Nutrient Transformation Research Articles

Contributions of the bacterial communities to the microcystin degradation and nutrient transformations during aerobic composting of algal sludge

Aerobic composting is a useful method for managing and disposing of salvaged algal sludge. To optimize the composting process and improve compost quality, it is necessary to understand the functions and responses of microbial communities therein. This work studied the degradation process of organic matter and the assemblage of bacterial communities in algal sludge composting via 16S rRNA amplicon sequencing. The results showed that 77.08% of the microcystin was degraded during the thermophilic stage of composting, which was the main period for microcystin degradation. Bacterial community composition and diversity changed significantly during the composting, and gradually stabilized as the compost matured. Different composting stages may be dominated by different module groups separately, as shown in the co-occurrence networks of composting bacterial communities. In the networks, all bacteria associated with microcystin degradation were identified as connectors between different module groups. The algal sludge composting process was driven primarily by deterministic processes, and the main driving forces for bacterial community assembly were temperature, dissolved organic carbon, ammonium, and microcystin. At last, by applying the structural equation modeling method, the bacterial communities under influences of physiochemical properties were proved as the main mediators for the microcystin degradation. This study provides valuable insights into the optimization of bacterial communities in composting to improve the efficiency of microcystin degradation and the quality of the compost product.

The impact of single and combined amendment of elemental sulphur and graphene oxide on soil microbiome and nutrient transformation activities

BackgroundSulphur (S) deficiency has emerged in recent years in European soils due to the decreased occurrence of acid rains. Elemental sulphur (S0) is highly beneficial as a source of S in agriculture, but it must be oxidized to a plant-accessible form. Micro- or nano-formulated S0 may undergo accelerated transformation, as the oxidation rate of S0 indirectly depends on particle size. Graphene oxide (GO) is a 2D-carbon-based nanomaterial with benefits as soil amendment, which could modulate the processes of S0 oxidation. Micro-and nano-sized composites, comprised of S0 and GO, were tested as soil amendments in a pot experiment with unplanted soil to assess their effects on soil microbial biomass, activity, and transformation to sulphates. Fourteen different variants were tested, based on solely added GO, solely added micro- or nano-sized S0 (each in three different doses) and on a combination of all S0 doses with GO. ResultsCompared to unamended soil, nano-S0 and nano-S0+GO increased soil pH(CaCl2). Micro-S0 (at a dose 4 g kg−1) increased soil pH(CaCl2), whereas micro-S0+GO (at a dose 4 g kg−1) decreased soil pH(CaCl2). The total bacterial and ammonium oxidizer microbial abundance decreased due to micro-S0 and nano-S0 amendment, with an indirect dependence on the amended dose. This trend was alleviated by the co-application of GO. Urease activity showed a distinct response to micro-S0+GO (decreased value) and nano-S0+GO amendment (increased value). Arylsulfatase was enhanced by micro-S0+GO, while sulphur reducing bacteria (dsr) increased proliferation due to high micro-S0 and nano-S0, and co-amendment of both with GO. In comparison to nano-S0, the amendment of micro-S0+GO more increased soluble sulphur content more significantly. ConclusionsUnder the conditions of this soil experiment, graphene oxide exhibited a significant effect on the process of sulphur oxidation.

Interaction Effects of Nutrient and Water on Crop Production System under Dry and Irrigated Agriculture System

Many areas in India, including dryland areas, are under stress from two main obstacles to agricultural output, namely, inadequate soil nutrients and a scarcity of water. In most rainfed regions, except for a few places that can conduct irrigation, low precipitation levels and their erratic distribution usually result in soil water deficiency which leads to water as well as the instances of nutritional stress. Hence, in sustainable agricultural production systems, soil water and nutrient stress are major concerns. In crop production systems, the interplay between water and nutrients might yield favourable results, contingent on the growth stages, volumes, combinations, and balance of the crops. In irrigated areas, water and nutrients have interdependent effects. Efficient water management can enhance nutrient availability and transformation in soil or fertilizers. Water boosts plant nutrient content, uptake, and overall efficiency. Water scarcity stresses plants, impeding root growth and nutrient absorption. Additionally, it has been discovered that there is typically a strong, nearly linear correlation between crop yield and nutrient and water management techniques. Water availability and nutrient efficiency are therefore intimately related. The water state of the soil should be taken into consideration when applying nutrients in a balanced manner, taking into account their types, ratios, amounts, timing, and methods, in addition to their capacity to give nutrients. Therefore, determining the best time or growth stage to add water and nutrients to various crops, as well as how water and nutrients interact, are essential for a sustainable crop production system.

Characteristics of Bacterial Community Structure and Function in Artificial Soil Prepared Using Red Mud and Phosphogypsum.

The preparation of artificial soil is a potential cooperative resource utilization scheme for red mud and phosphogypsum on a large scale, with a low cost and simple operation. The characteristics of the bacterial community structure and function in three artificial soils were systematically studied for the first time. Relatively rich bacterial communities were formed in the artificial soils, with relatively high abundances of bacterial phyla (e.g., Cyanobacteria, Proteobacteria, Actinobacteriota, and Chloroflexi) and bacterial genera (e.g., Microcoleus_PCC-7113, Rheinheimera, and Egicoccus), which can play key roles in various nutrient transformations, resistance to saline-alkali stress and pollutant toxicity, the enhancement of various soil enzyme activities, and the ecosystem construction of artificial soil. There were diverse bacterial functions (e.g., photoautotrophy, chemoheterotrophy, aromatic compound degradation, fermentation, nitrate reduction, cellulolysis, nitrogen fixation, etc.), indicating the possibility of various bacteria-dominated biochemical reactions in the artificial soil, which can significantly enrich the nutrient cycling and energy flow and enhance the fertility of the artificial soil and the activity of the soil life. The bacterial communities in the different artificial soils were generally correlated with major physicochemical factors (e.g., pH, OM, TN, AN, and AP), as well as enzyme activity factors (e.g., S-UE, S-SC, S-AKP, S-CAT, and S-AP), which comprehensively illustrates the complexity of the interaction between bacterial communities and environmental factors in artificial soils, and which may affect the succession direction of bacterial communities, the quality of the artificial soil environment, and the speed and direction of the development and maturity of the artificial soil. This study provides an important scientific basis for the synergistic soilization of two typical industrial solid wastes, red mud and phosphogypsum, specifically for the microbial mechanism, for the further evolution and development of artificial soil prepared using red mud and phosphogypsum.

Composting of Cow-Dung-Amended Soil by the Dung Beetle Catharsius molossus L. Improves Bacterial Ecological Functions Related to Nitrogen Mineralization and Human and Plant Pathogenesis

The Asian dung beetle (Catharsius molossus L.; Coleoptera: Scarabeidae) has been shown to positively affect soil bacterial diversity and the agronomic features of crop plants. In this study, we used bioinformatic tools to investigate the differences in bacterial functional phenotypes and ecological functions between control soil, cow dung-amended soil (CD), and cow dung-amended soil composted by dung beetles (DB). The soil bacterial metagenomes were sequenced and analyzed with the bioinformatic packages BugBase, PICRUSt2, Tax4Fun, and FAPROTAX to evaluate the effects of dung beetle-mediated composting on bacterial functions such as human and plant pathogenicity, trophic strategies, and soil nutrient transformation. BugBase proved useful for the determination of differences in major functional phenotypes, whereas FAPROTAX was effective at identifying differences in bacterial ecological functions between the treatments. Both tools suggested a relative decrease in human pathogens in the DB soil. This was corroborated by the pairwise comparison of abundances in bacterial species, which showed a significant reduction in the abundance of the broad-host-range pathogen Pseudomonas aeruginosa in the DB soil. In addition, FAPROTAX suggested a decrease in plant pathogens and an increase in chitinolytic bacteria, meaning that the DB treatment might be beneficial to the plant-growth-promoting bacteria involved in biological control. Finally, FAPROTAX revealed an array of ecological functions related to trophic strategies and macro- and micronutrient metabolism. According to these results, the activity of C. molossus beetles enhanced methanotrophy, ammonification, nitrification, sulfate reduction, and manganese oxidation, whereas iron respiration was decreased in the DB-treated soil. Our results represent a collection of general insights into the effects of C. molossus beetles on soil bacterial functions, which also reflect on the nutrient composition of dung beetle-composted soil.

Co-composting of tail vegetable with flue-cured tobacco leaves: analysis of nitrogen transformation and estimation as a seed germination agent for halophyte.

Resource utilization of tail vegetables has raised increasing concerns in the modern agriculture. However, the effect and related mechanisms of flue-cured tobacco leaves on the product quality, phytotoxicity and bacterially-mediated nitrogen (N) transformation process of tail vegetable composting were poorly understood. Amendments of high-dosed (5% and 10% w/w) tobacco leaves into the compost accelerated the heating process, prolonged the time of thermophilic stage, increased the peak temperature, thereby improving maturity and shortening composting duration. The tobacco leaf amendments at the 10% (w/w) increased the N conservation (TN and NH4-N content) of compost, due to the supply of N-containing nutrient and promotion of organic matter degradation by tobacco leaves. Besides, tobacco leaf amendments promoted the seed germination and root development of wild soybean, exhibiting the feasibility of composting product for promoting the growth of salt-tolerant plants, but no dose-dependent effect was found for tobacco leaf amendments. Addition of high dosed (5% and 10% w/w) tobacco leaves shifted the bacterial community towards lignocellulosic and N-fixing bacteria, contributing to increasing the compost maturity and N retention. PICRUSt 2 functional prediction revealed that N-related bacterial metabolism (i.e., hydroxylamine oxidation and denitrifying process) was enhanced in the tobacco leaf treatments, which contributed to N retention and elevated nutrient quality of composting. To the best knowledge, this was the first study to explore the effect of tobacco waste additives on the nutrient transformation and halophyte growth promotion of organic waste composting. These findings will deepen the understanding of microbially-mediated N transformation and composting processes involving flue-cured tobacco leaves.

Utilization of Diversified Cover Crops as Green Manure-Enhanced Soil Organic Carbon, Nutrient Transformation, Microbial Activity, and Maize Growth

Studying green manure in several returning methods to enhance soil fertility and crop benefits is a strong foundation for cropland nutrient management. However, how different types of green manures and their variable doses affect the efficacy of applied manures, either buried or mulched, remain overlooked. The objective of this study was to optimize green manure management to enhance soil fertility and maize biomass using five types of green manures (white mustard, forest rye, fiddleneck, sufflower, and pea) in two different doses (low, 5 g per pot, and high, 10 g per pot), which were either buried or mulched before and after maize sowing. Results revealed that total carbon content increased due to green manure treatments, representing a 10% increase over control, particularly through buried w. mustard (10% increase before maize cultivation) and mulched safflower and pea (12% and 11% increase after maize cultivation over control). Dry maize aboveground biomass yields also improved across all variants, with buried mustard yielding 18.4 g·plant−1 (compared to 8.6 g·plant−1 in the control), mulched mustard yielding 16.4 g·plant−1, and buried pea yielding 17.8 g·plant−1. Green mulching generally acidified the soil (pH 5.71 compared to 6.21 in the control), except for buried fiddleneck (pH 6.39 after maize cultivation) at a high dose of manures. Carbon-mineralizing enzyme activities (dehydrogenase and β-glucosidase) were significantly increased by green manures, with buried fiddleneck showing a 22.6% and 20.6% increase over the control, and mulched fiddleneck showing a 24.5% and 22.4% increase under high doses. The study suggests that partially decomposed and mineralized mulched biomass may induce a negative priming effect on carbon-mineralizing enzymes due to a decrease in the C/N ratio of the soil. It emphasizes that the nutrient content and stoichiometry of green manures, alongside soil characteristics such as the C/N ratio, are critical factors for sustainable soil management and carbon sequestration. These findings underscore the need for careful selection and management of green manures to optimize soil health and carbon-storage outcomes.

Uncovering the hidden world of riverbed sediments: The role of sediment heterogeneity and cross-bar channel fills in the hydrogeochemical dynamics of the hyporheic zone

Groundwater-surface water interaction (hyporheic exchange) is critical in numerous hydrogeochemical processes; however, hyporheic exchange is difficult to characterize due to the various spatial (e.g., sedimentary architecture) and temporal (e.g., stage fluctuations) variables that influence it. This interdisciplinary study brings forth novel insights by integrating various methodologies including geophysical surveys, physical and chemical sediment characterization, and water chemistry analysis to explore the interplay of the numerous facets governing hyporheic zone processes within a compound bar deposit. The findings reveal distinct sedimentary facies and geochemical zones within the compound bar, driven by the sedimentary architecture. Cross-bar channel fills are identified as critical structures influencing hydrogeochemical dynamics, acting as baffles to groundwater flow and modulating nutrient transformations. Geophysical imaging and hydrogeochemical analyses highlight the complex interplay between sediment characteristics and subsurface hydraulic connectivity, emphasizing the role of sediment heterogeneity in controlling hyporheic exchange and solute mixing. The study concludes that sediment heterogeneity, particularly the presence of cross-bar channel fills, plays a pivotal role in the hydrogeochemical dynamics of the hyporheic zone. These structures significantly influence hyporheic flow paths, solute residence times, and nutrient cycling, underscoring the necessity to consider the fine-scale sedimentary architecture in models of hyporheic exchange. The findings contribute to a deeper understanding of riverine ecosystem processes, offering insights that can inform management strategies for water quality and ecological integrity.

The role of halophyte-induced saline fertile islands in soil microbial biogeochemical cycling across arid ecosystems

Halophyte shrubs, prevalent in arid regions globally, create saline fertile islands under their canopy. This study investigates the soil microbial communities and their energy utilization strategies associated with tamarisk shrubs in arid ecosystems. Shotgun sequencing revealed that high salinity in tamarisk islands reduces functional gene alpha-diversity and relative abundance compared to bare soils. However, organic matter accumulation within islands fosters key halophilic archaea taxa such as Halalkalicoccus, Halogeometricum, and Natronorubrum, linked to processes like organic carbon oxidation, nitrous oxide reduction, and sulfur oxidation, potentially strengthening the coupling of nutrient cycles. In contrast, bare soils harbor salt-tolerant microbes with genes for autotrophic energy acquisition, including carbon fixation, H2 or CH4 consumption, and anammox. Additionally, isotope analysis shows higher microbial carbon use efficiency, N mineralization, and denitrification activity in tamarisk islands. Our findings demonstrate that halophyte shrubs serve as hotspots for halophilic microbes, enhancing microbial nutrient transformation in saline soils.

Analysis of growth inhibition of continuously planted Casuarina equisetifolia in relation to characteristic soil microbial functions and nutrient cycling

The effects of continuous planting on the growth of Casuarina equisetifolia (C. equisetifolia) have severely restricted the sustainable development of the industry. In this study, we investigated the diversity and functional changes of bacteria and fungi in the rhizosphere soil of continuously planted C. equisetifolia and their effects on soil nutrient transformation and C. equisetifolia growth. The results showed that after continuous planting, C. equisetifolia growth was significantly inhibited, the activities of nutrient transformation-related enzymes in rhizosphere soil were reduced, available nutrient content of the soil decreased, and soil bacterial diversity decreased, while fungi diversity increased. After continuous planting, 9 genera of significantly altered characteristic bacteria in the rhizosphere soil of C. equisetifolia were functionally enriched in animal parasites or symbionts, aromatic compound degradation, and nitrate reduction, with contributions mainly from the 3 characterisic bacteria such as Planctopirus, Bacillus, and Acinetobacter. After continuous planting, 7 genera of significantly altered characteristic fungi in the rhizosphere soil of C. equisetifolia were functionally enriched in soil saprotroph, lichen parasite, undefined saprotroph, endophyte, animal pathogen, wood saprotroph, litter saprotroph and plant pathogen, with contributions mainly from the 6 characteristic fungi such as Aspergillu, Fusarium, Saitozyma, Tolypocladium, Mortierella, and Funneliformis. Functional analysis and PLS-SEM equation analysis showed that the growth inhibition of C. equisetifolia due to continuous planting was the result of the joint action of the characteristic bacteria and fungi, but there was a difference between the functions of the two. The function of characteristic bacteria was mainly to provide conditions for the propagation of pathogenic organisms, which reduced soil nutrient content and hindered nutrient uptake by C. equisetifolia. The function of characteristic fungi was primarily to damage soil texture, nourish pathogenic bacteria to infest C. equisetifolia, and damage the root system to inhibit nutrient uptake. Characteristic bacteria and fungi together accelerated the effect of continuous planting on the growth of C. equisetifolia. This study provides an important reference for the cultivation regulation of continuously planted C. equisetifolia.

Linking reservoir annual residence time to nitrogen deposition using paleolimnological techniques

In river networks, reservoirs are hotspots for nutrient transformations, providing multiple pathways for nitrogen processing. One of the less measured pathways is nitrogen deposition. Here, we investigated the decadal relationship between water residence time and nitrogen deposition using sediment cores from eight mainstem reservoirs within a river system containing two contrasting watersheds. One watershed was significantly urbanized with regulated flow and the other watershed was unregulated with extensive rural land use. We explored the relationship of sediment nitrogen concentrations across a range of residence times, land uses, and other parameters throughout this linked river-reservoir system. Results show that average annual residence time had the strongest relationship to nitrogen deposition when compared to reservoir volume, mean depth, surface area, outflow, and land use. Pigment analysis revealed that residence time influences nitrogen by allowing for longer periods of algal uptake, followed by deposition in particulate organic form. Supporting this mechanism, sedimentary C:N, with low values representing greater algal influence, expressed a strong and negative relationship with average annual residence time, as well as a positive relationship between residence time and photosynthetic pigments diagnostic of cyanobacteria, diatoms, and a combination of green algae+cyanobacteria. Furthermore, we investigated how drought conditions could alter residence times and intensify nitrogen cycling through primary productivity in reservoirs. Drought increased residence time by 45–60 %. This increase was estimated to raise sediment nitrogen concentrations by roughly 2.5–4 %.

Evolution of river–aquifer disconnections and the migration and transformation of iron and manganese under non-time-varying/time-varying riverbed permeability

Changes in the composition, structure, and thickness of riverbed sediments caused by riverbed clogging strongly affect the hydraulic connection, migration and transformation of nutrients between river water and groundwater in groundwater source areas. However, previous studies have not extensively investigated the mechanisms of river–aquifer disconnection and the migration and transformation processes of iron and manganese under non-time-varying and time-varying conditions of riverbed permeability. This study developed a model using the COMSOL Multiphysics platform to characterize the riverbed clogging–groundwater exploitation–disconnection process, considering microbial growth and related biogeochemical processes, and investigated feedbacks between the reactive migration of iron and manganese and physical clogging-groundwater exploitation processes or bioclogging processes. The research findings showed that under non-time-varying conditions of riverbed permeability, the evolution of river–aquifer disconnection was strongly affected by the thickness and permeability coefficient of riverbed sediments. The dissolved oxygen attenuation rate in the disconnection zone decreased by up to 88.8 %. Additionally, the Mn2+ and Fe2+ generation rates in sediment pore water decreased by 65.8 % and 62.7 %, respectively. In contrast, during the riverbed bioclogging process, as the biofilms on the surface of the riverbed sediments developed, the sediment pores gradually clogged, leading to a significant reduction in the porosity and permeability coefficient. Consequently, the hydraulic connection between the river and aquifer transitioned from a saturated connection to a disconnection. However, reduced permeability due to riverbed bioclogging primarily controlled the release of Fe and Mn. When the river–aquifer was in complete disconnection, compared to the saturated connection state, the Mn2+ and Fe2+ generation rates increased by up to 5.8 and 3.8 times, respectively. This study deepens our understanding of the biogeochemical cycling mechanisms of Fe and Mn under riverbed clogging conditions in groundwater source areas and contributes to ensuring a secure and stable water supply in these areas.

Rate of Microelement Quantitative Changes during the Composting of Sewage Sludge With Various Bulking Agents

The composting of sewage sludge (SS) with structure-forming additives is a popular and inexpensive method for the management of biodegradable waste. During this process, a number of transformations of organic matter and nutrients occur. This study presents the rates and directions of quantitative changes in Cu, Zn, and Ni during the composting of various mixtures. The following substances were used for preparing compost mixtures: SS, sawdust, straw, and bark. These substances were mixed together in appropriate proportions as follows: C1: 45% SS + 50% sawdust + 5% straw; C2: 45% SS + 50% bark+ 5% straw; and C3: 45% SS + 35% bark + 15% sawdust + 5% straw. Single (DTPA solution) and sequential extraction methods (BCR protocol) were used for microelement mobility assessment. Compost valorization was performed in each individual composting phase. The chain relative increment analysis was used for such assessment. Additionally, the potential metal pollution in the composts was evaluated by applying the following indices: the pollutant accumulation index (PAI), heavy metal enrichment index (HMEI), and heavy metal pollution load index (HMPLI). During composting, generally, the amounts of Ni, Cu, and Zn increased in the various extracted combinations, which was independent of their susceptibility to decomposition. Despite of this, the tested composts should be considered as a source of slowly available microelements for plants. The most intense quantitative changes in metals occurred in the thermophilic phase, and the weakest changes occurred in the cooling phase. At the same time, the calculated indices indicated a lack of contamination of the composts with the analyzed metals, emphasizing their environmental safety and lack of negative impact. The bulking agents used for composting with SS did not significantly influence the intensity of the quantitative changes in the tested metals.

Variability of soil enzyme activities and nutrients with forest gap renewal interacting with soil depths in degraded karst forests

Forest gaps serve as crucial starting points for forest self-renewal. Within these gaps, soil enzymes play an essential role in driving nutrient transformation and species renewal. However, how forest gap renewal regulates soil fertility through soil enzyme across various soil depths remains unclear. This investigation delved into the dynamics of soil enzymes and nutrients within karst forest gaps at four developmental age stages: Infancy (<10 years), Youth (10–20 years), Middlescence (20–30 years), and Elder (>30 years) across different soil depths (0–10 cm, 10–20 cm, and 20–30 cm). The study determined the contents of CNP and the activities of soil enzymes such as polyphenol oxidase, catalase, protease, and alkaline phosphatase. Two-way ANOVA was employed to assess the variations in gap ages and soil depths, along with their interaction. Redundancy analysis (RDA) was used to reveal the correlations between soil enzyme activities and CNP fertility indicators. The results indicated that gap age significantly influenced the activities of alkaline phosphatase, polyphenol oxidase, and protease, as well as the contents of total and available nitrogen, phosphorus, and organic carbon, alongside the ratios of N/P, C/N, and C/P. Catalase activity, however, did not vary significantly with gap age, although soil depth influenced these parameters, excluding total phosphorus and the C/N ratio. Notably, in the 0–10 cm soil layer, alkaline phosphatase activity, total nitrogen, available nitrogen, and organic carbon contents significantly increased with gap age increase, followed by a significant decrease after the middlescence stage. In the 10–20 cm and 20–30 cm soil layers, Alkaline phosphatase and polyphenol oxidase activities, along with N/P and C/N ratios initially decreased and then increased with gap age increase. During the Infancy, Youth, and Middlescence stages, Polyphenol oxidase and protease activities, CNP contents, as well as N/P and C/P ratios generally decreased with soil depth increase or after an increase in the 10–20 cm soil layer. RDA highlighted the variational positive and negative correlations between soil enzyme activities and CNP fertility indicators across soil depths during forest gap renewal, with explanatory rates ranging from 88.05 % to 94.67 % across soil layers. Overall, this study suggests that forest gap renewal significantly influences soil enzymes, CNP content and stoichiometry, modifying soil CNP content through stoichiometric regulation across different soil depths, and ultimately sustaining soil fertility via soil enzymes.

Regulation of winter river input on the nutrient structure of typical tropical bays around Leizhou Peninsula, South China

Elucidating the regulatory mechanisms of terrestrial input on bay nutrients is essential for comprehending the ecological stability of bays. This paper investigates nutrients' structure, transport, and transformation processes in typical tropical bays of the Leizhou Peninsula during river input, utilizing fixed-site observation data from five distinct bay locations during November 2022. The results show that the average concentrations of TN, TP, DIN and DIP in the rivers of Leizhou Peninsula were 5.162 mg L−1 (2.263–13.610 mg L−1), 0.092 mg L−1 (0.026–0.288 mg L−1), 2.195 mg L−1 (0.897–4.081 mg L−1), 0.042 mg L−1 (0.002–0.147 mg L−1). The average concentrations of TN, TP, DIN and DIP in the bay were 0.491 mg L−1 (0.282–0.843 mg L−1), 0.041 mg L−1 (0.018–0.073 mg L−1), 0.245 mg L−1 (0.019–0.614 mg L−1), 0.021 mg L-1 (0.005–0.045 mg L−1). The ratio of TN/TP in the bay averaged 29 (17–48), and the ratio of DIN/DIP averaged 35.1 (8–298). The mean Chl-a concentration in the bay was 7.131 mg L−1 (0.927–25.076 mg L−1). The bays along the Leizhou Peninsula are still heavily influenced by rivers during winter. There are higher concentrations of nutrients in the bays, and there is higher nutrient input flux from rivers. The significant negative correlation between nutrient concentration and salinity in the bay indicates that river input is an important source of nutrients in the bay. As water transports from the river to offshore, the ratio of dissolved inorganic nitrate to dissolved inorganic phosphorus shifts from phosphorus limitation to nitrogen limitation. Leizhou Bay and Jianjiang Bay are heavily influenced by riverine inputs and coastal activities and are potentially at risk of eutrophication. Anpu Bay is subject to both riverine and other sources of inputs but has a better self-purification capacity. The results suggest that nutrient transport in Leizhou Peninsula rivers is regulated by both physical and biogeochemical processes. It is recommended that the monitoring of nutrient discharges from rivers be strengthened, total land-based pollution should be controlled, and industrial structures along the rivers should be adjusted and the control of total land-based pollution, and to adjust the industrial structure along the rivers to reduce the risk of water quality deterioration.

Understanding Dhatu Poshan Nyaya in the Light of Stem Cell Theory

The word Dhatu forms with ‘Dha’ and suffix ‘tin’. It means basic element which helps in construction. A living body comprises of 7 Dhatus (tissue), which not only does Dharan of the body but also provides Poshan or nutrition to the next forming Dhatu. Tissue nutrition is the continuous process which persists throughout the life, but it’s different during different phases of life. Acharayas postulated theories of tissue nutrition and transformation of tissue nutrients into bodily element through Dhatu Poshana Nyaya (tissue nutrition and differentiation theory). The theories of tissue nutrition are Ksheera Dadhi Nyaya (Law of Transformation), Khale Kapot Nyaya (Law of Selectivity), Kedari Kulya Nyaya (Law of Transportation) and Ek Kaal Dhatu Poshan Nyaya (simultaneous supply of nutrients to whole body). This review is an attempt to explore the Ayurveda’s view on tissue differentiation along with physiological and clinical significance of theories of tissue differentiation in a scientific mannery.

Enhanced Organic Carbon Triggers Transformations of Macronutrients, Micronutrients, and Secondary Plant Nutrients and Their Dynamics in the Soil under Different Cropping Systems-A Review

Enhanced Organic Carbon Triggers Transformations of Macronutrients, Micronutrients, and Secondary Plant Nutrients and Their Dynamics in the Soil under Different Cropping Systems-A Review

Towards a high-quality fertilizer based on algae residues treated via hydrothermal carbonization. Trends on how process parameters influence inorganics

The use of beach-cast macroalgae as a fertilizer (F) or soil amendment (SA) is coming back into focus, due to its highly efficient transformation of CO2, nutrients, salts and minerals from its aqueous surroundings into biomass. This research studied the hydrothermal carbonization (HTC) of Fucus vesiculosus macroalgae to hydrochar and evaluated its feasibility for use in soil applications. F. vesiculosus was submitted to HTC following a full factorial design of experiments with three HTC process parameters varied to assess their impact on the hydrochars: temperature (T: 160, 190, 220 °C), solid content (%So: 20, 35%), and process water recirculation (PWrec: yes and no). In general, F. vesiculosus and its hydrochars were rich in nutrients, but also contained regulated heavy metals. Investigation of the partitioning behavior of inorganic elements between the hydrochars and process water showed that heavy metals like Cr, Pb, Co and Cu tended to accumulate in the hydrochar, unaffected by HTC conditions. Nutrients such as P, N, B, and Mn were primarily found in the hydrochar and could be partially influenced to transfer to process water by changing %So and T. The correlation between the mass fractions of 22 elements in the hydrochar and HTC process parameters was studied. T was the most influential parameter, showing a significant positive correlation for eleven elements. %So and PWrec showed inconsistent effects on different elements. When process water was recirculated, some elements decreased (Ca, Cd, Fe) while others increased (K, Na, B, N) in the hydrochar. Assessment against various regulations and standards for F and SA revealed that F. vesiculosus complied with Cd limit values for most rules including the EURF and B, and was regulated only in the RAL for SA, over the limit value. In contrast, the limit value of Cd for both F and SA applications was surpassed in the 13 hydrochars. The contents of N, P, K, S, and Na in the feedstock and hydrochars complied with European F and SA rules, while they were too high for German rules on SA. The other limits for F rules were achieved (under certain HTC process parameters) except for P (lower than the requirements in F for F. vesiculosus and its hydrochars).Graphical

Integrating experiments with modeling to understand key bacterial taxa dynamics after episodic mixing of a stratified water column

Hydraulic mixing of stratified reservoirs homogenizes physicochemical gradients and microbial communities. This has potential repercussions for microbial metabolism and water quality, not least in dams and hydraulically controlled waters. A better understanding of how key taxa respond to mixing of such stratified water bodies is needed to understand and predict the impact of hydraulic operations on microbial communities and nutrient dynamics in reservoirs. We studied taxa transitions between cyanobacteria and sulfur-transforming bacteria following mixing of stratified water columns in bioreactors and complemented the experimental approach with a biogeochemical model. Model predictions were consistent with experimental observations, suggesting that stable stratification of DO is restored within 24 h after episodic and complete mixing, at least in the absence of other more continuous disturbances. Subsequently, the concentration of S2− gradually return to pre-mixing states, with higher concentration at the surface and lower in the bottom waters, while the opposite pattern was seen for SO42−. The total abundance of sulfate-reducing bacteria and phototrophic sulfur bacteria increased markedly after 24h of mixing. The model further predicted that the rapid re-oxygenation of the entire water column by aeration will effectively suppress the water stratification and the growth of sulfur-transforming bacteria. Based on these results, we suggest that a reduction of thermocline depth by optimal flow regulation in reservoirs may also depress sulfur transforming bacteria and thereby constrain sulfur transformation processes and pollutant accumulation. The simulation of microbial nutrient transformation processes in vertically stratified waters can provide new insights about effective environmental management measures for reservoirs.

Fungal Saprotrophic Promotion and Plant Pathogenic Suppression under Ditch-Buried Straw Return with Appropriate Burial Amount and Depth.

Fungi as heterotrophs are key participants in the decomposition of organic materials and the transformation of nutrients in agroecosystems. Ditch-buried straw return as a novel conservation management strategy can improve soil fertility and alter hydrothermal processes. However, how ditch-buried straw return strategies affect the soil fungal community is still unclear. Herein, a 7-year field trial was conducted to test the influences of burial depth (0, 10, 20, 30, and 40 cm) and the amount of ditch-buried straw (half, full, double) on the diversity, composition, and predicted functions of a soil fungal community, as well as the activities of carbon-degraded enzymes. Under the full amount of straw burial, the abundance of phylum Ascomycota was 7.5% higher as compared to other burial amount treatments. This further increased the activity of cellobiohydrolase by 32%, as revealed by the positive correlation between Ascomycota and cellobiohydrolase. With deeper straw burial, however, the abundance of Ascomycota and β-D-glucopyranoside activity decreased. Moreover, genus Alternaria and Fusarium increased while Mortierella decreased with straw burial amount and depth. FUNgild prediction showed that plant fungal pathogens were 1- to 2-fold higher, whilst arbuscular mycorrhizal fungi were 64% lower under straw buried with double the amount and at a depth of 40 cm. Collectively, these findings suggest that ditch-buried straw return with a full amount and buried at a depth less than 30 cm could improve soil nutrient cycles and health and may be beneficial to subsequent crop production.