Review on the Effects of Combined Pollution of Lead and Chromium on Soil Microorganisms and Treatment Methods

Heavy metals—Pb and Cr are important causes of environmental pollution, and they often coexist in nature. At present, the effects of Pb and Cr toxicity on soil microorganisms have been less studied, in soil environment which is extremely complex. Simulating soil environment and studying microbial reaction under various heavy metal conditions are of great significance for revealing microbial tolerance to heavy metals. In this paper, firstly, the related concepts of soil rechecking pollution are discussed, and the physical and chemical properties and forms of lead and chromium are introduced accordingly. Secondly, the effects of combined pollution of lead and chromium on soil microbial biomass, soil microbial community structure and soil microbial activity were discussed. Finally, the relevant treatment methods of heavy metal contaminated soil were put forward.

The Combination of Achnatherum inebrians Extracts and Soil Microorganisms Inhibited Seed Germination and Seedling Growth in Elymus nutans

In a greenhouse experiment,the effects of soil microorganisms and extracts of Achnatherum inebrians on the seed germination and seedling growth of Elymus nutans were studied.The results showed that both the extracts from aboveground and belowground parts of A.inebrians significantly inhibited the germination rate,germination potential,germination index,vigor index,seedling height,root length,and fresh weight of E.nutans,but increased malondialdehyde content,catalase,peroxidase and superoxide dismutase activity of E.nutans seedlings(p<0.05).The allelopathy of aqueous extracts of the aboveground parts of A.inebrians was stronger than that of the pre-cipitates.Aqueous extracts of the aboveground parts of A.inebrians decreased seed germination rate,germination potential,germination index,vigor index,seedling length,root length,and seedling fresh weight by 10.45%-74.63%,24.18%-32.50%,19.03%-73.36%,37.83%-88.41%,21.42%-53.14%,2.65%-40.21%,and 20.45%-61.36%,respectively,and malondialdehyde content,peroxidase,catalase,and superoxide dismutase activity increased by 8.09%-62.24%,27.83%-86.47%,22.90%-93.17%,and 11.15%-75.91%,respectively.The above indexes were higher in live soil than in sterilized soil.Soil microorganisms increased the allelopathy of A.inebrians.The seed germination rate,germination potential,germination index,vigor index,seedling length,and seedling fresh weight of E.nutans planted in live soil decreased by 8.22%-48.48%,10.00%-51.85%,8.19%-53.26%,16.43%-60.03%,12.91%-28.81%,and 9.09%-22.86%compared with sterilized soil,respectively.Malondialdehyde content,peroxidase,catalase,and superoxide dismutase activity of E.nutans planted in live soil increased by 53.91%-81.06%,15.71%-57.34%,33.33%-86.31%,and 9.78%-52.51%compared with sterilized soil,respectively.The existence of soil microorganisms enhanced the allelopathy of the secondary metabolites of A.inebrians.A combination of microorganisms and aqueous extracts from the aboveground parts of A.inebrians had the strongest allelopathic effect on E.nutans.

Responses of plant diversity and soil microorganism diversity to nitrogen addition in the desert steppe,China

Nitrogen(N)deposition is a significant aspect of global change and poses a threat to terrestrial biodiversity.The impact of plant-soil microbe relationships to N deposition has recently attracted considerable attention.Soil microorganisms have been proven to provide nutrients for specific plant growth,especially in nutrient-poor desert steppe ecosystems.However,the effects of N deposition on plant-soil microbial community interactions in such ecosystems remain poorly understood.To investigate these effects,we conducted a 6-year N-addition field experiment in a Stipa breviflora Griseb.desert steppe in Inner Mongolia Autonomous Region,China.Four N treatment levels(N0,N30,N50,and N100,corresponding to 0,30,50,and 100 kg N/(hm2•a),respectively)were applied to simulate atmospheric N deposition.The results showed that N deposition did not significantly affect the aboveground biomass of desert steppe plants.N deposition did not significantly reduce the alfa-diversity of plant and microbial communities in the desert steppe,and low and mediate N additions(N30 and N50)had a promoting effect on them.The variation pattern of plant Shannon index was consistent with that of the soil bacterial Chao1 index.N deposition significantly affected the beta-diversity of plants and soil bacteria,but did not significantly affect fungal communities.In conclusion,N deposition led to co-evolution between desert steppe plants and soil bacterial communities,while fungal communities exhibited strong stability and did not undergo significant changes.These findings help clarify atmospheric N deposition effects on the ecological health and function of the desert steppe.

Effects of long-term fencing on soil microbial community structure and function in the desert steppe,China

One of the goals of grazing management in the desert steppe is to improve its ecosystem.However,relatively little is known about soil microbe communities in the desert steppe ecosystem under grazing management.In this study,we investigated the diversity and aboveground biomass of Caragana korshinskii Kom.shrub communities in long-term fencing and grazing areas,combined with an analysis of soil physical-chemical properties and genomics,with the aim of understanding how fence management affects plant-soil-microbial inter-relationships in the desert steppe,China.The results showed that fence management(exclosure)increased plant diversity and aboveground biomass in C.korshinskii shrub area and effectively enhanced soil organic carbon(233.94%),available nitrogen(87.77%),and available phosphorus(53.67%)contents.As well,the Shannon indices of soil bacteria and fungi were greater in the fenced plot.Plant-soil changes profoundly affected the alpha-and beta-diversity of soil bacteria.Fence management also altered the soil microbial community structure,significantly increasing the relative abundances of Acidobacteriota(5.31%-8.99%),Chloroflexi(3.99%-5.58%),and Glomeromycota(1.37%-3.28%).The soil bacterial-fungal co-occurrence networks under fence management had higher complexity and connectivity.Based on functional predictions,fence management significantly increased the relative abundance of bacteria with nitrification and nitrate reduction functions and decreased the relative abundance of bacteria with nitrate and nitrite respiration functions.The relative abundances of ecologically functional fungi with arbuscular mycorrhizal fungi,ectomycorrhizal fungi,and saprotrophs also significantly increased under fence management.In addition,the differential functional groups of bacteria and fungi were closely related to plant-soil changes.The results of this study have significant positive implications for the ecological restoration and reconstruction of dry desert steppe and similar areas.

Degradation of Bioplastics in Soil and Their Degradation Effects on Environmental Microorganisms

Degradation of three kinds of bioplastics and their effects on microbial biomass and microbial diversity in soil environment were analyzed. The degradation rate of bioplastic in soil was closely related to the main components in the bioplastics. Poly (butylene succinate)-starch (PBS-starch) and poly (butylene succinate) (PBS) were degraded by 1% to 7% after 28 days in a soil with an initial bacterial biomass of 1.4 × 109 cells/g-soil, however poly lactic acid (PLA) was not degraded in the soil after 28 days. When the powdered-bioplastics were examined for the degradation in the soil, PBS-starch also showed the highest degradability (24.4% degradation after 28 days), and the similar results were obtained in the case of long-term degradation experiment (2 years). To investigate the effect of bacterial biomass in soil on biodegradability of bioplastics, PBS-starch was buried in three kinds of soils differing in bacterial biomass (7.5 × 106, 7.5 × 107, and 7.5 × 108 cells/g-soil). The rate of bioplastic degradation was enhanced accompanied with an increase of the bacterial biomass in soil. 16S rDNA PCR-DGGE analysis indicated that the bacterial diversity in the soil was not affected by the degradation of bioplastics. Moreover, the degradation of bioplastic did not affect the nitrogen circulation activity in the soil.

Response of soil microorganisms to vegetational succession in Ziwuling Forest

This study investigates the changes in soil microbial populations as vegetational succession progress from abandoned farmland to climax forest in the Ziwuling Forest,which is located in the northern part of the Loess Plateau,China.Different organic C and total extractable N between the fumigated and non-fumigated soils were assumed to be released from soil microorganisms.Soil microbial C was calculated using Kec=0.38 and microbial N was calculated using Ken=0.45.The released P was converted to microbial biomass P using Kep=0.40.Soil bacteria,fungi,and actinomycetes increased as the vegetational succession progressed.Microbial C was of the highest amount in farmland.Microbial C,N,and P generally increased from abandoned land to climax community.The results indicated significant(P<0.05)diversities of soil microbial biomass under different vegetation.There was a significant correlation between microbial biomass and soil nutrients.Knowledge about soil microbial populations is important for forecasting vegetational succession and determining the ecological condition of the environment.

Response of soil respiration to short-term changes in precipitation and nitrogen addition in a desert steppe

Changes in precipitation and nitrogen(N)addition may significantly affect the processes of soil carbon(C)cycle in terrestrial ecosystems,such as soil respiration.However,relatively few studies have investigated the effects of changes in precipitation and N addition on soil respiration in the upper soil layer in desert steppes.In this study,we conducted a control experiment that involved a field simulation from July 2020 to December 2021 in a desert steppe in Yanchi County,China.Specifically,we measured soil parameters including soil temperature,soil moisture,total nitrogen(TN),soil organic carbon(SOC),soil microbial biomass carbon(SMBC),soil microbial biomass nitrogen(SMBN),and contents of soil microorganisms including bacteria,fungi,actinomyces,and protozoa,and determined the components of soil respiration including soil respiration with litter(RS+L),soil respiration without litter(RS),and litter respiration(RL)under short-term changes in precipitation(control,increased precipitation by 30%,and decreased precipitation by 30%)and N addition(0.0 and 10.0 g/(m^(2)·a))treatments.Our results indicated that short-term changes in precipitation and N addition had substantial positive effects on the contents of TN,SOC,and SMBC,as well as the contents of soil actinomyces and protozoa.In addition,N addition significantly enhanced the rates of RS+L and RS by 4.8%and 8.0%(P<0.05),respectively.The increase in precipitation markedly increased the rates of RS+L and RS by 2.3%(P<0.05)and 5.7%(P<0.001),respectively.The decrease in precipitation significantly increased the rates of RS+L and RS by 12.9%(P<0.05)and 23.4%(P<0.001),respectively.In contrast,short-term changes in precipitation and N addition had no significant effects on RL rate(P>0.05).The mean RL/RS+L value observed under all treatments was 27.63%,which suggested that RL is an important component of soil respiration in the desert steppe ecosystems.The results also showed that short-term changes in precipitation and N addition had significant interactive effects on the rates of RS+L,RS,and RL(P<0.001).In addition,soil temperature was the most important abiotic factor that affected the rates of RS+L,RS,and RL.Results of the correlation analysis demonstrated that the rates of RS+L,RS,and RL were closely related to soil temperature,soil moisture,TN,SOC,and the contents of soil microorganisms,and the structural equation model revealed that SOC and SMBC are the key factors influencing the rates of RS+L,RS,and RL.This study provides further insights into the characteristics of soil C emissions in desert steppe ecosystems in the context of climate change,which can be used as a reference for future related studies.

Influence of salinity and water content on soil microorganisms

Salinization is one of the most serious land degradation problems facing world.Salinity results in poor plant growth and low soil microbial activity due to osmotic stress and toxic ions.Soil microorganisms play a pivotal role in soils through mineralization of organic matter into plant available nutrients.Therefore it is important to maintain high microbial activity in soils.Salinity tolerant soil microbes counteract osmotic stress by synthesizing osmolytes which allows them to maintain their cell turgor and metabolism.Osmotic potential is a function of the salt concentration in the soil solution and therefore affected by both salinity(measured as electrical conductivity at a certain water content)and soil water content.Soil salinity and water content vary in time and space.Understanding the effect of changes in salinity and water content on soil microorganisms is important for crop production,sustainable land use and rehabilitation of saline soils.In this review,the effects of soil salinity and water content on microbes are discussed to guide future research into management of saline soils.

Effects of deficit irrigation on soil microorganisms and growth of Arabica coffee(Coffea arabica L.)under different shading cultivation modes

In the present research,the rational coupling mode of irrigation and shading cultivation for rapid growth and water saving of young Arabica coffee shrubs was investigated from 2016 to 2017.Taking full irrigation(FI,1.2Ep)as the control,the effects of three deficit irrigation(DI)(DI1,DI2 and DI3,with 1.0Ep,0.8Ep and 0.6Ep)on soil water content,temperature,microorganism population density,photosynthetic characteristics,canopy structure and dry mass of Arabica coffee under three shading cultivation modes(S0,monoculture coffee;S1,mild shading cultivation,intercropping with one line of Arabica coffee and one line of castor(Ricinus communis L.);S2,severe shading cultivation,intercropping with one line of Arabica coffee and two lines of castor)were investigated using plot experiments.Compared to FI,DI1 not obviously changed the population density of soil bacteria and actinomycetes,but increased net photosynthetic rate(Pn),crown area and dry mass of Arabica coffee by 7.0%,9.53%and 10.46%,respectively.In addition,DI1 also decreased total radiation under canopy(TRUC)by 5.51%.DI2 and DI3 reduced the population density of soil bacteria,fungi and actinomycetes ranging 8.94%-47.06%.Compared to S0,S1 increased the population density of soil fungi,bacteria and actinomycetes by 13.99%,30.77%and 9.72%,respectively.S1 also increased Pn,transpiration rate(Tr),leaf apparent radiation use efficiency(ARUE),leaf area index(LAI)and dry mass by 9.29%,5.39%,60.98%,10.31%and 30.02%,respectively.DI1S1 obtained the highest Pn and dry mass and higher LAI and the lowest TRUC.DI1S1 increased Pn,ARUE and dry mass by 18.98%,72.37%and 62.90%respectively but decreased TRUC by 21.77%when compared to FIS0.Thus,DI1S1 was found to be the rational mode of irrigation and shading cultivation for young Arabica coffee.

Effects of the vegetation restoration years on soil microbial community composition and biomass in degraded lands in Changting County,China

We evaluated the effects of the number of years of restoration of vegetation on soil microbial community structure and biomass in degraded ecosystems.We investigated the microbial community structure by analyzing their phospholipid fatty acids then examined microbial biomass carbon and nitrogen by chloroform fumigation extraction of restoration soils over several years.The data were compared with those of highly degraded lands and native vegetation sites.The results show that the duration of vegetation on the sites substantially increased microbial biomass and shifted the microbial community structure even after only 4 years.However,microbial communities and biomass did not recover to the status of native vegetation even after 35 years of vegetation cover.A redundancy analysis and Pearson correlation analysis indicated that soil organic carbon,total nitrogen,available potassium,soil water content,silt content and soil hardness explained 98.4%of total variability in the microbial community composition.Soil organic carbon,total nitrogen,available potassium and soil water content were positively correlated with microbial community structure and biomass,whereas,soil hardness and silt content were negatively related to microbial community structure and biomass.This study provides new insights into microbial community structure and biomass that influence organic carbon,nitrogen,phosphorus and potassium accumulation,and clay content in soils at different stages of restoration.

Effects of root dominate over aboveground litter on soil microbial biomass in global forest ecosystems

Background:Inputs of above-and belowground litter into forest soils are changing at an unprecedented rate due to continuing human disturbances and climate change.Microorganisms drive the soil carbon(C)cycle,but the roles of above-and belowground litter in regulating the soil microbial community have not been evaluated at a global scale.Methods:Here,we conducted a meta-analysis based on 68 aboveground litter removal and root exclusion studies across forest ecosystems to quantify the roles of above-and belowground litter on soil microbial community and compare their relative importance.Results:Aboveground litter removal significantly declined soil microbial biomass by 4.9%but root exclusion inhibited it stronger,up to 11.7%.Moreover,the aboveground litter removal significantly raised fungi by 10.1%without altering bacteria,leading to a 46.7%increase in the fungi-to-bacteria(F/B)ratio.Differently,root exclusion significantly decreased the fungi by 26.2%but increased the bacteria by 5.7%,causing a 13.3%decrease in the F/B ratio.Specifically,root exclusion significantly inhibited arbuscular mycorrhizal fungi,ectomycorrhizal fungi,and actinomycetes by 22.9%,43.8%,and 7.9%,respectively.The negative effects of aboveground litter removal on microbial biomass increased with mean annual temperature and precipitation,whereas that of root exclusion on microbial biomass did not change with climatic factors but amplified with treatment duration.More importantly,greater effects of root exclusion on microbial biomass than aboveground litter removal were consistent across diverse forest biomes(expect boreal forests)and durations.Conclusions:These data provide a global evidence that root litter inputs exert a larger control on microbial biomass than aboveground litter inputs in forest ecosystems.Our study also highlights that changes in above-and belowground litter inputs could alter soil C stability differently by shifting the microbial community structure in the opposite direction.These findings are useful for predicting microbe-mediated C processes in response to changes in forest management or climate.

Effects of seasonal variation on soil microbial community structure and enzyme activity in a Masson pine forest in Southwest China

Soil microbial communities and enzyme activities play key roles in soil ecosystems.Both are sensitive to changes in environmental factors,including seasonal temperature,precipitation variations and soil properties.To understand the interactive mechanisms of seasonal changes that affect soil microbial communities and enzyme activities in a subtropical masson pine(Pinus massoniana)forest,we investigated the soil microbial community structure and enzyme activities to identify the effect of seasonal changes on the soil microbial community for two years in Jinyun Mountain National Nature Reserve,Chongqing,China.The soil microbial community structure was investigated using phospholipid fatty acids(PLFAs).The results indicated that a total of 36 different PLFAs were identified,and 16:0 was found in the highest proportions in the four seasons,moreover,the total PLFAs abundance were highest in spring and lowest in winter.Bacteria and actinomycetes were the dominant types in the study area.Seasonal changes also had a significant(P<0.05)influence on the soil enzyme activity.The maximum and minimum values of the invertase and catalase activities were observed in autumn and winter,respectively.However,the maximum and minimum values of the urease and phosphatase acid enzymatic activities were found in spring and winter,respectively.Canonical correspondence analysis(CCA)analysis revealed that the seasonal shifts in soil community composition and enzyme activities were relatively more sensitive to soil moisture and temperature,but the microbial community structure and enzyme activity were not correlated with soil pH in the study region.This study highlights how the seasonal variations affect the microbial community and function(enzyme activity)to better understand and predict microbial responses to future climate regimes in subtropical area.

Changes in Soil Microbial Activity and Community Composition as a Result of Selected Agricultural Practices

For a constantly growing human population, healthy and productive soil is critical for sustainable delivery of agricultural products. The soil microorganisms play a crucial role in soil structure and functioning. They are responsible for soil formation, ecosystem biogeochemistry, cycling of nutrients and degradation of plant residues and xenobiotics. Certain agricultural treatments, such as fertilizers and pesticides applications, crop rotation, or soil amendment addition, influence the composition, abundance and function of bacteria and fungi in the soil ecosystems. Some of these practices have rather negative effects;others can help soil microorganisms by creating a friendlier habitat or providing nutrients. The changes in microbial community structure cannot be fully captured with traditional methods that are limited only to culturable organisms, which represent less than 1% of the whole population. The use of new molecular techniques such as metagenomics offers the possibility to better understand how agriculture affects soil microbiota. Therefore, the main goal of this review is to discuss how common farming practices influence microbial activity in the soil, with a special focus on pesticides, fertilizers, heavy metals and crop rotation. Furthermore, potential practices to mitigate the negative effects of some treatments are suggested and treatments that can beneficially influence soil microbiota are pointed out. Finally, application of metagenomics technique in agriculture and perspectives of developing efficient molecular tools in order to assess soil condition in the context of microbial activities are underlined.

Chemical and Biological Properties of Apple Orchard Soils under Natural, Organic, Hybrid, and Conventional Farming Methods

Apples in Japan are generally cultivated under management systems that use chemical fertilizers and synthetic chemical pesticides. However, the continuous use of these fertilizers and pesticides damages the soil environment and reduces the number of soil microorganisms. In this study, we compared the chemical and biological properties of 12 soils from apple orchards in Aomori and Nagano Prefectures under four types of management systems, namely, natural conditions, with no cultivation, fertilizers, or pesticides;organic farming methods, using organic materials and pesticides approved by the Japanese Agricultural Standard organic certification system;hybrid farming methods, using a mix of organic and chemical fertilizers;and conventional farming, using chemical fertilizers and pesticides. Soil total carbon (TC), total nitrogen (TN), total phosphorus (TP), nitrate-nitrogen (NO? 3), and available phosphoric acid (SP) contents were generally found to be the highest where organic farming methods were used. Similarly, bacterial biomass, nitrification (N) circulation activity, ammonia (NH+ 4) oxidation activity, nitrite (NO? 2) oxidation activity, and phosphoric (P) circulation activity were the highest under organic farming, especially in comparison with conventional farming. This study indicated that the differences in apple sugar content, acidity, and sugar/acidity ratio between different orchard management systems were due to different soil conditions, and soil conditions under organic farming management system in apple cultivation increased bacterial biomass while enhancing N and P circulation activity and high TC. On the other hand, the soil of conventional farming has the lowest total number of bacterial biomass and lowest material cycle such as N and P circulation activity. Analysis of the chemical and biological properties of these orchard soils indicated that soil conditions under organic farming management are the most suitable for increasing microbial numbers and enhancing N and P circulation activity.

Effect of Organic and Chemical Fertilizer Application on Growth, Yield, and Soil Biochemical Properties of Landrace <i>Brassica napus</i>L. Leaf-and-Stem Vegetable and Landrace (Norabona)

Norabona is generally cultivated in Japan under management systems that use chemical fertilizers and synthetic chemical pesticides. However, the continuous use of these fertilizers and pesticides damages the soil environment and reduces the number of soil microorganisms. There has been little research investigating the effect of organic and chemical fertilizer applications on soil biochemistry and the growth and yield of norabona. In this study, we investigated the effect of organic and chemical fertilizer application on these factors during the norabona growing season from September 2019 to May 2020. Leaf length, shoot height, and shoot width were significantly higher under organic fertilizer management in the early stage of cultivation (in March) than under chemical fertilizer management. However, there was no significant difference between treatments for these growth parameters in later months, nor for any other parameters. Soil TN, and TP contents were significantly higher in the organic fertilizer treatment after harvest than prior to cultivation or after the chemical fertilizer treatment. In addition, soil TC, and volumetric water content were significantly higher in the organic fertilizer treatment than in chemical fertilizer treatment. The higher TC, TN, and C/N ratio in organic fertilizer treated soil appeared to increase the bacterial biomass, leading to enhanced nutrient circulation via N and P circulation activity, producing a rich soil environment with active soil microorganisms.

Impact of Microbial Inoculants on Microbial Quantity, Enzyme Activity and Available Nutrient Content in Paddy Soil

The experiment was conducted to study the impact of application of microbial inoculants, compared with no microbial fertilizer, on enzyme activity, microbial biomass and available nutrient contents in paddy soil in Heilongjiang Province. The application of soil phosphorus activator was able to increase the quantity of bacteria and fungi in soil, but its effect on actinomycetes in soil was not significant. The application of microbial inoculants increased the urease and sucrase activities in soil over the growing season, but only at the maturing stage soil acid phosphatase activity was enhanced with the applying soil phosphorus activator. The application of soil phosphorus activator increased alkali-hydrolyzable nitrogen and available phosphorus contents in soil, but did not increase available potassium content in soil. The optimal microbial inoculant application rate as applied as soil phosphorus activator was 7.5 kg·hm^(-2).

A Study on Rice Growth and Soil Environments in Paddy Fields Using Different Organic and Chemical Fertilizers

Currently, the majority of paddy fields in Japan are grown using chemical fertilizers and synthetic chemical pesticides, since chemical fertilizers can provide the nutrients necessary for plant growth. However, there are concerns regarding the environmental impact of chemical fertilizer and pesticides production, such as reduction of soil microorganisms and water pollution due to the runoff of fertilizer components from the soil caused by excessive fertilizer application. In this study, we investigated the effects of the application of organic and chemical fertilizers on the plant growth of paddy fields, in addition to their effects on the chemical and biological properties of the soil. The panicle numbers of rough and brown rice, the 1000-grain weight of the rough and brown rice, and the percentages of ripened grains were significantly higher in paddy soils grown with organic fertilizers than in those grown with chemical fertilizers. In addition, the total carbon (TC) contents and pH values were significantly higher in the soils of paddy fields grown with organic fertilizers. Furthermore, the soils of paddy fields grown with organic fertilizers exhibited greater bacterial biomasses, N circulation activity, and P circulation activity than the soils of paddy fields grown using chemical fertilizers, although the differences were not significant. In this study, the difference in plant growth was appeared in fertilizer application such as organic and chemical fertilizers. It was indicated that the organic fertilizer and pesticide reduction management increased the soil bacterial biomass and activated the material cycle such as N circulation activity.

Effects of Different Preceding Crops on Soil Micro-ecological Environment and Yield of Cucumber

Pepper,celery,eggplant and tomato were used as preceding crops to study their effects on the yield,soil microorganism quantity and soil enzyme activities of cucumber. Results showed that four preceding crops all increased soil microorganism quantity in cucumber,but decreased population of Fusarium oxysporum. The effect of pepper was more significant than that of the others. Populations of soil bacteria,fungi and actinomyces of pepper treatment were significantly higher than those of the other treatments,except that the populations of fungi had no significant difference with celery and eggplant treatments on 50 days after transplanting,while that of Fusarium oxysporum was fewer than that of the other treatments. The soil microorganism quantity in celery and eggplant treatment was more significant than tomato,but lower population of Fusarium oxysporum. Four preceding crops all increased soil enzyme activities. Invertase and urease activities of pepper treatment were significantly higher than those of the other treatments,catalase activities of pepper,celery and eggplant treatments were significantly higher than those of tomato and the control treatments. All preceding crops remarkably increased cucumber yield,with pepper as the highest. Comparing with the control,cucumber yields of pepper,celery and eggplant treatments increased by 24.9%,13.6% and 11.9%,respectively. Results suggested that four preceding crops all improved soil microbial ecology and increased cucumber yield. The pepper was the most suitable preceding crop,then followed by celery and eggplant. Tomato had the similar effect as the control.

Effect of Organic and Chemical Fertilizer Application on Growth, Yield, and Quality of Small-Sized Tomatoes

Tomatoes in Japan are generally cultivated under management systems that use chemical fertilizers and synthetic chemical pesticides. However, the continuous use of these fertilizers and pesticides damages the soil environment and reduces the number of soil microorganisms. Organic farming has a relatively low environmental impact compared to conventional farming techniques, but typically has lower and more unstable yields. In this study, we investigated the effect of organic and chemical fertilizer application on growth, yield, and quality of small-sized (cherry) tomatoes. Cherry tomatoes were cultivated using organic and chemical organic fertilizers. Average weight and lateral diameter were significantly higher under organic fertilizer than under chemical fertilizer. In addition, shoot dry weight was significantly higher under organic fertilizer than chemical fertilizer. Lycopene content was significantly higher under organic fertilizer than chemical fertilizer. The total carbon (TC), total phosphorus (TP), total potassium (TK), available phosphoric (SP) and exchangeable potassium (SK) contents, C/N ratio, and pH were significantly higher under organic fertilizer than chemical fertilizer. Bacterial biomass, nitrite (NO? 2-N) oxidation activity, nitrification (N) circulation activity, and phosphoric (P) circulation were higher under organic fertilizer than chemical fertilizer. From these results, the study indicates that appropriate controls such as TC, total nitrogen (TN), and C/N ratio of organic fertilizer increased microbial biomass and enhanced nutrient circulation such as N circulation activity and P circulation activity. These results can be used to improve current organic farming practices and promote soil conservation.

Effects of rumen microorganisms on the decomposition of recycled straw residue

Recently,returning straw to the fields has been proved as a direct and effective method to tackle soil nutrient loss and agricultural pollution.Meanwhile,the slow decomposition of straw may harm the growth of the next crop.This study aimed to determine the effects of rumen microorganisms(RMs)on straw decomposition,bacterial microbial community structure,soil properties,and soil enzyme activity.The results showed that RMs significantly enhanced the degradation rate of straw in the soil,reaching 39.52%,which was 41.37%higher than that of the control on the 30th day after straw return.After 30 d,straw degradation showed a significant slower trend in both the control and the experimental groups.According to the soil physicochemical parameters,the application of rumen fluid expedited soil matter transformation and nutrient buildup,and increased the urease,sucrase,and cellulase activity by 10%‒20%.The qualitative analysis of straw showed that the hydroxyl functional group structure of cellulose in straw was greatly damaged after the application of rumen fluid.The analysis of soil microbial community structure revealed that the addition of rumen fluid led to the proliferation of Actinobacteria with strong cellulose degradation ability,which was the main reason for the accelerated straw decomposition.Our study highlights that returning rice straw to the fields with rumen fluid inoculation can be used as an effective measure to enhance the biological value of recycled rice straw,proposing a viable solution to the problem of sluggish straw decomposition.