Health risk assessment of trace metal(loid)s in agricultural soils based on Monte Carlo simulation coupled with positive matrix factorization model in Chongqing, southwest China

This study aimed to investigate the pollution characteristics, source apportionment, and health risks associated with trace metal(loid)s(TMs) in the major agricultural producing areas in Chongqing, China. We analyzed the source apportionment and assessed the health risk of TMs in agricultural soils by using positive matrix factorization(PMF) model and health risk assessment(HRA) model based on Monte Carlo simulation. Meanwhile, we combined PMF and HRA models to explore the health risks of TMs in agricultural soils by different pollution sources to determine the priority control factors. Results showed that the average contents of cadmium(Cd), arsenic (As), lead(Pb), chromium(Cr), copper(Cu), nickel(Ni), and zinc(Zn) in the soil were found to be 0.26, 5.93, 27.14, 61.32, 23.81, 32.45, and 78.65 mg/kg, respectively. Spatial analysis and source apportionment analysis revealed that urban and industrial sources, agricultural sources, and natural sources accounted for 33.0%, 27.7%, and 39.3% of TM accumulation in the soil, respectively. In the HRA model based on Monte Carlo simulation, noncarcinogenic risks were deemed negligible(hazard index <1), the carcinogenic risks were at acceptable level(10^(-6)<total carcinogenic risk ≤ 10^(-4)), with higher risks observed for children compared to adults. The relationship between TMs, their sources, and health risks indicated that urban and industrial sources were primarily associated with As, contributing to 75.1% of carcinogenic risks and 55.7% of non-carcinogenic risks, making them the primary control factors. Meanwhile, agricultural sources were primarily linked to Cd and Pb, contributing to 13.1% of carcinogenic risks and 21.8% of non-carcinogenic risks, designating them as secondary control factors.

Nitrogen cycling and environmental impacts in upland agricultural soils in North China： A review

The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen(N) transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer's conventional high N fertilization practice in the winter wheat-summer maize rotation system(N application rate was approximately 600 kg ha–1 yr–1), crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion(approximately 54%) of Chinese cropland N_2O emissions. The "non-coupled strong ammonia oxidation" process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4+ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R(Right soure, Right rate, Right time, Right place) fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.

Assessment of the Quality of Sediments and Agricultural Soils: Case of the Ity-Floleu Area in the Prefecture of Zouan-Hounien, Western Côte d’Ivoire

The objective of this study is to assess the level of metal contamination of sediments and agricultural soils in the Ity-Floleu zone. The concentrations of trace elements (Fe, Mn, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were measured in different seasons over two successive years. The sediment pollution index made it possible to note that the sediments and agricultural soils of the various stations studied are highly polluted in all seasons. The calculation of the geoaccumulation index indicates that surface water sediments most often experience extreme or moderate pollution in As, Cd, Cu, Hg and Zn in the dry or rainy season except in Pb in some cases. We observed that the sediments of the Cavally river present a serious pollution due to extreme anthropic activities carried out along the river. Over the entire region, the results of the potential ecological risk index (RI) indicate that all the sediments and agricultural soils analysed present a moderate ecological risk in terms of Pb and Zn in certain cases and an ecological risk is observed low bound to other metals in all seasons. This metallic pollution generated by human activities in this region can have consequences for the environment and biodiversity.

Chemical Composition Assessment by Wavelength Dispersive X-Ray Fluorescence of Agricultural Soils in the Mining Town of Moanda, Gabon

This work focuses on the analysis of the chemical composition of soils dedicated to agriculture in order to assess the impacts of manganese mining activity in the city of Moanda in South-East Gabon. The result of the analysis obtained using wavelength dispersive X-ray fluorescence revealed the presence of twenty-seven elements in the seventeen soil samples collected namely: Na, K, Rb, Mg, Ca, Sr, Ba, Ti, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Cr, Mn, Al, O, C, P, S, Si, I, Ac and Th. Iron (Fe), aluminum (Al) and manganese (Mn) were respectively higher. The practice of agriculture near mining sites is not without risks for the quality of agricultural products and the health of the population.

Towards defining soil quality of Mediterranean calcareous agricultural soils:Reference values and potential core indicator set

To avoid soil degradation,adapt to climate change and comply with the Sustainable Development goals 2030(UN General Assembly),establishing the quality/fertility of the agricultural soils of the Mediterranean region and evaluate how these evolve with time is mandatory.This enables adequate management practices to be implemented.The Mediterranean calcareous region has received little attention in this sense,in spite its soil particularities.So,24 different representative calcareous agricultural soils of the Mediterranean region,including the main management strategies of agricultural soils(rainfed and irrigated),were sampled from the island of Mallorca;and their physical,chemical and biological properties determined.The values obtained for most of the soil characteristics allowed to establish an initial approach to the reference values for the type of calcareous agricultural soils considered,and to clearly distinguish the effect of rainfed or irrigation management practices on soils properties and dynamics.Some enzyme activities were not stimulated by the irrigation conditions assayed or they were only in dry conditions,suggesting optimum enzyme activities could be obtained when alternating dry and humid soil conditions.Soil organic carbon,calcium carbonate and active lime revealed of significant importance in the collection of soils.Finally,the results obtained clearly indicate the heterogeneity of the region and its implications on the different soil characteristics.Therefore,this study could serve as a starting point to adequately establish the quality(fertility)for Mediterranean calcareous agricultural soils and their reference values by conducting further research in this region and including more type of soils.

Detection of the foreign object positions in agricultural soils using Mask-RCNN

Objects in agricultural soils will seriously affect the farming operations of agricultural machinery.At present,it still relies on human experience to judge abnormal Gounrd-penetrting Radar(GPR)signals.It is difficult for traditional image processing technology to form a general positioning method for the randomness and diversity characteristics of GPR signals in soil.Although many scholars had researched a variety of image-processing techniques,most methods lack robustness.In this study,the deep learning algorithm Mask Region-based Convolutional Neural Network(Mask-RCNN)and a geometric model were combined to improve the GPR positioning accuracy.First,a soil stratification experiment was set to classify the physical parameters of the soil and study the attenuation law of electromagnetic waves.Secondly,a SOIL-GPR geometric model was proposed,which can be combined with Mask-RCNN's MASK geometric size to predict object sizes.The results proved the effectiveness and accuracy of the model for position detection and evaluation of objects in soils;then,the improved Mask RCNN method was used to compare the feature extraction accuracy of U-Net and Fully Convolutional Networks(FCN);Finally,the operating speed of agricultural machinery was simulated and designed the A-B survey line experiment.The detection accuracy was evaluated by several indicators,such as the survey line direction,soil depth false alarm rate,Mean Average Precision(mAP),and Intersection over Union(IoU).The results showed that pixel-level segmentation and positioning based on Mask RCNN can improve the accuracy of the position detection of objects in agricultural soil effectively,and the average error of depth prediction is 2.87 cm.The results showed that the detection technology proposed in this study integrates the advantage of soil environmental parameters,geometric models,and artificial intelligence algorithms to provide a high-precision and technical solution for the GPR non-destructive detection of soils.

Source apportionment of heavy metals in soils around a coal gangue heap with the APCS-MLR and PMF receptor models in Chongqing,southwest China

This study studied the characteristics and source apportionment of heavy metal pollution in the agricultural soil surrounding a gangue coal heap in Chongqing,China by using absolute principal component scores-multiple linear regression(APCSMLR)model and positive matrix factorization(PMF)model.The applicability of the models was compared in the assessment of source apportionment.The results showed that the average contents of Cd,Hg,As,Pb,Cr,Cu,Ni,and Zn in the surface soil were 0.46,0.14,9.66,31.2,127,95.6,76.0,and 158 mg/kg,respectively.Combined with the spatial distribution and correlation analyses,the results of source apportionment were consistent for both the APCSMLR and PMF models.Cd,Hg,As,and Pb were mainly affected by the gangue heap accumulation,with respective contributions of 74.6%,79.4%,69.1%,and 67.2%based on the APCS-MLR model and respective contributions of 69.7%,60.7%,57.4%,and 41.9%based on the PMF model.Ni and Zn were mainly affected by industrial and agricultural activities,while Cr and Cu were mainly affected by natural factors.The results of the source apportionment were approximately consistent between the APCS-MLR and PMF models.The combined application of the two receptor models can make the results of source apportionment more comprehensive,accurate,and reliable.

Heavy Metals in Soils Associated with Fertilizers in Trinidad

Heavy metals in agricultural soil pose human health risks through food consumption. In a novel study for Trinidad, concentration and pollution index levels of heavy metals were assessed from 18 agricultural farms using the X-Ray fluorescence technique, then to evaluate the Geo-accumulation and Nemerow’s Integrated Pollution indexes. Toxic elements Pb and As were present but soil quality due to anthropogenic input was found as unpolluted. Overall heavy metal pollution was classified at a precautionary level for 33% of farms, slightly polluted for 61% and moderately polluted for 6% of the farms assessed, thus, regular monitoring and mitigation measures are important for food safety and human health in Trinidad.

Heavy Metals in the Northwest Agricultural Region Dominican Republic

Heavy metals currently represent a very important source of contamination, since their intake by humans and animals in many cases is the cause of serious damage to health. Soil, air, water and food are the most common pathways for heavy metals to reach organisms. Since soil is their origin, in this study we focus on soil analysis to determine the concentration of Cr, Ni, Cu, Zn, As, Hg, Cd and Pb, which are the most toxic metals. The study site is the agricultural soils of the northwestern region of the Dominican Republic where bananas and rice are the main crops grown. Chromium levels in most samples exceeded the NOAA-USEPA Probable Effects Level (PEL). Other heavy metals were within the acceptable ranges for healthy soil, according to the Food and Agriculture Organization (FAO).

Characteristics and Development of Agricultural Soil in Hetao Irrigation District,Inner Mongolia

Hetao Irrigation District is located in the cold and arid region of Hetao Plain,Inner Mongolia,where the agricultural soil has unique characteristics.Although the agricultural soil properties in Hetao Irrigation Districts have been reported,the overall characteristics remain unclear.Through literature review and investigation,the overall characteristics,development patterns,and related reasons were explored,consequently providing theoretical support for enhancing soil utilization and formulating sustainable soil development strategies.The results showed that the agricultural soil in Hetao Irrigation District originated from the sedimentary layer and anthropogenic mellowing produced by the diversions of the Yellow River.The soil has periodic secondary salinization characteristics,accompanied by a slightly increasing pH value over time.It has low soil organic contents with a stable changing trend,low nitrogen,and phosphorus contents but high potassium and sulfur content,uneven nutrient distribution,diverse production performance,weak but stable ecological performance,and heterogeneous soil quality with a stable change trend.These findings indicate that this kind of soil can be used to plant diverse crops tolerant to different saline-alkali and requiring various nutrients.This agricultural soil is sustainable,but it is also faced with the problems of increased saline-alkali,nutrient loss,and pollution.

COMPARISON OF THE ALKALI MARSH SOIL ANDAGRICULTURE SOIL ON NUTRIENT RETENTIONIN WESTERN JILIN, CHINA

An intact alkali marsh soil (MS) core and an agriculture soil (AS) core were studied by the simulated test in order to get the comparison of the nutrients retention in alkali MS and AS. The soil cores extracted from the Xiang hai Wetland, western Jilin Province, China, were leached with solution contained carbon, nitrogen and phosphorus.Then the effluent water from the outlets of soil core with different depths was measured, including chemical oxygen demand (COD), total phosphorus (TP), phosphate (PO3-4 - P) and nitrogen existed as nitrate (NO-3 - N), nitrite (NO-2 - N) and ammonia nitrogen (NH+4 - N) and the total nitrogen (TN) in the effluent water. COD and TP are decreased with the depth, the changing trends of TN, NO-3 - N and NH+4 - N contents are similar to COD and TP,whereas NO-2 - N in both MS and AS effluent have a little transition at 40cm depth. It is similar efficiency of MS to AS in significantly cutting down COD, TP, PO3-4 - P, TN, NO-3 - N, NH+4 - N and NO-2 - N in nutrient water.The function of MS would be same efficiency of the nutrients retention as the AS. Although the SOM and pH have some impacts on nutrients retention in the soil, the MS with higher soil organic matter (SOM) and pH have the same effluent water as the AS with the lower SOM and pH at the depth of 60 cm, the bottom of the soil cores.

Characteristics and Risk Assessment of Soil Heavy Metal Contents in Facility Agriculture of Guangxi

[Objectives]To study the characteristics of soil heavy metal contents in facility agriculture of Guangxi and analyze its risks.[Methods]The heavy metal content of 30 surface soil samples taken from facility agriculture in Guangxi was analyzed.The status of soil heavy metal pollution in facility agriculture of Guangxi was evaluated by the single factor index method,geo-accumulation index method and Hakanson potential ecological risk index method with reference to the soil background value in Guangxi.[Results]Compared with the soil background value in Guangxi,the over-limit rates of heavy metals cadmium,lead,arsenic,chromium,mercury,copper and zinc in soil samples were 56.67%,56.67%,16.67%,30.00%,50.00%,60.00%and 80.00%,respectively.Compared with the screening values of the Soil Environmental Quality-Risk Control Standard for Soil Contamination of Agricultural Land(for trial implementation)(GB15618-2018),the overlimit rates of the heavy metals cadmium,arsenic,copper and zinc in the surface soil of agricultural facilities in Guangxi were 56.67%,10.00%,16.67%and 23.33%,respectively.Except for the average content of soil cadmium exceeding the screening value,the evaluation content of the other six soil heavy metals did not exceed the screening value.According to the evaluation results of the single factor pollution index method,the surface soil arsenic and chromium of the agricultural facilities in Guangxi belonged to the clean level,lead,mercury,and copper belonged to mild pollution,and cadmium and zinc belonged to moderate pollution.According to the evaluation results of the geo-accumulation index,the lead,arsenic,chromium and mercury in the surface soil of the agricultural facilities in Guangxi belonged to the pollution-free level,while the cadmium,copper and zinc belonged to the mild-moderate pollution.According to the evaluation results of the potential ecological risk index method,the potential ecological risks of the heavy metals of lead,arsenic,chromium,copper and zinc in the soil of agricultural facilities in Guangxi belonged to low potential ecological risk level,and the potential ecological risks of cadmium and mercury belonged to moderate risk level.The potential ecological risk index(RI)of the seven heavy metals in the soil was 132.46,which belonged to moderate potential ecological risk.The largest contribution of soil heavy metals to the potential ecological risk index was cadmium and mercury.[Conclusions]Taking the soil of facility agriculture in Guangxi as the object,this paper studied the characteristics of heavy metal content in facility agricultural soil and its risk assessment,in order to provide a scientific basis for facility soil heavy metal risk prevention and control and provide safe technology for facility agriculture.

Influence of Soil Types on Establishment and Early Growth of Populus trichocarpa

When planning poplar plantations there are many factors to consider that can influence young plant development. In addition to soil preparation, vegetation management, protection against browsers, and plant-type, it is important to have information on how soil properties influence young plant development. Comparisons of establishment and growth in different soils are complicated as experimental sites often are geographically distant where temperature, precipitation and vegetation can vary, thus complicate the analysis. In this case study, a new approach of studying growth of different soil at one experimental site are undertaken by translocating agricultural soils, a silty clay loam and a sandy soil, and common forest soil types, forest moraine soil and forest peat to a single experimental site, thus guaranteeing identical climatic conditions. In all soils, transplanted P. trichocarpa cuttings initially developed in to plants. After 4 weeks though, plants grown in forest peat stopped their growth while plants in the other soils gradually continued their growth with no evidence that soil types influenced above ground plant development. Unlike above-ground growth, root growth and morphology were influenced by soil texture with more root growth occurring if soils have sandy texture. These findings give advice to some of the limitations when planning for establishment of poplar plantations either at agricultural or at forest land.

Bacterial and archaeal communities in saline soils from a Los Negritos geothermal area in Mexico

In recent years,there has been a growing need to understand how salinity affects microbial communities in agricultural soils.Archaeal and bacterial community diversities and structures were investigated by high-throughput sequencing analysis of their 16S rRNA in two arable soils with low electrical conductivity(EC)(2.3 and 2.6 dS m^(-1))and a saline soil(EC=17.6 dS m^(-1)).The dominant bacterial phyla in the soils were Proteobacteria(relative abundance(RA)=46.2%),followed by Acidobacteria(RA=13.1%)and Actinobacteria(RA=10.0%),whereas Serratia(RA=6.0%)and Bacillus(RA=4.0%)were the dominant bacterial genera.Candidatus Nitrososphaera(53.5%)was the dominant archaeal phylotype in the arable soils,whereas Nitrosopumilus(RA=0.4%)dominated in the saline soil.The archaeal and bacterial community structures were different between the soils and significantly correlated with soil sand,arsenic,barium,and antimony contents,but not with soil salinity.

Heavy metals in agricultural soil in China: A systematic review and meta-analysis

Research about farmland pollution by heavy metals/metalloids in China has drawn growing attention.However,there was rare information on spatiotemporal evolution and pollution levels of heavy metals in the major grainproducing areas.We extracted and examined data from 276 publications between 2010 and 2021 covering five major grain-producing regions in China from 2010 to 2021.Spatiotemporal evolution characteristics of main heavy metals/metalloids was obtained by meta-analysis.In addition,subgroup analyses were carried out to study preliminary correlations related to accumulation of the pollutants.Cadmium(Cd)was found to be the most prevailing pollutant in the regions in terms of both spatial distribution and temporal accumulation.The Huang-Huai-Hai Plain was the most severely polluted.Accumulation of Cd,mercury(Hg)and copper(Cu)increased from 2010 to 2015 when compared with the 1990 background data.Further,the levels of five key heavy metals(Cd,Cu,Hg,lead[Pb]and zinc[Zn])showed increasing trends from 2016 to 2021 in all five regions.Soil pH and mean annual precipitation had variable influences on heavy metal accumulation.Alkaline soil and areas with less rainfall faced higher pollution levels.Farmlands cropped with mixed species showed smaller effect sizes of heavy metals than those with single upland crop,suggesting that mixed farmland use patterns could alleviate the levels of heavy metals in soil.Of various soil remediation efforts,farmland projects only held a small market share.The findings are important to support the research of risk assessment,regulatory development,pollution prevention,fund allocation and remediation actions.

Predicting chemical speciation of metals in soil using Visual Minteq

From soil contamination and risk assessment perspectives,it is imperative to understand the ecological processes occurring in soils.Certain soil processes greatly affect chemical speciation of potentially toxic metals(PTMs),and thus also influence their biogeochemical activity.The current study analyzed chemical speciation of eight PTMs(Cd,Cr,Fe,Cu,Mn,Ni,Zn,and Pb)in upper and lower soil layers for 15 agronomic fields of Vehari-Pakistan using Visual Minteq software.The divalent forms of most PTMs(PTM^(2+))generally predominated in both soil layers(79.9%overall occurrence).However,chromium revealed a different pattern of chemical speciation(95.8%as CrOH^(+))compared to other PTMs.The mean percentage of all the PTMs2+was slightly higher for the lower soil layer(81.3%)than in the upper layer(78.4%),the trend being same for all the PTMs,except Cr.This higher PTMs^(2+)percentage in lower soil layers than upper layers was due to lower content of organic matter and other anions such as Cl^(−)and HCO_(3)_(−).The mean percentage ages of all the PTMs^(2+)was similar among all the 15 agronomic fields,which was confirmed by strong Pearson correlation values(R^(2)>0.95).The PCA graph grouped all the agronomic fields and PTM^(2+) closely,except Cr^(2+) and Cu^(2+).This grouping confirmed the similar chemical speciation of PTMs,except Cu and Cr in studied fields.

Linking microbial carbon pump capacity and efficacy to soil organic carbon storage and stability under heavy metal pollution

Heavy metal pollution can lead to a great loss of soil organic carbon(SOC).However,the microbial mechanisms that link heavy metal pollution to SOC remain poorly understood.Here,we investigated five apple-orchard soils at different distances from a Pb-Zn smelter.After assessing the heavy metal pollution level based on Grade Ⅱ of the national soil environmental quality standard(China),we found SOC stocks and microbial carbon pump(MCP)capacity(i.e.,microbial residue carbon)under medium and heavy pollution levels were significantly lower than those under safe,cordon and light pollution levels.The structural equation model showed causality in the SOC variations linked to pollution level through MCP capacity,which could contribute 77.8% of the variance in SOC storage.This verified MCP capacity can serve as a key parameter for evaluation of SOC storage under heavy metal pollution.Soil MCP efficacy,i.e.,the proportion of microbial residue carbon to SOC,also decreased under medium and heavy pollution.This suggested that,with a heavier pollution level,there was a higher rate of reduction of microbial residue carbon in soil than the rate of reduction of SOC.As MCP efficacy can be a useful assessment of SOC stability,the significantly positive relationship between MCP efficacy and clay content in correlation analysis implied that lower MCP efficacy was correlated with SOC stability under the heavier pollution level.Our study provides valuable insights to identify the mechanisms of microbially mediated C transformation processes that are influenced by heavy metal pollution in agroecosystems.

Distribution of microplastics in soil aggregates after film mulching

Microplastic distribution is non-homogeneous in agricultural soil following plastic film degradation.However,the distribution of microplastics by shape and particle size in different soil aggregates remains unknown.To elucidate the distribution of microplastic shapes and particle sizes in soil aggregates with increasing years of film mulching,four paired fields with film mulching(FM)and no mulching(NM)were examined at 1,5,10,and 20 years after continuous mulching.An increase in soil aggregates of 0.053–0.25 mm diameter was observed;however,soil organic carbon content decreased after long-term FM.Microplastics primarily combined with 0.053–2 mm soil aggregates.Specifically,long-term FM was associated with dominance of film-and fiber-shaped microplastics in soil aggregates of 0.25–2 mm and 0.053–0.25 mm diameter,respectively.Fiber-and granule-shaped microplastics of 0.25–1 mm diameter primarily combined with 0.053–0.25 and 0.25–2 mm soil aggregates,respectively.Film-shaped microplastics of diameter>1 mm and diameter 0.05–0.25 mm primarily combined with 0.25–2 mm soil aggregates.Therefore,distribution of microplastics in soil aggregates can be used to monitor soil health and quality,greatly enhancing our understanding of the risk posed by microplastics to the environment.

Vermicompost:In situ retardant of antibiotic resistome accumulation in cropland soils

The dissemination of antibiotic resistance genes(ARGs)in soil has become a global environmental issue.Vermicomposting is gaining prominence in agricultural practices as a soil amendment to improve soil quality.However,its impact on soil ARGs remains unclear when it occurs in farmland.We comprehensively explored the evolution and fate of ARGs and their hosts in the field soil profiles under vermicompost application for more than 3years.Vermicompost application increased several ARG loads in soil environment but decreased the high-risk bla-ARGs(bla_(ampC),bla_(NDM),and bla_(GES-1))by log(0.04-0.43).ARGs in soil amended with vermicompost primarily occurred in topsoil(approximately 1.04-fold of unfertilized soil),but it is worth noting that their levels in the 40-60 cm soil layer were the same or even less than in the unfertilized soil.The microbial community structure changed in soil profiles after vermicompost application.Vermicompost application altered the microbial community structure in soil profiles,showing that the dominant bacteria(i.e.,Proteobacteria,Actinobacteriota,Firmicutes)were decreased 2.62%-5.48%with the increase of soil depth.A network analysis further revealed that most of ARG dominant host bacteria did not migrate from surface soil to deep soil.In particular,those host bacteria harboring high-risk bla-ARGs were primarily concentrated in the surface soil.This study highlights a lower risk of the propagation of ARGs caused by vermicompost application and provides a novel approach to reduce and relieve the dissemination of ARGs derived from animals in agricultural production.

Which are the most favourable conditions for reducing soil CO_(2)emissions with no-tillage?Results from a meta-analysis

No-tillage practices have a recognised beneficial impact on soil and water conservation while reducing erosion processes and enhancing soil organic matter content.However,scientists continue to debate the effectiveness of no-tillage in reducing soil carbon dioxide(CO_(2))emissions from farming.Following the same line of inquiry pursued by the authors who reviewed the impact of conservative practices on direct CO_(2)emissions,we applied meta-analytic and machine learning techniques to unravel the effect of no-tillage under contrasting pedo-environmental conditions and agricultural management.We analysed fifty-six experimental studies investigating direct soil CO_(2)emissions from no-tillage and conventional tillage practices(102 paired observations),considering pedological(soil texture,soil organic carbon content),environmental(climate type),and management(crop rotation,experiment duration)factors.We estimated the effect of different practices on the daily amount of soil CO_(2)emissions,and the impact of tillage in the period immediately following the event.The main insights of this study are:(i)the conditions leading to the highest reduction of CO_(2)emissions due to no-tillage were long-term experiments(standardised mean differenceβ=0.64)conducted in arid environments(β=0.76)and clay soils(β=0.81),with low organic carbon content(β=0.79)where crop rotations(β=0.65)were performed;(ii)the same conditions were associated with the lowest absolute CO_(2)emissions,irrespective of soil management;(iii)the highest contribution to the variability of absolute soil CO_(2)emissions was associated with soil texture(mean decrease in accuracy of Random Forest models,MDA=4.57),rotation(MDA=3.07),experiment duration(MDA=2.93)and soil organic carbon content(MDA=2.24),rather than to tillage practices;(iv)soil CO_(2)emissions almost doubled in the first day after a tillage event,consistently across studies(p=0.001).This meta-analysis offers quantitative figures on the impact of tillage practices on soil CO_(2)emissions and releases data for informing policies aimed at promoting climate change mitigation.