Activity Of Soil Microorganisms Research Articles

Exogenous glucose modulated the diversity of soil nitrogen-related bacteria and promoted the nitrogen absorption and utilisation of peanut

Exogenous carbon (C) not only regulates plant growth but also provides energy for microbes and improves the soil environment. We hypothesised that exogenous C could improve plant growth by affecting the soil environment. Therefore, pot experiments were conducted and peanut cvs. Huayu 22(H) and NN-1(B) were used under three different treatments (the control, single nitrogen (N), and N combined with glucose (CN)). The results showed that the abundance and diversity of N-fixing bacteria are obviously influenced by the C and N, and exogenous C can promote the restoration of microbial diversity. The relative abundances of Burkholderiales were increased under HCN and BCN to 9.8% and 9.5%, respectively, compared to the control (3.9%, 2.5%). The abundance of N fixation bacteria increased mainly due to the soil nutrient change. In comparison with the single N treatment, the addition of the C significantly decreased the soil NH4+-N and NO3–-N contents by 31.0% and 13.3%, respectively. And the activities of soil urease and nitrogenase were significantly increased. Compared to the control, single N significantly limited the root development, while the addition of C played a promoting role in root growth. Plant N accumulation increased compared with the control, but there was no significant difference between N treatment and CN treatment. These results indicated that exogenous C promoted soil microorganism activity and strengthened plant growth by changing the soil environment.

Relationships between soil properties, vegetation and soil biota in extremely sulfurized mine soils

The study aimed to assess the influence of high sulfur (S) contamination and the properties of the reclaimed (e.g. neutralization/liming of contamination) soil on the regeneration of soil vegetation and fauna in the example of the former sulfur mine. An attempt was also made to assess minimal conditions for the development of soil microorganisms and mesofauna depending on the type of cover (reforestation/herbaceous vegetation/bare soil). Thirty sample plots were situated on three mainland categories–– i) plant cover vegetated mainly Pinus sylvestris L. (Scots pine stand category), ii) Betula pendula Roth (silver birch stand category), and iii) degraded area with bare soil (Bare_Central – in the central place of the plot and Bare_Edge usually 5.5 m from Bare_Central, Veg – 1 m from Bare_Edge). Basic soil chemicals (as pH, electrical conductivity EC, total sulfur S, total nitrogen TN, total organic carbon TOC), biological parameters (e.g. fungal and bacterial phospholipid fatty acids PLFAs, GRAM+, GRAM−, actinobacteria, total microbial biomass TM), and mesofauna density were analyzed to assess the level of contamination and colonization of the area by plants and soil fauna. The PLFA and the presence of soil microorganisms, always increased from a central point (Bare_Central) to an outer one (Bare_Edge) that was very close (about 1 m) to the vegetation (Veg). However, the highest biological parameters was found in Veg near the bare soil than in the stands with Scots pine. It was found that the highest microbiological biomass was positively correlated with the occurrence of vegetation. Mesofauna was limited by a high content of sulfur in the soil and high EC. Silver birch stands, through the larger and more favorable properties of plant litter, create conditions in which the growth of microorganisms is much greater than under Scots pine stands. On the other hand grasses area with single Scots pine was characterized by higher biological parameters than with the silver birch. In the plots with tree stands it was quite the opposite. To properly restoration this type of place, it is necessary to ensure the accuracy of the technical measures performed. The best effects of activating soil microorganisms are the introduction of trees with appropriate density. The activity of soil microorganisms allows for the growth of herbaceous vegetation, which will be a start-up source of organic matter and nourishment for soil biota. Herbaceous vegetation will create a good mixture with hard decomposed pines litterfall.

Mycorrhizae helper bacteria for managing the mycorrhizal soil infectivity

Arbuscular mycorrhizal fungi are major components of soil microbiota and mainly interact with other microorganisms in the rhizosphere. Mycorrhiza establishment impacts the plant physiology and some nutritional and physical properties of the rhizospheric soil. These effects alter the development of the root or mycorrhizas resulting from the activity of soil microorganisms. The rhizosphere of mycorrhizal plants (mycorrhizosphere), is inhabited by large microbial activities responsible for several key ecosystem processes. This review is focused on the microbial interactions between mycorrhizal fungi and components of rhizosphere microbiota and highlight the agronomic potentialities of the Mycorrhiza Helper Bacteria on mycorrhiza formation. The main conclusion is that this MHB effect in the rhizosphere of mycorrhizal plants, enhance plant fitness and soil quality and are of great interest to ensure sustainable agricultural development and ecosystem functioning.

Variety and action of soil microorganisms in diverse Ukraine climatic zones

The study aims to summarize the important results of the long-term studies of soil microorganisms: structure, interaction, functioning, activity, and diversity in the main types of soils in different natural and climatic zones of Ukraine. Methods for the study are the generalization and analysis of literary sources and scientific papers, and materials, as well as our own research. The initial information for the assay’s calculations, matheanalysis were the resokution of many year discovering of soil microorganisms in the period 2005-2021. The researches have shown a powerful action and diversity of soil microorganisms of the ecosystems. The Chernozem of the Steppe zone was characterized by a more stable and balanced structure of microbiocenosis, processes of mineralization-immobilization, decomposition of organic matter, and humus accumulation than the sod-podzolic, forest soils of Polesie. Studies of soil microbiome showed a direct correlation between natural conditions and soil treatment methods and the activity of microbiocenoses, a decrease in the biodiversity of bacterial groups through the use of plowing. The increase in the proportion of micellar organisms occurred with the prolonged application of mineral fertilizers.

Application of Empty Fruit Bunches of Oil Palm and Indigofera zollingeriana for Conservation of Oil Palm Plantation

Oil palm empty fruit bunches are materials used as organic fertilizers that can be applied to oil palm plantations, thereby reducing the use of inorganic fertilizers. Indigofera zollingeriana is an appropriate alternative as an interplant because of its high branch and leaf development. Functions as a ground cover and a supplier of carbon stocks naturally plays a role in water and soil conservation. This study aims to determine the effect of oil palm empty fruit bunches and I. zollingeriana on land improvement to support oil palm growth and production. Variables observed included changes in soil water content, soil microorganism activity, and carbon stock. The results showed that the soil planted with I. zollingeriana and given the empty fruit bunches of oil palm had a higher soil moisture content. The highest soil carbon stock, oil palm carbon stock, and vegetation carbon stock were 81.6 t ha-1, 36.60 t ha-1, and 1.89 t ha-1, respectively. The population and activity of microorganisms varies. The highest total microorganisms were treated with I. zollingeriana and oil palm EFB 105 (10⁵CFU g-1), while the lowest was 60 (10⁵CFU g-1). Planting I. zollingeriana and providing oil palm empty fruit bunches increased groundwater reserves by 36.71%.

Designing degradable lignin-grafted magnetic nano-composite materials for cost-effectively sustainable removal of fluoroquinolone antibiotics from environmental water

Developing a novel green adsorbent to meet the requirements of low-cost, high quality of enrichment for analytes, and environmental sustainability is significant but remains a challenge. Herein, an eco-friendly dealkaline lignin-grafted magnetic iron oxide nanoparticle (Fe 3 O 4 @DAL) used as a dispersion solid adsorbent for the removal of fluoroquinolone antibiotics (FQs) from environmental water was developed based on the amide reactions between cost-effective plant-derived dealkaline lignin (DAL) and amino-functionalized Fe 3 O 4 nanoparticles at room temperature. Fe 3 O 4 @DAL combined with the advantages of lignin and magnetic nanoparticles , which had abundant functional groups (phenols and aliphatic hydroxyl, carboxyl, phenyl) and high separation efficiency, so typical FQs including pefloxacin (PEF), lomefloxacin (LOM), enrofloxacin (ENR) and difluoxacin (DIF) could be easily removed by multiple interactions. The Langmuir isotherm model and pseudo-second-order model could be more suitable to describe the adsorption process of FQs on Fe 3 O 4 @DAL. The maximum adsorption capacities of Fe 3 O 4 @DAL for PEF, LOM, ENR, DIF were 25.2 mg g −1 , 19.2 mg g −1 , 30.0 mg g −1 , 33.7 mg g −1 , respectively. And the total maximum adsorption capacities of four FQs could reach 108.2 mg g −1 . The whole adsorption process was spontaneous and endothermic based on thermodynamic data . Moreover, Fe 3 O 4 @DAL was of great reusability and could be used at least 5 cycles. In particular, the recycled adsorbent can be degraded as slow-release fertilizer under the action of soil microorganisms , which helps the growth of plants and further expands application range of lignin. As an effective, environmental-friendly, low-cost adsorbent for alleviating FQs contamination not only increased the added value of natural raw materials, but also had a great potential in the field of water treatment . • The environment-friendly dealkaline lignin-grafted Fe 3 O 4 nanoparticles (Fe 3 O 4 @DAL) were first prepared. • Multiple interactions resulting in highly efficient removal of FQs. • Superior adsorption and reusability performance of Fe 3 O 4 @DAL were confirmed. • The recovered Fe 3 O 4 @DAL could be degraded as fertilizer to help the growth of crops. • Fe 3 O 4 @DAL increased added the value of natural raw materials.

Resource Cycling: Application of Anaerobic Utilization Methods

Human activity and modern production contribute to the formation of a certain amount of waste that can be recycled to obtain useful products and energy sources. Today, the higher the level of industrial development, the greater the amount of waste generated, and as a result, the more important the need for disposal. A similar pattern is typical for any human production activity; as a result of large-scale production, at least 70–80% of waste is generated in relation to the amount of raw materials used. The large-scale use of polymeric materials and the plastic waste generated after their use lead to environmental pollution. While a small part of the waste is utilized naturally due to the vital activity of soil microorganisms, and a part is purposefully processed by humans into products for various purposes, a fairly large amount of waste occupies large areas in the form of a variety of garbage. After the removal of garbage by incineration, the liberated territories cannot be transferred to agricultural land due to the high content of harmful contaminants. The harm to the environment is quite obvious. In practice, certain types of waste consist of more than 70% content of valuable substances that can find further practical application in a wide variety of industries.

Experimental evidence for the impact of phages on mineralization of soil-derived dissolved organic matter under different temperature regimes

Microbial mineralization of dissolved organic matter (DOM) plays an important role in regulating C and nutrient cycling. Viruses are the most abundant biological agents on Earth, but their effect on the density and activity of soil microorganisms and, consequently, on mineralization of DOM under different temperatures remains poorly understood. To assess the impact of viruses on DOM mineralization, we added soil phage concentrate (active vs. inactive phage control) to four DOM extracts containing inoculated microbial communities and incubated them at 18 °C and 23 °C for 32 days. Infection with active phages generally decreased DOM mineralization at day one and showed accelerated DOM mineralization later (especially from day 5 to 15) compared to that with the inactivated phages. Overall, phage infection increased the microbially driven CO2 release. Notably, while higher temperature increased the total CO2 release, the cumulative CO2 release induced by phage infection (difference between active phages and inactivated control) was not affected. However, higher temperatures advanced the response time of the phages but shortening its active period. Our findings suggest that bacterial predation by phages can significantly affect soil DOM mineralization. Therefore, higher temperatures may accelerate host-phage interactions and thus, the duration of C recycling.

Impact of agricultural abandonment on soil organic carbon: The case of semi‐steppe rangeland in Central Iran

AbstractThis study investigated the change in soil organic carbon (SOC), soil labile carbon (C), soil total nitrogen (N), particulate organic carbon (POC), mineralizable soil C (Min‐C) in soil aggregate fractions, and soil particles size at 0–30 cm soil depth of the semi‐steppe rangelands in Central Iran (Sheida and Khargosh regions). The study used a fully randomized design with four land uses in the rangelands including covered with rainfed wheat (CR0), abandoned rangelands (ARs) for 5–15 years (AR15), abandoned rangeland for 16–40 years (AR40), and permanently uncultivated rangelands (UR) as the reference sites that were replicated three times (n = 3) with at most 2 km distance from each other in an area of 25 ha. For each treatment, the soil samples were randomly obtained at 0–30 cm soil depth in three replicated plots of 2 × 2 m using a core size of 7 cm in diameter. The samples were mixed to take a composite soil sample (12 soil samples in each region) in June 2018. The results indicated that soil POC is the most sensitive fraction for the identification of shifts in the total SOC after the cultivation cessation because by increasing the abandoned land and the cessation of cropland activities, the POC has also increased. In conclusion, after the cessation of rainfed cropping and the recovery of natural vegetation, the increases in soil microorganism activity can result in a higher nutrient cycling in the degraded rangeland ecosystems.

Deep soil microbial carbon metabolic function is important but often neglected: a study on the Songnen Plain reed wetland, Northeast China

Soil microbial carbon metabolism is critical in wetland soil carbon cycling, and is also a research hotspot at present. However, most studies focus on the surface soil layer in the wetlands and the microorganisms associated with this layer. In this study, 0-75 cm soil profiles were collected from five widely separated reed wetlands in the Songnen Plain. which has a large number of middle-high latitude inland saline-sodic wetlands. The Biolog-ECO method was used to determine the carbon metabolic activity and functional diversity of soil microorganisms. The results showed that soil carbon metabolic activity decreased with increasing soil depth. The carbon metabolic activity of soil microorganisms in the 60-75 cm layer was approximately 57.41%-74.60% of that in the 0-15 cm layer. The soil microbial Shannon index and utilization rate of amines decreased with an increase in soil depth, while the Evenness index and utilization rate of polymers tended to increase with soil depth. Dissolved organic carbon (DOC) is the most important factor affecting microbial carbon source utilization preference, because microorganisms mainly obtain the carbon source from DOC. The result of the correlation analysis showed that the soil microbial carbon metabolic activity, Shannon index, and Evenness index significantly correlated with soil total carbon (TC), microbial biomass carbon (MBC), DOC, total nitrogen (TN), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N) contents, and electrical conductivity (EC). This study emphasized the important role of microbial carbon metabolic function in deep soil.

The Analysis Of Peat Soil Biological Characteristics After Being Incubated Using Vermicompost From A Mixture Of Chicken Dung, Banana Hump, And Tofu Waste

Peatlands are formed from piles of trapped plant residues, obstructing their decomposition process. The organic matter decomposition process certainly involves soil microbes. This study aims to determine the biological characteristics of peat soil after incubation with vermicompost. This research was conducted at Kampung Perlabian Village, Kampung Rakyat Sub-district, South Labuhanbatu Regency, North Sumatra. Soil biological analysis was conducted in the soil biology laboratory, Faculty of Agriculture, University of North Sumatra. This study used a non-factorial Randomized Block Design (RAK) with three treatments: P0 (control), P1 (1 kg peat soil + 500-gram vermicompost), and P2 (1 kg peat soil + 1 kg vermicompost). The results showed that adding vermicompost fertilizer to peat soil with treatment two could increase the total bacteria by 6.17 x 106 cfu/ml and the total fungus by 8.8 x 105cfu/ml, and CO2 respiration by 4.125 (mg CO/day). As a result, the soil's microorganism's activity is a process in which microorganisms live and do activities in a soil mass.

Effect of Molasses Application Alone or Combined with Trichoderma asperellum T-34 on Meloidogyne spp. Management and Soil Microbial Activity in Organic Production Systems

The effect of molasses alone or combined with Trichoderma asperellum T34 Biocontrol® was assessed on Meloidogyne reproduction, disease severity, and density and activity of soil microorganisms in pot and field experiments. Firstly, molasses application at 1 mL m−2 was assessed in four different textured soils. Secondly, molasses application at 5, 10, 20, and 40 mL m−2, alone or combined with T34, was assessed in pot and field experiments at 10 mL m−2 in two different textured soils. The application of 1 mL m−2 of molasses was effective in reducing nematode reproduction in the loam textured soil but not in sandy clay loam, sandy loam, or clay loam textured soils. Increasing molasses dosage reduced the tomato dry shoot and fresh root weights, producing phytotoxicity at 40 mL m−2. The disease severity and nematode reproduction were reduced between 23% and 65% and 49% and 99%, respectively. In the field experiment, molasses applied at 10 mL m−2 reduced the disease severity and the nematode reproduction in the loam textured soil. The soil microbial density and activity did not increase in sites where the nematode reproduction and the disease severity were reduced by molasses application, irrespective of T34.

Phytoremediation of crude oil contaminated soil using Sudanese plant species Acacia sieberiana Tausch

Phytoremediation is a new technology for cleaning contaminated soil with crude oil. Oil pollution is a serious problem worldwide; the aim of this study was to use the plant for Phytoremediation. Leguminous plant Acacia seiberiana Tausch was tested for it is efficiency to remediate soil polluted with 0.5, 1, 1.5 and 2% (w/w) crude oil and it is the ability to enhance the activity of soil microorganisms. Plant parameters, degradation percentage, Total Petroleum Hydrocarbon and bacterial count were measured. Results showed that the concentration of the crude oil did not affect plant growth indicating the significant success of the Phytoremediation process. Shoot length and shoot and root weights have not been negatively affected by oil, compared to the control plant, up to a concentration of 1.5% for up to six months. Crude oil degradation percentages were found to be in the range of 49–79%. The highest degradation percentage was recorded for the soil collected from underneath A. sieberiana Tausch seedlings (79%). A total of 81 different hydrocarbons were detected in soil samples at zero time and most of them were found to be of long (≥30 carbon atoms) and moderate (10–29 C) hydrocarbon chains. Fraction analyses were conducted in plant A. sieberiana Tausch seedlings at intervals of 60, 120 and 180 days of incubation, six different hydrocarbons were detected. The most abundant hydrocarbon detected were Heneicosane (21 C), Tetracosane (24 C) and Octacosane (28 C). The viable microorganism’s count in oil-contaminated soil at any of the concentrations tested was significantly (P ≤ 0.01) higher than that in oil-free soil at any sampling interval. High efficiency of biodegradation was achieved using A. seiberiana Tausch indicating the unique mechanism of this plant in remediating contaminated soil with crude oil.

Exploration of Soil Functional Microbiomes-A Concept Proposal for Long-Term Fertilized Grasslands.

Exploring grassland microbiomes is a challenge in the current context of linking soil microorganism activity with the balance of these ecosystems. Microbiologists are constantly attempting to develop faster and lower-cost methods, and propose new and best-fitted indicators that will provide a more complex data analysis. A different concept was proposed for assessing functional microbiomes by splitting the functional ecological niche into complementary segments. The comparison with the upper and lower limits of the ecological niche provides a clearer image of community alterations due to long-term applied treatments. The method allows the extraction of the most sensitive and stable functional guilds, with the extraction of the most critical dominant–codominant functional groups in every segment of the functional niche. The resulting microbial functional–sociological model is ready to use on community-level physiological profile databases and also can be applied backward for vegetation analysis.

Influence of Organomineral Fertiliser from Sewage Sludge on Soil Microbiome and Physiological Parameters of Maize (Zea mays L.)

The use of a soil fertiliser results in high, good quality yields. The most widely used fertilisers are mineral or organic, but there is increasing attention on organomineral fertilisers produced from sewage sludge. These contain beneficial components which may improve soil fertility and thus plant productivity, but there are some concerns associated with their application due to their composition. Using a short-term pot experiment the effect of such a soil conditioner called FS, produced from sewage sludge after stabilisation with lime, on the qualitative−quantitative composition and activity of soil microorganisms and selected physiological parameters of the maize was analysed. The study was carried out in a completely randomised design, including a control (soil + lime + NPK). The application of the FS had a positive effect on the soil pH, equivalent to the application of lime. Organomineral fertiliser, as a source of organic carbon and macroelements, had a positive effect on the number of soil microorganisms and their activity, and this influence was stable during maize vegetation. FS did not influence the gas exchange activity of maize, the content of assimilation pigments in leaves or and the efficiency of the photosynthetic apparatus determined by chlorophyll “a” fluorescence analysis, but it increased the light absorption efficiency of the PSII photosystem. Differences in biomass yield from organomineral and mineral fertilisation were statistically insignificant.

Role of earthworms in soil fertility and its impact on agriculture: A review

Soil fertility is defined as the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. Perhaps no other living organism in the soil is as important as an earthworm in helping to increase soil health. Earthworms are the most commonly occur in the soil. The activities of burrowing and feeding by earthworms have many valuable effects generally on soil quality for crop production. Earthworms increase soil aeration, infiltration, structure, nutrient cycling, water movement, and plant growth. Earthworms are one of the major decomposers of organic matter. They get their nutrition from microorganisms that live on organic matter and in soil material. When they move through the soil eating, earthworms form tubular channels or burrows. These burrows can persist for a long time in the soil. Earthworm burrows increase soil porosity which increases the amount of air and water that get into the soil. Increased porosity also lowers bulk density and increases root development. Earthworm excrement or casts increase soil fertility because it contains nitrogen, phosphorus, potassium, and magnesium. Earthworm casts also contain microorganisms which increase in abundance as organic matter is digested in their intestines. The cycling of nutrients from organic matter and the increase in microorganisms facilitates plant growth. They cast along with binding agents released by earthworms also improve soil structure and increase aggregate stability. The soil biota benefits soil productivity and contributes to the sustainable function of all ecosystems. The cycling of nutrients is a critical function that is essential to life on earth. Earthworms (EWs) are a major component of soil fauna communities in most ecosystems and comprise a large proportion of macrofauna biomass. Their activity is beneficial because it can enhance soil nutrient cycling through the rapid incorporation of detritus into mineral soils. In addition to this mixing effect, mucus production associated with water excretion in earthworm guts also enhances the activity of other beneficial soil microorganisms. This is followed by the production of organic matter. So, in the short term, a more significant effect is the concentration of large quantities of nutrients (N, P, K, and Ca) that are easily assimilable by plants in fresh cast depositions. In addition, earthworms seem to accelerate the mineralization as well as the turnover of soil organic matter. Earthworms are known also to increase nitrogen mineralization, through direct and indirect effects on the microbial community. The increased transfer of organic C and N into soil aggregates indicates the potential for earthworms to facilitate soil organic matter stabilization and accumulation in agricultural systems, and that their influence depends greatly on differences in land management practices.

Variation of microbial activities and communities in petroleum-contaminated soils induced by the addition of organic materials and bacterivorous nematodes

Bacterivorous nematodes are abundant in petroleum-contaminated soils. However, the ecological functions of bacterivorous nematodes and their impacts together with the addition of organic materials on the activity and diversity of microorganisms in petroleum-contaminated soils remain unknown. To assess such effects, six treatments were established in this study, including uncontaminated nematodes-free soil (Control), petroleum-contaminated soil (PC), petroleum-contaminated soil + 5 nematodes per gram dry soil (PCN), and petroleum-contaminated soil + 5 nematodes per gram dry soil + 1% wheat straw (PCNW), or + 1% rapeseed cake (PCNR), or + 1% biochar (PCNB). Results showed that the enzyme activities in the six treatments generally increased firstly and then decreased during the incubation period. Compared with Control, the invertase activity in PCNW, PCNR, and PCNB increased by 80.6%, 313.5%, and 12.4%, respectively, whereas the urease activity in PC, PCN, PCNW, PCNR, and PCNW increased by 1.2%, 25.5%, 124.3%, 105.3%, and 25.5%, respectively. Petroleum pollution, inoculation of bacterivorous nematodes, and the addition of organic materials all significantly boosted the concentrations of phospholipid fatty acids (PLFAs) of soil bacteria, actinobacteria, and total microorganisms, and increased the concentrations of both G+ and G− bacteria PLFAs and the ratio of G−/G+. The concentration of fungi PLFAs and the ratio of fungi to bacteria were significantly higher in PCNW and PCNR than those in other treatments. Overall, adding bacterivorous nematodes and organic materials to the petroleum-contaminated soil significantly improved soil microbial activity and community structure, suggesting that bacterivorous nematodes could be used for the bioremediation in petroleum contaminated soils.

Effects of lead pollution on soil microbial community diversity and biomass and on invertase activity

Lead (Pb) pollution is one of the most widespread and harmful environmental problems worldwide. Determination of changes in soil properties and microbial functional diversity due to land use is needed to establish a basis for remediation of soil pollution. This study aimed to investigate soils contaminated by Pb from different sources and to analyze the functional diversity and metabolism of soil microbial communities using Biolog technology. Pb pollution (>300 mg kg−1) significantly influenced the diversity and metabolic functions of soil microbial communities. Specifically, Pb contamination significantly reduced soil microbial biomass carbon (C) and nitrogen (N) levels and catalase activity while increasing invertase activity. Furthermore, Biolog EcoPlate assays revealed that Pb pollution reduced the general activities of soil microorganisms, suppressing their ability to utilize C sources. In Pb-contaminated areas lacking vegetation cover, Shannon, Simpson, and McIntosh diversity indices of soil microorganisms were significantly reduced. The microbial diversity and biomass C and N levels were affected by land use and soil properties, respectively, whereas soil enzyme activity was primarily affected by the interaction between land use and soil properties. Our results provide a reference and a theoretical basis for developing soil quality evaluation and remediation strategies.

Identifying the spatiotemporal vulnerability of soils to antimicrobial contamination through land application of animal manure in Minnesota, United States

Antimicrobials may reach the soil environment from a variety of sources and pathways, including land application of human biosolids and animal manure. Once in soil, antimicrobials can affect the abundance and activity of soil microorganisms and exert selection pressures that enhance the emergence and spread of antimicrobial resistance (AMR). To mitigate the spread of AMR it is important to understand the spatial and temporal interactions between antimicrobials and soil. The goal of this study was to assess the vulnerability of Minnesota (U.S.) soil to contamination with specific antimicrobial compounds at temperatures experienced throughout the year. Soil contamination potential was estimated based upon specific antimicrobial drug binding and permanence, and average monthly temperature. Minnesota soil vulnerability was estimated by incorporating spatially explicit soil contamination potential, land cover type, and livestock density. Assessment of antimicrobials used in livestock production showed that soils are most vulnerable to antimicrobial contamination in southwestern Minnesota, to enrofloxacin, chlortetracycline, and oxytetracycline, and in the months of April and October. While the assessment herein was not based on actual on-farm antimicrobial use data and subsequent excretion of antimicrobial metabolites into the environment, this study provides an overview of the spatial and temporal potential for Minnesota soil to be contaminated by several antimicrobial drugs and demonstrates how specific vulnerability assessments might be conducted for geographic areas with known exposure (e.g., cropland fertilized with livestock manure and/or human biosolids). Such assessments might be used to identify best practices for mitigating antimicrobial exposure to soils and guide additional research to understand the role of environmental antimicrobial contamination in the problem of AMR.

Poplar agroforestry systems in eastern China enhance the spatiotemporal stability of soil microbial community structure and metabolism

AbstractAgroforestry systems provide soil microorganisms with a rich variety of carbon sources and a relatively stable living environment. However, the effects of agroforestry systems on the metabolic dynamics of soil microorganisms have not been well studied, especially in the subsoil. To assess the vertical and seasonal variations in soil microbial metabolic capacity as a consequence of various planting systems, five typical planting systems, including three poplar agroforestry systems, were investigated. The Biolog EcoPlate method was used to determine the vertical and seasonal variations in soil microbial metabolic capacity. The average well colour development, carbon source utilization ability, and microbial diversity index values were higher throughout the soil profile, and highly stable with seasonal changes in the poplar (Populus × euramericana “Nanlin 895”) + wheat (Triticum aestivum L.) + soybean (Glycine max) and poplar + potherb mustard (Brassica juncea var. multiceps) agroforestry systems. Furthermore, the influence of the planting systems and seasonal changes on the metabolic activity of soil microorganisms decreased with an increase in soil depth. Over‐stocking chickens in the forest reduced the metabolic activity of soil microorganisms. It was also found that plants influenced soil microbial metabolism through affecting the available carbon source types. Therefore, agroforestry systems improved the metabolic potential of the soil microbial community. Our results demonstrated that soil microbial communities are affected by the planting system and soil depth. The findings enhance our understanding of the functional diversity of soil microorganisms in agroforestry systems.