Collected Soil Samples Research Articles

Bioaccummulation and health risk assessment of some potentially toxic elements in crops from farms round granite quarry sites in ibadan southwestern nigeria

Potentially toxic elements (PTEs) in food crops have significant apprehension in the environment because of their impending human health risks. This study thus assessed PTEs concentrations in soils and crops from farmlands around quarry sites, quantifies their level of uptake by the crops and their potential health risks to human. Collection of Soil and crop (Dioscorea alata, Colocasia esculenta and Manihot esculenta ) samples were done and analysed for Fe, Mn, Pb, Zn, Cu, Cr, Co, Ni and Cd using suitable instrumentation methods Data were evaluated using accumulation factor (AF), calculated daily intakes (CDI), target hazard quotent (THQ) and hazard index (HI). Farmlands soils that are closer to studied sites had higher PTEs concentrations than those that are farther away. Mean PTEs concentrations in the crops were in the order of Dioscorea alata > Colocasia esculenta > Manihot esculenta. Mean values of AF are less than one indicating low potential PTEs accumulation in the crops. The mean CDI in mg/kg/day of PTEs in crops for children and adults were 0.0001 -0.060 while THQ values are in order Pb> Mn>Cu> Cd>Ni> Co>Fe >Zn>Cr. Hazard index (HI) is greater than one in all the crops from the farmlands closer to quarry sites, indicating risk upon consumption. Thus, necessary remediation methods should be taken to reduce the effect of these PTEs on the environment.

Quantifying shrub encroachment through soil seed bank analysis in the Ethiopian highlands.

This study aimed to understand the impact of shrub encroachment on native species in the Guassa Community Conservation Area in Ethiopia. We assessed the soil seed bank composition and density across different elevations and aspects, and management systems within the area. The vegetation was stratified and eight blocks were selected across a range of elevation (<3350 m and >3350 m) and aspect (northeast, northwest, southeast, southwest). Within each block we established twenty 5m x 5m plots for a total of 160. We then collected soil samples from five subplots (1 m x 1 m) at three depths (0-3 cm, 3-6 cm and 6-9 cm) for a total of 480 samples, which were established in pots in greenhouse. We calculated species abundance by totaling the number of seedlings that emerged from each sample. To determine the variability in the abundance of Festuca macrophylla and Helichrysum splendidum in the soil seed bank along altitudinal gradient, we used two-way ANOVA using SAS statistical software version 9.0.1. Shannon diversity index was used to determine species diversity in the soil seedbank. After counting all the seeds, we identified 74 plant species represented in the soil seedbank which belong to 55 genera and 23 families. Eleven species are endemic to Ethiopia. At the lower elevation range, the effects of aspect (P <0.0088) and soil depth (P <0.005) are not significant to determine the abundance of seeds of H. splendidum and F. macrophylla. But when the factors are segregated, both aspect and soil depth play a significant role (p<0.0001) regarding the abundance of the seeds of the competing species at lower elevation. At higher elevation, only the effect of soil depth is significant (P<0.0001) for determining the abundance of H. splendidum. Soil depth and aspect have no significant effects on soil seed bank abundance at this elevation.

Assessment of Soil Fertility through GIS Techniques and Thematic Mapping in Rice Growing Areas of Jagtial District in Telangana State, India

Survey was conducted in Jagtial district of Telangana state to identify the soil fertility status of rice growing areas. Soil fertility is one of the major limiting factor for maintaining sustainability in crop yields. Totally 90 surface soil samples collected from the selected rice cultivated farmers’ field. Collected soil samples were tested for texture, pH, EC, organic carbon, available N, P, K and S in order to identify the nutrient status in soils and develop the corrective measures. The soil fertility maps generated through Global Positioning System (GPS) and Arc Geographic Information System (GIS) software to formulate balanced fertilizer recommendations and to understand the spatial variability of nutrients in soil. Survey results showed that the sand was ranged from 44 to 80% and that of silt was 3 to 20 % while the range of clay was 13 to 42% and varied three textural classes viz., sandy clay loam, sandy loam and loamy sand. Soil pH was neutral to slightly alkaline (6.8 to 8.2), electrical conductivity rated as non-saline (0.23 to 0.69 dS m-1), organic carbon was low-medium (0.3 to 0.6%), available-N was low (101 to 195 kg ha-1), available-P was high (26.8 to 61.5 kg ha-1), available-K was medium to high (120 to 449 kg ha-1) and available-S was medium to high (10.0 to 26.8 mg kg-1). Among these organic carbon (%) and available-N were important constraints in soil fertility in rice growing areas of Jagtial district of Telangana state.

Assessment and GIS Mapping of Soil Quality Indicators of Agroecological Unit 9 of Kerala, India

Context: The agroecological unit 9 (AEU 9) in Alappuzha district of Kerala represents the south central laterites. The soils are acidic, gravelly, having low activity clay, often underlain by plinthite with low water and nutrient retention capacity. Assessment of soil quality indicators and mapping of resources and soil fertility status is essential for planning and development activities.&#x0D; Aims: Soil quality assessment was made by collecting observations on physical, chemical and biological indicators, soil quality index was computed and generated maps using GIS.&#x0D; Study Design: Survey, collection of soil samples and principal component analysis.&#x0D; Place and Duration of Study: A study was conducted in agroecological unit 9 (south central laterites) in Alappuzha district of Kerala during 2020.&#x0D; Methods: Geo-referenced composite soil samples were collected from 75 locations of AEU9 in Alappuzha district, and were characterized for physical, chemical and biological attributes for evaluating soil quality. Principal component analysis (PCA) was carried out for soil parameters and a minimum data set (MDS) was arrived from seven principal components (PC 1 to PC 7) with eigen values greater than 1. The selected soil quality indicators were categorized into classes, assigned with scores and soil quality index was computed. Based on soil quality index, soils were rated as poor, medium or good. GIS based thematic maps of soil quality indicators and index were prepared.&#x0D; Results: The soils of AEU 9 are sandy loam in texture, strongly acidic (pH 4.5-5.5), medium in organic carbon, low in available N, medium in available P and K, deficient in available Ca, Mg and B. Majority (80%) of the soils are rated poor and 20% rated medium in soil quality. From the study it is concluded that pH, clay%, bulk density, available nutrients N, P, K, Ca and S are the key indicators of soil quality in AEU 9.

Improved description of terrestrial habitat types by including microbial communities as indicators

Soils host diverse communities of microorganisms essential for ecosystem functions and soil health. Despite their importance, microorganisms are not covered by legislation protecting biodiversity or habitats, such as the Habitats Directive. Advances in molecular methods have caused breakthroughs in microbial community analysis, and recent studies have shown that parts of the communities are habitat-specific. If distinct microbial communities are present in the habitat types defined in the Habitats Directive, the Directive may be improved by including these communities. Thus, monitoring and reporting of biodiversity and conservation status of habitat types could be based not only on plant communities but also on microbial communities. In the present study, bacterial and plant communities were examined in six habitat types defined in the Habitats Directive by conducting botanical surveys and collecting soil samples for amplicon sequencing across 19 sites in Denmark. Furthermore, selected physico-chemical properties expected to differ between habitat types and explain variations in community composition of bacteria and vegetation were analysed (pH, electrical conductivity (EC), soil texture, soil water repellency, soil organic carbon content (OC), inorganic nitrogen, and in-situ water content (SWC)). Despite some variations within the same habitat type and overlaps between habitat types, habitat-specific communities were observed for both bacterial and plant communities, but no correlation was observed between the alpha diversity of vegetation and bacteria. PERMANOVA analysis was used to evaluate the variables best able to explain variation in the community composition of vegetation and bacteria. Habitat type alone could explain 46% and 47% of the variation in bacterial and plant communities, respectively. Excluding habitat type as a variable, the best model (pH, SWC, OC, fine silt, and Shannon's diversity index for vegetation) could explain 37% of the variation for bacteria. For vegetation, the best model (pH, EC, ammonium content and Shannon's diversity index for bacteria) could explain 25% of the variation. Based on these results, bacterial communities could be included in the Habitats Directive to improve the monitoring, as microorganisms are more sensitive to changes in the environment compared to vegetation, which the current monitoring is based on.

An Analysis of the Correlation between Physiochemical Characteristics of Soil and the Morphological Characteristics of Grewia optiva Drummond in the Northwestern Himalayan Region

Continued research on the physiochemical properties of soil is critical for the long-term maintenance of cropping systems, (including trees), in order to harness their economic benefits. The current study was carried out in the Department of Tree Improvement and Genetic Resources, COF, Nauni, Solan (H.P.) during the period 2020-2023 to quantify the impact of soil nutrient variation on the morphological characteristics of Grewia optiva Drummond in different districts with variable climate and heterogeneous soils. The impacts on growth parameters (tree height, crown spread, leaf traits) of selected populations of Grewia optiva Drummond statistically analyzed using Karl Pearson correlation coefficient. Two composite soil samples representative of the different populations were drawn from the two depths i.e., 0-15 cm (surface layer) and 15-30 cm (subsurface layer). These samples were collected underneath the selected populations of Grewia optiva Drummond. The collected soil samples were tested using standard soil methods and results were analysed using OPSTAT software. There was highly positive correlation observed between leaf area and soil N (0.509), leaf area and SOC (0.407), leaf area and soil P (0.728) and leaf area and soil K (0.577). Leaf length showed a highly significant correlation with SOC (0.401), soil N (0.509), soil P (0.710), and soil K (0.592). The tree height (0.385), tree diameter (0.602), crown spread (N-S) (0.629), crown spread (E-W) (0.334), branch nodal length (0.436) and leaf width (0.470) showed a significant positive correlation with soil P. Soil K showed a significant positive correlation with tree height (0.774), tree diameter (0.645), crown spread (N-S) (0.576), crown spread (E-W) (0.314), branch nodal length (0.737) and leaf width (0.592). Soil pH demonstrated highly significant correlation with Leaf width (0.449). The correlation developed between tree morphological and soil characteristics will help in quantify the impact of different soil characteristics on tree and leaf morphometric characteristics. It will further help in identification and selection of superior genotypes of Grewia optiva for further propagation to get improved genetic gain and for production of quality planting material.

Assembly Processes and Biogeographical Characteristics of Soil Bacterial Sub-communities of Different Habitats in Urban Green Spaces.

The process of urbanization is one of the most important human-driven activities that reshape the natural distribution of soil microorganisms. However, it is still unclear about the effects of urbanization on the different taxonomic soil bacterial community dynamics. In this study, we collected soil samples from highly urbanized the regions of Yangtze River Delta, Beijing-Tianjin-Hebei in China, to explore the bio-geographic patterns, assembly processes, and symbiotic patterns of abundant, moderate, and rare bacterial communities. We found that the number of moderate and rare taxa species were lower than that of abundant taxa, but their α-diversity index was higher than abundant taxa. Proteobacteria, Acidobacteria, Actinobacteria, Bacterioidetes, and Chloroflexi were the dominant phylum across all three sub-communities. And the β-diversity value of rare taxa was significantly higher than those of moderate and abundant taxa. Abundant, moderate, and rare sub-communities showed a weak distance-decay relationship, and the moderate taxa had the highest turnover rate of microbial geography in the context of urbanization. Diffusion limitation was the dominant process of soil bacterial community assembly. The co-occurrence networks of abundant, moderate, and rare taxa were dominated by positive correlations. The network of moderate taxa had the highest modularity, followed by abundant taxa. The main functions of the abundant, moderate, and rare taxa were related to Chemoheterotrophy and N transformations. Redundancy analysis showed that the dispersal limitation, climate, and soil properties were the main factors dominating bio-geographic differences in soil bacterial community diversity. We conclude that human-dominated urbanization processes have generated more uncertain survival pressures on soil bacteria, which resulted in a stronger linkage but weak bio-geographic variation for soil bacteria. In the future urban planning process, we suggest that such maintenance of native vegetation and soil types should be considered to maintain the long-term stability of local microbial ecosystem functions.

Detecting the temporal trend of cultivated soil organic carbon content using visible near infrared spectroscopy

Monitoring changes in soil properties is essential to ensure ecosystem function and agricultural productivity. This study evaluated the ability of visible near infrared (Vis-NIR) spectroscopy to detect the temporal trend in soil organic carbon (SOC) content after 5 years in a 12 km2 agricultural catchment in western France. Partial least squares regression models were developed using soil samples from a local dataset collected in 2013 at two depths (198 samples at 0–15 cm and 196 samples at 15–25 cm) to predict SOC content of 111 new samples collected in 2018 at the same locations and at similar depths (0–15 cm and 15–25 cm). Two approaches, which differed in whether or not they considered the SOC content variability that can result from collecting soil samples at two depths, were applied. For both approaches, the potential benefit of “temporal spiking” was evaluated by adding 10% of 2018 samples to the 2013 dataset. The results showed that removing outliers and stratifying the calibration dataset by depth yielded the highest accuracy, with SOC RMSEP of 4.1 and 2.7 g.kg−1 for 0–15 and 15–25 cm, respectively. Moreover, temporal spiking improved five of eight predictions (stratifying or not the calibration dataset by depth, removing or not poorly predicted outliers), with increases in the ratio of performance to deviation of 0.10–0.44. Furthermore, comparing observed and predicted changes in SOC content showed that Vis-NIR spectroscopy estimated its trend over time in most cases.

Mycorrhizal Fungal Diversity Associated with Six Understudied Ectomycorrhizal Trees in the Republic of Korea.

Mycorrhizal fungi are key components of forest ecosystems and play essential roles in host health. The host specificity of mycorrhizal fungi is variable and the mycorrhizal fungi composition for the dominant tree species is largely known but remains unknown for the less common tree species. In this study, we collected soil samples from the roots of six understudied ectomycorrhizal tree species from a preserved natural park in the Republic of Korea over four seasons to investigate the host specificity of mycorrhizal fungi in multiple tree species, considering the abiotic factors. We evaluated the mycorrhizal fungal composition in each tree species using a metabarcoding approach. Our results revealed that each host tree species harbored unique mycorrhizal communities, despite close localization. Most mycorrhizal taxa belonged to ectomycorrhizal fungi, but a small proportion of ericoid mycorrhizal fungi and arbuscular mycorrhizal fungi were also detected. While common mycorrhizal fungi were shared between the plant species at the genus or higher taxonomic level, we found high host specificity at the species/OTU (operational taxonomic unit) level. Moreover, the effects of the seasons and soil properties on the mycorrhizal communities differed by tree species. Our results indicate that mycorrhizal fungi feature host-specificity at lower taxonomic levels.

Crop tillage, soil depth, and their influence on extracellular enzyme activities

Agricultural practices can alter both physicochemical properties and soil microbial parameters, modifying the dynamics of soil biochemical functioning and, consequently, nutrient cycling. This study evaluated the effect of land use on chemical and biochemical attributes, and relationships between environmental variables. We used a sampling design to collect soil samples at different depths in different agroecosystems. Soil samples from natural ecosystems (native Cerrado) and agroecosystems (cotton and sugarcane cultivation) were collected at 0–0.1 m, 0.1–0.2 m, 0.2–0.5 m, and 0.5–1.0 m from 12 areas in the State of Goiás, Brazil. Twelve chemical properties and two biochemical attributes (enzyme activity and microbial biomass carbon) were evaluated using a generalized linear model of variance and Tukey’s test with three factors: correlation between all soil attributes, multiple regression between soil attributes, and biochemical variables. Soil chemical and biochemical attributes were significantly affected by variable depth (p&lt;0.05). Most of the metabolic activity in the soil occurred at 0 to 0.2 m, independent of land use class. Seasonality also affected enzyme activity in the soil, with higher activity during the rainy season. In contrast, microbial biomass carbon, an attribute generally related to organic matter and carbon mineralization, did not vary significantly with different soil depths and seasons. Thus, enzyme activity is an important indicator of soil fertility variations and is more sensitive than chemical and microbial parameters

Assessment of Physico-Chemical Properties of Soil from Different Villages of Kushinagar District, Uttar Pradesh, India

The present experiment was carried out during 2022 and consisted of soil sample collection from the designated sitesand laboratory experiments which was conducted in Department of Soil Science &amp; Agricultural Chemistry, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj-211007(U.P.). The primary goals of this study were to investigate the physico-chemical characteristics of soil at various depths. To determine the availability of macronutrients in soil samples from Kushinagar, District, UttarPradesh, and to provide an assessment, 9 sampling locations were chosen. The depths at which soil samples were taken were 0–15, 15–30 and 30–45 cm, respectively. The soil colour (dry condition) Results revealed that the soil colour in dry condition varies from Olive yellow to Olive grey and the colour in wet condition varies from Olive brown to Dark greyish. The soil texture was dominantly sandy loam in almost every site.The bulk density (Mg m⁻3) ranged from 1.35(Mg m⁻3) to 1.43(Mg m⁻3). The practical density (Mg m⁻3) ranged from 2.41 (Mg m⁻3) to 2.53(Mgm⁻3). The pore space (%) ranged from 43.87(%)to 48.87(%). The water holding capacity (%) ranged from 34.01(%) to 42.36(%). The soil pH ranged from 7.50 to 7.99 Indicating Neutral to alkalinein nature. The electrical conductivity ranged from 0.12 (dS m-1) to 0.33(dS m-1). The soil organic carbon (%) ranged from 0.23(%) to 0.39(%). The Available nitrogen (kg ha-1) ranged from 233.23(kg ha-1) to 278.24 (kg ha-1). The Available phosphorous (kg ha-1) ranged from 13.89 (kg ha-1) to 25.39 (kg ha-1). The Available potassium (kg ha-1) ranged from 187.99(kg ha-1 to 238.32 (kg ha- 1). The Exchangeable calcium [cmol (p+) kg-1] ranged from 3.03 to 4.24 [cmol (p+) kg-1]. The Exchangeable Magnesium [cmol (p+) kg -1] ranged from 1.45 to 2.21 [cmol (p+) kg-1]. It suggests that still improvement can be done by improving cropping pattern, decomposition of organic waste, mulching, tillage practices and proper irrigation by management practices with knowledge and experience gained through studies and lead farmers to achieve quality produce and high yield through soil conservation.

Long-term nitrogen fertilization and sweetpotato cultivation in the wheat-sweetpotato rotation system decrease alkaline phosphomonoesterase activity by regulating soil phoD-harboring bacteria communities

The alkaline phosphomonoesterase (ALP)-harboring community (phoD-harboring community) plays a crucial role in the conversion of organic phosphorus (P) into available P (AP). However, the response mechanisms of phoD-harboring communities to fertilization strategies, crop types, and their interactions within the wheat-sweetpotato rotation are poorly understood. A nine-year field experiment of different fertilization strategies was established under the wheat-sweetpotato rotation. After harvesting the crop, we collected soil samples without fertilization (CK), inorganic NK fertilization (NK), inorganic NPK fertilization (NPK), and a combined application of inorganic NPK and organic fertilizer (NPKM). We employed high-throughput sequencing and enzymology techniques to analyze the composition and functional activity of phoD-harboring bacterial communities as well as their correlation with soil physicochemical properties. The results showed that long-term nitrogen (N) fertilization, especially inorganic N, significantly reduced soil pH and ALP activity while increasing AP compared with CK. The AP content in sweetpotato season was significantly higher than that in wheat season. Inorganic N fertilization dramatically reshaped the communities of phoD-harboring bacteria and decreased diversity. The phoD-harboring bacterial communities in sweetpotato season were significantly different from those in wheat season. The N fertilization significantly reduced the relative abundance of Acuticoccus, Methylibium, Rhizobacter, and Roseivivax, which was positively correlated with ALP activity. These groups in sweetpotato season decreased significantly compared with wheat season. A structural equation model indicates that pH and AP play a significant role in regulating the phoD-harboring bacteria communities, ALP activity, and their interactions. We demonstrate that fertilization strategies and crop types have a substantial impact on the phoD-harboring bacteria communities and functions, which are closely linked to soil pH and AP levels. Our study highlights the detrimental effects of soil acidification resulting from inorganic N fertilization on P-cycling bacterial communities and functions. However, the combination of inorganic and organic fertilizer can mitigate these adverse effects.

Physical and Chemical Properties of Hidimundige (Crown Choking) Affected and Healthy Arecanut Gardens of Chitradurga District, Karnataka, India

The present investigation was undertaken at College of Agriculture, Shivamogga during 2018-2019 to delineate the causes for hidimundige syndrome in arecanut. Soil samples from two depths 0 to 30 cm and 30 to 60 cm were collected at 60 cm away from the trunk of arecanut from both healthy and affected gardens of Holalkere, Hiriyur, Chitradurga and Hosadurga taluks. The collected soil samples were analyzed for various physical and chemical properties and also for macro and micro nutrients. The results of the investigation indicated that soils coming under affected gardens showed the high mean clay content than healthy gardens. There was a significant increase in bulk density of affected gardens compared to healthy gardens in Holalkere (from 1.63-1.84 Mg m-3) and Hosadurga (from 1.84-1.96 Mg m-3) taluk at lower depth. Whereas, the drainable porosity decreased significantly in affected gardens compared to healthy gardens of Holalkere (from 33.54-25.69 %) and Hosadurga (from 25.79-21.23 %) taluk at lower depth. In all taluks, majority of the soils from both healthy and affected arecanut gardens were neutral to alkaline in reaction. The study showed that availability of N, P, K, S, Fe, Mn, Cu and B and also the content of exchangeable Ca and Mg was quite heterogeneous in both healthy and affected gardens. Whereas, available zinc status in the soil showed significant decrease in affected gardens compared to healthy gardens of Hiriyur, Chitradurga and Holalkere taluks.

Soil Nutrient Availability Regulates Microbial Community Composition and Enzymatic Activities at Different Soil Depths along an Elevation Gradient in the Nanling Nature Reserve, China

Improving our understanding of how soil microbial community composition and enzyme activities vary with elevation will elucidate the impact of climate change on ecosystem function. We collected soil samples at three elevations (1000 m, 1200 m, 1400 m) from two soil depths in a subtropical forest in the Nanling Nature Reserve to analyze soil nutrient availability and the Gram-positive (GP) to Gram-negative (GN) bacteria ratio. We conducted a vector analysis of soil enzymatic stoichiometry to examine the spatial distribution of soil microbial C, N, and P limitations. The soil C:N ratio decreased with increasing elevation. The GP:GN ratio and vector length (read-outs of relative C versus nutrient limitation) were the highest at 1400 m due to lower C availability. At an elevation of 1200 m, lower P availability was reflected in higher soil C:P and N:P ratios and lower GP:GN ratios, as lower P availability suppressed microbial C decomposition. Furthermore, the GP:GN ratio and vector length showed contrasting responses to variations in soil depth. The validation of enzyme vector analysis to capture the responses of microbial community composition to soil properties is dependent on environmental conditions and should be considered in the development of future soil organic C (SOC) dynamics models.

Utilizing X-ray fluorescence (XRF) method to evaluate the content of metal elements in soil and their effects on the total phenolic and flavonoid contents of some medicinal plants.

Soil factors, especially metal elements in the soil, play a significant role in forming and accumulating secondary metabolites, which determine the medicinal properties of medicinal herbs. In this study, the concentrations of some metal elements (K, Mn, Fe, Cu, Zn, and Cr) in Cam Mountain and Tinh Bien Town, An Giang Province, Vietnam, were determined using the XRF method. We simultaneously determined the total phenolic and flavonoid content of some medicinal herbs collected from the collected soil sample areas, thereby assessing the influence of these elements on the formation of secondary metabolites in medicinal plants. The results showed that K, Mn, and Cr were mainly concentrated in the topsoil and transition layers; Fe and Cu elements tended to concentrate in the transition layer and the subsoil when surveying the soil profile. K, Mn, Cu, and Cr concentrations were more focused in Tinh Bien area, while Fe and Zn had higher concentrations at Cam Mountain. Additionally, results from evaluating the relationship between the content of the elements in the soil and the content of two active compounds also showed the correlation regression model between Zn and flavonoid expression by level 4 at the 5% significance level. Thus, the nonlinear model is suitable for evaluating the relationship between the content of metal elements in the soil and the active compound in medicinal plants.

Fire shapes fungal guild diversity and composition through direct and indirect pathways.

Fire has shaped global ecosystems for millennia by directly killing organisms and indirectly altering habitats and resources. All terrestrial ecosystems, including fire-prone ecosystems, rely on soil-inhabiting fungi, where they play vital roles in ecological processes. Yet our understanding of how fire regimes influence soil fungi remains limited and our knowledge of these interactions in semiarid landscapes is virtually absent. We collected soil samples and vegetation measurements from sites across a gradient in time-since-fire ages (0-75 years-since-fire) and fire frequency (burnt 0-5 times during the recent 29-year period) in a semiarid heathland of south-eastern Australia. We characterized fungal communities using ITS amplicon-sequencing and assigned fungi taxonomically to trophic guilds. We used structural equation models to examine direct, indirect and total effects of time-since-fire and fire frequency on total fungal, ectomycorrhizal, saprotrophic and pathogenic richness. We used multivariate analyses to investigate how total fungal, ectomycorrhizal, saprotrophic and pathogenic species composition differed between post-fire successional stages and fire frequency classes. Time-since-fire was an important driver of saprotrophic richness; directly, saprotrophic richness increased with time-since-fire, and indirectly, saprotrophic richness declined with time-since-fire (resulting in a positive total effect), mediated through the impact of fire on substrates. Frequently burnt sites had lower numbers of saprotrophic and pathogenic species. Post-fire successional stages and fire frequency classes were characterized by distinct fungal communities, with large differences in ectomycorrhizal species composition. Understanding the complex responses of fungal communities to fire can be improved by exploring how the effects of fire flow through ecosystems. Diverse fire histories may be important for maintaining the functional diversity of fungi in semiarid regions.

Effects of straw and plastic film mulching on microbial functional genes involved in soil nitrogen cycling.

Microorganisms regulate soil nitrogen (N) cycling in cropping systems. However, how soil microbial functional genes involved in soil N cycling respond to mulching practices is not well known. We collected soil samples from a spring maize field mulched with crop straw (SM) and plastic film (FM) for 10-year and with no mulching (CK) in the Loess Plateau. Microbial functional genes involved in soil N cycling were quantified using metagenomic sequencing. We collected soil samples from a spring maize field mulched with crop straw (SM) and plastic film (FM) for 10-year and with no mulching (CK) in the Loess Plateau. Microbial functional genes involved in soil N cycling were quantified using metagenomic sequencing. Compared to that in CK, the total abundance of genes involved in soil N cycling increased in SM but had no significant changes in FM. Specifically, SM increased the abundances of functional genes that involved in dissimilatory nitrate reduction to ammonium (nirB, napA, and nrfA), while FM decreased the abundances of functional genes that involved in ammonification (ureC and ureA) in comparison with CK. Other genes involved in assimilatory nitrate reduction, denitrification, and ammonia assimilation, however, were not significantly changed with mulching practices. The nirB and napA were derived from Proteobacteria (mainly Sorangium), and the ureC was derived from Actinobacteria (mainly Streptomyces). Mental test showed that the abundance of functional genes that involved in dissimilatory nitrate reduction was positively correlated with the contents of soil microbial biomass N, potential N mineralization, particulate organic N, and C fractions, while ammonification related gene abundance was positively correlated with soil pH, microbial biomass C and N, and mineral N contents. Overall, this study showed that SM could improve soil N availability and promote the soil N cycling by increasing the abundance of functional genes that involved in DNRA, while FM reduced the abundance of functional genes that involved in ammonification and inhibited soil N cycling.

Effects of Wind-Water Erosion and Topographic Factor on Soil Properties in the Loess Hilly Region of China.

Wind and water erosion processes can lead to soil degradation. Topographic factors also affect the variation of soil properties. The effect of topographic factors on soil properties in regions where wind and water erosion simultaneously occur remains complicated. To address this effect, we conducted this study to determine the relationships between the changes in wind-water erosion and soil properties in different topographic contexts. We collected soil samples from conical landforms with different slope characteristics and positions in the wind-water erosion crisscross region of China. We examined the soil 137Cs inventory, soil organic carbon (SOC), total nitrogen (TN), soil particles, soil water content (SWC), and biomass. 137Cs was applied to estimate soil erosion. The results show that the soil erosion rate followed the order of northwest slope > southwest slope > northeast slope > southeast slope. The soil erosion rate on the northwest slope was about 12.06-58.47% higher than on the other. Along the slopes, the soil erosion rate decreased from the upper to the lower regions, and was 65.65% higher at the upper slope than at the lower one. The change in soil erosion rate was closely related to soil properties. The contents of SOC, TN, clay, silt, SWC, and biomass on the northern slopes (northwest and northeast slopes) were lower than those on the southern slopes (southeast and southwest slopes), and they were lower at the upper slope than at the lower one. Redundancy analysis showed that the variation in soil properties was primarily affected by the slope aspect, and less affected by soil erosion, accounting for 56.1% and 30.9%, respectively. The results demonstrate that wind-water erosion accelerates the impact of topographic factors on soil properties under slope conditions. Our research improves our understanding of the mechanisms of soil degradation in gully regions where wind and water erosion simultaneously occur.

Bacterial Community Composition Under Paddy Conditions Is More Strongly Affected by the Difference in Soil Type than by Field Management.

In this study, we aimed to investigate the effects of soil type and field management on bacterial communities in paddy soils, taking into account the differences in soil physicochemical properties. We collected soil samples from 51 paddy fields in six prefectures in Japan. The paddy fields were managed under organic regimes (26 fields), natural-farming regimes (12 fields), or conventional regimes (13 fields). The paddy fields were classified into four soil types: andosol, gray lowland soil, gley soil, and gray upland soil. Soil DNA was extracted from the soil samples collected 2 to 10 weeks after the flooding, and the 16S rRNA gene amplicon sequencing analysis was performed. The bacterial community compositions were dominated by the phylum Proteobacteria, Chloroflexi, Actinobacteria, Acidobacteria, and Firmicutes in all fields. The difference in soil type had significant effects on α-diversities of the bacterial communities, although the field management had no effect. The soil bacterial communities in the gley soils and gray upland soils individually formed different groups from those in the other soils, while the andosol and gray lowland soils tended to form relatively similar bacterial communities. On the other hand, the effects of the field management were estimated to be smaller than those of soil type. The β-diversity of the bacterial community compositions were significantly correlated with soil pH, total nitrogen content, total carbon content, and divalent iron content. Our results suggest that the soil microbial community in paddy fields may be strongly influenced by soil physiochemical properties derived from differences in soil type.

The Physicochemical Properties and Microbial Populations of Nicosulfuron Treated Soil in Yola, Adamawa State, Nigeria

The use of herbicides in the modern system of farming has really help in boosting crop production, this way meeting up with the ever increasing demand for food by the always increasing human population. However, these herbicides have different mode of actions and effect on soil components; and their continued usage has affected the soil microbial communities and other soil components most of which are the non-target. This study, therefore, was focused on evaluating the physicochemical properties and microbial population of nicosulfuron treated soils of Yola, Adamawa State, Nigeria. The study was carried out in both 2021 and 2022 in the Research Farm of the Department of Plant Science, Modibbo Adama University, Yola. The samples of the soil treated with the different concentrations of nicosulfuron were obtained at 0, 2, 4 and 6 Weeks after Treatment (WAT) at the depth between 0-12 cm. The physicochemical properties and the bacterial and fungal populations of the collected soil samples were determined using standard laboratory procedures. The results revealed that the soils treated with the 50, 100, 150 and 200 g/ha concentrations of nicosulfuron had a comparable values for physicochemical (except percentage moisture content, organic carbon and matter and total nitrogen) properties that include: pH, electrical conductivity, Calcium, magnesium and potassium ions, total exchangeable acidity, total exchangeable base, effective cation exchange capacity, percentage base saturation. On the basis of duration of application, however, the nicosulfuron had significant effect on the physicochemical properties with 6 WAT having the highest values for the physicochemical properties compared to other sampling durations. On the bacterial (except the fungal) population, the nicosulfuron also had a significant effect with the treated soils having the lowest populations of both bacteria and fungi. The study therefore, concluded that the duration of application of nicosulfuron have significant effect on physicochemical properties of soil in Yola. On the bacterial and fungal populations of the soil, nicosulfuron also had significant effect.