Composted biochar affects structural dynamics, function and co-occurrence network patterns of fungi community

Enhancing mango yield and soil health with organic and slow-release fertilizers: A multifaceted evaluation

Excessive utilization of chemical fertilizers in mango orchards not only hampers the attainment of sustainable harvests but also poses significant ecological detriments. This investigation proposes a promising solution by advocating the judicious replacement of chemical fertilizers with organic fertilizer (OF) and slow-release fertilizer (SRF), with potential to bolster soil health and augment crop productivity. In light of the promise held by these alternatives, it is imperative to establish detailed fertilization protocols for enhanced sustainable practices in mango farming. This two-year field study employed a comprehensive suite of seven fertilization strategies, unveiling that a 25 % chemical fertilizers substitution with OF and SRF improved mango yields by 12.5 % and 11.3 %, respectively, over standard practices. Additionally, these approaches substantially augmented the nutritional quality of mangoes, evident from Vitamin C enhancements of 53.9 % to 56.9 %, and improvements in sugar-to-acid ratio (19.2 %-30.3 %) and solid-to-acid ratio (12.1 %-25.3 %). Notably, the application of OF and SRF led to increased leaf nitrogen and phosphorus concentrations, while simultaneously reducing soil phosphorus and potassium levels. Furthermore, these fertilizers fostered the growth of beneficial soil microorganisms, namely Actinobacteria and Proteobacteria, and strengthened the synergy within the soil bacterial community, hence optimizing bacterial competition and nutrient cycling. The study proposes that the adoption of OF or SRF can effectively regulate soil nutrient balance, promote resilient and functional soil bacterial ecosystems, and ultimately improve mango yield and fruit quality. It recommends a fertilization scheme incorporating 25 % organic or slow-release nitrogen to align with ecological sustainability goals, promoting a more vigorous and resilient soil and crop system.

Mechanisms of heavy metal-induced rhizosphere changes and crop metabolic evolution: The role of carbon materials

To investigate the effects of modified carbon-based materials on soil environmental remediation and crop physiological regulation, this research relied on rice pots with lead (Pb) and cadmium (Cd) composite contamination. Dolomite, montmorillonite, attapulgite and sepiolite modified biochar with different doses have been developed to explore the mechanisms on heavy metal passivation, nutrient improvement, microbial activation, and crop growth. The results indicated that the modified materials effectively reduced heavy metal bioavailability and accumulation in plant tissues through adsorption complexation. Specifically, under montmorillonite and sepiolite modified treatments, the Grains-Pb content significantly decreased by 29.23-30.31% and 27.49-30.58%, compared to the control group (CK). Meantime, carbon-based materials increased available nutrient levels, providing a biological substrate for soil microorganisms metabolism. The content of ammonium nitrogen (NH4+-N) and available phosphorus (AP) in different proportions of montmorillonite modified biochar increased by 10.99-13.98% and 55.76-77.86%, respectively, compared to CK. Furthermore, sepiolite modified biochar enhanced bacterial community diversity, significantly improving the tolerance and resistance of bacterial communities such as Proteobacteria and Acidobacteria to heavy metals. Meanwhile, carbon-based materials enhanced community stability and network complexity, improving microbial stress resistance to adverse environments. In summary, montmorillonite and sepiolite modified biochar regulated microbial community interaction mechanisms by mitigating the physiological toxicity of heavy metals. This process enhanced soil available nutrients and ecological function stability, which had significant implications for improving crop growth and quality.

Biochar amendment affects the microbial genetic profile of the soil, its community structure and phospholipid fatty acid contents

Biochar (BC) amendment has been proposed as a promising strategy for mitigating greenhouse gas (GHG) emissions, specifically carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Conducting a meta-analysis to evaluate the impact of biochar on microbial genetic profile, community structure, and phospholipid fatty acid (PLFA) contents can aid in identifying key microbial groups involved in GHG production and consumption, and assessing the overall effectiveness of biochar in reducing GHG emissions. The present meta-analysis revealed that the addition of biochar resulted in a 22 % and 41 % reduction in pmoA and mcrA genes of methanogenic microorganisms, respectively. The mcrA/pmoA ratio significantly increased by 81 %. Gene abundances exhibited a positive response to biochar amendment, with increases observed in nifH, nirK, nirS, nosZ, and nosZ (nirS + nirK) genes by 13 %, 32 %, 37 %, 42 %, and 79 %, respectively. Moreover, biochar amendment influenced the microbial community structure accordingly. The concentration of PLFAs increased in response to BC treatment in the following order: A-bacteria (+49 %) < Fungi (+30 %) < Gram-pb (+21 %) < G-bacteria (+17 %) < Gram-nb (+11 %). These findings indicate that biochar amendment shapes the microbial community structure, further emphasizing its significance in enhancing soil fertility.

Upgrade from aerated static pile to agitated bed systems promotes lignocellulose degradation in large-scale composting through enhanced microbial functional diversity

Composting presents a viable management solution for lignocellulose-rich municipal solid waste. However, our understanding about the microbial metabolic mechanisms involved in the biodegradation of lignocellulose, particularly in industrial-scale composting plants, remains limited. This study employed metaproteomics to compare the impact of upgrading from aerated static pile (ASP) to agitated bed (AB) systems on physicochemical parameters, lignocellulose biodegradation, and microbial metabolic pathways during large-scale biowaste composting process, marking the first investigation of its kind. The degradation rates of lignocellulose including cellulose, hemicellulose, and lignin were significantly higher in AB (8.21%-32.54%, 10.21%-39.41%, and 6.21%-26.78%) than those (5.72%-23.15%, 7.01%-33.26%, and 4.79%-19.76%) in ASP at three thermal stages, respectively. The AB system in comparison to ASP increased the carbohydrate-active enzymes (CAZymes) abundance and production of the three essential enzymes required for lignocellulose decomposition involving a mixture of bacteria and fungi (i.e., Actinobacteria, Bacilli, Sordariomycetes and Eurotiomycetes). Conversely, ASP primarily produced exoglucanase and β-glucosidase via fungi (i.e., Ascomycota). Moreover, AB effectively mitigated microbial stress caused by acetic acid accumulation by regulating the key enzymes involved in acetate conversion, including acetyl-coenzyme A synthetase and acetate kinase. Overall, the AB upgraded from ASP facilitated the lignocellulose degradation and fostered more diverse functional microbial communities in large-scale composting. Our findings offer a valuable scientific basis to guide the engineering feasibility and environmental sustainability for large-scale industrial composting plants for treating lignocellulose-rich waste. These findings have important implications for establishing green sustainable development models (e.g., a circular economy based on material recovery) and for achieving sustainable development goals.

Soil microbial community construction under revegetation in newly created land

Revegetation represents the primary method for restoring the ecological balance of the Loess Plateau. The assessment of revegetation efficacy on degraded lands can be facilitated through the utilization of soil microorganisms as indicators. We chose Medicago sativa L. (MX), Trifolium repens L. (BSY), Festuca arundinacea Schreb. (GYM), Elymus dahuricus Turcz. (PJC) and natural grass (CK) as the research objects, the soil microbial community composition, function and co-occurrence patterns of the five treatments were analyzed. The results showed that the microbial community composition was similar among the different vegetation types, but there were differences in abundance. Bacteria were significantly correlated with OM, BD and sand. Fungi were significantly correlated with sand and BD. Notably, BD showed highly significant correlation with microbial communities (P < 0.001). Microbial function prediction was dominated by metabolism at the bacterial level, and fungal function was predicted with eight trophic types dominated by parthenogenetic trophic types, and the microbial function prediction analyses showed that in bacteria, BSY had a high abundance of gene functions, and in fungi, PJC had a high abundance of gene functions. Network analysis revealed that the microbial community had small-world characteristics, a modular structure and a non-random co-occurrence pattern. Bacterial interactions included both competition and cooperation, further suggesting that growing raw grass increased the stability of the bacterial community. Overall, our results elucidated the changes in microbial communities and their correlations after raw grass cultivation, which could provide a more comprehensive perspective on microbial community assembly, and provide a theoretical basis for future ecological restoration on the Loess Plateau.

Shifts in fungal community diversity and potential function under natural forest succession and planted forest restoration in the Kunyu Mountains, East China

Soil fungi participate in various ecosystem processes and are important factors driving the restoration of degraded forests. However, little is known about the changes in fungal diversity and potential functions under the development of different vegetation types during natural (secondary forest succession) and anthropogenic (reforestation) forest restoration. In this study, we selected typical forest succession sequences (including Pinus densiflora Siebold & Zucc., pine-broadleaf mixed forest of P. densiflora and Quercus acutissima Carruth., and Q. acutissima), as well as natural secondary deciduous broadleaved mixed forests and planted forests of Robinia pseudoacacia on Kunyu Mountain for analysis. We used ITS rRNA gene sequencing to characterize fungal communities and used the FUNGuild database to predict fungal functional groups. The results showed that forest succession affected fungal β-diversity, but not the α-diversity. There was a significant increase in Basidiomycota and a decrease in Ascomycota in the later successional stage, accompanied by an increase in the functional groups of ectomycorrhizal fungi (ECM). Conversely, planted forests exhibited decreased fungal α-diversity and altered community compositions, characterized by fewer Basidiomycota and more Ascomycota and Mucoromycota. Planted forests led to a decrease in the relative abundances of ECM and an increase in animal pathogens. The TK content was the major factor explaining the distinction in fungal communities among the three successional stages, whereas pH, AP, and NH4 + were the major factors explaining community variations between natural and planted forests. Changes in vegetation types significantly affected the diversity and functional groups of soil fungal communities during forest succession and reforestation, providing key insights for forest ecosystem management in temperate forests.

Synergistic enhancement of cadmium immobilization and soil fertility through biochar and artificial humic acid-assisted microbial-induced calcium carbonate precipitation

Microbially induced carbonate precipitation (MICP) is emerging as a favorable alternative to traditional soil remediation techniques for heavy metals, primarily due to its environmental friendliness. However, a significant challenge in using MICP for farmland is not only to immobilize heavy metals but also to concurrently enhance soil fertility. This study explores the innovative combination of artificial humic acid (A-HA), biochar (BC), and Sporosarcina pasteurii (S. pasteurii) to mitigate the bioavailability of cadmium (Cd) in contaminated agricultural soils through MICP. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that the integration of BC and A-HA significantly enhances Cd immobilization efficiency by co-precipitating with CaCO3. Moreover, this treatment also improved soil fertility and ecological functions, as evidenced by increases in total nitrogen (TN, 9.0-78.2 %), alkaline hydrolysis nitrogen (AN, 259.7-635.5 %), soil organic matter (SOM, 18.1-27.9 %), total organic carbon (TOC, 43.8-48.8 %), dissolved organic carbon (DOC, 36.0-88.4 %) and available potassium (AK, 176.2-193.3 %). Additionally, the relative abundance of dominant phyla such as Proteobacteria and Firmicutes significantly increased with the introduction of BC and A-HA in MICP. Consequently, the integration of BC and A-HA with MICP offers a promising solution for remediating Cd-contaminated agricultural soil and synergistically enhancing soil fertility.

Manure enriched with nitrogen derived from high-protein food waste in a large dining facility

Food waste (FW) from large dining facility has been a pressing environmental challenge in China recently. This study developed an innovative species-specific feeding strategy for producing pigeon meat and excellent manure from FW. Adding FW to the feed of pigeons significantly increased their feed intake and promoted their growth although the pigeons showed a strong aversion to the FW. We produced a "super manure" with exceptionally high nitrogen (N) content (mean = 10.77 % on a dry basis, 8.04-12.57 %, n = 264) by feeding slowly-growing pigeon species (Columba livia vs. and Caoge Huzhou 11) with protein-high commercial feed and FW. A significant negative relationship between the N and carbon (C) contents in the pigeon manure was found, with C depletion higher than N depletion. Furthermore, the N content in the anaerobic composting (AnC) manure was 29.16 % higher than that in the FW. Fourier transform infrared (FT-IR) analysis and stable isotopes δ13C and δ15N in the manure clearly identified the transformations of nutrients during pigeon feeding and the AnC process. This study opens a path for producing N-high manure using protein-high food waste.

Effects of oilfield-produced water discharge on the spatial patterns of microbial communities in arid soils

Recently intensified oil exploitation has resulted in the discharge of large amounts of wastewater containing high concentrations of organic matter and nutrients into the receiving aquatic and soil environments; however, the effects of oilfield-produced water on the soil microbiota are poorly understood. In this study, we conducted a comprehensive analysis to reveal the composition and diversity of the microbial community at horizontal and vertical scales in a typical arid soil receiving oilfield-produced water in Northwest China. Oilfield-produced water caused an increase in microbial diversity at the horizontal scale, and the communities in the topsoil were more variable than those in the subsoil. Additionally, the microbial taxonomic composition differed significantly between the near- and far-producing water soils, with Proteobacteria and Halobacterota dominating the water-affected and reference soil communities, respectively. Soil property analysis revealed that pH, salt, and total organic content influenced the bacterial communities. Furthermore, the oil-produced water promoted the complexity and modularity of distance-associated microbial networks, indicating positive interactions for soil ecosystem function, but not for irrigation or livestock watering. This is the first detailed examination of the microbial communities in soil receiving oilfield-produced water, providing new insights for understanding the microbial spatial distributions in receiving arid soils.

Dynamics of microbial functional guilds involved in the humification process during aerobic composting of chicken manure on an industrial scale

Proper composting treatment of poultry manure waste is recommended before its use as a fertilizer. This involves many bioprocesses driven by microorganisms. Therefore, it is important to understand microbial mechanisms behind these bioprocesses in manure composting systems. Many efforts have been made to study the microbial community structure and diversity in these systems using high-throughput sequencing techniques. However, the dynamics of microbial interaction and functionality, especially for key microbial functional guilds, are not yet fully understood. To address these knowledge gaps, we collected samples from a 150-day industrial chicken manure composting system and performed the microbial network analysis based on the sequencing data. We found that the family Bacillaceae and genus Bacillus might play important roles in organic matter biodegradation at the mesophilic/thermophilic phases. Genera Virgibacillus, Gracilibacillus, Nocardiopsis, Novibacillus, and Bacillaceae_BM62 were identified as the key ones for humic acid synthesis at the mature phases. These findings improve our understanding about the fundamental mechanisms behind manure composting and can aid the development of microbial agents to promote manure composting performance.

Humification and fungal community succession during pig manure composting: Membrane covering and mature compost addition

The objective of this study was to elucidate the combined effect of a semi-permeable membrane (M) and mature compost (MC) on humification and fungal community succession in pig manure composting. Compared with the control, the concentrations of humic substances (HSs) increased by 44.54 % (M + 15 % MC) and 43.90 % (M). During the thermophilic phase, Aspergillus (67.26 %) was the dominant genus in the M + 15 % MC treatment. Membrane covering increased the relative abundance (RA) of other phyla (except for Ascomycetes and Basidiomycetes) on the 14th day and Basidiomycetes on the 80th day in M treatment. Humic acid, HSs were positively correlated with the RA of genera Myceliophthora, Kernia, and Mycothermus. Myceliophthora was the key genus in the M + 15 % MC treatment on the 80th day. The results showed that 15 % MC addition under membrane covering optimizes the quality of composting products.

Straw Soil Conditioner Modulates Key Soil Microbes and Nutrient Dynamics across Different Maize Developmental Stages

Soil amendments may enhance crop yield and quality by increasing soil nutrient levels and improving nutrient absorption efficiency, potentially through beneficial microbial interactions. In this work, the effects of amending soil with straw-based carbon substrate (SCS), a novel biochar material, on soil nutrients, soil microbial communities, and maize yield were compared with those of soil amendment with conventional straw. The diversity and abundance of soil bacterial and fungal communities were significantly influenced by both the maize growth period and the treatment used. Regression analysis of microbial community variation indicated that Rhizobiales, Saccharimonadales, and Eurotiales were the bacterial and fungal taxa that exhibited a positive response to SCS amendment during the growth stages of maize. Members of these taxa break down organic matter to release nutrients that promote plant growth and yield. In the seedling and vegetative stages of maize growth, the abundance of Rhizobiales is positively correlated with the total nitrogen (TN) content in the soil. During the tasseling and physiological maturity stages of corn, the abundance of Saccharimonadales and Eurotiales is positively correlated with the content of total carbon (TC), total phosphorus (TP), and available phosphorus (AP) in the soil. The results suggest that specific beneficial microorganisms are recruited at different stages of maize growth to supply the nutrients required at each stage. This targeted recruitment strategy optimizes the availability of nutrients to plants and ultimately leads to higher yields. The identification of these key beneficial microorganisms may provide a theoretical basis for the targeted improvement of crop yield and soil quality. This study demonstrates that SCS amendment enhances soil nutrient content and crop yield compared with conventional straw incorporation and sheds light on the response of soil microorganisms to SCS amendment, providing valuable insights for the future implementation of this material.

Size matters: Powder biochar promotes the elimination of antibiotics resistance genes and potential hosts during swine manure composting

Livestock manure faced acute environmental pollution and ecology risky caused by antibiotic resistance genes (ARGs). This study investigated the effects of biochar particle size including powder biochar (75 μm, PB), and granular biochar (2 mm, GB) on ARGs variation during the aerobic composting. The results showed that the total relative abundance (RA) of the ARGs decreased significantly in all the treatments after composting. While compared to the removal efficiency of total RA in the control (CK), PB decreased by 90.99 % and GB increased by 93.25 %, and both PB and GB removed MGEs completely. Sulfonamide antibiotic resistance genes were the main contributor of the ARGs rebounding. PB addition could hinder the rebounding of sulfonamide antibiotic resistance genes during the later stage of the composting. Co-occurrence network analysis showed that the addition of biochar (both types) increased the complexity of the microbial community the competition of inter-phylum, which was indicated by the higher number of edge and density and lower positive connection. The different ARGs removal efficiency in these two treatments might be that PB promoted the competition both inter-phylum and potential hosts-other microbes, resulted in fewer kinds and abundance of ARGs hosts, while GB increased the stability of ARGs hosts making it more resistant to environment changes. Totally, compared with the global adjustment strategy of microbial communities, more exclusive methods focusing on the controlling of ARGs hosts should be explored to decrease the ecological risk of composting products during composting process.

Disentangling the impact of biogas slurry topdressing as a replacement for chemical fertilizers on soil bacterial and fungal community composition, functional characteristics, and co-occurrence networks

The application of biogas slurry topdressing with drip irrigation systems can compensate for the limitation of traditional solid organic fertilizer, which can only be applied at the bottom. Based on this, we attempted to define the response of soil bacterial and fungal communities of maize during the tasseling and full maturity stages, by using a no-topdressing control and different ratios of biogas slurry nitrogen in place of chemical fertilizer topdressing. The application of biogas slurry resulted in the emergence of new bacterial phyla led by Synergistota. Compared with pure urea chemical topdressing, the pure biogas slurry topdressing treatment significantly enriched Firmicutes and Basidiomycota communities during the tasseling stage, in addition to affecting the separation of bacterial and fungal α-diversity indices between the tasseling and full maturity stages. Based on the prediction of community composition and function, the changes in bacterial and fungal communities caused by biogas slurry treatment stimulated the ability of microorganisms to decompose refractory organic components, which was conducive to turnover in the soil carbon cycle, and improved multi-element (such as sulfur) cycles; however it may also bring potential risks of heavy metal and pathogenic microbial contamination. Notably, the biogas slurry treatment reduced the correlation and aggregation of bacterial and fungal symbiotic networks, and had a dual effect on ecological randomness. These findings contribute to a deeper comprehension of the alterations occurring in soil microbial communities when substituting chemical fertilizers treated with biogas slurry topdressing, and promote the efficient and sustainable utilization of biogas slurry resources.

Legacy effects of wheat season organic fertilizer addition on microbial co-occurrence networks, soil function, and yield of the subsequent maize season in a wheat-maize rotation system

Organic fertilizer can alleviate soil degradation. While numerous studies have explored the immediate impacts of organic fertilizer on soil properties and crop production, the legacy effects of organic fertilizer addition remain less understood. This research investigated the subsequent effects of organic fertilizer addition during the winter wheat season on soil microbial community structure, co-occurrence networks, soil function, and summer maize yield from 2018 to 2020. Six fertilization treatments were implemented as chemical nitrogen fertilizer (N) alone or combined sheep manure and nitrogen fertilizer (SMN) at low, medium, and high fertilization levels during the winter wheat season, with only N fertilizer applied during the maize season. The findings revealed significant variations in bacterial and fungal community structures between the SMN and N treatments. The SMN treatments increased the relative abundance of Proteobacteria, Actinobacteria, and Bacteroidetes and decreased the relative abundance of Rokubacteria, Acidobacteria, Gemmatimonadetes, Chloroflexi, and Nitrospirae compared to the N treatment. The SMN treatments had higher fungal network connectivity and lower mean path distance and modularity than the N treatment, resulting in heightened sensitivity of fungi to environmental changes. The legacy effects of organic fertilizer changed the functional potential of the N and C cycles, with keystone taxa such as Proteobacteria, Actinomycetes, Acidobacteria, Gemmatimonadetes, Bacteroides, and Ascomycota significantly correlating with functional genes related to the C and N cycles. Surprisingly, no significant differences in summer maize yield occurred between the SMN and N treatments. However, the random forest model revealed that the SMN treatments had significantly higher explanatory power of soil microbial community structure for maize yield (74.31%) than the N treatment (13.07%). These results were corroborated in subsequent studies and underscore the legacy effects of organic fertilizer addition on soil microbial communities. This research offers valuable insights into organic fertilizer use for enhancing soil quality and sustaining agricultural productivity.

Impact of Aerated Drip Irrigation and Nitrogen Application on Soil Properties, Soil Bacterial Communities and Agronomic Traits of Cucumber in a Greenhouse System

Root hypoxia stress and soil nutrient turnover have been related to reduced crop productivity. Aerated drip irrigation (ADI) can effectively enhance crop productivity and yield. However, the response of the soil bacterial community to different irrigation water dissolved oxygen (DO) concentrations remains elusive due to the extreme sensitivity of microorganisms to environmental variations. We investigated the effects of aerated irrigation with different concentrations of DO on soil properties and agronomic performance of cucumber, as well as the contribution of the bacterial community. We performed experiments on cucumber cultivation in Shouguang, China, including different irrigation methods (ADI: O2-10 and O3-20 mg L-1, non-aerated groundwater: O1-5 mg L-1) and nitrogen (N) application rates: 240 and 360 kg N ha-1. ADI (particularly O2) significantly improved soil properties, root growth, cucumber yields, and irrigation water use efficiency (IWUE), and appropriate DO concentrations reduced N fertilizer application and increased crop yields. Furthermore, these changes were associated with bacterial community diversity, aerobic bacteria abundance, and consolidated bacterial population stability within the network module. Environmental factors such as soil respiration rate (Rs), DO, and NO3--N have significant effects on bacterial communities. The FAPROTAX results demonstrated enhanced nitrification (Nitrospira) and aerobic nitrite oxidation by soil bacteria under ADI, promoting the accumulation of effective soil N and improved soil fertility and crop yield. Appropriate DO concentration is conducive to the involvement of soil bacterial communities in regulating soil properties and cucumber growth performance, which are vital for the sustainable development of facility agriculture.

Biochar and Chlorella increase rice yield by improving saline-alkali soil physicochemical properties and regulating bacteria under aquaculture wastewater irrigation

The combined effects of biochar and Chlorella under aquaculture wastewater irrigation in improving saline-alkali soil physicochemical properties, microbial communities, and rice yield, is not yet clear. This study utilized soil physicochemical indicators and gene sequencing to examine the effect of salinity stress, biochar and Chlorella under aquaculture wastewater irrigation on soil properties, bacterial community compositions, and rice production. Treatments included three factors in a randomized complete block design with three replications: (i) Biochar - 40 tons ha -1 (BW) versus no-biochar (BN); (ii) Salinity - 3‰ salinity (SH) versus 1‰ salinity (SL); and (iii) Chlorella - with 107 cells mL -1 Chlorella (CW) versus no-Chlorella (CN). The results revealed that increased salinity adversely affected the soil nutrients (TOC, NO3⁻-N, NH4+-N, Olsen-P), and enzyme activity (urease, sucrase, catalase), resulting in a 9.67% reduction in rice yield compared to SL treatment. However, the close correlation between alterations in soil bacterial communities, functions, and soil physicochemical properties, as well as rice yield, indicated that biochar and Chlorella promoted rice yield by enhancing the physicochemical properties of saline-alkali soil and bacterial community when irrigated with aquaculture wastewater: (1) addition of biochar increased the146.05% rice yield by increasing TOC content, the complexity of bacterial co-occurrence patterns, nitrogen fixation potential, and nitrification potential, (2) addition of Chlorella increased TOC, NO3⁻-N, NH4+-N, enhanced urease, sucrase, catalase activity, and nitrification potential to increased rice yield by 60.29%, and (3) compared with the treatment T3 (SHBNCN), the treatments with biochar (BW) and Chlorella (CW) increased the yield by 561.30% and 445.03% under 1‰ and 3‰ salinity, respectively. These findings provide novel perspectives on the capacity of biochar and Chlorella to improve saline-alkali soil properties and increase rice yield irrigated with aquaculture wastewater.

Sulfur-aided aerobic biostabilization of swine manure and sawdust mixture: Humification and carbon loss

To investigate how sulfur addition affects humification and carbon loss during swine manure (SM) biostabilisation, various proportions of sulfur, i.e., 0 (CK), 0.2%-0.8% (S1-S4) were added to SM in a 70-day pilot-scale test. Compared to CK (16.07%), sulfur addition resulted in the mineralization of 17.05%-24.27% of the total organic carbon. Sulfur addition also reduced CH4 emissions, which were 3.7%-29.3% lower than that of CK. The total global warming potential values were in the range of 913.1-968.2 g CO2 eq kg-1 for all treatments. Although the sulfur-added treatments showed lower HA/FA ratios than CK after 70 days, no significant impact on the maturity of the final products was observed. Sulfur addition impacted the microbial community, CH4, CO2, N2O emissions, and affected the variation of temperature in biowaste biostabilization. These discoveries provided an important basis for understanding the function of sulfur in regulating the aerobic bio-decomposition of organic waste.

Influence of biochar on succession of fungal communities during food waste composting

This study aims to examine the effects of biochar on fungal dynamics during food waste composting. The different dosage of wheat straw biochar from 0 to 15% (0%, 2.5%, 5%, 7.5%, 10%, and 15%) were used as an additive to composting and examined for 42 days. The results showed that Ascomycota (94.64%) and Basidiomycota (5.36%) were the most dominant phyla. The most common fungal genera were Kluyveromyces (3.76%), Candida (5.34%), Trichoderma (2.30%), Fusarium (0.46%), Mycothermus-thermophilus (5.67%), Trametes (0.46%), and Trichosporon (3.38%). The average number of operational taxonomic units were 469, with the greatest abundance seen in the 7.5% and 10% treatments. Redundancy analysis revealed that different concentrations of biochar applied treatments have significantly distinct fungal communities. Additionally, correlation analyses of fungal interactions with environmental elements, performed through a heatmap, also indicate a distinct difference among the treatments. The study clearly demonstrates that 15% of biochar has a positive impact on fungal diversity and improves the food waste composting.

Investigation of underlying links between nitrogen transformation and microorganisms' network modularity in the novel static aerobic composting of dairy manure by "stepwise verification interaction analysis"

Conventional composting is a viable method treating agricultural solid waste, and microorganisms and nitrogen transformation are the two major components of this proces. Unfortunately, conventional composting is time-consuming and laborious, and limited efforts have been made to mitigate these problems. Herein, a novel static aerobic composting technology (NSACT) was developed and employed for the composting of cow manure and rice straw mixtures. During the composting process, physicochemical parameters were analyzed to evaluate the quality of compost products, and microbial abundance dynamics were determined using high-throughput sequencing technique. The results showed that NSACT achieved compost maturity within 17 days as the thermophilic stage (≥55 °C) lasted for 11 days. GI, pH, and C/N were 98.71 %, 8.38, and 19.67 in the top layer, 92.32 %, 8.24, and 22.38 in the middle layer, 102.08 %, 8.33, and 19.95 in the bottom layer. These observations indicate compost products maturated and met the requirements of current legislation. Compared with fungi, bacterial communities dominated NSACT composting system. Based on the stepwise verification interaction analysis (SVIA), the novel combination utilization of multiple statistical analyses (Spearman, RDA/CCA, Network modularity, and Path analyses), bacterial genera Norank Anaerolineaceae (-0.9279*), norank Gemmatimonadetes (1.1959*), norank Acidobacteria (0.6137**) and unclassified Proteobacteria (-0.7998*), and fungi genera Myriococcum thermophilum (-0.0445), unclassified Sordariales (-0.0828*), unclassified Lasiosphaeriaceae (-0.4174**), and Coprinopsis calospora (-0.3453*) were the identified key microbial taxa affecting NH₄⁺-N, NO₃^--N, TKN and C/N transformation in the NSACT composting matrix respectively. This work revealed that NSACT successfully managed cow manure-rice straw wastes and significantly shorten the composting period. Interestingly, most microorganisms observed in this composting matrix acted in a synergistic manner, promoting nitrogen transformation.

How does the pattern of root metabolites regulating beneficial microorganisms change with different grazing pressures?

Grazing disturbance can change the structure of plant rhizosphere microbial communities and thereby alter the feedback to promote plant growth or induce plant defenses. However, little is known about how such changes occur and vary under different grazing pressures or the roles of root metabolites in altering the composition of rhizosphere microbial communities. In this study, the effects of different grazing pressures on the composition of microbial communities were investigated, and the mechanisms by which different grazing pressures changed rhizosphere microbiomes were explored with metabolomics. Grazing changed composition, functions, and co-expression networks of microbial communities. Under light grazing (LG), some saprophytic fungi, such as Lentinus sp., Ramichloridium sp., Ascobolus sp. and Hyphoderma sp., were significantly enriched, whereas under heavy grazing (HG), potentially beneficial rhizobacteria, such as Stenotrophomonas sp., Microbacterium sp., and Lysobacter sp., were significantly enriched. The beneficial mycorrhizal fungus Schizothecium sp. was significantly enriched in both LG and HG. Moreover, all enriched beneficial microorganisms were positively correlated with root metabolites, including amino acids (AAs), short-chain organic acids (SCOAs), and alkaloids. This suggests that these significantly enriched rhizosphere microbial changes may be caused by these differential root metabolites. Under LG, it is inferred that root metabolites, especially AAs such as L-Histidine, may regulate specific saprophytic fungi to participate in material transformations and the energy cycle and promote plant growth. Furthermore, to help alleviate the stress of HG and improve plant defenses, it is inferred that the root system actively regulates the synthesis of these root metabolites such as AAs, SCOAs, and alkaloids under grazing interference, and then secretes them to promote the growth of some specific plant growth-promoting rhizobacteria and fungi. To summarize, grasses can regulate beneficial microorganisms by changing root metabolites composition, and the response strategies vary under different grazing pressure in typical grassland ecosystems.

Bacterial community dynamics and co-occurrence network patterns during different stages of biochar-driven composting

Bacterial communities were dynamically tracked at four stages of biochar-driven sheep manure pile composting, and the co-occurrence networks with keystone taxa were established. The succession of bacterial community obvious varied during the composting process, Proteobacteria predominant in initial stage (39%) then shifted into Firmicutes in thermophilic (41%) and mesophilic (27%) stages, finally the maturation stage dominant by Bacteroidota (26%). Visualizations of bacterial co-occurrence networks demonstrate more cooperative mutualism and complex interactions in the thermophilic and mesophilic phases. Noticeably, the 7.5 and 10% biochar amended composts shown highest connections (736 and 663 total links) and positive cooperation (97.37 and 97.13% positive link) as well as higher closeness centrality and betweenness centrality of keystone taxa. Overall, appropriate biochar addition alters bacterial community succession and strengthens connection between keystone taxa and other bacteria, with 7.5 and 10% biochar amended composts has intense mutualistic symbiosis among bacterial communities.

Plant growth stages covered the legacy effect of rotation systems on microbial community structure and function in wheat rhizosphere

Legume-based crop rotation is conducive to improve soil multifunctionality, but how the legacy effect of previous legumes influenced the rhizosphere  microbial community of the following crops along with growth stages remains unclear. Here, the wheat rhizosphere microbial community was assessed at the regreening and filling stages with four previous legumes (mungbean, adzuki bean, soybean, and peanut), as well as cereal maize as a control. The composition and structure of both bacterial and fungal communities varied dramatically between two growth stages. The differences in fungal community structure among rotation systems were observed at both the regreening and filling stages, while the difference in bacterial community structure among rotation systems was observed only at the filling stage. The complexity and centrality of the microbial network decreased along with crop growth stages. The species associations were strengthened in legume-based rotation systems than in cereal-based rotation system at the filling stage. The abundance of KEGG orthologs (KOs) associated with carbon, nitrogen, phosphorus, and sulfur metabolism of bacterial community decreased from the regreening stage to the filling stage. However, there was no difference in the abundance of KOs among rotation systems. Together, our results showed that plant growth stages had a stronger impact than the legacy effect of rotation systems in shaping the wheat rhizosphere microbial community, and the differences among rotation systems were more obvious at the late growth stage. Such compositional, structural, and functional changes may provide predictable consequences of crop growth and soil nutrient cycling.

Tea biochar-immobilized Ralstonia Bcul-1 increases nitrate nitrogen content and reduces the bioavailability of cadmium and chromium in a fertilized vegetable soil

Pyrolytic biochar (PL-BC, pyrochar) and hydrothermal biochar (HT-BC, hydrochar) derived from branches and leaves of tea plants had different pH, electrical conductivity (EC), total carbon nitrogen content, BET surface area, total pore volume, average pore diameter, and functional groups. HT-BC had a larger specific surface area and more functional groups than PL-BC. Ralstonia Bcul-1 (R-B) was the dominant and functional bacteria in a fertilized vegetable soil supplemented with TBB-immobilized R-B (TBB + R-B). R-B vitality was more closely related to BET surface area, total pore volume, and functional groups of tea-based biochar (TBB: PL-BC and HT-BC). R-B was able to maintain high oxidase activity. R-B and TBB + R-B can increase the activities of urease and peroxidase in vegetable soil playing an essential role in the biotransformation of ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^--N). TBB was able to simultaneously increase the content of NO₃^--N and NH₄⁺-N, and TBB + R-B also significantly increased NO₃^--N content but decreased NH₄⁺-N content in a fertilized vegetable soil. These results indicated that R-B promoted nitrification in the soil, i.e. conversion of NH₄⁺-N into NO₃^--N, by enhancing the activities of urease and peroxidase. R-B had high adsorption capacity for cadmium (Cd) and chromium (Cr) (Cd&Cr: Cd and Cr). Moreover, TBB + R-B was able to convert weak acid extractable and reducible Cd&Cr into a more stable residual fraction and oxidizable Cd&Cr. The overall effect of the treatments was to reduce plant uptake of Cd&Cr by cabbage. TBB + R-B significantly promoted R-B growth, changed inorganic nitrogen speciation, increased NO₃^--N supply, reduced Cd&Cr bioavailability, and decreased plant tissue Cd&Cr content.

Deciphering biochar compost co-application impact on microbial communities mediating carbon and nitrogen transformation across different stages of corn development

Under current climatic conditions, developing eco-friendly and climate-smart fertilizers has become increasingly important.The co-application of biochar and compost on agricultural soils has received considerable attention recently.Unfortunately, little is known about its effects on specific microbial taxa involved in carbon and nitrogen transformation in the soil.Herein, we report the efficacy of applying biochar-based amendments on soil physicochemical indices, enzymatic activity, functional genes, bacterial community, and their network patterns in corn rhizosphere at seedling (SS), flowering (FS), and maturity (MS) stages.The applied treatments were: compost alone (COM), biochar alone (BIOC), composted biochar (CMB), fortified compost (CMWB), and the control (no fertilizer (CNTRL).The non-metric multidimensional scaling (NMDS) indicated total nitrogen (TN), pH, NO₃^--N, urease, protease, and microbial biomass C (MBC) as the dominant environmental factors driving soil bacteria in this study.The dominant N mediating genes belonged to nitrate reductase (narG) and nitronate monooxygenase (amo), while beta-galactosidase, catalase, and alpha-amylase were the dominant genes observed relating to C cycling.Interestingly, the abundance of these genes was higher in COM, CMWB, and CMB compared with the CNTRL and BIOC treatments.The bacteria network properties of CWMB and CMB indicated robust niche overlap associated with high cross-feeding between bacterial communities compared to other treatments.Path and stepwise regression analyses revealed norank_Reyranellaceae and Sphingopyxis in CMWB as the major bacterial genera and the major predictive indices mediating soil organic C (SOC), NH₄⁺-N, NO₃^--N, and TN transformation.Overall, biochar with compost amendments improved soil nutrient conditions, regulated the composition of the bacterial community, and benefited C/N cycling in the soil ecosystem.

Organomineral fertilizer application enhances Perilla frutescens nutritional quality and rhizosphere microbial community stability in karst mountain soils

Introduction

Applications of organomineral fertilizer (OMF) are important measures for developing organic agriculture in karst mountain areas. However, the influence of OMF on the structure and function of soil microbial diversity and their relationship with crop yield and quality are still unclear.

Methods

Based on soil science, crop science, and high-throughput sequencing methods, we investigated the changes of rhizosphere soil microbial communities of Perilla frutescens under different fertilization measures. Then, the relationship between P. frutescens yield and quality with soil quality was analyzed.

Results

The results showed that the addition of OMF increased the amount of total carbon and total potassium in soil. OF, especially OMF, improved P. frutescens yield and quality (e.g., panicle number per plant, main panicle length, and unsaturated fatty acid contents). Both OF and OMF treatments significantly increased the enrichment of beneficial microorganism (e.g., Bacillus, Actinomadura, Candidatus_Solibacter, Iamia, Pseudallescheria, and Cladorrhinum). The symbiotic network analysis demonstrated that OMF strengthened the connection among the soil microbial communities, and the community composition became more stable. Redundancy analysis and structural equation modeling showed that the soil pH, available phosphorus, and available potassium were significantly correlated with soil microbial community diversity and P. frutescens yield and quality.

Discussion

Our study confirmed that OMF could replace CF or common OF to improve soil fertility, crop yield and quality in karst mountain soils.

Bio-fertilizer Affects Structural Dynamics, Function, and Network Patterns of the Sugarcane Rhizospheric Microbiota

Fertilizers and microbial communities that determine fertilizer efficiency are key to sustainable agricultural development. Sugarcane is an important sugar cash crop in China, and using bio-fertilizers is important for the sustainable development of China's sugar industry. However, information on the effects of bio-fertilizers on sugarcane soil microbiota has rarely been studied. In this study, the effects of bio-fertilizer application on rhizosphere soil physicochemical indicators, microbial community composition, function, and network patterns of sugarcane were discussed using a high-throughput sequencing approach. The experimental design is as follows: CK: urea application (57 kg/ha), CF: compound fertilizer (450 kg/ha), BF1: bio-fertilizer (1500 kg/ha of bio-fertilizer + 57 kg/ha of urea), and BF2: bio-fertilizer (2250 kg/ha of bio-fertilizer + 57 kg/ha of urea). The results showed that the bio-fertilizer was effective in increasing sugarcane yield by 3-12% compared to the CF treatment group, while reducing soil acidification, changing the diversity of fungi and bacteria, and greatly altering the composition and structure of the inter-root microbial community. Variance partitioning canonical correspondence (VPA) analysis showed that soil physicochemical variables explained 80.09% and 73.31% of the variation in bacteria and fungi, respectively. Redundancy analysis and correlation heatmap showed that soil pH, total nitrogen, and available potassium were the main factors influencing bacterial community composition, while total soil phosphorus, available phosphorus, pH, and available nitrogen were the main drivers of fungal communities. Volcano plots showed that using bio-fertilizers contributed to the accumulation of more beneficial bacteria in the sugarcane rhizosphere level and the decline of pathogenic bacteria (e.g., Leifsonia), which may slow down or suppress the occurrence of diseases. Linear discriminant analysis (LDA) and effect size analysis (LEfSe) searched for biomarkers under different fertilizer treatments. Meanwhile, support vector machine (SVM) assessed the importance of the microbial genera contributing to the variability between fertilizers, of interest were the bacteria Anaerolineace, Vulgatibacter, and Paenibacillus and the fungi Cochliobolus, Sordariales, and Dothideomycetes between CF and BF2, compared to the other genera contributing to the variability. Network analysis (co-occurrence network) showed that the network structure of bio-fertilizers was closer to the network characteristics of healthy soils, indicating that bio-fertilizers can improve soil health to some extent, and therefore if bio-fertilizers can be used as an alternative to chemical fertilizers in the future alternative, it is important to achieve green soil development and improve the climate.

Response of bacterial community composition and co-occurrence network to straw and straw biochar incorporation

Microbial decomposition plays a crucial role in the incorporation of straw and straw biochar (SSB) into soil. Lime concretion black soil (LCBS) is a typical low-medium crop yield soil, and it is also one of the main soil types for grain production in China. However, the link between SSB additions and soil bacterial communities in LCBS remains unclear. This study explored the effects of SSB incorporation on bacterial community composition, structure and co-occurrence network patterns at different soil depths and maize growth stages. The results showed that soil PH, soil organic matter and total nitrogen significantly affected the seasonality and stratification of the soil bacterial community. The composition and diversity of bacterial communities were significantly affected by growth period and treatment rather than soil depth. Specifically, the bacterial community diversity increased significantly with crop growth at 0–20 cm, decreased the relative abundance of Actinobacteria, and increased the relative abundance of Proteobacteria and Acidobacteria. SF (straw with fertilizer) and BF (straw biochar with fertilizer) treatments decreased bacterial community diversity. Co-occurrence networks are more complex in BF, S (straw), and SF treatments, and the number of edge network patterns is increased by 92.5, 40, and 60% at the maturity stage compared with F (fertilizer) treatment, respectively. Moreover, the positive effect of straw biochar on the bacterial network pattern increased with time, while the effect of straw weakened. Notably, we found that rare species inside keystone taxa (Gemmatimonadetes and Nitrospirae) play an indispensable role in maintaining bacterial network construction in LCBS. This study offers a comprehensive understanding of the response of soil bacterial communities to SSB addition in LCBS areas, and provides a reference for further improvement of LCBS productivity.

A Metagenomic and Gene Expression Analysis in Wheat (T. durum) and Maize (Z. mays) Biofertilized with PGPM and Biochar

Commodity crops, such as wheat and maize, are extremely dependent on chemical fertilizers, a practice contributing greatly to the increase in the contaminants in soil and water. Promising solutions are biofertilizers, i.e., microbial biostimulants that when supplemented with soil stimulate plant growth and production. Moreover, the biofertilizers can be fortified when (i) provided as multifunctional consortia and (ii) combined with biochar with a high cargo capacity. The aim of this work was to determine the molecular effects on the soil microbiome of different biofertilizers and delivery systems, highlight their physiological effects and merge the data with statistical analyses. The measurements of the physiological parameters (i.e., shoot and root biomass), transcriptomic response of genes involved in essential pathways, and characterization of the rhizosphere population were analyzed. The results demonstrated that wheat and maize supplemented with different combinations of selected microbial consortia and biochar have a positive effect on plant growth in terms of shoot and root biomass; the treatments also had a beneficial influence on the biodiversity of the indigenous rhizo-microbial community, reinforcing the connection between microbes and plants without further spreading contaminants. There was also evidence at the transcriptional level of crosstalk between microbiota and plants.

Responses of soil fungal communities and functional guilds to ~160 years of natural revegetation in the Loess Plateau of China

Natural revegetation has been widely confirmed to be an effective strategy for the restoration of degraded lands, particularly in terms of rehabilitating ecosystem productivity and soil nutrients. Yet the mechanisms of how natural revegetation influences the variabilities and drivers of soil residing fungal communities, and its downstream effects on ecosystem nutrient cycling are not well understood. For this study, we investigated changes in soil fungal communities along with ~160 years of natural revegetation in the Loess Plateau of China, employing Illumina MiSeq DNA sequencing analyses. Our results revealed that the soil fungal abundance was greatly enhanced during the later stages of revegetation. As revegetation progresses, soil fungal richness appeared first to rise and then decline at the climax Quercus liaotungensis forest stage. The fungal Shannon and Simpson diversity indexes were the lowest and highest at the climax forest stage among revegetation stages, respectively. Principal component analysis, Bray–Curtis similarity indices, and FUNGuild function prediction suggested that the composition, trophic modes, and functional groups for soil fungal communities gradually shifted along with natural revegetation. Specifically, the relative abundances of Basidiomycota, Agaricomycetes, Eurotiomycetes, and ectomycorrhizal fungi progressively increased, while that of Ascomycota, Sordariomycetes, Dothideomycetes, Tremellomycetes, saprotrophic, pathotrophic, arbuscular mycorrhizal fungi, and endophyte fungi gradually decreased along with natural revegetation, respectively. The most enriched members of Basidiomycota (e.g., Agaricomycetes, Agaricales, Cortinariaceae, Cortinarius, Sebacinales, Sebacinaceae, Tricholomataceae, Tricholoma, Russulales, and Russulaceae) were found at the climax forest stage. As important carbon (C) sources, the most enriched symbiotic fungi (particularly ectomycorrhizal fungi containing more recalcitrant compounds) can promote organic C and nitrogen (N) accumulation in soils of climax forest. However, the most abundant of saprotrophic fungi in the early stages of revegetation decreased soil organic C and N accumulation by expediting the decomposition of soil organic matter. Our results suggest that natural revegetation can effectively restore soil fungal abundance, and modify soil fungal diversity, community composition, trophic modes, and functional groups by altering plant properties (e.g., plant species richness, diversity, evenness, litter quantity and quality), quantity and quality of soil nutrient substrates, soil moisture and pH. These changes in soil fungal communities, particularly their trophic modes and functional groups along with natural revegetation, impact the accumulation and decomposition of soil C and N and potentially affect ecosystem C and N cycling in the Loess Plateau of China.

Magnesite driven the complementary effects of core fungi by optimizing the physicochemical parameters in pig manure composting

The effects of magnesite (MS) on fungi communities and the core fungi complementarity during pig manure (PM) composting were explored. Different dosage of MS [0% (T1), 2.5% (T2), 5% (T3), 7.5% (T4) and 10% (T5)] as amendments mixed with PM for 42 days composting. The results showed the dominant of phyla were Ascomycota (78.87%), Neocallimastigomycota (41.40%), Basidiomycota (30.81%) and Aphelidiomycota (29.44%). From day 7 to 42, the abundance of Ascomycota and Aphelidiomycota were increased from 7.75% to 42.41% to 57.27%-78.87% and 0-0.70% to 11.73%-29.44% among all treatments. Nevertheless, the phyla abundance of Neocallimastigomycota and Basidiomycota decreased from day 7 to 42. The co-occurrence network indicated that the high additive amendment could enhance the core fungi complementarity effects capacity. The 10% MS addition was a promisable candidate to optimum fungal communities, and causing a better compost quality. This study illustrated the potential and fungi communities changing of MS as additives in composting.

Enhancing microplastics biodegradation during composting using livestock manure biochar

Biodegradation of microplastics (MPs) in contaminated biowastes has received big scientific attention during the past few years. The aim here is to study the impacts of livestock manure biochar (LMBC) on the biodegradation of polyhydroxyalkanoate microplastics (PHA-MPs) during composting, which have not yet been verified. LMBC (10% wt/wt) and PHA-MPs (0.5% wt/wt) were added to a mixture of pristine cow manure and sawdust for composting, whereas a mixture without LMBC served as the control (CK). The maximum degradation rate of PHA-MPs (22-31%) was observed in the thermophilic composting stage in both mixtures. LMBC addition significantly (P < 0.05) promoted PHA-MPs degradation and increased the carbon loss and oxygen loading of PHA-MPs compared to CK. Adding LMBC accelerated the cleavage of C-H bonds and oxidation of PHA-MPs, and increased the O-H, CO and C-O functional groups on MPs. Also, LMBC addition increased the relative abundance of dominant microorganisms (Firmicutes, Proteobacteria, Deinococcus-Thermus, Bacteroidetes, Ascomycota and Basidiomycota) and promoted the enrichment of MP-degrading microbial biomarkers (e.g., Bacillus, Thermobacillus, Luteimonas, Chryseolinea, Aspergillus and Mycothermus). LMBC addition further increased the complexity and connectivity between dominant microbial biomarkers and PHA-MPs degradation characteristics, strengthened their positive relationship, thereby accelerated PHA-MPs biodegradation, and mitigated the potential environmental and human health risk. These findings provide a reference point for reducing PHA-MPs in compost and safe recycling of MPs contaminated organic wastes. However, these results should be validated with other composting matrices and conditions.

Bacterial extracellular polymeric substances: Impact on soil microbial community composition and their potential role in heavy metal-contaminated soil

In this study, six different treatments involving extracellular polymeric substances (EPS) from Enterobacter sp. FM-1 (FM-1) (no EPS (control), original bacterial cells (FM-1), FM-1 cells with EPS artificially removed (EPS-free cells, EPS-R), different forms of EPS (soluble EPS (S-EPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS)) obtained from FM-1) and three types of soils (non-contaminated soil (NC soil), high-contamination soil (HC soil) and low-contamination soil (LC soil)) were used to investigate the impact of different EPS treatments on soil microbial community composition and their potential role in the remediation of heavy metal (HM)-contaminated soil. The results indicate that the EPS secreted by FM-1 played a vital role in changing soil pH and helped increase soil bio- HMs. In addition, EPS secretion by FM-1 helped increase the soil EPS-polysaccharide and EPS-nucleic acid contents; even in HC soil, where the HM content was relatively high, LB-EPS addition still increased the EPS-polysaccharide and EPS-nucleic acid contents in the soil by 1.18- and 15.54-fold, respectively. FM-1, LB-EPS and TB-EPS addition increased the soil invertase, urease and alkaline phosphatase activities and increased the soil organic matter (SOM), NH₄⁺-N and available phosphorus (AP) contents, which helped regulate soil nutrient reserves. Moreover, the addition of different EPS fractions modified the soil microbial community composition to help microbes adapt to an HM-contaminated environment. In the HC and LC soils, where the HM content was relatively high, the soil bacteria were dominated by Protobacteria, while fungi in the soil were dominated by Ascomycota. Among the soil physicochemical properties, the soil SOM and NH₄⁺-N contents and invertase activity significantly impacted the diversity and community composition of both bacteria and fungi in the soil.

Sustainable biochar-based soil fertilizers and amendments as a new trend in biochar research

Today's world is struggling with many environmental problems. Due to the ever-growing size of the population, it is necessary to produce more and more food. The consequence of such a large demand for food is excessive fertilization of soils, often in an uncontrolled manner. The paper presents an overview of the different types of biochar (BC) fertilizers obtained by: coating BCs with a protective layer, coating commercial fertilizers with a layer of BCs, or mixing BCs with commercial fertilizers. Although the use of these new types of fertilizers has a positive effect on soil properties and crop yields, the production and use of "simple" inorganic fertilizers are dominant. The solution to starting the change of this trend may be the use of BC-compost systems as an effective soil amendment, due to the fact that composts are still the most frequently used products by farmers. The review summarized two types of BC-compost soil amendments: BC mixed with ready-made compost and BC co-composted with compost raw material. These types of soil amendments contribute to a significant reduction in the consumption of commercial inorganic fertilizers, and thus less pollution of the natural environment, while allowing for a high yield of safe food.

Microecological insight to fungal structure and key fungal communities regulating nitrogen transformation based on spatial heterogeneity during cow manure composting by multi-angle and multi-aspect analyses

Composting is the mainstream technology for the treatment of agricultural solid waste, but limited efforts were made to investigate fungal composition and its contributions to nitrogen transformation in different depths of compost. In this study, spatial distributions of fungi were analyzed using high throughput sequencing by multi-angle analyses, and the key fungal communities determining nitrogen transformation were quantified and identified by multi-aspect analyses during cow manure composting. Multi-angle analyses showed that fungal structure, biomarkers and trophic mode composition varied in different layers, revealing that spatial heterogeneity is the distinctive attribute of composting system. Ascomycota and Basidiomycota were dominant phyla during composting, the two phyla peaked in top and bottom layer respectively. At mesophilic stage, Tremellales, and unclassified Ascomycota (order) were biomarkers in top and middle layer respectively, and so were Remersonia, Pyrenochaetopsis, and Wallemia in bottom layer by LEfSe analysis. Based on multi-aspect analyses, Unclassified Dothideomycetes mainly affected NH₄⁺-N transformation both in top (1.2816***) and middle layers (1.1726*). Trichocladium asperum (0.9536***) and Zopfiella (-0.9484***) mainly affected TN transformation in top layer. Guehomyces pullulans (-0.9684**) and Preussia (-1.0508**) regulated NO₃^--N transformation in middle layer. Thermomyces lanuginosus (0.7127***) and Typhula sp. UW973129 (0.7298***) were the key species promoting TN and C/N transformation in bottom layer, respectively. Interestingly, different fungal communities showed a complex network interaction driving nitrogen transformation, and the abundance of microbial community could be conducive to characterizing nitrogen transformation in the vertical space of composting.

Phytoextraction of metal(loid)s from contaminated soils by six plant species: A field study

Phytoextraction is an in situ remediation technique that uses (hyper)accumulator plant species to extract metal(loid)s from contaminated soils. Field studies can help in selecting appropriate plants for phytoextraction and in better understanding their phytoextraction performance. Hence, a field study was conducted using six (hyper)accumulator species (Solanum nigrum L., Bidens pilosa L., Xanthium strumarium L., Helianthus annuus L., Lonicera japonica T. and Pennisetum sinese R.) over two years in Jiaoxi town, Liuyang city, Hunan Province, China, to determine the effect of the (hyper)accumulator rhizospheres on field soils contaminated with multiple metal(loid)s and to analyze the variations in rhizosphere soil microbial community diversity and composition. After two years of field experiments, compared to the other four (hyper)accumulators, Bidens pilosa L. and Xanthium strumarium L. exhibited not only better metal(loid) phytoextraction abilities but also higher shoot biomasses. The contents of diethylenetriaminepentaacetic acid (DTPA)-extractable Pb, Cd and Zn decreased in the rhizosphere soils of all six (hyper)accumulators after repeated phytoextraction. Moreover, our findings illustrated that hyperaccumulator planting helps improve and rebuild the soil bacterial community composition and structure in contaminated soils by shifting the soil physiochemical properties. After repeated planting, the soil bacterial communities were reconstructed and dominated by Proteobacteria, Actinobacteriota, Chloroflexi and Acidobacteriota at the phylum level. The soil fungal communities were dominated by Ascomycota, Basidiomycota and Mortierellomycota at the phylum level. The reconstruction of soil microbial communities may help (hyper)accumulators adapt to metal(loid)-contaminated environments and improve their phytoextraction abilities.

Studying Microbial Communities through Co-Occurrence Network Analyses during Processes of Waste Treatment and in Organically Amended Soils: A Review

Organic wastes have the potential to be used as soil organic amendments after undergoing a process of stabilization such as composting or as a resource of renewable energy by anaerobic digestion (AD). Both composting and AD are well-known, eco-friendly approaches to eliminate and recycle massive amounts of wastes. Likewise, the application of compost amendments and digestate (the by-product resulting from AD) has been proposed as an effective way of improving soil fertility. The study of microbial communities involved in these waste treatment processes, as well as in organically amended soils, is key in promoting waste resource efficiency and deciphering the features that characterize microbial communities under improved soil fertility conditions. To move beyond the classical analyses of metataxonomic data, the application of co-occurrence network approaches has shown to be useful to gain insights into the interactions among the members of a microbial community, to identify its keystone members and modelling the environmental factors that drive microbial network patterns. Here, we provide an overview of essential concepts for the interpretation and construction of co-occurrence networks and review the features of microbial co-occurrence networks during the processes of composting and AD and following the application of the respective end products (compost and digestate) into soil.