Soil Plant Research Articles

Light grazing reduces the abundance of carbon cycling functional genes by decreasing oligotrophs microbes in desert steppe

Understanding the functional genes of microorganisms involved in carbon cycling processes can link microbial community structure to potential ecological functions. However, the effects of grazing on the relationship between carbon cycling functional genes and soil environment need to be further investigated as a global land use activity. A replicated sheep grazing platform was established in Northern China in 2004 with four different stocking rates: no grazing (0 sheep ha−1 month−1), light grazing (0.15 sheep ha−1 month−1), moderate grazing (0.30 sheep ha−1 month−1), and heavy grazing (0.45 sheep ha−1 month−1). To examine the effects of biotic and abiotic factors on microbial species and functional gene abundance, we collected soil samples after 17 years of grazing analyzed for the abundance of microbial communities, the abundance of carbon function genes, plant carbon input and soil environmental factors. We found that light grazing reduced carbon cycling functional genes compared to no grazing (fencing). With increasing grazing intensity, the absolute abundance of functional genes increased. Changes in microbial species abundance were mainly responsible for the changes in the structure of carbon cycling functional genes. Our results emphasize that elucidating how grazing affects the carbon cycling functional genes through the effects of plant carbon inputs and the environment, and the interactions between them, will provide important information for understanding carbon cycling processes in grassland ecosystems.

Effect of crop geometry and nitrogen levels on leaf chlorophyll content of cotton (Gossypium hirsutum) at different growth stages under rainfed Vertisols

A field experiment was conducted during the rainy (kharif) season of 2018–19 at the Regional Agricultural Research Station, Acharya N.G. Ranga Agricultural University, Lam, Gunter, Andhra Pradesh on Vertisols under rainfed conditions. To study the effect of crop geometry and nitrogen levels on compact cotton (Gossypium hirsutum L.). Leaf chlorophyll content was measured with the Soil Plant Analysis Development meter (SPAD 502 Plus Chlorophyll Meter) at different crop growth stages. Among the various crop geometry studied, maximum chlorophyll (SPAD index) content, functional leaves per square meter and leaf area index (LAI) were recorded with close crop geometry 60 cm × 10 cm. Among nitrogen levels application of 180 kg N/ha recorded maximum chlorophyll content, functional leaves per square meter and LAI. Combined effect on crop geometry and nitrogen levels on chlorophyll content was recorded significant with closer geometry 60cm x10cm along with an application of 180kg N ha-1 at 90 days after sowing. Dry matter accumulation (kg/ha) at 30 DAS, 60 DAS, 90 DAS and at harvest was significantly affected by crop geometry and levels of nitrogen but not by their interaction.

The impact of desertification on soil health stability in Semi-Arid alpine Regions: A case study of the Qilian Mountains in the northeastern Tibetan Plateau, China

Desertification poses a serious threat to ecosystem health, and with global changes, the variability and uncertainty of ecological functions in semi-arid alpine regions are increasing. A pressing issue is quantifying how desertification affects the soil system functions in these areas. However, empirical evidence is still lacking in exploring the interaction between desertification degradation gradients and soil functions under natural conditions by coupling soil physicochemical properties, soil microbiota, and vegetation. For this purpose, we conducted a survey sampling of soil and vegetation at five sites with no, light, moderate, severe and extremely severe desertification in Qinghai Area of Qilian Mountains National Park, China. We introduced a new concept soil health stability (SHS) to represent the actual health status of soil systems in semi-arid alpine regions and assessed the impact of desertification on this stability. We observed that the intensification of desertification has led to a significant decrease in soil organic matter, relative abundance of soil microorganisms, and plant factors. The contributions of plant factors and soil microbiota to SHS showed a negative correlation with the degradation gradient. SHS varied across different degradation gradients, rather than following a single linear relationship, with a relatively rapid decline in the transition from non-desertification to moderate desertification. Our work emphasizes that the coupled contributions of soil physicochemical properties, soil microbiota, and vegetation to SHS. It calls for intensified prevention and treatment of mild and moderate desertification, while providing new methods and deeper scientific understanding for accurately evaluating soil system functions in semi-arid alpine regions.

The effect of amorphous silica on soil–plant–water relations in soils with contrasting textures

This study investigates how amorphous silica (ASi) influences soil–plant–water interactions in distinct soil textures. A sandy loam and silty clay soil were mixed with 0 and 2% ASi, and their impact on soil retention and soil hydraulic conductivity curves were determined. In parallel, tomato plants (Solanum lycopersicum L.) were grown in experimental pots under controlled conditions. When plants were established, the soil was saturated, and a controlled drying cycle ensued until plants reached their wilting points. Soil water content, soil water potential, plant transpiration rate, and leaf water potential were monitored during this process. Results indicate a positive impact of ASi on the sandy loam soil, enhancing soil water content at field capacity (FC, factor of 1.3 times) and at permanent wilting point (PWP, a factor of 3.5 times), while its effect in silty clay loam was negligible (< 1.05 times). In addition, the presence of ASi prevented a significant drop in soil hydraulic conductivity (Kh\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{h}$$\\end{document}) at dry conditions. The Kh\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{h}$$\\end{document} of ASi-treated sandy loam and silty clay at PWP were 4.3 times higher than their respective control. Transpiration rates in plants grown in ASi-treated sandy loam soil under soil drying conditions were higher than in the control, attributed to improved soil hydraulic conductivity. At the same time, no significant difference was observed in the transpiration of plants treated with ASi in silty clay soil. This suggests ASi boosts soil–plant–water relationships in coarse-textured soils by maintaining heightened hydraulic conductivity, with no significant effect on fine-textured soils.

Effect of artisanal gold mining on woody plant diversity in Western Burkina Faso

Although artisanal gold mining strongly contribute to enhance people incomes in West Africa, this activity can lead to habitat fragmentation and loss of woody species. Therefore, studying the impact of artisanal gold mining on woody plant diversity is needed for efficient management of forest resources. In this study, we investigated the impact of artisanal gold mining on woody plant diversity and dynamics in the Kari classified forest in Western Burkina Faso. Forest inventories were carried out at two sites including a gold panning site and a control site, following a systematic sampling design. We identified all woody species and measured all woody species with a diamtere at breast height ≥5 cm. A total 60 plots of 900 m² were surveyed. Diversity indices and dendrometric parameters were calculated and compared between the two sites. The results showed a higher species richness (59 woody species distributing in 39 genera and 18 families) in the control site compared to the gold panning site (38 species distributing in 25 genera and 12 families). The mean values of the number of species per plot and the Shannon diversity index were higher in the control site (15.50 ± 8.80; 2.16 ± 0.43, respectively) than in the artisal mining site (5.47 ± 2.71; 1.40 ± 0.53, respectively), showing that the control site is more diverse than the site that is under gold panning. The control site also had the highest density (683.33 ± 262.99 ft/ha) and stable woody stands compared to the less gold panning site (137.41 ± 102.31 ft/ha) where unstable woody stands were found. While the gold-panning site was characterised by biophysical impacts such as destruction of the plant cover and soil excavation, no visible impact was observed at the control site.Theses findings highlight the negative impact of artisanl gold mining on woody species diversity and structure. The study provides essential information for decision-making on sustainable forest management in the context of mining boom in Burkina Faso's.

Effects of organic contaminants on arbuscular mycorrhiza formation: A meta-analysis

Arbuscular mycorrhizal fungi (AMF) function mostly depends on their colonization to roots. However, it has not been systematically clear how arbuscular mycorrhiza (AM) formation is affected by organic contaminants. In this study, a meta-analysis was performed to estimate the effects of three groups of organic contaminants (polycyclic aromatic hydrocarbons (PAHs), crude oil, and pesticide) in soil on mycorrhizal colonization rates (MCRs) from various moderators, such as AMF (genus, species, and inoculation mode), contaminant (level, type, and source), and experimental conditions (plant type, duration, and soil sterilization). Our results showed that all MCRs (total, vesicular, arbuscular and hyphal) significantly decreased under the stresses of three contaminants. Generally, pesticide caused larger decrease in all MCRs than PAHs and crude soil except for vesicular MCRs. Mixed AMF showed larger decrease in the total and vesicular MCRs than single AM fungus, but contrary trends in the arbuscular and hyphal MCRs. Moreover, man-made contaminant seemed to produce larger negative effects on the total, vesicular, and arbuscular MCRs than industry contaminant. The inhibitive effects of three contaminants on the total and vesicular MCRs increased with increasing experimental duration, and were larger in the non-sterilized soil than in the sterilized soil. Hyphal and spore growth were also inhibited by three contaminants in most cases. Hyphal length and spore number of single AM fungus were lower than those of mixed AMF, and pesticide produced larger inhibition on the hyphal length and spore number than PAHs and crude oil. Similar trend was found in the non-sterilized soil relative to the sterilized soil. This study indicated that AM formation and AM structure were negatively affected by three organic contaminants, whereas the inhibitive degrees varied with AMF, organic contaminant and experimental conditions.

The effect of woody encroachment on taxonomic and functional diversity and soil properties in Cerrado wetlands

The encroachment of woody species has been affecting wetlands in the Cerrado biome, Brazil. This process has resulted in changes in plant diversity, soil physicochemical properties, and water availability. This study assessed changes in the taxonomic and functional diversity of plants and soil in Veredas wetlands in process of reduction in water availability and woody plant encroachment. Over a 14-year interval, we quantified taxonomic and plant functional diversity, soil physicochemical properties, groundwater depth, and its relationship with historical soil moisture using remote sensing in veredas. We investigated the effect of increased groundwater depth, woody vegetation cover, and changes in soil properties on species cover and richness. We observed a five to seven-fold increase in woody vegetation cover, accompanied by an increased in the richness of woody species from 21.4 % to 28.9 %. Nevertheless, this was counterbalanced by a 15.8 % to 35.2 % reduction in overall species richness and taxonomic diversity. At the same time, functional diversity decreased, leading to a community with more acquisitive traits. Groundwater depth increased from 20 to 60 cm. Soil properties changed, especially organic matter content, which increased two to 14 times. Changes in species richness and cover were related to increased organic matter and groundwater depth. The surveyed veredas exhibited considerable changes in plant species richness, soil, and hydrological properties, as well as woody vegetation cover, over 14 years. The veredas formed distinct functional composition groups between sampling times. However, only one vereda exhibited a reduction in functional richness, and neither showed temporal functional divergence. Woody encroachments are leading these veredas to an alternative state with a reduced herbaceous diversity, structurally denser, and with more resource-acquisitive plant traits in the community. The Woody encroachment reducing soil water availability, may impact ecosystem services, particularly water provision and biodiversity loss in the Cerrado region.

Unveiling allelopathic dynamics and impacts of invasive Erigeron bonariensis and Bidens pilosa on plant communities and soil parameters

Invasive alien species are becoming more and more prevalent worldwide, Erigeron bonariensis and Bidens pilosa are two invasive species of Asteraceae in Egypt. To mitigate their detrimental effects and understand their differences in invasiveness, we compared the allelopathic potentials of E. bonariensis and B. pilosa using leachates, decaying residues, and volatilization processes. Notably, the allelopathic variances in leachates were significant, influenced by plant types, concentrations, and response patterns of target plant traits, as indicated by EC50. The relative phytotoxicity of the invasive species decayed residues peaked between 20 and 25 days in the soil, with a positive correlation with concentrations and soil properties. The highest quantities of phenolic acids were chlorogenic acid and caffeic acid reaching (5.41 and 4.39 µg g−1) E. bonariensis and (4.53 and 4.46 µg g−1) B. pilosa, in leachates extracts respectively, while in the soil extract of decayed residues were coumaric acid and ferulic acid measuring (1.66 and 1.67 µg g−1) E. bonariensis and (1.47 and 1.57 µg g−1) B. pilosa, respectively. Using GC/MS analysis, the main volatile components in E. bonariensis were 1, 8 cineole (5.62%), and α-terpinene (5.43%) and iso-Caryophyllene (5.2%) which showed the greatest inhibitory effects. While B. pilosa main constituents were trans-sabinene (5.39%) and Camphene (5.11%), respectively. Finally, the high invasion level displayed from E. bonariensis (0.221) compared with B. pilosa (0.094) which correlated with the stronger allelopathic activities against plant species, and soil properties. Therefore, the allelopathic potentialities of these species are critically relevant to their invasion success.

Shift in the effects of invasive soil legacy on subsequent native and invasive trees driven by nitrogen deposition

Invasive plants can interact with soil microbes to enhance their own performance. Such interactive effects may persist and later affect plant performance and their population dynamics. Such ‘invasive soil legacy’ is the specific plant–soil feedback that can affect future invasions, while it is not clear how nitrogen deposition and interspecific competition influence invasive soil legacy. Thus, we collected field soil and conducted a greenhouse experiment to investigate the effects of soil legacy of the invasive tree Rhus typhina on the performance, functional traits and soil microbial communities of R. typhina and the native tree Ailanthus altissima under three nitrogen levels with and without interspecific competition. The experiment revealed that the outcomes of invasive soil legacies were context-specific and depended on local soil nutrient levels and species competition. Specifically, nitrogen addition changed the negative conspecific soil legacy on subsequent R. typhina to a positive effect, while it became negative in A. altissima. The invasive soil legacy promoted the transpirational rate of R. typhina and A. altissima in monoculture, but inhibited it in a mixture under nitrogen deposition. Nitrogen deposition reduced bacteria and fungi biomass of A. altissima in monocultures and mixtures. In contrast, nitrogen deposition decreased bacterial and fungal biomass of R. typhina in monocultures, but enhanced them in mixtures. Therefore, changes in plant growth, transpiration rate and soil microbial biomass might contribute to the different responses of invasive and native plants to invasive soil legacies. Nitrogen deposition and interspecific competition promote the viability of invasive plants from plant–soil feedback and indicate that ranges of subsequent plants might further expand through below-ground process under nitrogen deposition in the future.

Phyto-parasitic nematodes of bell pepper plant and farm soil in Abua, Rivers State, Nigeria

Bell pepper farming significantly contributes to economic development in Abua. However, phyto-parasitic nematodes are endemic in the area and affect quality of crop yield. Hence, this study was undertaken to investigate the dynamics of occurrence of nematodes in bell pepper roots and soil samples of the farms in Abua. Roots and soil from the root rhizosphere were simultaneously collected at 0-20 cm depth using an improvised soil auger and knife. Modified sieve plate technique was employed for nematode detection and a pictorial key was used for nematode identification at the genera level. An overall nematode abundance of 746 nematodes in the soil around the root region and 216 nematodes in the root tissues of the bell peppers were recorded. Gracilachus species (10.6 %) was more prevalent in the soil, and Meloidogyne species (35.2 %) exhibited the highest population in roots. The study found that Abua's cultivated soil is susceptible to nematode infestation, limiting crop performance. The nematodes showcased root burrowing which is an inherent pattern for survival. The result on root nematodes across the five bell farms surveyed was not significant (p &gt; 0.05). The result opined that farmers in Abua, Rivers State, should understand the role of the soil nematodes and implement soil improvement strategies for improved crop performance and rural economic development.

Cyanobacteria-green microalgae consortia enhance soil fertility and plant growth by shaping the native soil microbiome of Capsicum annuum

Alternative solutions to chemical fertilizers that can enhance soil fertility, increase crop yield, promote sustainable agriculture and reduce harmful environmental impacts are urgently required. Microalgal bio-inoculants can improve soil fertility, plant growth and crop yield, yet the response of native soil microbiome to microalgal application remains largely unexplored. A pot experiment was conducted to assess the effects of microalgae (a consortium of cyanobacteria and green microalgae) inoculation on the growth and yield of chili plant, soil fertility and soil microbiome. Our results showed that microalgal inoculation significantly enhanced plant morphometric parameters and increased dehydrogenase activity (p < 0.05). Similarly, soil organic carbon , soil chlorophyll , total polysaccharides and nutrients such as carbon , nitrogen , phosphorus , potassium and manganese were also significantly (p < 0.05) enriched in microalgal treatment groups (50% and 100%) compared to the control. Results showed that microalgal inoculation increased the soil microbial diversity, with the richness being higher in treated soils than control. Metagenomics analysis revealed a shift in bacterial and fungal community composition with firmicutes, chloroflexi, planctomycetes, proteobacteria, bacillariophyta, basidiomycota and glomeromycota dominating microalgal- treated soils, while actinobacteria, bacteroidetes, and streptomycota dominating control soils. The findings suggested that microalgal bio-inoculation can increase the diversity and composition of native soil microbiomes, enhance soil fertility, growth, and yield in chili plants.

Enhancing potassium assimilation in soil for Zingiber officinale plant by rhizosphere bacterial isolate and optimization studies by response surface modeling

Rhizosphere bacteria have always proven their worth towards their associated plant in their defense mechanism and nutritional functions. This study was made to understand the impact of rhizosphere-associated bacterial isolate PGK01 in complimenting associated Zingiber officinale plants in their potassium nutritional requirements. The screening of the isolate suggested that it can solubilize potassium, which the plant shall use for its nutritional purposes. Molecular sequencing suggested that the strain belonged to Bacillus subtilis, whose sequence has been submitted to NCBI under the accession number OQ652138. In-situ analysis of the effect of bacteria on the growth parameters and yield of the plant indicated that in the presence of microbe, plants tend to grow more when compared to without the organism. The optimization studies conducted by response surface modeling suggested that only half of the potassium fertilizer is necessary when a plant is grown in the presence of isolate compared to the conventional method. The adequacy of the statistical model was verified by analyzing the Sequential Model Sum of Squares and Cook’s distance diagnostic, wherein the observation proved the significance of the mathematical model.

“Hg distribution and accumulation in soil and vegetation in areas impacted by artisanal gold mining in the Southern Amazonian region of Madre de Dios, Peru.”

Artisanal and small-scale gold mining (ASGM) is the primary global source of anthropogenic mercury (Hg) emissions. It has impacted the Amazon rainforest in the Peruvian region of Madre de Dios. However, few studies have investigated Hg's distribution in terrestrial ecosystems in this region. We studied Hg's distribution and its predictors in soil and native plant species from artisanal mining sites. Total Hg concentrations were determined in soil samples collected at different depths (0-5 cm and 5-30 cm) and plant samples (roots, shoots, leaves) from 19 native plant species collected in different land cover categories: L1 naked soil (L1), gravel piles (L2), natural regeneration (L3), reforestation (L4), and primary forest (L5) in the mining sites. Hg levels in air were also studied using passive air samplers. The highest Hg concentrations in soil (average 0.276 and 0.210 mg kg-1 dw.) were found in the intact primary forest (L5) at 0-5 cm depth and in the plant rooting zones at 5-30 cm depth, respectively. Moreover, the highest Hg levels in plants (average 0.64 mg kg-1 dw) were found in foliage of intact primary forest (L5). The results suggest that the forest in these sites receives Hg from the atmosphere through leaf deposition and that Hg accumulates in the soil surrounding the roots. The Hg levels found in the plant leaves of the primary forest are the highest ever recorded in this region, exceeding values found in forests impacted by Hg pollution worldwide and raising concerns about the extent of the ASGM impact in this ecosystem. Correlations between Hg concentrations in soil, bioaccumulation in plant roots, and soil physical-chemical characteristics were determined. Linear regression models showed that the soil organic matter content (SOM), pH, and electrical conductivity (EC) predict the Hg distribution and accumulation in soil and bioaccumulation in root plants.

Physio-biochemical Behavior and Health Effects of Pepper Plants Subjected to Lead Stress and Their Responses to Remediating Agents as Microbial Activity and Phosphorus

This work assessed the alleviating effects of bacteria (Bacillus subtilis) and phosphorus as environmentally friendly materials on the cultivation of pepper plants in polluted soil with lead (Pb) in forms of PbSO4, and Pb(NO3)2 at rates of 0, 1000, 2000 and 3000 µg Pb/g soil. Pot experiments were conducted to study the growth parameters, some physiological factors, biochemical constituents, and yield attributes, as well as the tolerance index (TI), translocation factor (TF), bioconcentration factor (BCF), and health effects [daily intake of heavy metals (DIM), health risk index (HRI), and carcinogenic risk (CR)]. Increasing the Pb concentration of all Pb salt used in soil severely affected the plant vegetative growth parameters. In comparison with other Pb salt forms, Pb(NO3)2 salt had a strong inhibitory impact. Additionally, the photosynthetic pigments in leaves were negatively impacted by all Pb salt forms. The application of Pb in all salt forms led to changes in the leaf water deficit (LWD), osmotic pressure, and membrane integrity and decreased the total water content, relative water content (RWC), transpiration rate, and leaf succulence. Pollution with Pb salts considerably decreased the yield constituents and various chemical properties of pepper, more so in the presence of Pb nitrate than in the presence of Pb sulfate type. A comparison of the concentration of Pb presence of Pb nitrate was greatly increased than the Pb sulfate in the whole plants. The safe limit of 0.3 mg/kg was exceeded by the Pb concentration in pepper fruits (6.3 and 4.3 mg/kg) cultivated in Pb-contaminated soil [with Pb(NO3)2 and PbSO4, respectively]. Additionally, Pb sulfate had a greater detrimental effect on Pb uptake in several plant organs than other Pb salt forms. The TI of pepper plants treated with salt types was &gt;60% with PbSO4 (75.6%), whereas it was &lt;60% with Pb(NO3)2 (35.2%). The BCF values of pepper plants in the polluted Pb soils varied from 0.10 to 0.41, indicating a moderate accumulator plant. At every level of Pb contamination with all Pb salt types, the sequence of Pb TF values was as follows: roots (TFr) &gt; shoots (TFsh) &gt; fruits (TFf), with TF values &lt; 1. When compared with TFr and TFsh, TFs for shoot to fruits (TFf) had the lowest values (range, 0.07–0.22). The DIM, HRI, and CR values of pepper plants revealed that the Pb of fruit of stressed pepper plants is within safe limits. In addition to reducing the detrimental effects of intolerable Pb levels (2000 and 3000 µg Pb/g soil) on the majority of the aforementioned characters, adding Bacillus bacteria as a bio-agent and phosphorus as a chemo-agent to Pb-polluted soils also stimulated growth, increased yield, controlled plant water relations, protected photosynthetic pigments, and sharply decreased the Pb accumulation in plant organs. The Bacillus bacteria application resulted in some superior characteristics, such as root length, leaf number, leaf length, leaf area, leaf area index, fresh biomass, dry biomass, photosynthetic pigments, quantity yield attributes, reduction Pb accumulation in all plant organs, TI, TFr, TFf, BCF, in health effects trials, whereas phosphorus application improved plant height, leaf width, RWC, LWD, osmotic pressure, total soluble solids, acidity, total carbohydrates, total protein, and TFsh.

Co-application of biochar and selenium nanoparticles improves yield and modifies fatty acid profile and essential oil composition of fennel (Foeniculum vulgare Mill.) under cadmium toxicity.

Fatty acids and essential oils (EOs) are the primary variables that influence the quality of fennel (Foeniculum vulgare Mill.). Soil toxicity to cadmium (Cd) is the main environmental issue facing fennel, and priming methods like soil amendments and nanoparticles (NPs) are commonly utilized to deal with it. The goal of the current study was to examine the effects of biochar (BC) and selenium nanoparticles (Se NPs) on fennel plants in Cd-contaminated soils. The pot experiment was conducted with Cd stress at 0, 10, and 20mgkg-1 soil, BC at 5% (v/v), and foliar-spraying Se NPs at 40mg L-1 as a factorial completely randomized design (CRD) at a greenhouse condition in 2022. The findings demonstrated that Cd toxicity significantly decreased plant performance, while BC and Se NPs enhanced it. Without BC and Se NPs, Cd toxicity at 20mgkg-1 soil decreased biological yield (39%), seed yield (37%), EO yield (32%), and monounsaturated fatty acids (14%), while increased saturated fatty acid (26%) and polyunsaturated fatty acids (40%) of fennel. The main EO profile was anethole (65.32-73.25%), followed by limonene (16.12-22.07%), fenchone (5.57-6.83%), and estragole (2.25-3.65%), which mainly were oxygenated monoterpenes. The combined application of BC and Se NPs improved the yield, EO production, and fatty acid profile of fennel plants under Cd stress, increasing the plants' resistance to Cd toxicity.

Can hydraulic-energy-indices be effectively used to describe the saturated hydraulic conductivity?

The saturated hydraulic conductivity (Ks) and water retention curve (SWRC) parameters are important properties for simulating soil hydrological processes and characterizing soil conservation around the world. Therefore, Ks and SWRC are related with the soil physical quality (SPQ) and several SPQ indices can be derived from SWRC, such as the pore size distribution, relative field capacity, plant available water, drainable porosity, and soil hydraulic-energy indices (SHEI). It is well known that the soil structure can be assessed by using SHEI, but a possible physical relationship between Ks and SHEI was not examined yet. Therefore, the objective of this study was to investigate the behavior of Ks as function of SHEI for several soil textural classes. If this relationship be proved, then SHEI might be applied to improve the Ks prediction by PTF models. In this work, a data set of 395 measured SWRC's were fitted to the vG equation to obtain the SHEI to verify whether they are statistically correlated and physically dependent on Ks. The resulting parametric and non-parametric correlation results were split up according to six textural classes. The significant influence of Ks on at least one of the absolute SHEI (Aa or WRa) was verified on the numerical scale when all textures were grouped and on numerical and pF scales for clayey and silty textures. Ks showed significant impact on Aa and WRa indices in four textural classes. Furthermore, Ks had influence on the sum Aa + WRa denoted in pF scale for five of the six textural classes, with a significant linear correlation in the clayey texture when log (Aa + WRa) was applied. The significant and high correlation of Ks on the ratios WRa/AWC and Aa/ϕD was also observed in four of the six classes, and therefore the use of these indices is recommended for the development of PTFs for Ks prediction.

Changes in soil microbial diversity under present land degradation scenario

Soil biological characteristics are drastically altered by land degradation. Degradation may reduce the number of microorganisms in the soil. Multiple activities and services provided by grassland ecosystems are impacted by land use change because of the resulting shifts in plant community composition and soil characteristics. A large body of research has examined the geographical and temporal dynamics of bacterial community structure and bacterial responses to human management in grassland ecosystems. As one of the most consequential environmental shifts occurring today, land use modification can affect microbial communities through modifying soil environmental parameters, nutritional conditions, and biological interactions. Whereas, soil microbes play crucial roles in nutrient cycling, organic matter decomposition, disease suppression, and overall soil health. Land degradation practices, such as deforestation, overgrazing, intensive agriculture, and improper land management, can disrupt the balance and diversity of soil microbial communities, leading to negative consequences for ecosystem functioning. To mitigate the negative effects of land degradation on soil microbial communities, sustainable land management practices should be adopted. These practices include soil conservation, reforestation, crop rotation, reduced tillage, organic farming methods, and proper nutrient management. By promoting soil health and restoring ecosystem processes, these approaches can help rebuild and maintain diverse and functional soil microbial communities.The purpose of this review is twofold: (1) to assess the diversity and composition of soil microorganisms in response to distinct land-use scenarios; and (2) to compare the relative importance of environmental factors driving these variations

Oceanobacillus picturae alleviates cadmium stress and promotes growth in soybean seedlings

Cadmium (Cd) is a heavy metal that significantly impacts human health and the environment. Microorganisms play a crucial role in reducing heavy metal stress in plants; however, the mechanisms by which microorganisms enhance plant tolerance to Cd stress and the interplay between plants and microorganisms under such stress remain unclear. In this study, Oceanobacillus picturae (O. picturae) was isolated for interaction with soybean seedlings under Cd stress. Results indicated that Cd treatment alone markedly inhibited soybean seedling growth. Conversely, inoculation with O. picturae significantly improved growth indices such as plant height, root length, and fresh weight, while also promoting recovery in soil physiological indicators and pH. Metabolomic and transcriptomic analyses identified 157 genes related to aspartic acid, cysteine, and flavonoid biosynthesis pathways. Sixty-three microbial species were significantly associated with metabolites in these pathways, including pathogenic, adversity-resistant, and bioconductive bacteria. This research experimentally demonstrates, for the first time, the growth-promoting effect of the O. picturae strain on soybean seedlings under non-stress conditions. It also highlights its role in enhancing root growth and reducing Cd accumulation in the roots under Cd stress. Additionally, through the utilization of untargeted metabolomics, metagenomics, and transcriptomics for a multi-omics analysis, we investigated the impact of O. picturae on the soil microbiome and its correlation with differential gene expression in plants. This innovative approach unveils the molecular mechanisms underlying O. picturae's promotion of root growth and adaptation to Cd stress.

Numerical modeling of PFAS movement through the vadose zone: Influence of plant water uptake and soil organic carbon distribution

In this study, we investigated the effects of soil organic carbon (SOC) distribution and water uptake by plant roots on PFAS movement in the vadose zone with a deep groundwater table under temperate, humid climate conditions. Two series of numerical simulations were performed with the HYDRUS computer code, representing the leaching of historical PFOS contamination and the infiltration of water contaminated with PFOA, respectively. We considered soil profiles with three distributions of SOC (no SOC, realistic SOC distribution decreasing with depth, and uniform SOC equal to the content measured in topsoil), three root distributions (bare soil, grassland, and forest), and three soil textures (sand, sandy loam, and loam). The SOC distribution had a profound impact on the velocity of PFOS movement. The apparent retardation factor for realistic SOC distribution was twice as large as for the scenario with no SOC and more than three times smaller than for the scenario with uniformly high SOC content. We also showed that the root distribution in soil profoundly impacts the simulations of PFAS migration through soil. Including the root zone significantly slows down the movement of PFAS, primarily due to increased evapotranspiration and reduced downward water flux. Another effect of water uptake by plant roots is an increase of PFAS concentrations in soil water (evapo-concentration). The evapo-concentration and the slowdown of PFAS movement due to root water uptake are more significant in fine-textured soils than in sand.

Global evidence for joint effects of multiple natural and anthropogenic drivers on soil nitrogen cycling.

Global soil nitrogen (N) cycling remains poorly understood due to its complex driving mechanisms. Here, we present a comprehensive analysis of global soil δ15N, a stable isotopic signature indicative of the N input-output balance, using a machine-learning approach on 10,676 observations from 2670 sites. Our findings reveal prevalent joint effects of climatic conditions, plant N-use strategies, soil properties, and other natural and anthropogenic forcings on global soil δ15N. The joint effects of multiple drivers govern the latitudinal distribution of soil δ15N, with more rapid N cycling at lower latitudes than at higher latitudes. In contrast to previous climate-focused models, our data-driven model more accurately simulates spatial changes in global soil δ15N, highlighting the need to consider the joint effects of multiple drivers to estimate the Earth's N budget. These insights contribute to the reconciliation of discordances among empirical, theoretical, and modeling studies on soil N cycling, as well as sustainable N management.