs对辣椒根长与植株中碳含量有促进作用,但降低了株高与产量,对其生物量未见显著影响,鲜质量、光合色素含量与氮磷含量则与生长阶段和PE-MPs浓度有关.综上,PE-MPs对辣椒生长存在一定的影响,因此,农业生产等活动中应尽量避免微塑料进入土壤环境中.

Microplastics are widely distributed in the soil environment, threatening the soil ecological environment system and changing soil physicochemical properties and microbial characteristics. Biochar is often used as a soil amendment to improve soil quality due to its special pore structure and good soil nutrient retention ability. However, the understanding of the effects and mechanisms of biochar application on the physicochemical properties and bacterial communities of microplastic-contaminated soils is still very limited. Therefore, a 21-day micro-soil culture experiment was conducted to analyze the effects of biochar application on physicochemical properties and bacterial community changes in soil contaminated with different concentrations of microplastics using 16S rRNA high-throughput sequencing technology. The results revealed that the application of biochar slowed down the decrease in nitrate nitrogen and Olsen-P contents in microplastic-contaminated soil and increased the total phosphorus content. Biochar addition increased the relative abundance of tolerant phylum such as Acidobacteriota, Actinobacteriota, and Bacteroidota in microplastic-contaminated calcareous soil. Proteobacteria, Acidobacteriota, and Actinobacteriota were the dominant bacteria of the soil bacterial community in each treatment on day 7 and day 21. Compared with that on day 7, the relative abundance of Proteobacteria and Firmicutes significantly decreased, and the relative abundance of Acidobacteriota, Actinobacteriota, Bacteroidota, Chloroflexi, and Myxococcota increased on day 21. Biochar application also increased the relative abundance of Lysobacter in microplastic-contaminated soils. This study demonstrated that the application of biochar increased microplastic-resistant bacteria, enhanced the stability of microplastic-contaminated soil, and slowed down the pollution of microplastics to the soil. Moreover, biochar had great potential to improve the quality of microplastic-contaminated calcareous soil.

Microplastics (MPs) have been confirmed as a novel type of environmental pollutant. They have long-term existence in the soil environment and threaten the soil ecological environment system. Biochar soil amendment is capable of enhancing the water and nutrient holding capacity and improving the soil structure and quality of terrestrial ecosystems. However, the effect of biochar amendment on bacterial community in MPs-contaminated soil–plant system remain unclear, in particular the prediction of bacterial function of these systems. In this study, the effects of biochar amendment on the bacterial community structure of MPs-contaminated soil were investigated through different treatments at three pepper growth stages, and the bacterial function of MPs-contaminated soil was predicted. As indicated by the results of this study, biochar amendment led to the increased species evenness and richness of bacterial community in MPs-contaminated soil, the enhanced relative abundance of MPs-contaminated tolerant bacteria (e.g., Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes), as well as the improved relative abundance of Massilia, Lysobacter, and Terrimonas. Furthermore, soil total phosphorus (TP), soil organic carbon (SOC), NH4+-N, NO3−-N, and pH served as the main factors for the composition of soil bacterial community, as revealed by the result of Pearson correlation analysis and redundancy analysis. Bacterial genera Massilia, Lysobacter, and Terrimonas significantly affected the growth indicator of pepper. PICRUSt functional prediction suggested that the bacterial community of MPs-contaminated soil primarily comprised four level-1 functional layers and 16 level-2 functional layers, and the active soil bacterial community was identified in Metabolism, Genetic information processing, as well as Cellular processes. Biochar amendment enhanced the abundance of genes correlated with Amino acid metabolism and Carbohydrate metabolism of bacteria in MPs-contaminated soil, thus facilitating the nitrogen and phosphorus metabolism cycle of MPs-contaminated soil plants. Our results confirmed that biochar amendment increase the beneficial bacteria in MPs-contaminated soil, more significantly facilitate the nitrogen and phosphorus metabolism cycle within MPs-contaminated soil plants, while effectively expediting the growth of plants in MPs-contaminated soil. This study provides more insights into the correlation of plant and bacterial communities in response to biochar amendment in MPs-contaminated soil system.

微塑料(MPs)作为新型环境污染物长期稳定地存在于土壤环境中,污染地表系统生态环境.对土壤环境中微塑料进行分离和检测是治理土壤环境微塑料污染的基础.介绍了微塑料分离和检测技术的研究进展,并提出分离和检测方法存在的问题.研究表明:筛分-过滤法和密度分离法具有简单、可操作性强且分离效果好的特点,但是在提取过程中交叉污染率较高,提取高密度微塑料的回收率不高.加压流体萃取技术方便快捷、操作简便,但是可能对微塑料的粒子形态造成影响.目视检测法、拉曼光谱和红外光谱、色谱和质谱联用热解分析法存在成本较高、耗时长和损失样品等问题.未来需要进一步探究微塑料的分析方法,研发不损失微塑料的分离和检测方法.

Ecological restoration is an important intervention strategy to halt biodiversity loss and land degradation. Under natural conditions, diazotrophs regulate terrestrial productivity by alleviating nitrogen limitation. However, little is known on the effects of revegetation on diazotroph community (composition, diversity and functioning). Here, by using nifH gene amplicon sequencing, community assembly models, and N-15(2)-labeling technique, we investigated the dynamics of soil diazotroph communities along a revegetation chronosequence of 0 (cropland), 5, 10, 20 and 30 years of Chinese prickly ash (CP) in a karst area of Southwest China. Diazotroph diversity decreased and its composition was significantly changed after revegetation. Soil pH was the edaphic factor which correlated the most with diazotroph community composition and diversity. The most abundant diazotrophs belonged to the Proteobacteria phylum and changed along revegetation chronosequence: the genus Azohydromonas dominated at early stages (5-y CP), while at later stages (20-y CP) the genera Azospirillum and Bradyrhizobium became more abundant. The N-fixation rates were highest in the 5-y CP plantation, and relatively lower N-fixation rates were observed in the cropland and 10-y CP plantation. The Sloan neutral and null models showed: i) a phylogenetic turnover in the diazotrophic taxa assembly, which was largely deterministic at 5- and 10-y, and stochastic at 20- and 30-y; and ii) a bacterial community which was assembled largely by stochastic processes along the revegetation chronosequence. Taken together, our results highlight that knowledge on dynamics of diazotroph community (composition, diversity and functioning) is important to understand ecological mechanisms regulating belowground community along revegetation process.

为探究西南喀斯特干热河谷地区土壤碳(C)、氮(N)、磷(P)含量及酶活性沿海拔梯度的垂直分布特征及驱动机制,选取贵州省花江石漠化治理示范区4个海拔梯度(500,700,900,1100 m)的林地土壤为研究对象,对土壤的基本理化性质、碳氮磷储量以及酶活性进行分析.结果表明:土壤有机碳(SOC)、总磷(TP)含量随海拔升高呈先增加后减少再增加的变化趋势,总氮(TN)含量的变化不明显且变异系数远小于有机碳和总磷含量的,三者在各海拔处的表聚现象明显,随海拔梯度的变化受总碳(TC)和总钾(TK)的影响较为显著(P<0.01);碳氮比(C/N)和氮磷比(N/P)随海拔升高呈现出两种相反的变化趋势,前者为先增大后减小再增大,后者为先减小后增大再减小,土壤中总氮含量过高是其主要限制因素;受淋溶作用的影响,在海拔升高过程中碳磷比(C/P)呈现出逐渐减小的趋势.研究区内林地土壤的磷有效性较低,在之后的生态恢复过程中应注重土壤有效磷的补充;土壤脲酶(Ure)、蔗糖酶(Suc)、过氧化氢酶(Cat)活性在整体空间中的相互耦合性较好,随海拔升高呈先升高后降低的变化趋势,在海拔700 m处活性最强.土壤水分、总碳含量、有机碳含量、总氮含量、pH值是影响酶活性变化的主控因子.

Deciphering how communities assemble in gut bacteria in response to antimony (Sb) stress is beneficial to better understand the detoxification mechanism of earthworms to Sb, which is crucial for comprehensive understanding in situ remediation of Sb contaminated soil. However, little is known about the assembly processes of generalists and specialists in earthworm gut, particularly with their environmental adaptation potential. Herein, we conducted a 4-week exposure experiment, and analyzed the evolutionary characteristics, community assembly processes and network stability of generalists and specialists in earthworm (Eisenia fetida) gut and soil taxa. The results demonstrated that the taxonomic distance and phylogenetic distance of generalists were significantly lower than those of specialists (P < 0.001) both in earthworm gut and in soil. The environmental thresholds of generalists in earthworm gut were generally higher than those in soil, while the environmental thresholds of specialists in earthworm gut were lower. Generalists had stronger phylogenetic signals than specialists did both in earthworm gut and in soil. The binary-state speciation and extinction model revealed that the speciation rates of generalists and specialists in earthworm gut were 7.67 and 0.96, which increased by 7.42 and decreased by 1.72 compared with the corresponding rates in soil, respectively. Generalists and specialists had higher evolutionary efficiency in earthworm gut than in soil. The null model analysis exhibited that the stochastic processes of generalists and specialists in earthworm gut were mainly determined by undominated part (98.48% and 86.36%, respectively), while those in soil were primarily determined by homogenizing dispersal (80.30%) and dispersal limitation (78.79%), respectively. The network analysis displayed that the nodes and edges of the global network and the specialist sub-networks in soil were more than those in earthworm gut, while the nodes and edges of the generalist sub-networks in soil were less than those in earthworm gut. The sub-networks of generalists and specialists had stronger robustness at low Sb concentration, and generalist sub-network was more vulnerable than specialist sub-network. These results make up for the knowledge gaps of the speciation, evolution and maintenance mechanism of bacterial communities in earthworm gut under Sb stress, and provide new evidence for formulating bioremediation strategies of Sb contaminated soil.

土壤中的养分丰缺决定了葡萄果实的产出质量,明确京津冀地区葡萄园的土壤养分状况,可以采取对应的措施,有助于葡萄增产,为葡萄园合理施用肥料提供科学依据.采集了京津冀地区38个典型葡萄园的土壤样品,通过测定不同年限、不同土层深度的土壤pH值、EC值、有机质、有效磷、速效钾、全氮、全磷、全钾等化学指标,分析京津冀地区主要葡萄产区的土壤性质随葡萄种植年限及土层深度不同、种植区域不同的演变规律,并对此区域的葡萄园土壤质量进行分析评价.京津冀地区不同种植年限的葡萄土壤中除全钾外在不同的土层都表现出了显著的变化,有效磷、速效钾整体而言表现出了富集的趋势.全磷含量平均值虽然有下降的趋势但整体而言含量仍较高,而有机质含量平均值较低且天津地区的有机质含量还在逐渐下降,pH值呈略高的碱性.为实现京津冀地区葡萄园的长期绿色可持续发展,应当注重碱性土壤修复以改善pH值较高的状况,减少磷肥的施用以减轻磷的富集,同时应加强有机肥的施用.

[目的]为进一步提高黄色石灰土的土壤质量.[方法]以贵州典型的黄色石灰土为例,采用3种秸秆还田和设置两种还田量,共8个处理,即空白试验(CK)、仅厌氧淹水(CK1)、少量水稻秸秆(R1)、高量水稻秸秆(R2)、少量玉米秸秆(C1)、高量玉米秸秆(C2)、少量芒草秸秆(M1)以及高量芒草秸秆(M2),研究厌氧淹水条件下不同秸秆与不同秸秆还田量对土壤pH、有机质、全量养分、速效养分及作物生物量等指标的动态影响,分析厌氧淹水结束后各处理的土壤化学计量特征,并运用相关分析法评估土壤养分与养分、养分与作物生物量之间的影响.[结果]①秸秆在厌氧淹水处理下能提高土壤的养分含量,土壤各养分指标含量随着厌氧淹水的时间延长逐渐呈现上升的趋势,除全氮外;②与CK相比,各处理的碳氮比显著较高,碳磷比和氮磷比显著较低;③通过相关分析发现,pH值、全氮与其他各养分无显著相关,有机质与其他养分指标呈显著相关,全钾、全磷分别与速效钾、速效磷呈显著相关,有机质、全钾、速效钾、速效磷与番茄生物量呈显著相关.[结论]玉米秸秆的处理效果优于水稻、芒草秸秆处理,并且高量秸秆处理的效果优于低量秸秆处理,从作物的生物量也反映出高量玉米秸秆处理的效果最佳.

以贵州花江峡谷花椒(Zanthoxylum bungeamun)林为研究对象,采用16S rRNA高通量测序技术,分析种植5、10、20、30 a花椒根际土壤细菌群落结构和多样性特征,探讨不同种植年限花椒土壤理化因子对根际细菌群落分布的影响,为喀斯特石漠化地区花椒农业可持续发展提供有效的理论依据.结果表明,随着花椒种植年限的增加,土壤含水率、pH和有效磷逐渐升高,有机质、铵态氮和硝态氮含量先降低后升高(P<0.05).根际土壤细菌Shannon、Simpson指数总体呈现上升趋势,OTUs、Chao1指数在10 a较低.PCoA分析显示,不同种植年限花椒根际细菌群落组成差异显著,并且随着年限的增加,群落结构趋于相似;差异指示种分析表明,5—30 a差异指示种分别为Firmicutes(厚壁菌门)、Cyanobacteria(蓝藻菌门)、Planctomycetes(浮霉菌门)、Entotheonellaeota(肠杆菌门).RDA分析表明,有机质和含水率与细菌群落分布显著相关(P<0.05).系统发育多样性分析表明,丰富类群多样性与环境因子存在较多的正相关,稀有类群比丰富类群有更强的发育信号.BugBase预测分析发现:随着年限增加根际土壤好氧细菌增加,厌氧细菌下降,5、10 a氧化胁迫耐受菌低于20、30 a,致病菌在5、10 a高于20、30 a.综上,种植年限影响了花椒根际土壤细菌群落多样性,不同年限根际土壤肥力不同使得土壤细菌选择性生长,随着一定时间发育花椒抗病能力提高.