Amendment of Agricultural Soil with Metal Nanoparticles: Effects on Soil Enzyme Activity and Microbial Community Composition

Higher remediation efficiency of Cd and lower CO2 emissions in phytoremediation systems with biochar application

Biochar has been considered a promising material for soil carbon sequestration. However, there are huge knowledge gaps regarding the carbon reduction effects of biochar-plant-polluted soil. Here, rice straw biochar (RB) was applied in ryegrass-cadmium (Cd)-contaminated soil to investigate the full-cycle carbon dioxide (CO2) emission and intrinsic mechanism. RB resulted in a 37.00 %-115.64 % reduction in accumulative CO2 emissions and a 31.61 %-45.80 % reduction in soil bioavailable Cd throughout the whole phytoremediation period. CO2 emission reduction triggered by RB can be attributed to the regulation of plant and rhizosphere ecological functions. RB could bolster photosynthetic carbon fixation by maintaining the stability of the structure of the chloroplasts and thylakoids, accelerating the consumption of terminal photosynthate, upregulating photosynthetic pigments, and mitigating oxidative damage. Besides, RB reduced the metabolism of readily mineralizable carbon sources while reinforcing the utilization of certain nutrient substrates. Besides, the composition of rhizosphere microbial communities was altered, especially those associated with carbon cycling (Chloroflexi, Actinobacteriota, and Acidobacteriota phyla) to orient soil microbial evolution to lower soil CO2 emission. This study aims to establish a win-win paradigm of "carbon reduction-pollution alleviation" to deepen the understanding of biochar in carbon neutrality and soil health and provide a theoretical basis for field pilot-scale studies.

Nanospecific effect rather than dissolved Cu2+ dominates the impact of CuO nanoparticles on soil microbiota

CuO nanoparticles (NPs) have raised significant concerns due to their extensive application in agriculture and potential ecological impacts in recent decades. Identification of the action mechanisms for soil microbiota response in a long exposure time with respect to the chemical speciation of CuO NPs remained scarce. A 63-day laboratory soil microcosms experiment was conducted to evaluate the impact of CuO NPs along with its dissolved Cu2+ on soil microbiota. Illumina MiSeq sequencing of microbial communities revealed that CuO NPs significantly (p < 0.05) reduced both bacterial diversity and richness, as well as a shift in overall bacterial community composition and structure. Some genera responded differently to CuO NPs and Cu2+, while for the most of impacted genera, no matter inhibition or facilitation induced by CuO NPs was much stronger than Cu2+. The dissolution rate of CuO NPs was substantially lower compared to that of Cu(NO3)2 in soil. It was demonstrated that nanospecific effect played a crucial role in shaping the response of microbial communities to CuO NPs, rather than dissolved Cu2+. This finding has significant implications for understanding the ecological consequences of agriculture application of CuO NPs as antibacterial agents and for developing appropriate management strategies to mitigate their negative impacts.

Managing Arsenic Pollution from Soil-Plant Systems: Insights into the Role of Biochar

Soil contamination with arsenic (As) is becoming a serious concern for living organisms. Arsenic is a nonessential metalloid for plants, humans, and other living organisms. Biochar (BC) is a very effective amendment to remediate polluted soils and it received great attention owing to its appreciable results. Arsenic toxicity negatively affects plant morph-physiological and biochemical functioning and upsurges the generation of reactive oxygen species (ROS), which negatively affect cellular structures. Arsenic toxicity also reduces seed germination and impedes plant growth by decreasing nutrient uptake, causing oxidative damage and disrupting the photosynthetic efficiency. Plants use different strategies like antioxidant defense and increased osmolyte synthesis to counteract As toxicity; nevertheless, this is not enough to counter the toxic impacts of As. Thus, applying BC has shown tremendous potential to counteract the As toxicity. Biochar application to As-polluted soils improves water uptake, maintains membrane stability and nutrient homeostasis, and increases osmolyte synthesis, gene expression, and antioxidant activities, leading to better plant performance. Additionally, BC modulates soil pH, increases nutrient availability, causes As immobilization, decreases its uptake and accumulation in plant tissues, and ensures safer production. The present review describes the sources, toxic impacts of As, and ways to lower As in the environment to decrease its toxic impacts on humans, the ecosystem, and the food chain. It concentrates on different mechanisms mediated by BC to alleviate As toxicity and remediate As-polluted soils and different research gaps that must be fulfilled in the future. Therefore, the current review will help to develop innovative strategies to minimize As uptake and accumulation and remediate As-polluted soils to reduce their impacts on humans and the environment.

Persistence and Recovery of Polystyrene and Polymethyl Methacrylate Microplastic Toxicity on Diatoms

The increasing pollution of polystyrene (PS) and polymethyl methacrylate (PMMA) microplastics (MPs) has become a global marine environmental problem. Diatoms contribute nearly 40% of marine primary productivity and shape the nitrogen cycle in the oceans. However, the persistence of the phytotoxicity of MPs on diatoms, especially nitrogen assimilation, remains largely unknown. To examine the persistence of PS and PMMA toxicity in diatoms, two subexperiments (a 96 h exposure followed by a recovery phase) were conducted on Thalassiosira pseudonana at concentrations ranging from 0.001 to 1 mg/L. The results showed that PS and PMMA inhibited algal growth by 3.76-6.49% and 4.44-8.37%; increased oxidative stress by 10.06-30.51% and 30.46-38.12%; and caused ultrastructural damage by 14.24-25.56% and 12.28-20%, respectively, consistent with the downregulation of glyoxylate, dicarboxylate metabolism, and glutathione metabolism. At the recovery stage, the algal density induced by PS was significantly recoverable at 0.001 and 0.01 mg/L, consistent with the enhanced carbohydrate metabolisms. After recovery, the cell permeability and reactive oxygen species (ROS) levels induced by PS and PMMA were significantly decreased at 1 mg/L, respectively, which was closely related to the downregulation of glycine, serine, and threonine metabolism and the upregulation of pantothenate and coenzyme A biosynthesis. Moreover, the inhibition of nitrogen assimilation enzymic activities induced by PS and PMMA was significantly recovered at 1 mg/L despite the downregulation of nitrogen metabolism. This study highlights the phenomena and mechanisms of phytotoxicity and recovery, and provides new insights for comprehensive understanding and evaluation of environmental risks of MPs.

Microdroplet-Mediated Enzyme Activity Enhancement for Potentiometric Sensing of Peroxidase in Soil

On-site measurements of enzyme activity in complex solid matrices such as soil and sediment could offer invaluable insights for the soil health evaluation and sustainable management. As such, sensors for on-site measurements of soil enzyme activity are highly required but remain unachieved to date. Herein, a potentiometric sensor for rapid, direct, and in-field analysis of soil enzyme activity is proposed, in which soil particle separation and soil enzyme extraction can be achieved within a single device. More importantly, the enzyme activity mediated by microdroplets can be greatly enhanced for potentiometric measurements. By using a classic soil redox enzyme-peroxidase and an anti-interference substrate 3,3',5,5'-tetramethylbenzidine as a model, the potentiometric sensor enables directly measuring peroxidase activity in the field with a detection limit that can reach as low as 10-7 U mL-1 within 5 min. Moreover, the potentiometric sensor was deployed for on-site analysis of the peroxidase activity of Suaeda salsa (L.) Pall. rhizosphere soil under salinity stress, showing excellent sensitivity and anti-interference capability, and retaining promising potential for evaluating the mechanisms and feedback in response to environment stresses.

Diversity of copper-containing nanoparticles and their influence on plant growth and development

Copper (Cu) is an important microelement for plants, but in high concentrations it can be toxic. Cu-containing nanoparticles (Cu NPs) are less toxic, their use for plants is safer, more effective and economical than the use of Cu salts. This review presents detailed information on the chemical diversity of Cu NPs and various methods of their synthesis. The mechanisms of the effect of Cu NPs on plants are described in detail, and examples of research in this area are given. The main effects of Cu NPs on plants are reviewed including on their growth and development (organogenesis, mitosis, accumulation of biomass), biochemical processes (intensity of photosynthesis, antioxidant status and intensity of lipid peroxidation processes), gene expression, plant resistance to abiotic and biotic stress factors. The prospects of using Cu NPs as mineral fertilizers are shown by describing their stimulation effects on seed germination, plant growth and development, and on increase of plant resistance to stress factors. The protective effect of Cu NPs is often explained by their antioxidant activity. At the same time, there are a number of studies demonstrating the negative impact of Cu NPs on plant growth, development and the intensity of photosynthesis, depending on their concentration. Cu NPs have a pronounced antibacterial effect on bacterial phytopathogens of cultivated plants, as well as on a number of phytopathogenic fungi and nematodes. Thus, Cu NPs are promising agents for agriculture, while their effect on plants requires careful selection of optimal concentrations and comprehensive studies to avoid a toxic effect.

Altered precipitation affects soil enzyme activity related to nitrogen and phosphorous but not carbon cycling: A meta-analysis

Altered precipitation significantly influences soil function in terrestrial ecosystems. As a bioindicator of soil function, soil extracellular enzyme activity (EEA) plays a crucial role in mediating ecosystem responses to altered precipitation. However, the global patterns and regulatory mechanisms of altered precipitation impacts on soil EEAs remain unclear. We conducted hierarchical mixed-effects meta-analyses to explore the responses and regulators of carbon, nitrogen, phosphorus hydrolytic EEAs, and carbon oxidative EEA to changes in precipitation, using the largest dataset to date, comprising 1185 observations of 14 soil EEAs from 73 publications. The results indicated that soil nitrogen hydrolytic EEA increased by 14.3% under increased precipitation, while phosphorus hydrolytic EEA decreased by 8.8% under decreased precipitation, showing higher sensitivity to altered precipitation compared to carbon-degrading EEAs. These responses varied across ecosystem types and depended on the magnitude of precipitation manipulation (MPM). Specially, decreased precipitation significantly reduced phosphorus hydrolytic EEA in forests, while increased precipitation enhanced nitrogen hydrolytic EEA in grasslands. Furthermore, these effects were linearly correlated with MPM, deviating from the expected nonlinear double asymmetric model. The response of soil hydrolytic EEAs was predominately regulated by soil water content, organic carbon, and microbial biomass. These findings underscore the higher sensitivity of nitrogen and phosphorus cycling EEAs to altered precipitation compared to carbon cycling EEAs and extend the application of the double asymmetric model for understanding soil EEAs' responses to precipitation changes. This synthesis provides essential insights for predicting biogeochemical cycling and improving ecosystem models to evaluate ecosystem functions under altered precipitation.

Nanomaterials in Agriculture: A Pathway to Enhanced Plant Growth and Abiotic Stress Resistance

Nanotechnology has emerged as a transformative field in agriculture, offering innovative solutions to enhance plant growth and resilience against abiotic stresses. This review explores the diverse applications of nanomaterials in agriculture, focusing on their role in promoting plant development and improving tolerance to drought, salinity, heavy metals, and temperature fluctuations. The method classifies nanomaterials commonly employed in plant sciences and examines their unique physicochemical properties that facilitate interactions with plants. Key mechanisms of nanomaterial uptake, transport, and influence on plants at the cellular and molecular levels are outlined, emphasizing their effects on nutrient absorption, photosynthetic efficiency, and overall biomass production. The molecular basis of stress tolerance is examined, highlighting nanomaterial-induced regulation of reactive oxygen species, antioxidant activity, gene expression, and hormonal balance. Furthermore, this review addresses the environmental and health implications of nanomaterials, emphasizing sustainable and eco-friendly approaches to mitigate potential risks. The integration of nanotechnology with precision agriculture and smart technologies promises to revolutionize agricultural practices. This review provides valuable insights into the future directions of nanomaterial R&D, paving the way for a more resilient and sustainable agricultural system.

The Role of Nano-Fertilizers in Sustainable Agriculture: Boosting Crop Yields and Enhancing Quality

With the rising need for sustainable agricultural practices, nano-fertilizers have emerged as an innovative alternative to traditional fertilizers. These advanced fertilizers enhance nutrient use efficiency, promote crop growth, and minimize environmental harm by enabling precise nutrient delivery. This review evaluates various nano-fertilizer application techniques and their influence on plant growth, yield, and quality. Additionally, it explores their interactions with soil composition and microbial communities, emphasizing their role in enzymatic activity and nutrient cycling. While nano-fertilizers offer significant benefits, challenges such as proper dosage regulation, potential toxicity, and long-term ecological effects necessitate further research. This study highlights recent advancements in nano-fertilizer technology and underscores the importance of an integrated approach to optimize agricultural productivity while preserving soil health and environmental sustainability.

The Impact of Nanoparticles and Molecular Forms of TiO2 on the Rhizosphere of Plants in the Example of Common Wheat (Triticum aestivum L.)-Shifts in Microbiome Structure and Predicted Microbial Metabolic Functions

This study investigated the effects of various titanium nanoparticles (TiO2NPs) on the structure, function, and trophic levels of the wheat rhizobiome. In contrast to the typically toxic effects of small nanoparticles (~10 nm), this research focused on molecular TiO2 and larger nanoparticles, as follows: medium-sized (68 nm, NPs1) and large (>100 nm, NPs2). The results demonstrated significant yet diverse impacts of different TiO2 forms on the rhizosphere microbiota. Large TiO2NPs2 and molecular TiO2 adversely affected the bacteriobiome and mycobiome, leading to an increase in autotrophic microbial groups. In contrast, medium-sized TiO2NPs1 shifted the microbiome toward chemoheterotrophy, promoting plant growth-associated bacteria, fungal saprotrophs, and potential phytopathogens, suggesting a beneficial r-strategy within the rhizosphere. Other treatments induced oligotrophic conditions, resulting in a less flexible rhizobiome with diminished root associations but an increased abundance of Trichoderma spp. Structural modelling revealed that even minor changes in operational taxonomic units (OTUs) could significantly alter the microbiota's metabolic potential. These findings highlight the importance of further research to optimize nanoparticle applications for sustainable agriculture.

Nanoscale‑boron nitride positively alters rhizosphere microbial communities and subsequent cucumber (Cucumis sativa) growth: A metagenomic analysis

Boron (B) deficiency affects over 132 crop species globally, making effective B supplement crucial for enhancing agricultural yield and health. This study explores an innovative application of nanoscale boron nitride (nano-BN) as a sustainable solution for addressing B deficiency in crops. Cucumber seedlings were treated with different contents of nano-BN under greenhouse conditions and both B and N ionic treatments were set as comparisons. Results show that soil application of 10 mg/kg nano-BN achieved a remarkable 15.8 % increase in fresh weight compared to the control. Notably, nano-BN exhibited superior efficiency in providing essential micronutrients without inducing toxicity as compared to traditional ionic B sources. Phytohormone correlation analysis reveals that nano-BN application significantly enhances levels of indole-3-acetic acid (IAA) and cytokinins while reducing abscisic acid (ABA), fostering optimal plant growth conditions. Furthermore, increases in dissolved organic matter (DOM) and dissolved organic carbon (DOC) levels in the rhizosphere improve nutrient availability and promote beneficial microbial activity in the soil as affected by nano-BN. Metagenomics techniques were used to investigate the impact of nano-BN on soil carbon and nitrogen cycling, alongside its effects on the soil microbiome. The upregulation of genes associated with fermentation pathways as affected by nano-BN suggests the enhanced carbon cycling. Additionally, nano-BN upregulated a number of functional genes involved in nitrogen-based processes, leading to a significant increase in microorganisms harboring nitrogen-fixing genes, including Phenylobacterium, Novosphingobium, and Reyranella. Overall, these findings provide valuable insight into the application of nano-BN in agriculture to sustainably increase crop productivity and enhance the efficiency of carbon and nitrogen cycling.

Analysis of changes and influencing factors of stablization treatment effects and bioavailability after freeze-thaw: a case study of Pb-contaminated soil in a non-ferrous metal factory in Northeast China

Introduction

Solidification/Stabilization techniques are commonly used for the containment and isolation of Pb-contaminated soil, but they cannot reduce the amount of contaminants. Freeze - thaw after stabilization may affect Pb's environmental behavior and increase the uncertainty of environmental risk.

Methods

In vitro experiments can simulate the bioavailability of heavy metals to the human body, accurately assessing their environmental health risks. In this study, soil samples from Pbcontaminated site are collected from a non-ferrous metal plant in Northeastern China. Through the results of stabilization and freeze-thaw after stabilization experiments, analyzing the changes of physicochemical property, Pb treatment effects (total concentration, leaching concentration, and occurrence forms) and microbial communities, and studying the influencing factors of Pb's bioavailability.

Result and discussion

The results show that stabilization and freeze - thaw after stabilization directly alter soil physicochemical property, thereby affecting the leaching and occurrence form of Pb and microbial communities, and closely related to changes in bioavailability of Pb. Both stabilization and freeze-thaw treatment reduced the leaching concentration of Pb, decreased the proportion of available Pb (acid-soluble state, oxidation state and reduction state), increased the bioavailability of Pb in the gastric phase, but decreased in the intestinal phase; And the dominant bacterial phylum in the soil changed to Firmicutes, the dominant bacterial genus changed to Bacillus; The analysis of the results shows that the bioavailability of Pb is related to soil pH, cation exchange capacity (CEC), soil organic matter (SOM), soil moisture content (SMC), Pb (leaching, acid soluble state, oxidation state, residual state), types of microorganisms in soil.

Nanocolloids in the soil environment: Transformation, transport and ecological effects

Nanocolloids (Ncs) are ubiquitous in natural systems and play a critical role in the biogeochemical cycling of trace metals and the mobility of organic pollutants. However, the environmental behavior and ecological effects of Ncs in the soil remain largely unknown. The accumulation of Ncs may have detrimental or beneficial effects on different compartments of the soil environment. This review discusses the major transformation processes (e.g., agglomeration/aggregation, absorption, deposition, dissolution, and redox reactions), transport, bioavailability of Ncs, and their roles in element cycles in soil systems. Notably, Ncs can act as effective carriers for other pollutants and contribute to environmental pollution by spreading pathogens, nutrients, heavy metals, and organic contaminants to adjacent water bodies or groundwater. Finally, the key knowledge gaps are highlighted to better predict their potential risks, and important new directions include exploring the geochemical process and mechanism of Ncs's formation; elucidating the transformation, transport, and ultimate fate of Ncs, and their long-term effect on contaminants, organisms, and elemental cycling; and identifying the impact on the growth and quality of important crops, evaluating its dominant effect on agro-ecosystems in the soil environment.

Manipulation in root-associated microbiome via carbon nanosol for plant growth improvements

BACKGROUND

Modulating the microbiome with nanomaterials has been proposed to improve plant growth, and reduce reliance on external inputs. Carbon Nanosol (CNS) was attracted for its potential to improve plant productivity. However, the mechanism between CNS and rhizosphere microorganisms remained largely elusive.

RESULTS

Here, we tried to systematically explore the effects of CNS (600 and 1200 mg/L by concentration) on tobacco growth, soil physical properties, and root-associated microbiome. The influence of CNS on soil physicochemical properties and plant growth was significant and dose-dependent, leading to a 28.82% increase in biomass accumulation by 600 mg/L CNS. Comparison between the CNS-treated and control plants revealed significant differences in microbiome composition, including 1148 distinct ASVs (923 bacteria and 225 fungi), microbiome interactions, and metabolic function of root-associated microbiomes. Fungal and bacterial communities had different response patterns for CNS treatment, with phased and dose-dependent effects, with the most significant changes in microbial community structure observed at 1200 mg/L after 10 days of treatment. Microbial networks of CNS-treated plants had more nodes and edges, higher connectivity, and more hub microorganisms than those of control plants. Compared with control, CNS significantly elevated abundances of various bacterial biomarkers (such as Sphingomonas and Burkholderia) and fungi biomarkers (including Penicillium, Myceliophthora, and Talaromyces), which were potential plant-beneficial organisms. Functional prediction based on metagenomic data demonstrated pathways related to nutrient cycling being greatly enriched under CNS treatment. Furthermore, 391 culturable bacteria and 44 culturable fungi were isolated from soil and root samples. Among them, six bacteria and two fungi strains enriched upon CNS treatment were validated to have plant growth promotion effect, and two fungi (Cladosporium spp. and Talaromyces spp.) played their roles by mediating volatile organic compounds (VOCs). To some extent, the driving and shaping of the microbiome by CNS contributed to its impact on plant growth and development.

CONCLUSION

Our results revealed the key role of root-associated microbiota in mediating the interaction between CNS and plants, thus providing valuable insights and strategies for harnessing CNS to enhance plant growth.

Nanoparticles and plants: A focus on analytical characterization techniques

Nanotechnology has brought about significant progress through the use of goods based on nanomaterials. However, concerns remain about the accumulation of these materials in the environment and their potential toxicity to living organisms. Plants have the ability to take in nanomaterials (NMs), which can cause changes in their physiology and morphology. On the other hand, nanoparticles (NPs) have been used to increase plant development and control pests in agriculture by including them into agrochemicals. The challenges of the interaction, internalization, and accumulation of NMs within plant tissues are enormous, mainly because of the various characteristics of NMs and the absence of reliable analytical tools. As our knowledge of the interactions between NMs and plant cells expands, we are able to create novel NMs that are tailored, targeted, and designed to be safe, thus minimizing the environmental consequences of nanomaterials. This review provides a thorough examination and comparison of the main microscopy techniques, spectroscopic methods, and far-field super-resolution methodologies used to examine nanomaterials within the cell walls of plants.

TiO2 nanoparticles: Green synthesis and their role in lessening the damage of Colletotrichum graminicola in sorghum

Fungal pathogens pose a persistent threat to crop plants, risking global food security. Anthracnose of sorghum caused by Colletotrichum graminicola causes a considerable loss in sorghum production. This study aimed to manage the anthracnose disease in sorghum using green-synthesized TiO2 nanoparticles using pomegranate peel and to assess their impacts on the agroeconomic attributes of sorghum. Synthesized TiO2 nanoparticles showed strong dose-dependent antifungal activity against C. graminicola and significantly reduced mycelial radial growth, comparable to commercial fungicides. Foliar application of TiO2 at concentrations of 150 and 200 ppm reduced the disease index >60% in pot trials. Additionally, the effect of TiO2 NPs on the growth and yield of sorghum plants and the possible mechanism(s) behind the suppression of anthracnose disease were deciphered. TiO2 NPs also improved shoot and root length, biomass accumulation, penile size, number of grains, and grain weight in sorghum plants infected with C. graminicola. Application of TiO2 NPs significantly increased the content of defense-related biochemicals, including total phenolic contents, activities of defense-related enzymes (PO, PPO, and PAL), photosynthetic pigments (total chlorophyll contents and carotenoids), and total protein contents. Collectively, our study verified the potential of green-synthesized titanium dioxide nanoparticles to suppress anthracnose disease by activating a defense system and stimulating growth and yield promotion under pathogen stress.

Metal nanoparticles and pesticides under global climate change: Assessing the combined effects of multiple abiotic stressors on soil microbial ecosystems

The soil is a vital resource that hosts many microorganisms crucial in biogeochemical cycles and ecosystem health. However, human activities such as the use of metal nanoparticles (MNPs), pesticides and the impacts of global climate change (GCCh) can significantly affect soil microbial communities (SMC). For many years, pesticides and, more recently, nanoparticles have contributed to sustainable agriculture to ensure continuous food production to sustain the significant growth of the world population and, therefore, the demand for food. Pesticides have a recognized pest control capacity. On the other hand, nanoparticles have demonstrated a high ability to improve water and nutrient retention, promote plant growth, and control pests. However, it has been reported that their accumulation in agricultural soils can also adversely affect the environment and soil microbial health. In addition, climate change, with its variations in temperature and extreme water conditions, can lead to drought and increased soil salinity, modifying both soil conditions and the composition and function of microbial communities. Abiotic stressors can interact and synergistically or additively affect soil microorganisms, significantly impacting soil functioning and the capacity to provide ecosystem services. Therefore, this work reviewed the current scientific literature to understand how multiple stressors interact and affect the SMC. In addition, the importance of molecular tools such as metagenomics, metatranscriptomics, proteomics, or metabolomics in the study of the responses of SMC to exposure to multiple abiotic stressors was examined. Future research directions were also proposed, focusing on exploring the complex interactions between stressors and their long-term effects and developing strategies for sustainable soil management. These efforts will contribute to the preservation of soil health and the promotion of sustainable agricultural practices.

Effect of CeO2, TiO2 and SiO2 nanoparticles on the growth and quality of model medicinal plant Salvia miltiorrhiza by acting on soil microenvironment

In this study, a six-month pot experiment was conducted to explore the effects of nanoparticles (NPs), including CeO2, TiO2 and SiO2 NPs at 200 and 800 mg/kg, on the growth and quality of model medicinal plant Salvia miltiorrhiza. A control group was implemented without the application of NPs. Results showed that NPs had no significant effect on root biomass. Treatment with 200 mg/kg of SiO2 NPs significantly increased the total tanshinone content by 44.07 %, while 200 mg/kg of CeO2 NPs were conducive to a 22.34 % increase in salvianolic acid B content. Exposure to CeO2 NPs induced a substantial rise in the MDA content in leaves (176.25 % and 329.15 % under low and high concentration exposure, respectively), resulting in pronounced oxidative stress. However, TiO2 and SiO2 NPs did not evoke a robust response from the antioxidant system. Besides, high doses of CeO2 NP-amended soil led to reduced nitrogen, phosphorus and potassium contents. Furthermore, the NP amendment disturbed the carbon and nitrogen metabolism in the plant rhizosphere and reshaped the rhizosphere microbial community structure. The application of CeO2 and TiO2 NPs promoted the accumulation of metabolites with antioxidant functions, such as D-altrose, trehalose, arachidonic acid and ergosterol. NPs displayed a notable suppressive effect on pathogenic fungi (Fusarium and Gibberella) in the rhizosphere, while enriching beneficial taxa with disease resistance, heavy metal antagonism and plant growth promotion ability (Lysobacter, Streptomycetaceae, Bacillaceae and Hannaella). Correlation analysis indicated the involvement of rhizosphere microorganisms in plant adaptation to NP amendments. NPs regulate plant growth and quality by altering soil properties, rhizosphere microbial community structure, and influencing plant and rhizosphere microbe metabolism. These findings were beneficial to deepening the understanding of the mechanism by which NPs affect medicinal plants.

Earthworms improve the rhizosphere micro-environment to mitigate the toxicity of microplastics to tomato (Solanum lycopersicum)

Microplastics (MPs) are widespread in agricultural soil, potentially threatening soil environmental quality and plant growth. However, toxicological research on MPs has mainly been limited to individual components (such as plants, microbes, and animals), without considering their interactions. Here, we examined earthworm-mediated effects on tomato growth and the rhizosphere micro-environment under MPs contamination. Earthworms (Eisenia fetida) mitigated the growth-inhibiting effect of MPs on tomato plant. Particularly, when exposed to environmentally relevant concentrations (ERC, 0.02% w/w) of MPs, the addition of earthworms significantly (p < 0.05) increased shoot and root dry weight by 12-13% and 13-14%, respectively. MPs significantly reduced (p < 0.05) soil ammonium (NH4+-N) (0.55-0.69 mg/kg), nitrate nitrogen (NO3--N) (7.02-8.65 mg/kg) contents, and N cycle related enzyme activities (33.47-42.39 μg/h/g) by 37.7-50.9%, 22.6-37.2%, and 34.2-48.0%, respectively, while earthworms significantly enhanced (p < 0.05) inorganic N mineralization and bioavailability. Furthermore, earthworms increased bacterial network complexity, thereby enhancing the robustness of the bacterial system to resist soil MPs stress. Meanwhile, partial least squares modelling showed that earthworms significantly influenced (p < 0.01) soil nutrients, which in turn significantly affected (p < 0.01) plant growth. Therefore, the comprehensive consideration of soil ecological composition is important for assessing MPs ecological risk.

Advancing Simultaneous Extraction and Sequential Single-Particle ICP-MS Analysis for Metallic Nanoparticle Mixtures in Plant Tissues

Engineered nanoparticles (ENPs) have been increasingly used in agricultural operations, leading to an urgent need for robust methods to analyze co-occurring ENPs in plant tissues. In response, this study advanced the simultaneous extraction of coexisting silver, cerium oxide, and copper oxide ENPs in lettuce shoots and roots using macerozyme R-10 and analyzed them by single-particle inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, the standard stock suspensions of the ENPs were stabilized with citrate, and the long-term stability (up to 5 months) was examined for the first time. The method performance results displayed satisfactory accuracies and precisions and achieved low particle concentration and particle size detection limits. Significantly, the oven drying process was proved not to impact the properties of the ENPs; therefore, oven-dried lettuce tissues were used in this study, which markedly expanded the applicability of this method. This robust methodology provides a timely approach to characterize and quantify multiple coexisting ENPs in plants.

Biochar and nano-hydroxyapatite combined remediation of soil surrounding tailings area: Multi-metal(loid)s fixation and soybean rhizosphere soil microbial improvement

The soil near tailings areas is relatively barren and contaminated by multi-metal(loid)s, seriously threatening the safety of crop production. Here, biochar and nano-hydroxyapatite (nHAP) were combined to improve the sterilized and unsterilized polymetallic contaminated soil, and soil incubation and soybean pot experiments were designed. Results showed that biochar and nHAP not only increased soil C, N, and P but also effectively reduced multi-metal bioavailability, wherein the combined application of the two amendments had the best effect on metal immobilization. The synergistic effect of the two amendments decreased the acid-soluble contents of Co, Cu, Fe, and Pb in rhizosphere soils up to 86.75%, 80.69%, 89.09%, and 96.70%, respectively. The ameliorant reduced the accumulation of metal(loid)s in soybean plants, and rhizosphere microorganisms inhibited the migration of soil metals to plants. Additionally, biochar and nHAP regulated the rhizosphere soil microbial community. The rhizosphere soil of the sterilization group tended to prioritize the restoration of the original dominant bacteria. As, Pb, Fe, Urease, OM, TN, and TP were the critical environmental variables affecting rhizosphere soil bacterial communities. Therefore, combining biochar and nHAP is an environmentally friendly strategy to reduce polymetallic mobility in tailings soil and crops and improve soil microbial community structure.

Controllable chemical redox reactions to couple microbial degradation for organic contaminated sites remediation: A review

Global environmental concern over organic contaminated sites has been progressively conspicuous during the process of urbanization and industrial restructuring. While traditional physical or chemical remediation technologies may significantly destroy the soil structure and function, coupling moderate chemical degradation with microbial remediation becomes a potential way for the green, economic, and efficient remediation of contaminated sites. Hence, this work systematically elucidates why and how to couple chemical technology with microbial remediation, mainly focused on the controllable redox reactions of organic contaminants. The rational design of materials structure, selective generation of reactive oxygen species, and estimation of degradation pathway are described for chemical oxidation. Meanwhile, current progress on efficient and selective reductions of organic contaminants (i.e., dechlorination, defluorination, -NO2 reduction) is introduced. Combined with the microbial remediation of contaminated sites, several consideration factors of how to couple chemical and microbial remediation are proposed based on both fundamental and practical points of view. This review will advance the understanding and development of chemical-microbial coupled remediation for organic contaminated sites.

Green synthesis of chitosan nanoparticles using tea extract and its antimicrobial activity against economically important phytopathogens of rice

The aim of the present work is to biosynthesize Chitosan nanoparticles (CTNp) using tea (Camellia sinensis) extract, with potent antimicrobial properties towards phytopathogens of rice. Preliminary chemical analysis of the extract showed that they contain carbohydrate as major compound and uronic acid indicating the nature of acidic polysaccharide. The structure of the isolated polysaccharide was analyzed through FTIR and 1H NMR. The CTNp was prepared by the addition of isolated tea polysaccharides to chitosan solution. The structure and size of the CTNp was determined through FTIR and DLS analyses. The surface morphology and size of the CTNp was analysed by SEM and HRTEM. The crystalinity nature of the synthesized nanoparticle was identified by XRD analysis. The CTNp exhibited the antimicrobial properties against the most devastating pathogens of rice viz., Pyricularia grisea, Xanthomonas oryzae under in vitro condition. CTNp also suppressed the blast and blight disease of rice under the detached leaf assay. These results suggest that the biosynthesized CTNp can be used to control the most devastating pathogens of rice.

Magnesium oxide nanoparticles reduce clubroot by regulating plant defense response and rhizosphere microbial community of tumorous stem mustard (Brassica juncea var. tumida)

Clubroot, caused by Plasmodiophora brassicae, is a major disease that significantly impairs the yield of cruciferous crops and causes significant economic losses across the globe. The prevention of clubroot, especially in tumorous stem mustard (without resistant varieties), are is limited and primarily relies on fungicides. Engineered nanoparticles have opened up new avenues for the management of plant diseases, but there is no report on their application in the prevention of clubroot. The results showed that the control efficacy of 500 mg/L MgO NPs against clubroot was 54.92%. However, when the concentration was increased to 1,500 and 2,500 mg/L, there was no significant change in the control effect. Compared with CK, the average fresh and dry weight of the aerial part of plants treated with MgO NPs increased by 392.83 and 240.81%, respectively. Compared with the F1000 treatment, increases were observed in the content of soil available phosphorus (+16.72%), potassium (+9.82%), exchangeable magnesium (+24.20%), and water-soluble magnesium (+20.64%) in the 1,500 mg/L MgO NPs treatment. The enzyme-linked immune sorbent assay (ELISA) results showed that the application of MgO NPs significantly increased soil peroxidase (POD, +52.69%), alkaline protease (AP, +41.21%), alkaline phosphatase (ALP, +79.26%), urease (+52.69%), and sucrase (+56.88%) activities; And also increased plant L-phenylalanine ammonla-lyase (PAL, +70.49%), polyphenol oxidase (PPO, +36.77%), POD (+38.30%), guaiacol peroxidase (POX, +55.46%) activities and salicylic acid (SA, +59.86%) content. However, soil and plant catalase (CAT, -27.22 and - 19.89%, respectively), and plant super oxidase dismutase (SOD, -36.33%) activities were significantly decreased after the application of MgO NPs. The metagenomic sequencing analysis showed that the MgO NPs treatments significantly improved the α-diversity of the rhizosphere soil microbial community. The relative abundance of beneficial bacteria genera in the rhizosphere soil, including Pseudomonas, Sphingopyxis, Acidovorax, Variovorax, and Bosea, was significantly increased. Soil metabolic functions, such as oxidative phosphorylation (ko00190), carbon fixation pathways in prokaryotes (ko00720), indole alkaloid biosynthesis (ko00901), and biosynthesis of various antibiotics (ko00998) were significantly enriched. These results suggested that MgO NPs might control clubroot by promoting the transformation and utilization of soil nutrients, stimulating plant defense responses, and enriching soil beneficial bacteria.

Transport of Nanoparticles into Plants and Their Detection Methods

Nanoparticle transport into plants is an evolving field of research with diverse applications in agriculture and biotechnology. This article provides an overview of the challenges and prospects associated with the transport of nanoparticles in plants, focusing on delivery methods and the detection of nanoparticles within plant tissues. Passive and assisted delivery methods, including the use of roots and leaves as introduction sites, are discussed, along with their respective advantages and limitations. The barriers encountered in nanoparticle delivery to plants are highlighted, emphasizing the need for innovative approaches (e.g., the stem as a new recognition site) to optimize transport efficiency. In recent years, research efforts have intensified, leading to an evendeeper understanding of the intricate mechanisms governing the interaction of nanomaterials with plant tissues and cells. Investigations into the uptake pathways and translocation mechanisms within plants have revealed nuanced responses to different types of nanoparticles. Additionally, this article delves into the importance of detection methods for studying nanoparticle localization and quantification within plant tissues. Various techniques are presented as valuable tools for comprehensively understanding nanoparticle-plant interactions. The reliance on multiple detection methods for data validation is emphasized to enhance the reliability of the research findings. The future outlooks of this field are explored, including the potential use of alternative introduction sites, such as stems, and the continued development of nanoparticle formulations that improve adhesion and penetration. By addressing these challenges and fostering multidisciplinary research, the field of nanoparticle transport in plants is poised to make significant contributions to sustainable agriculture and environmental management.

Development and testing of environment friendly nanohybrid coatings for sustainable agriculture technologies

Less than 50% of the applied urea fertilizer is taken up by plants due to poor nitrogen (N) use efficiency which affects overall agricultural productivity and leads to serious environmental and economic problems. Additionally, soils with high salinity might limit zinc (Zn) availability. Low Zn use efficiency (<30%) when applied as synthetic salts, e.g., zinc sulfate has therefore minimized their applicability. Within the past two decades, nanotechnology has gained a lot of interest in the development of effective nano fertilizers with high nutrient use efficiency (NUE). In this perspective, the approach of coating conventional fertilizers with nano materials especially, the ones which are essential nutrients has researched because of their high use efficiency and reduced losses. In this work, a novel and innovative formulation of hybrid nano fertilizer has been prepared for the sustainable release of nutrients. Zinc oxide nanoparticles (ZnO-NPs <50 nm) were incorporated into the biodegradable polymer (gelatin) and coated on urea using a fluidized bed coater. Among all the formulations, GZnSNPs (1.5% gelatin+0.5% elemental Zn as ZnO-NPs) showed a significant delay in urea release (<80 %) after 120 min). The sand column experiment showed sustainable Zn release for GZnSNPs i.e., 2.7 ppm vs. 3.5 ppm (GZnS) after the 6th day. Moreover, a substantial increase in wheat grain yield (6500 kg/ha), N uptake (46.5 kg/ha) and Zn uptake (21.64 g/ha) were observed for fields amended with GZnSNPs. The composition of GZnSNPs was valuable since this attracted the highest return relative to the other treatments. Gelatin supplied small N-containing molecules, resulting in extra value addition with ZnO-NPs thus increasing yield and fertilizer properties more relative to the same amount of elemental Zn given via bulk salt. Therefore, the findings of the current study recommend the use of ZnO-NPs in the agricultural sector without any negative effects on yield and NUE.

Comprehensive response of microbes to Ag and Ag2S nanoparticles and silver spatial distribution in constructed wetlands

This study investigated functional bacteria, key enzymes, and nitrogen metabolism in vertical flow constructed wetlands (CWs) after exposing to silver, silver sulfide nanoparticles (Ag NPs and Ag2S NPs), and silver iron (Ag+), and silver spatial distribution in CWs for 155 days. Ag NPs and Ag2S NPs affected species richness and diversity whereas Ag+ showed the higher the species diversity indices. Sequencing analysis exhibited that Ag NPs or Ag+ significantly inhibited nitrogen metabolic process by hindering the relative activity of functional enzymes, downregulating relative abundances of nrfA, norB and napA for Ag NPs, nxrA gene for Ag+, while Ag2S NPs inhibited relative abundance of nirA. The above results confirmed that NPs or Ag+ significantly reduced nitrogen removal and Ag NPs mainly inhibited NO3--N removal while Ag+ significantly suppressed NH4+-N removal. This study also found that CWs could effectively remove NPs or Ag+ (about 98 %), and nanoparticles showed higher translocation factors (TFs) values (0.81-1.15 or 0.36), indicating nanoparticles transported easily through substrate layers.

Responses of soil bacterial and fungal denitrification and associated N2O emissions to organochloride pesticide

The extensive application of organochloride pesticides in agriculture has raised concerns about their potential negative impacts on soil microbial denitrification and associated N2O emissions. However, most studies have primarily focused on bacteria, and the contribution of fungi to N2O emissions and their response to organochloride pesticides have often been overlooked. In this study, 15N tracing combined with the respiration inhibition method was applied to examine the impacts of chlorothalonil on both fungal and bacterial denitrification. The results demonstrated that fungal N2O emissions dominated in the absence of chlorothalonil, accounting for 73 % of total N2O emissions. Chlorothalonil inhibited fungal and bacterial denitrification via different mechanisms and altered the main pathways of soil N2O emissions. Amplicon sequencing analyses indicated that chlorothalonil significantly reduced the abundances of N2O-producing fungi owing to its fungicidal effect and fungal N2O emissions significantly dropped. Molecular biological analyses revealed that chlorothalonil induced lower electron generation, transport, and consumption efficiencies, which led to the inhibition of denitrifying enzymes in bacteria. Bacterial N2O emissions dramatically increased and became the dominant source. These findings provide insights into the mechanisms by which N2O emissions from fungal and bacterial denitrification are influenced by chlorothalonil.

Microbial bioprocess performance in nanoparticle-mediated composting

Microbial composting is one of the most cost-effective techniques for degradation, remediation, nutrition, etc. Currently, there is faster growth and development in nanotechnology in different sectors. This development leads nanoparticles (NPs) to enter into the composts in different ways. First, unintentional entry of NPs into the composts via: waste discharge, buried solid waste, surface runoff, direct disposal into wastes (consumer goods, food, pharmaceuticals, and personal care products). Second, intentional mediation of the NPs in the composting process is a novel approach developed to enhance the degradation rate of wastes and as a nutrient for plants. The presence of NPs in the composts can cause nanotoxicity. Conversely, their presence might also be beneficial, such as soil reclamations, degradation, etc. Alternatively, metal NPs are also helpful for all living organisms, including microorganisms, in various biological processes, such as DNA replication, precursor biosynthesis, respiration, oxidative stress responses, and transcription. NPs show exemplary performance in multiple fields, whereas their role in composting process is worth studying. Consequently, this article aids the understanding of the role of NPs in the composting process and how far their presence can be beneficial. This article reviews the significance of NPs in: the composting process, microbial bioprocess performance during nano composting, basic life cycle assessment (LCA) of NP-mediated composting, and mode of action of the NPs in the soil matrix. This article also sheds insight on the notion of nanozymes and highlights their biocatalytic characterization, which will be helpful in future composting research.

Differences in microbial communities and potato growth in two soil types under organic cultivation

Organic agriculture plays a positive role in promoting genetic diversity, including living organisms, plants, and cultivated crops in the soil. However, few comparative studies reported whether different soil types were suitable for organic cultivation. In this study, loam and clay-loam soils under continuous organic cultivation were analyzed. The results showed that there were no significant differences between two soil types in soil pH, bulk density, total porosity, moisture content and three soil phases. The capillary porosity and organic matter content of loam were significantly higher than those of clay-loam. Compared with clay-loam soil, the contents of total nitrogen, phosphorus, potassium, calcium, zinc and silicon in loam soil were also significantly higher. The microbial diversity was higher in loam and the dominant microbes differed between the two soils. Glycosyl transferases and carbohydrate esterases were enriched in loam, whereas glycoside hydrolases and carbohydrate-binding modules were enriched in clay loam. The potato yield in loam was significantly higher than that in clay loam. Among the tuber quality indicators, the protein content of potatoes in loam was higher than that in clay-loam, but the reducing sugar content was lower for loam than for clay-loam. In conclusion, compared with clay loam, loam was more suitable for organic cultivation of potatoes on account of the high contents of nitrogen, phosphorus, and potassium and the rich microbial community, thus promoting a high yield of tubers. This study provided a theoretical reference for the selection of soil type suitable for organic cultivation.

Environmental effects and interaction of nanoparticles on beneficial soil and aquatic microorganisms

A steadily increasing production volume of nanoparticles reflects their numerous industrial and domestic applications. These economic successes come with the potential adverse effects on natural systems that are associated with their presence in the environment. Biological activities and effects of nanoparticles are affected by their entry method together with their specificities like their size, shape, charge, area, and chemical composition. Particles can be classified as safe or dangerous depending on their specific properties. As both aquatic and terrestrial systems suffer from organic and inorganic contamination, nanoparticles remain a sink for these contaminants. Researching the sources, synthesis, fate, and toxicity of nanoparticles has advanced significantly during the last ten years. We summarise nanoparticle pathways throughout the ecosystem and their interactions with beneficial microorganisms in this research. The prevalence of nanoparticles in the ecosystem causes beneficial microorganisms to become hazardous to their cells, which prevents the synthesis of bioactive molecules from undergoing molecular modifications and diminishes the microbe population. Recently, observed concentrations in the field could support predictions of ambient concentrations based on modeling methodologies. The aim is to illustrate the beneficial and negative effects that nanoparticles have on aqueous and terrestrial ecosystems, as well as the methods utilized to reduce their toxicity.

Microbial Catabolic Activity: Methods, Pertinence, and Potential Interest for Improving Microbial Inoculant Efficiency

Microbial catabolic activity (MCA) defined as the degrading activity of microorganisms toward various organic compounds for their growth and energy is commonly used to assess soil microbial function potential. For its measure, several methods are available including multi-substrate-induced respiration (MSIR) measurement which allow to estimate functional diversity using selected carbon substrates targeting specific biochemical pathways. In this review, the techniques used to measure soil MCA are described and compared with respect to their accuracy and practical use. Particularly the efficiency of MSIR-based approaches as soil microbial function indicators was discussed by (i) showing their sensitivity to different agricultural practices including tillage, amendments, and cropping systems and (ii) by investigating their relationship with soil enzyme activities and some soil chemical properties (pH, soil organic carbon, cation exchange capacity). We highlighted the potential of these MSIR-based MCA measurements to improve microbial inoculant composition and to determine their potential effects on soil microbial functions. Finally, we have proposed ideas for improving MCA measurement notably through the use of molecular tools and stable isotope probing which can be combined with classic MSIR methods. Graphical abstract describing the interrelation between the different parts and the concepts developed in the review.

Arsenic pollution from human activities drives changes in soil microbial community characteristics

Soil arsenic (As) pollution not only decreases plant productivity but also soil quality, in turn hampering sustainable agricultural development. Despite the negative effects of As contamination on rice yield and quality being reported widely, the responses of microbial communities and co-occurrence networks in paddy soil to As pollution have not been explored. Here, based on high-throughput sequencing technologies, we investigated bacterial abundance and diversity in paddy soils with different levels of As contamination, and constructed associated microbial co-occurrence networks. As pollution reduced soil bacterial diversity significantly (p < 0.001). In addition, bioavailable As concentrations were negatively correlated with Actinobacteria and Acidobacteria relative abundance (p < 0.05). Conversely, As pollution had a positive relationship with Chloroflexi, Betaproteobacteria, and Bacteroidetes relative abundance (p < 0.05). Firmicutes relative abundance decreased with an increase in total As concentration. The ecological clusters and key groups in bacterial co-occurrence networks exhibited distinct trends with an increase in As pollution. Notably, Acidobacteria play an important role in maintaining microbial networks in As contaminated soils. Overall, we provide empirical evidence that As contamination influences soil microbial community structure, posing a threat to soil ecosystem health and sustainable agriculture.

Panorama of biogenic nano-fertilizers: A road to sustainable agriculture

The ever-increasing demand for food from the growing population has augmented the consumption of fertilizers in global agricultural practices. However, the excessive usage of chemical fertilizers with poor efficacy is drastically deteriorating ecosystem health through the degradation of soil fertility by diminishing soil microflora, environment contamination, and human health by inducing chemical remnants to the food chain. These challenges have been addressed by the integration of nanotechnological and biotechnological approaches resulting in nano-enabled biogenic fertilizers (NBF), which have revolutionized agriculture sector and food production. This review critically details the state-of-the-art NBF production, types, and mechanism involved in cultivating crop productivity/quality with insights into genetic, physiological, morphological, microbiological, and physiochemical attributes. Besides, it explores the associated challenges and future routes to promote the adoption of NBF for intelligent and sustainable agriculture. Furthermore, diverse applications of nanotechnology in precision agriculture including plant biosensors and its impact on agribusiness and environmental management are discussed.

Siddique K, Li B. Nanobiotechnology to advance stress resilience in plants: Current opportunities and challenges

A sustainable and resilient crop production system is essential to meet the global food demands. Traditional chemical-based farming practices have become ineffective due to increased population pressures and extreme climate variations. Recently, nanobiotechnology is considered to be a promising approach for sustainable crop production by improving the targeted nutrient delivery, pest management efficacy, genome editing efficiency, and smart plant sensor implications. This review provides deeper mechanistic insights into the potential applications of engineered nanomaterials for improved crop stress resilience and productivity. We also have discussed the technology readiness level of nano-based strategies to provide a clear picture of our current perspectives of the field. Current challenges and implications in the way of upscaling nanobiotechnology in the crop production are discussed along with the regulatory requirements to mitigate associated risks and facilitate public acceptability in order to develop research objectives that facilitate a sustainable nano-enabled Agri-tech revolution. Conclusively, this review not only highlights the importance of nano-enabled approaches in improving crop health, but also demonstrated their roles to counter global food security concerns.

Recent advances in stimuli-response mechanisms of nano-enabled controlled-release fertilizers and pesticides

Nanotechnology-enabled fertilizers and pesticides, especially those capable of releasing plant nutrients or pesticide active ingredients (AIs) in a controlled manner, can effectively enhance crop nutrition and protection while minimizing the environmental impacts of agricultural activities. Herein, we review the fundamentals and recent advances in nanofertilizers and nanopesticides with controlled-release properties, enabled by nanocarriers responsive to environmental and biological stimuli, including pH change, temperature, light, redox conditions, and the presence of enzymes. For pH-responsive nanocarriers, pH change can induce structural changes or degradation of the nanocarriers or cleave the bonding between nutrients/pesticide AIs and the nanocarriers. Similarly, temperature response typically involves structural changes in nanocarriers, and higher temperatures can accelerate the release by diffusion promoting or bond breaking. Photothermal materials enable responses to infrared light, and photolabile moieties (e.g., o-nitrobenzyl and azobenzene) are required for achieving ultraviolet light responses. Redox-responsive nanocarriers contain disulfide bonds or ferric iron, whereas enzyme-responsive nanocarriers typically contain the enzyme's substrate as a building block. For fabricating nanofertilizers, pH-responsive nanocarriers have been well explored, but only a few studies have reported temperature- and enzyme-responsive nanocarriers. In comparison, there have been more reports on nanopesticides, which are responsive to a range of stimuli, including many with dual- or triple-responsiveness. Nano-enabled controlled-release fertilizers and pesticides show tremendous potential for enhancing the utilization efficiency of nutrients and pesticide AIs. However, to expand their practical applications, future research should focus on optimizing their performance under realistic conditions, lowering costs, and addressing regulatory and public concerns over environmental and safety risks.

Analog soil organo-ferrihydrite composites as suitable amendments for cadmium and arsenic stabilization in co-contaminated soils

Remediation of CdAs co-contaminated soils has long been considered a difficult problem to solve, as Cd and As have distinctly different metallic characters. Amending contaminated soils with traditional single passivation materials may not always work well in the stabilization of both Cd and As. Here, we reported that analog soil organo-ferrihydrite composites made with either living or non-living organics (bacterial cells or humic acid) could achieve stabilization of both Cd and As in contaminated soils. BCR and Wenzel sequential extractions showed that organo-ferrihydrite, particularly at 1 wt% loading, shifted liable Cd and As to more stable phases. Organo-ferrihydrite amendments significantly (p < 0.05) increased soil urease, alkaline phosphatase and catalase enzyme activities. With organo-ferrihydrite amendments, the bioavailable fraction of Cd decreased to 35.3 % compared with the control (65.1 %), while the bioavailable As declined from 29.4 % to 12.4%. Soil pH, microbial community abundance and diversity were almost unaffected by organo-ferrihydrite. Ferrihydrite and organo fractions both contributed to direct Cd-binding, while the organo fraction probably maintained the Fe-bound As via lowering ferrihydrite phase transformation. Compared to pure ferrihydrite, organo-ferrihydrite composites performed better not only in reducing liable Cd and As, but also in maintaining soil quality and ecosystem functions. This study demonstrates the applications of organo-ferrihydrite composites in eco-friendly remediation of CdAs contaminated soils, and provides a new direction in selecting appropriate soil amendments.

Pristine and Sulfidized Zinc Oxide Nanoparticles Promote the Release and Decomposition of Organic Carbon in the Legume Rhizosphere

The effects and mechanisms of zinc oxide nanoparticles (ZnO NPs) and their aging products, sulfidized (s-) ZnO NPs, on the carbon cycling in the legume rhizosphere are still unclear. We observed that, after 30 days of cultivation, in the rhizosphere soil of Medicago truncatula, under ZnO NP and s-ZnO NP treatments, the dissolved organic carbon (DOC) concentrations were significantly increased by 1.8- to 2.4-fold compared to Zn²⁺ treatments, although the soil organic matter (SOM) contents did not change significantly. Compared to Zn²⁺ additions, the additions of NPs significantly induced the production of root metabolites such as carboxylic acids and amino acids and also stimulated the growth of microbes involved in the degradations of plant-derived and recalcitrant SOM, such as bacteria genera RB41 and Bryobacter, and fungi genus Conocybe. The bacterial co-occurrence networks indicated that microbes associated with SOM formation and decomposition were significantly increased under NP treatments. The adsorption of NPs by roots, the generation of root metabolites (e.g., carboxylic acid and amino acid), and enrichment of key taxa (e.g., RB41 and Gaiella) were the major mechanisms by which ZnO NPs and s-ZnO NPs drove DOC release and SOM decomposition in the rhizosphere. These results provide new perspectives on the effect of ZnO NPs on agroecosystem functions in soil-plant systems.

Nano-Nd2O3 reduced soil bacterial community function by altering the relative abundance of rare and sensitive taxa

Nanoparticulate-Nd₂O₃ (nano-Nd₂O₃) has been excessively utilized in agriculture, industry, and medicine. Hence, nano-Nd₂O₃ can have environmental implications. However, the impact of nano-Nd₂O₃ on alpha diversity, composition, and function of soil bacterial communities has not been thoroughly evaluated. We amended soil to achieve different concentrations of nano-Nd₂O₃ (0, 10, 50, and 100 mg kg^-1 soil) and incubated the mesocosms for 60 days. On days 7 and 60 of the experiment, we measured the effect of nano-Nd₂O₃ on alpha diversity and composition of soil bacterial community. Further, the effect of nano-Nd₂O₃ on the function of soil bacterial community was assessed based on changes in the activities of the six potential enzymes that mediate the cycling of nutrients in the soil. Nano-Nd₂O₃ did not alter the alpha diversity and composition of the soil bacterial community; however, it negatively affected community function in a dose-dependent manner. Specifically, the activities of β-1,4-glucosidase and β-1,4-n-acetylglucosaminidase that mediate soil carbon and nitrogen cycling, respectively, were significantly affected on days 7 and 60 of the exposure. The effect of nano-Nd₂O₃ on the soil enzymes correlated with changes in relative abundances of the rare and sensitive taxa, viz., Isosphaerales, Isosphaeraceae, Ktedonobacteraceae, and Streptomyces. Overall, we provide information for the safe implementation of technological applications that use nano-Nd₂O₃.

Bioremediation system consisted with Leclercia adecarboxylata and nZVI@Carbon/Phosphate for lead immobilization: The passivation mechanisms of chemical reaction and biological metabolism in soil

Bioremediation is one of the most promising strategies for heavy metal immobilization. A new remediation system was demonstrated in this research, which combined phosphate solubilizing bacteria (PSB) with nZVI@Carbon/Phosphate (nZVI@C/P) composite to remediate lead contaminated soil. Experimental results indicated that the new system (nZVI@C/P + PSB) could effectively convert the labile Pb into the stable fraction after 30 days of incubation, which increased the maximum residual fraction percentage of Pb by 70.58%. The characterization results showed that lead may exist in the forms of Pb₅(PO₄)₃Cl, PbSO₄ and 3PbCO₃·2Pb(OH)₂·H₂O in the soil treated with nZVI@C/P + PSB. Meanwhile, soil enzyme activities and Leclercia abundance were enhanced in the treated soil compared with CK during the incubation time. In addition, the specialized functions (e.g. ABC transporters, siderophore metabolism, sulfur metabolism and phosphorus metabolism) in PSB and nZVI@C/P + PSB group were also enhanced. These phenomena proved that the key soil metabolic functions may be maintained and enhanced through the synergistic effect of incubated PSB and nZVI@C/P. The study demonstrated that this new bioremediation system provided feasible way to improve the efficacy for lead contaminated soil remediation.

Assessment of CuO NPs on soil microbial community structure based on phospholipid fatty acid techniques and phytotoxicity of bok choy seedlings

In this study, a soil culture and a hydroponic experiment were conducted to assess the toxicology effects of copper oxide nanoparticles (CuO NPs) on soil microbial community structure and the growth of bok choy. Results showed CuO NPs had an inhibitory effect on soil microbial abundance, diversity, and activity, as well as the bok choy seedling growth, whereas CuO NPs at low concentrations did not significantly affect the soil microbial biomass or plant growth. In soil, CuO NPs at high dose (80 mg kg^-1) significantly reduced the indexes of Simpson diversity, Shannon-Wiener diversity and Pielou evenness by 3.7%, 4.9% and 4.5%, respectively. In addition, CuO NPs at 20 and 80 mg kg^-1 treatment significantly reduced soil enzymes (urease, alkaline phosphatase, dehydrogenase, and catalase) activities by 25.5%-58.9%. Further, CuO NPs at 20 mg L^-1 significantly inhibited the growth of plant root by 33.8%, and catalase (CAT) activity by 17.9% in bok choy seedlings. The present study can provide a basis for a comprehensive evaluation of the toxicity effect of CuO NPs on soil microorganisms and phytotoxicity to bok choy seedlings.

Biosynthesis and characterization of nanoparticles, its advantages, various aspects and risk assessment to maintain the sustainable agriculture: Emerging technology in modern era science

The current review aims to gain knowledge on the biosynthesis and characterization of nanoparticles (NPs), their multifactorial role, and emerging trends of NPs utilization in modern science, particularly in sustainable agriculture, for increased yield to solve the food problem in the coming era. However, it is well known that an environment-friendly resource is in excessive demand, and green chemistry is an advanced and rising resource in exploring eco-friendly processes. Plant extracts or other resources can be utilized to synthesize different types of NPS. Hence NPs can be synthesized by organic or inorganic molecules. Inorganic molecules are hydrophilic, biocompatible, and highly steady compared to organic types. NPs occur in numerous chemical conformations ranging from amphiphilic molecules to metal oxides, from artificial polymers to bulky biomolecules. NPs structures can be examined by different approaches, i.e., Raman spectroscopy, optical spectroscopy, X-ray fluorescence, and solid-state NMR. Nano-agrochemical is a unification of nanotechnology and agro-chemicals, which has brought about the manufacture of nano-fertilizers, nano-pesticides, nano-herbicides, nano-insecticides, and nano-fungicides. NPs can also be utilized as an antimicrobial solution, but the mode of action for antibacterial NPs is poorly understood. Presently known mechanisms comprise the induction of oxidative stress, the release of metal ions, and non-oxidative stress. Multiple modes of action towards microbes would be needed in a similar bacterial cell for antibacterial resistance to develop. Finally, we visualize multidisciplinary cooperative methods will be essential to fill the information gap in nano-agrochemicals and drive toward the usage of green NPs in agriculture and plant science study.

Environmental effect of agriculture-related manufactured nano-objects on soil microbial communities

Agriculture-related manufactured nano-objects (MNOs) can revolutionize the crop production and help to achieve sustainable development goals. MNOs with diverse physico-chemical properties and ability to encapsulate and deliver active ingredients in controlled, targeted and stimuli responsive manner can enhance the efficiency while minimizing collateral damage to non-target organisms and environment. Application of MNOs in the form of nanopesticides and nanofertilizers is known to affect soil microbial communities both positively and negatively, but detailed studies with varying dose, type and environmental conditions are scarce. Therefore, it is imperative to understand the complex mechanisms and factors which shape the MNOs-microbial interactions through integrating state of the art technologies including omics (transcriptomics, metabolomics, and proteomics), artificial intelligence, and statistical frameworks. Lastly, we propose the idea of MNOs-mediated manipulation of soil microbiome to modify the soil microbial communities for improved microbial services. These microbial services, if harnessed appropriately, can revolutionize modern agriculture and help in achieving sustainable development goals.

Biochar and metal-tolerant bacteria in alleviating ZnO nanoparticles toxicity in barley

The constant use of zinc oxide nanoparticles (ZnO NPs) in agriculture could increase their concentration in soil, and cause a threat to sustainable crop production. The present study was designed to determine the role of spore-forming and metal-tolerant bacteria, and biochar in alleviating the toxic effects of a high dose of ZnO NPs (2000 mg kg^-1) spiked to the soil (Haplic Chernozem) on barley (Hordeum sativum L). The mobile compounds of Zn in soil and their accumulation in H. sativum tissues were increased significantly. The addition of biochar (2.5% of total soil) and bacteria (10¹⁰ CFU kg^-1) separately and in combination showed a favorable impact on H. sativum growth in ZnO NPs polluted soil. The application of bacteria (separately) to the contaminated soil reduced the mobility of Zn compounds by 7%, due to loosely bound Zn compounds, whereas only biochar inputs lowered Zn mobile compounds mobility by 33%, even the combined application of biochar and bacteria also suppressed the soil Zn mobile compounds. Individual application of biochar and bacteria reduced the Zn plant uptake, i.e., underground parts (roots) by 44% and 20%, and in the above-ground parts of H. sativum plants by 39% and 13%, respectively, compared to ZnO NPs polluted soil treatments. Biochar, both separately and in combination with bacteria improved the root length by 48 and 85%, and plant height by 53 and 40%, respectively, compared to the polluted control. The root length and plant height decreased by 52 and 40% in ZnO NPs spiked soil compared clean soil treatments. Anatomical results showed an improvement in the structural organization of cellular-sub-cellular tissues of root and leaf. The changes in ultrastructural organization of assimilation tissue cells were noted all treatments due to the toxic effects of ZnO NPs compared with control treatment. The results indicate that metal-tolerant bacteria and biochar could be effective as a soil amendment to reduce metal toxicity, enhance crop growth, and improve soil health.

Activation of persulfate by vanadium oxide modified carbon nanotube for 17β-estradiol degradation in soil: Mechanism, application and ecotoxicity assessment

Steroid hormones in the environment have attracted public attention because of their high endocrine-disrupting activity even at rather low exposure level. Excessive hormones in the soil from the pollutant discharge of intensive farming would pose a potential threat to the ecology and the human health. Vanadium oxide modified carbon nanotube (VO_X-CNT) was synthesized and applied as persulfate (PDS) activator to reduce17β-estrogen (17β-E2) in soil. 86.06 % 17β-E2 could be degraded within 12 h. Process of materials exchange during oxidation was interfered by soil, resulting in insufficient degradation of 17β-E2, but the active species involved in 17β-E2 degradation would also be enriched by it. 17β-E2 was adsorbed on the VO_X-CNT surface and directly degraded mainly by the active species generated on the catalyst surface, and ^•OH dominated the degradation of 17β-E2 in VO_X-CNT/PDS system. CO, defective sites and vanadium oxides on the surface of VO_X-CNT contributed to the generation of activate species. Oxidizer dosage, catalyst dosage, water-soil ratio and soil properties would affect the degradation of 17β-E2. The ecotoxicological impact on soil caused by VO_X-CNT/PDS was acceptable, and would be weakened with time. Additionally, a rapid decrease in the concentration of 17β-E2 and the promotion of maize growth were observed with VO_X-CNT/PDS in situ pilot-scale remediation. Those results reveal that VO_X-CNT/PDS is a potential technology to remove excessive steroid hormone from soil around large-scale livestock and poultry farms.

Elevated CO2 exacerbates effects of TiO2 nanoparticles on rice (Oryza sativa L.) leaf transcriptome and soil bacteria

Elevated CO₂ affects the plant rhizosphere and can therefore affect the fate and toxicity of soil contaminants. However, little is known about how the effects of nanoparticles on plants and soil bacteria will change under future CO₂ levels. A free-air CO₂ enrichment system with two CO₂ levels (ambient, 390 μmol mol^-1; elevated, 590 μmol mol^-1) was used to investigate the responses of rice (Oryza sativa L.) and soil bacteria to titanium dioxide nanoparticles (nano-TiO₂, 0 and 200 mg kg^-1). Results showed that nano-TiO₂ alone did not significantly affect rice growth but affected soil bacteria involved in the carbon and sulfur cycles. Elevated CO₂ alone increased rice plant biomass and up-regulated genes related to ribosomes, but its combination with nano-TiO₂ down-regulated genes related to photosynthesis and photosynthetic antennae. Elevated CO₂ also exacerbated the disturbance by nano-TiO₂ to soil bacteria involved in carbon and nitrogen cycles, and consequently inhibited the rice growth. These findings provide a reference for the comprehensive evaluation for the risk of soil pollution.

Development and testing of zinc sulfate and zinc oxide nanoparticle-coated urea fertilizer to improve N and Zn use efficiency

Nitrogen (N) losses from conventional fertilizers in agricultural systems are very high, which can lead to serious environmental pollution with economic loss. In this study, innovative slow-release fertilizers were prepared using zinc (Zn) [nanoparticles (NPs) or in bulk], using molasses as an environmentally friendly coating. Several treatments were prepared using Zn in different concentrations (i.e., 0.25%, 0.5%, and 4% elemental Zn). The zinc oxide nanoparticles (ZnO-NPs) were prepared from zinc sulfate heptahydrate (ZnSO₄·7H₂O), and were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the Zn-loaded urea samples were tested for urea N release rate, leaching of water from soil, and crushing strength to assess the impact of coating on the final finished product. Pot experiments were conducted simultaneously to check the agronomic effects of Zn-coated slow-release urea on the growth and development of wheat (Triticum aestivum L.). The laboratory and pot results confirmed that the ZnO-NP treatments boost wheat growth and yield as a result of reduced N and Zn release. UZnNPs2 (urea coated with 0.5% ZnO-NPs and 5% molasses) demonstrated the best results among all the treatments in terms of slow nutrient release, N and Zn uptake, and grain yield. The UZnNPs2 treatment increased plant yield by 34% (i.e., 4,515 vs. 3,345 kg ha^-1) relative to the uncoated prill-treated crop because of the slower release of Zn and N.

Effect of zinc and iron oxide nanoparticles on plant physiology, seed quality and microbial community structure in a rice-soil-microbial ecosystem

In this study, we assessed the impact of zinc oxide (ZnO) and iron oxide (FeO) (<36 nm) nanoparticles (NPs) as well as their sulphate salt (bulk) counterpart (0, 25, 100 mg/kg) on rice growth and seed quality as well as the microbial community in the rhizosphere environment of rice. During the rice growing season 2021-22, all experiments were conducted in a greenhouse (temperature: day 30 °C; night 20 °C; relative humidity: 70%; light period: 16 h/8 h, day/night) in rice field soil. Results showed that low concentrations of FeO and ZnO NPs (25 mg/kg) promoted rice growth (height (29%, 16%), pigment content (2%, 3%)) and grain quality parameters such as grains per spike (8%, 9%), dry weight of grains (12%, 14%) respectively. As compared to the control group, the Zn (2%) and Fe (5%) accumulations at their respective low concentrations of NP treatments showed stimulation. Interestingly, our results showed that at low concentration of both the NPs the soil microbes had more diversity and richness than those in the bulk treated and control soil group. Although a number of phyla were affected by the presence of NPs, the strongest effects were observed for change in the abundance of the three phyla for Proteobacteria, Actinobacteria, and Planctomycetes. The rhizosphere environment was notably enriched with potential streptomycin producers, carbon and nitrogen fixers, and lignin degraders with regard to functional groups of microorganisms. However, microbial communities mainly responsible for chitin degradation, ammonia oxidation, and nitrite reduction were found to be decreased. The results from this study highlight significant changes in several plant-based endpoints, as well as the rhizosphere soil microorganisms. It further adds information to our understanding of the nanoscale-specific impacts of important micronutrient oxides on both rice and its associated soil microbiome.

The Widespread Use of Nanomaterials: The Effects on the Function and Diversity of Environmental Microbial Communities

In recent years, as an emerging material, nanomaterials have rapidly expanded from laboratories to large-scale industrial productions. Along with people's productive activities, these nanomaterials can enter the natural environment of soil, water and atmosphere through various ways. At present, a large number of reports have proved that nanomaterials have certain toxic effects on bacteria, algae, plants, invertebrates, mammalian cell lines and mammals in these environments, but people still know little about the ecotoxicology of nanomaterials. Most relevant studies focus on the responses of model strains to nanomaterials in pure culture conditions, but these results do not fully represent the response of microbial communities to nanomaterials in natural environments. Over the years, the effect of nanomaterials infiltrated into the natural environment on the microbial communities has become a popular topic in the field of nano-ecological environment research. It was found that under different environmental conditions, nanomaterials have various effects on the microbial communities. The medium; the coexisting pollutants in the environment and the structure, particle size and surface modification of nanomaterials may cause changes in the structure and function of microbial communities. This paper systematically summarizes the impacts of different nanomaterials on microbial communities in various environments, which can provide a reference for us to evaluate the impacts of nanomaterials released into the environment on the microecology and has certain guiding significance for strengthening the emission control of nanomaterials pollutants.

Biosynthesized metal oxide nanoparticles for sustainable agriculture: next-generation nanotechnology for crop production, protection and management

The current agricultural sector is not only in its most vulnerable state but is also becoming a threat to our environment due to expanding population and growing food demands along with worsening climatic conditions. In addition, numerous agrochemicals presently being used as fertilizers and pesticides have low efficiency and high toxicity. However, the rapid growth of nanotechnology has shown great promise to tackle these issues replacing conventional agriculture industries. Since the last decade, nanomaterials especially metal oxide nanoparticles (MONPs) have been attractive for improving agricultural outcomes due to their large surface area, higher chemical/thermal stability and tunable unique physicochemical characteristics. Further, to achieve sustainability, researchers have been extensively working on ecological and cost-effective biological approaches to synthesize MONPs. Hereby, we have elaborated on recent successful biosynthesis methods using various plants/microbes. Furthermore, we have elucidated different mechanisms for the interaction of MONPs with plants, including their uptake/translocation/internalization, photosynthesis, antioxidant activity, and gene alteration, which could revolutionize crop productivity/yield through increased nutrient amount, photosynthesis rate, antioxidative enzyme level, and gene upregulations. Besides, we have briefly discussed about functionalization of MONPs and their application in agricultural-waste-management. We have further illuminated recent developments of various MONPs (Fe₂O₃/ZnO/CuO/Al₂O₃/TiO₂/MnO₂) as nanofertilizers, nanopesticides and antimicrobial agents and their implications for enhanced plant growth and pest/disease management. Moreover, the potential use of MONPs as nanobiosensors for detecting nutrients/pathogens/toxins and safeguarding plant/soil health is also illuminated. Overall, this review attempts to provide a clear insight into the latest advances in biosynthesized MONPs for sustainable crop production, protection and management and their scope in the upcoming future of eco-friendly agricultural nanotechnology.