Soil Microbial Abundance Research Articles

Dynamics of Soil N and P Nutrient Heterogeneity in Mixed Forest of Populus × Euramercana ‘Neva’ and Robinia pseucdoacacia in Coastal Saline–Alkali Land

The mixing of poplar and robinia in coastal saline land is a useful attempt at difficult site afforestation. Investigating the long–term mixing effects of nitrogen–fixing and non–nitrogen–fixing tree species on the spatial heterogeneity of N and P nutrients and their ecological stoichiometric characteristics in the coastal saline–alkali soil can provide a scientific basis for soil improvement and plantation management in the coastal saline–alkali soil. By replacing time with space, poplar and robinia mixed forests and corresponding pure forests with the ages of 3, 7 and 18 years were selected, and soil profiles of 0–20 cm, 20–40 cm and 40–60 cm were dug up to determine the contents of total nitrogen, hydrolyzed nitrogen, total phosphorus and available phosphorus, the activities of soil urease and phosphatase and the number of soil bacteria, fungi and actinomycetes in rhizosphere soil. The mixture of poplar and robinia and the increase in planting years led to the heterogeneity of soil N and P in a coastal saline–alkali forest, which could significantly increase the contents of soil total nitrogen, hydrolyzed nitrogen, total phosphorus and available phosphorus between soil layers. Compared with the pure forest of poplar and robinia at the same age, the soil urease activity in the 0–20 cm soil layer of an 18a poplar and robinia mixed forest increased by 94.75% and 73.36%, and the soil phosphatase activity increased by 30.36% and 70.27%. The mix of poplar and robinia significantly increased the abundance of soil microorganisms in saline–alkali soil. The number of bacteria, fungi and actinomycetes in the 0–20 cm soil layer of the 18a poplar and robinia mixed forest was the highest, which were 703,200, 31,297 and 1903, respectively. Redundancy analysis showed that there was a significant positive correlation between soil N and P nutrient contents, soil enzyme activities and microbial abundance. The soil depth of N and P nutrient decomposition and transformation in the mixed poplar and robinia plantation was expanded. The soil N and P nutrient contents, enzyme activities and microbial abundance in the 40–60 cm soil layer of the mixed forest were higher than those of the pure forest. With the increase in plantation years, the depth of soil that can be used in the forest land is increasing. The mixture of poplar and robinia plantation is an excellent choice for the construction of coastal saline–alkali land plantation, which has a significant mixed gain for the decomposition and transformation of N and P nutrients and increases the depth of the available soil layer in the forest land in coastal saline–alkali land. However, the coastal saline–alkali land soil N/P is < 14 and is still restricted by nitrogen, so the application of nitrogen fertilizer can be increased during the afforestation process.

Effects of energetic compounds on soil microbial communities and functional genes at a typical ammunition demolition site.

High concentrations of energetic compounds such as 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in military-contaminated sites pose a serious threat to human health and ecosystems. Better understanding about their effects on microbial diversity and functional genes in soil of ammunition demolition sites is required. In this study, the information of soil microbial community composition was obtained by macrogenome sequencing, and the impacts of energetic compounds on microbial community structure at the level of functional genes and enzymes based on Nr (Non-Redundant Protein Sequence Database), KEGG (Kyoto Encyclopedia of Genes and Genomes), CAZy (Carbohydrate-Active En-zymes Database) and other databases were discussed. The results showed that soil microbial diversity and functional gene abundance decreased significantly with the increase of the concentrations of energetic compounds. Conversely, the relative abundance of Proteobacteria increased significantly, reaching over 80% in the heavily TNT-contaminated area near explosive-waste water pool. Furthermore, functional gene analysis indicated that Proteobacteria had an advantage in degrading energetic compounds, and thus had the potential to improve the soil quality at ammunition demolition sites. This study provides a scientific basis for the future remediation and management of contaminated soils at ammunition demolition sites, as well as for the selection of efficient degraders of energetic compounds.

Effects of Rhizobium Inoculation on Rhizosphere Soil Microbial Communities, Physicochemical Properties, and Enzyme Activities in Caucasian Clover Under Field Conditions

Excessive use of chemical fertilizers in agriculture has become a major global source of pollution, leading to issues such as soil compaction, reduced fertility, eutrophication of water bodies, and air pollution. To address these challenges, the application of biofertilizers, such as rhizobial inoculants, has gradually become an effective, low-cost, and sustainable solution. In this study, the variety Trifolium ambiguum Bieb. (Mengnong clover No. 1) was used as the test material, and two rhizobial strains (R1 and R2) were employed for field inoculation trials. In April 2022, Caucasian clover was planted in an experimental field at Inner Mongolia Agricultural University. Each plot measured 3 m × 4 m and was arranged in a completely randomized design with three replications. In the regreening stage of 2023, rhizobial inoculation treatments were applied, with a control group included for comparison. This research examined the effects of rhizobial inoculation on the growth indicators of Caucasian clover, soil physicochemical properties, soil enzyme activities, and soil microbial communities. The results showed that rhizobial treatment increased the plant height and yield of Caucasian clover, improved soil physicochemical properties and enzyme activities, and positively affected soil microbial diversity and abundance. These changes enhanced soil fertility and optimized microbial community structure, promoting plant growth. The inoculation effect of strain R1 was superior to R2. In conclusion, rhizobial inoculants R1 and R2 can serve as effective biofertilizers for agricultural production.

Improving the Microenvironmental of Spring Soybean Culture and Increasing the Yield by Optimization of Water and Nitrogen

Optimizing water and nitrogen management is an effective measure to reduce nitrogen fertilizer loss and environmental pollution risks. This study aims to quantify the impacts of different water and nitrogen management strategies on the soil microenvironment and yield of spring soybeans in southern Xinjiang. In this study, two irrigation quotas were established: W1—36 mm (low water) and W2—45 mm (high water). Three nitrogen application gradients were established: low nitrogen (150 kg·hm−2, N1), medium nitrogen (225 kg·hm−2, N2), and high nitrogen (300 k kg·hm−2, N3). The analysis focused on soil physicochemical properties, enzyme activities, microbial community diversity, soybean yield, and soybean quality changes. The results indicate that the activities of nitrate reductase and urease, as well as total nitrogen content, increased with higher irrigation and nitrogen application rates. The W2N3 treatment significantly increased 0.15 to 4.39, 0.18 to 1.04, and 0.31 to 1.73 times. (p < 0.05). Alkaline protease and sucrase activities increased with higher irrigation amounts, while their response to nitrogen application exhibited an initial increase followed by a decrease. The W2N2 treatment significantly increased by 0.10 to 0.34 and 0.07 to 1.46 times (p < 0.05). Irrigation significantly affected the soil bacterial community structure, while the coupling effects of water and nitrogen notably influenced soil bacterial abundance (p < 0.05). Increases in irrigation and nitrogen application enhanced bacterial diversity and species abundance. Partial least squares path analysis indicated that water–nitrogen coupling directly influenced the soil microenvironment and indirectly produced positive effects on soybean yield and quality. An irrigation quota of 4500 m3 hm−2 and a nitrogen application rate of 300 kg·hm−2 can ensure soybean yield while enhancing soil microbial abundance. The findings provide insights into the response mechanisms of soil microbial communities in spring soybeans to water–nitrogen management, clarify the relationship between soil microenvironments and the yield and quality of spring soybeans, and identify optimal irrigation and fertilization strategies for high quality and yield. This research offers a theoretical basis and technical support for soybean cultivation in southern Xinjiang.

Cross-climatic comparison of microbial stress-responsive genes in urban parks: A comparative analysis

Understanding the distribution and abundance of microbial stress-related genes (SRGs) is crucial for unraveling the intricate dynamics of microbial communities and their responses to diverse environmental conditions. Despite the importance of these genes in shaping microbial adaptation and resilience, a comprehensive examination of their relative abundance across distinct climatic regions, such as boreal, temperate, and tropical environments, remains notably scarce in the existing literature. This study seeks to address this research gap by exploring and comparing the relative abundances of microbial SRGs using GeoChip 5.0 functional gene array in these three climatic regions. Our data indicate a greater relative abundance of SRGs such as nsrR, degP, cpxR, ahpF, Obg and cisD in the tropical region than in the other two regions whereas ecf and glnA showed higher abundance in both temperate and tropical regions in terms of reference forests and old parks. The distinct characteristics of the tropical biome are likely to influence both SRGs and the profile of SRG-hosts, consequently enhancing soil microbial abundances. Moreover, multivariate analyses unveiled distinct SRG profiles in urban parks and climatic regions. Additionally, we explored the influence of plant functional types (recalcitrant and labile tree litter, lawn) on SRGs. The impact of vegetation type on SRGs was not statistically significant, except in the tropical region, where its influence was notably pronounced compared to the boreal and temperate regions. Furthermore, several genes (nsrR, degP, cpxR, degS, dnaK, Obg, cisD, and glnA) were more prevalent in old parks when compared to young parks in all three climatic regions. However, urban parks displayed a significantly elevated abundance of SRGs compared to forest areas. This study provides new insights into the prevalence of SRGs across different climatic regions, enhancing our understanding of their dynamics in both human-influenced environments and pristine habitats.

Response of Long-Term Water and Phosphorus of Wheat to Soil Microorganisms

Phosphorus deficiency critically constrains crop growth. Soil microbial diversity, which is crucial for maintaining terrestrial ecosystem integrity, plays a key role in promoting soil P cycling. Therefore, it is imperative to understand the survival strategies of microorganisms under P-limited conditions and explore their roles in community regulation. We initiated a comprehensive, long-term, in situ wheat field experiment to measure soil physicochemical properties, focusing on the different forms of soil inorganic P. Subsequently, 16S rRNA and ITS marker sequencing was employed to study changes in soil microbial abundance and community structure and predict functional alterations. The results showed that soil water and P deficiencies significantly affected wheat growth and development, soil physicochemical properties, and microbial diversity and function. Prolonged P deficiency lowered soil pH, significantly increasing phosphatase content (58%) under W1 (normal irrigation) conditions. Divalent calcium phosphate decreased significantly under W0 (lack of irrigation) and W1 conditions, and the most stable ten-valent calcium phosphate began to transform under W0 conditions. Soil microbial diversity increased (e.g., Proteobacteria and Vicinamibacterales) and enhanced the transport capacity of bacteria. P deficiency affected the coexistence networks between bacteria and fungi, and SEM (structural equation modeling) analysis revealed a stronger correlation in bacteria (r2 = 0.234) than in fungi (r2 = 0.172). In soils deprived of P for 7 years, the soil P content and forms were coupled with microbial changes. Microorganisms exhibited community and functional changes in response to low-phosphorus soil, concurrently influencing soil P status. This study enhances our understanding of rhizospheric processes in soil P cycling under microbial feedback, particularly the impact of microbial interactions on changes in soil P forms under P-limited conditions.

Denitrifying Anaerobic Methane Oxidation Activity and Microbial Mechanisms in Riparian Zone Soils of the Yulin River, a Tributary of the Three Gorges Reservoir

Riparian zones are recognized as major sources of greenhouse gas emissions, particularly methane (CH4). Denitrifying anaerobic methane oxidation (DAMO) has garnered growing attention due to its significant contribution to mitigating CH4 emissions in wetland environments. Nonetheless, the specific role and microbial mechanisms of DAMO in controlling CH4 release within riparian zones are still not well comprehended. This study employed isotopic labeling experiments to measure the nitrate-dependent anaerobic methane oxidation (NaDAMO) and nitrite-dependent anaerobic methane oxidation (NiDAMO) potential of soil samples from riparian zones that were collected during different hydrological cycles. Moreover, soil physicochemical properties, DAMO activity, and microbial abundance were integrated to analyze the key factors and mechanisms influencing DAMO in riparian zone soils. The isotope tracer results showed that NaDAMO activities (1.4–11.93 nmol 13CO2 g-1day-1) were significantly higher than NiDAMO activities (0.66–9.19 nmol 13CO2 g-1day-1) in the riparian zone (p<0.05). NiDAMO activities were more strongly influenced by hydrological variations compared to NaDAMO activities, exhibiting higher levels during the discharge period (2.78–9.19 nmol 13CO2 g-1day-1) compared to the impoundment period (0.66–4.10 nmol 13CO2 g-1day-1). The qPCR analysis showed that the gene copies of NaDAMO archaeal mcrA (107 copies g-1) were approximately ten times greater than those of NiDAMO bacterial pmoA (106 copies g-1) in the majority of the sampling sites. Correlation analyses revealed that NiDAMO activity was influenced by soil pH (p<0.05), while NaDAMO microbes were influenced by temperature, organic carbon, and ammonia nitrogen concentrations (p<0.05). In summary, this research explored how hydrological changes in the riparian zone influence DAMO activities and their underlying mechanisms, providing a theoretical basis for mitigating CH4 emissions in riparian zones of reservoir regions.

Effects of soil acidification on humus, electric charge, and bacterial community diversity.

Soil acidification due to the long-term application of nitrogenous fertilizers and the consequent impact on crop growth have been frequently reported. The effects of acidification on soil humus, charge, and microbial communities need to be studied. In this experiment, fertilizer drenching was used to simulate the effects of multiple years of fertilizer application on the black soil. The results showed that 25years of soil acidification treatment resulted in a decrease of 8.97% in the content of stable humus and led to a decrease of 58% and 51.18% in the humic acid (HA) content and degree of humification (PQ) value in stable humus, respectively. In addition, soil acidification leads to a significant decrease in total negative charge (CEC8.2) and variable negative charge (CECv), with both decreasing by 63.28% and 88.67%, respectively, at 25years. Acidification treatments affected both soil microbial community abundance and diversity, with a significant decrease in Acidobacteriota and Gemmatimonadota abundance and an increase in Bacteroidia abundance and Acidobacteriota abundance at 25years.

No-Till and Crop Rotation Are Promising Practices to Enhance Soil Health in Cotton-Producing Semiarid Regions: Insights from Citizen Science

This on-farm study was conducted to assess the impact of six prevalent crop management practices adopted by growers in West Texas on various indicators of soil health. This study is a part of a citizen science project, where we collaborated with cotton growers who helped with standardized sample and data collection from 2017 to 2022. This project aimed to identify soil management practices that increase carbon sequestration, enhance biological activities, and improve overall soil health. We monitored soil moisture, soil organic matter (SOM), inorganic nitrogen (NH4+-N and NO3−-N) and other exchangeable nutrients, and soil microbial abundances as obtained via fatty acid methyl ester (FAME) in 85 fields, incorporating different management practices during the cotton growing season. In our study, volumetric moisture content (VWC) was increased by no-till, irrigation, and crop rotation, but the addition of residue decreased VWC. No-till, irrigation, and crop rotation increased SOM, but a cover crop decreased SOM. No-till and residue retention also increased microbial biomass carbon (MBC). Tillage, irrigation, and crop rotation influenced the abundance of the main microbial groups, including bacterial, fungi, and arbuscular mycorrhizal fungi (AMF). Additionally, water content, SOM, and microbial abundances are correlated with clay percentage. Our results indicate that no-till and crop rotation are the two most crucial soil management approaches for sustainable soil health. As such, implementing both no-till and crop rotation in the cropping systems has the most promising potential to increase the soil resilience in dryland cotton production in semiarid regions, thereby helping growers to maintain cotton production.

The combined nitrogen and phosphorus fertilizer application reduced soil multifunctionality in Qinghai-Tibet plateau grasslands, China

The impact of nitrogen (N) and phosphorus (P) fertilizer inputs on soil nutrient cycling and ecological function processes has garnered significant attention. Soil multifunctionality primarily refers to the soil's ability to perform multiple functions simultaneously, particularly the functions related to the genes involved in carbon (C), nitrogen (N), and phosphorus (P) cycles, which are critical for ecosystem sustainability. Despite this, the effects of N and P fertilizers on the expression of genes involved in soil carbon (C), nitrogen (N), and phosphorus (P) cycles, and their consequent influence on soil multifunctionality, remain unclear. To investigate this, we conducted a long-term nine-year experiment. The experimental site was fenced to prevent grazing and included four treatments: Control (no fertilizer), N (10 g N m−2 y−1, urea), P (5 g P m−2 y−1, Ca(H2PO4)2), and NP (10 g N and 5 g P m−2 y−1, urea and Ca(H2PO4)2). We examined the effects of these treatments on soil microbial functional gene abundance and multifunctionality. Our findings revealed that N addition altered the composition of soil microbial functional genes but did not affect functional diversity. Both N and P inputs, as well as their combination, negatively impacted soil carbon fixation and the genes encoding enzymes for the degradation of starch, hemicellulose, cellulose, and chitin. N input also disrupted soil nitrogen and phosphorus cycling by inhibiting the expression of soil denitrification genes (nirS and nosZ), phytate hydrolase gene (cphy), and a phosphatase gene (phoD). Additionally, P input significantly inhibited functional genes involved in soil nitrification, denitrification, ammonification, nitrogen fixation, and ammonia oxidation processes. It also adversely affected phytate synthesis and degradation. The combined N and P inputs had a substantial negative impact on soil nitrification (hao), denitrification (narG, nirK, nirS, and norZ), ammonification (gdh), nitrogen fixation, annamox, and nitrogen reduction, and inhibited the expression of soil phosphorus cycle genes. Long-term phosphorus application was found to have a more detrimental effect on soil multifunctionality compared to nitrogen application. Furthermore, our study showed that vegetation diversity and abundance are crucial drivers of soil carbon, nitrogen, and phosphorus cycling functional genes and multifunctionality. We concluded that N and P inputs alter soil multifunctionality by influencing vegetation diversity; therefore, maintaining vegetation diversity is essential for sustaining soil multifunctionality.

Influence of various organic nutrient management technologies on microbial abundance, growth, and yield of rice (Oryza sativa L.) under field conditions

A field study (three years) was carried out to evaluate the outcome of various organic nutrient management technologies including farmyard manure (FYM) and poultry manure (PM) integrated with chemical fertilizers for microbial dynamics and growth and yield of rice at Experimental Farm of Nuclear Institute of Agriculture (NIA), Tandojam, Sindh, Pakistan. The most broadly grown rice variety, NIA-Shandar was selected for this study. The experiment involved integrating organic technologies, specifically Farm Yard Manure (FYM) and Poultry Manure (PM), each applied at 10 tons per hectare. These organic technologies were combined with varying levels of inorganic fertilizers: half (60 kg N ha-1 and 45 kg P2O5 ha-1) and full (120 kg N ha-1 and 90 kg P2O5 ha-1) recommended doses. Additionally, zinc was applied at 10 kg ha-1. The study employed a randomized complete block design (RCBD) with three replications to assess treatment effects. Both organic technologies perform better for microbial dynamics and rice growth and yield enhancement either alone technology or combined with chemical fertilizers during three rice seasons. The maximum general microbial abundance (9.70 log10 CFU g soil-1), N2 fixing (7.37 log10 CFU g soil-1), P solubilizing (7.97 log10 CFU g soil-1) and Zn solubilizing(6.75 log10 CFU g soil-1) population was recorded in FYM alone or with half N and P2O5 fertilizer application. The highest plant height (106 cm), tiller numbers(17.10), panicle numbers (26.53), panicle length (26.32 cm), one thousand grainweight (26.53 g) and rice grain yield (7.92 t ha-1) were perceived in FYM with full rate N and P2O5 fertilizer application. Both technologies along with chemical fertilizer induced soil properties and soil nutrients which reflected to increase soil microbial abundance and growth and yield of rice however, FYM showed higher potential than poultry manure during the three years rice cultivation seasons. Hence, it was indicated that a significant contribution to the development of sustainable agricultural technologies that prioritize soil health,environmental stewardship, and food security.

Metagenomic Analysis to Assess the Impact of Plant Growth-Promoting Rhizobacteria on Peanut (Arachis hypogaea L.) Crop Production and Soil Enzymes and Microbial Diversity.

Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.

Carbendazim adsorption on polyethylene microplastics and the toxicity mechanisms on cotton plants, soil enzyme activity and rhizosphere bacterial community under combined stress conditions

Polyethylene (PE) and carbendazim are common pollutants in soil, and their individual toxicities have been widely studied. However, there are few reports on PE as a carrier for carbendazim and their combined toxicity to plants and soil. Therefore, in this study, we focused on the adsorption effects of different PE particle sizes (25 μm, 150 μm) at different concentrations (1 %, 5 %, m/m) on carbendazim (2.0 mg·kg−1, 5.0 mg·kg−1) and the combined toxicity to cotton and soil microbiota. The results showed that the carbendazim adsorption by PE followed secondary kinetics and was consistent with the Freundlich model. Due to adsorption, the half-life of carbendazim in soil was extended (from 6.31 d to 14.20 d), and the capacity of carbendazim to control cotton Verticillium wilt was weakened. Combined stress exacerbated the inhibitory effects on cotton biomass, chlorophyll content, soil enzyme activity compared to the individual carbendazim or PE treatments. The high-throughput sequencing analysis indicated that combined stress (5.0 mg·kg−1 carbendazim, 5 % 25 μm PE) significantly reduced the richness and diversity, changed the structural composition of rhizosphere soil bacterial community, and greatly increased the abundance of bacteria with potential degrading functions, such as Marmoricola. Functional and network analysis showed that combined stress altered the soil microbial function and abundance, as well as the network structure and key bacterial groups, decreased the number of positively correlated connections. This study provides a theoretical basis for evaluating the effects of combined PE and carbendazim stress on crops and soils.

Untargeted Metabolomics and Soil Community Metagenomics Analyses Combined with Machine Learning Evaluation Uncover Geographic Differences in Ginseng from Different Locations.

Panax ginseng C.A. Meyer, known as the "King of Herbs," has been used as a nutritional supplement for both food and medicine with the functions of relieving fatigue and improving immunity for thousands of years in China. In agricultural planting, soil environments of different geographical origins lead to obvious differences in the quality of ginseng, but the potential mechanism of the differences remains unclear. In this study, 20 key differential metabolites, including ginsenoside Rb1, glucose 6-phosphate, etc., were found in ginseng from 10 locations in China using an ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS)-untargeted metabolomics approach. The soil properties were analyzed and combined with metagenomics technology to explore the possible relationships among microbial elements in planting soil. Through Spearman correlation analysis, it was found that the top 10 microbial colonies with the highest abundance in the soil were significantly correlated with key metabolites. In addition, the relationship model established by the random forest algorithm and the quantitative relationship between soil microbial abundance and ginseng metabolites were successfully predicted. The XGboost model was used to determine 20(R)-ginseng Rg2 and 2'(R)-ginseng Rg3 as feature labeled metabolites, and the optimal ginseng production area was discovered. These results prove that the accumulation of metabolites in ginseng was influenced by microorganisms in the planting soil, which led to geographical differences in ginseng quality.

Impact of floods and landslides on rhizosphere bacterial communities: a high-throughput 16S rRNA gene sequencing study.

This study investigates the diversity and composition of soil bacterial communities in the rhizosphere of Attapadi and Nelliyampathy, prominent hill stations in Palakkad district, Kerala, India. The persistent flooding and landslides in 2018 and 2019 significantly impacted agricultural productivity in these regions. Utilizing high-throughput 16S rRNA gene sequencing (Illumina MiSeq), we conducted a comprehensive analysis of soil samples. Correlative assessments between soil parameters and microbial relative abundance at the phylum level revealed noteworthy positive associations. Notably, nitrogen (N) exhibited a positive relation with Crenarchaeota, Chloroflexi, Actinobacteriota, and Acidobacteriota; pH correlated with Firmicutes; organic carbon (OC) with WPS-2; and phosphorous with Proteobacteria. A total of 31,402 operational taxonomic units (OTUs) were identified, with the highest feature counts observed in undisturbed soils from Attapadi (AUD) and Nelliyampathy (NUD) (13,007 and 12,915, respectively). Disturbed soils in Nelliyampathy (ND) and Attapadi (AD) displayed a substantial decline in microbial diversity and composition, harbouring 1409 and 4071 OTUs, respectively. Alpha and beta diversity indices further underscored the more severe impairment of ND soils compared to AD soils. Interestingly, a majority of ND samples were landslide-affected (four out of five), while flood-affected soils accounted for four out of six AD samples. This indicates that landslides exert a more pronounced impact on microbial diversity and composition than floods. The observed decline in microbial count, composition, and diversity, even after 2years of the disaster, raises concerns about potential threats to agricultural output. The findings emphasize the need for corrective measures, including the incorporation of microbial inoculum, to restore soil fertility in post-disaster landscapes.

Assessment of nematode and microbial diversity and screening of entomopathogens in revegetated post-coal-mining land in Kutai Kartanegara District, East Kalimantan, Indonesia

Abstract. Sopialena, Rosfiansyah, Suryadi A. 2024. Assessment of nematode and microbial diversity and screening of entomopathogens in revegetated post-coal-mining land in Kutai Kartanegara District, East Kalimantan, Indonesia. Biodiversitas 25: 2921-2930. Post-coal-mining management should strive toward site revegetation. The success of such revegetation efforts is largely determined by the soil's fertility status, which encompasses physical, chemical, and biological components. Biological fertility is indicated by the presence and abundance of soil microbes and nematodes. The objective of this study was to identify the diversity of nematodes and soil microbes in ex-coal-mining land revegetated with oil palm in Kutai Kartanegara District (East Kalimantan, Indonesia), to screen for entomopathogenic nematodes and microbes, and to analyze their relationships with the chemical fertility status of the land. As a control, non-mining land was also investigated. The results showed that microbial diversity and density (including fungi and bacteria) in the ex-coal-mining area were significantly lower compared to the control. Additionally, a decrease in microbial diversity and density was found in deeper soil layers of both post-mining and non-mining lands. In contrast, soil nematodes were more abundant in post-mining land, both in terms of diversity and density, and were also more plentiful in the deeper soil layers. Among the nematodes and microbes studied, only Heterorhabditis and Steinernema (nematodes), Trichoderma (fungi), and Bacillaceae (bacteria) were identified as entomopathogens, causing death in Tenebrio molitor L. larvae. Overall, soil fertility in ex-coal-mining land was observed to be lower, characterized by decreased soil pH, basic saturation, Soil Organic Carbon (SOC), and nutrient content, which contributed to a reduced microbial community compared to non-mining land.

Multiple cropping effectively increases soil bacterial diversity, community abundance and soil fertility of paddy fields

BackgroundCrop diversification is considered as an imperative approach for synchronizing the plant nutrient demands and soil nutrient availability. Taking two or more crops from the same field in one year is considered as multiple cropping. It improves the diversity and abundance of soil microbes, thereby improving the growth and yield of crops. Therefore, the present study was conducted to explore the effects of different multiple winter cropping on soil microbial communities in paddy fields. In this study, eight rice cropping patterns from two multiple cropping systems with three different winter crops, including Chinese milk vetch (CMV), rape, and wheat were selected. The effects of different multiple winter cropping on soil microbial abundance, community structure, and diversity in paddy fields were studied by 16 S rRNA high-throughput sequencing and real-time fluorescence quantitative polymerase chain reaction (PCR).ResultsThe results showed that different multiple winter cropping increased the operational taxonomic units (OTUs), species richness, and community richness index of the bacterial community in 0 ~ 20 cm soil layer. Moreover, soil physical and chemical properties of different multiple cropping patterns also affected the diversity and abundance of microbial bacterial communities. The multiple cropping increased soil potassium and nitrogen content, which significantly affected the diversity and abundance of bacterial communities, and it also increased the overall paddy yield. Moreover, different winter cropping changed the population distribution of microorganisms, and Proteobacteria, Acidobacteria, Nitrospira, and Chloroflexi were identified as the most dominant groups. Multiple winter cropping, especially rape-early rice-late rice (TR) andChinese milk vetch- early rice-late rice (TC) enhanced the abundance of Proteobacteria, Acidobacteria, and Actinobacteria and decreased the relative abundance of Verrucomicrobia and Euryarchaeota.ConclusionIn conclusion, winter cropping of Chinese milk vetch and rape were beneficial to improve the soil fertility, bacteria diversity, abundance and rice yield.

Unveiling the Impact of Soil Prebiotics on Rhizospheric Microbial Functionality in Zea mays L.

Prebiotics, a subset of biostimulants, have garnered attention for their potential to enhance soil conditions and promote plant growth, offering a promising alternative to conventional agricultural inputs. This study explores how two commercial prebiotics, K1® and NUTRIGEO L® (SPK and SPN), impact soil functions compared to a control (SP). The experiment involved agricultural soil amended with organic wheat straws and cultivated with Zea mays L. Previous research demonstrated substantial effects of these prebiotics on plant biomass, soil parameters, and microbial community ten weeks after application. The present study delves deeper, focusing on soil microbial abundance, enzyme activities, and metabolic diversity. Analysis revealed that SPN notably increased the fungi-to-bacteria ratio, and both prebiotics elevated the activity of several key enzymes. SPN enhanced α-glucosidase and β-galactosidase activities, while SPK increased arylsulfatase, phosphatase, alkaline phosphatase, and urease activities. Enzymatic indexes confirmed the positive impact on soil functional diversity and fertility. Additionally, prebiotic treatments showed distinct metabolic profiles, with SPK degrading eleven carbon sources more rapidly across five groups and SPN accelerating the decomposition rate of four carbon sources from three groups. These findings highlight the ability of prebiotics to shape microbial communities and enhance soil fertility by modulating their functional activity and diversity.

Permaculture Management of Arable Soil Increases Soil Microbial Abundance, Nutrients, and Carbon Stocks Compared to Conventional Agriculture

Conventional agricultural practices severely deplete the soil of essential organic matter and nutrients, increasing its vulnerability to disease, drought, and flooding. Permaculture is a form of agroecology adopting a whole ecosystem approach to create a set of principles and design frameworks for enriching soil fertility, but there is little scientific evidence of its efficiency. This study compares two permaculture managed sites with a conventional arable site to investigate the effect of permaculture management on soil fertility. We used phospholipid fatty acid analysis to estimate microbial abundance and diversity and related these to measured soil nutrients and carbon stocks. The potential of permaculture management to mitigate soil greenhouse gas emissions was assessed during a laboratory soil incubation and measurement of greenhouse gases via gas chromatography. Overall, the permaculture managed allotments had three times higher microbial biomass, one and a half times higher nitrogen, and four times higher carbon content than the arable site. Permaculture soils had larger carbon dioxide and nitrous oxide fluxes compared to arable soil, but all sites had a mean negative flux in methane. Permaculture management by use of organic amendments and no-dig practices provides a constant slow release of nutrients and build-up of organic matter and carbon and consequently promotes greater bacterial and fungal biomass within the soil.

Impacts of Climate change on soil microbial diversity, distribution and abundance

Climate change, driven by anthropogenic activities, has far-reaching consequences for our planet. Among its many impacts, changes in temperature, elevated carbon dioxide levels, and shifts in greenhouse gas concentrations significantly affect soil ecosystems. In particular, soil microbial communities play a pivotal role in nutrient cycling, organic matter decomposition, and overall soil health. Soil microbial communities respond differently to the effects of climate change, like elevated warming and precipitation. The change in climatic conditions is reported to be adversely affecting soil biological activity directly through either drying or wetting of soil or affecting their associated plants. This review delves into the intricate relationship between climate change and soil microbial abundance, diversity, and distribution. The paper also discusses climatic change pressure on soil enzymatic activity and microbial biomasses, as well as soil faunal activity, as they are key indicators of soil health in a changing climate. Soil microbial communities cope with climate change by changing their diversity and physiological characteristics and by changing their symbiotic plants, which indicates the role of soil microbes in withstanding the negative impact of climate change.