Ammonia Nitrogen Concentration Research Articles

Оцінка сучасного гідрохімічного стану деяких рибогосподарських ставів Київщини

Purpose. To assess the quality of the hydrochemical regime of fishponds, the territory of which suffered massive missile strikes or was directly a combat zone or close to the front line. Methodology. Chemical parameters of water including the content of ammonium nitrogen, nitrites, nitrates, phosphates and total iron were measured by the photometric method, while chloride concentration of chlorides by the argentometric titration method. The hydrogen indicator (pH) was determined electrometrically, and sulfate content and mineralization by the gravimetric method. All the above-mentioned methods are generally accepted in the comprehensive assessment of the ecological state of fishponds. Findings. The total amount of mineral salts dissolved in water was studied and analyzed in laboratory conditions, namely: the concentrations of calcium, magnesium, chlorine, bicarbonate ions and sulfate ions. The determined permanganate oxidizability in the investigated ponds exceeded the normative values by 72, 49, 31, and 42%, respectively. The concentration of nitrates ranged from 19.96 to 6.34 mg N/dm3, nitrites from 0.33 to 0.11 mgN/dm3, which indicates the intensity of decomposition of organic substances and indicates a certain degree of contamination of ponds. The amount of total iron in the studied ponds ranged from 1.98 to 1.17 mgFe/dm3, respectively. A slight increase in mineral phosphorus in ponds No. 1 and No. 2 was established by 31 and 26%, respectively, which can probably be related to both the decomposition of zooplankton and the input of pollutants from the outside from the surrounding areas. The obtained results of the laboratory analysis of the chemical composition of water samples as well as their comparison with the normative values for water bodies used for aquaculture provide a basis for assessing the current hydrochemical state of the investigated ponds of Kyiv region Originality. For the first time, a hydrochemical analysis of fishponds in Kyiv Region was conducted, the territory of which suffered massive missile strikes or was directly a combat zone or close to the front line. Practical value. The obtained results will contribute to a better understanding of the current ecological state of fishponds in Kyiv region. Keywords: water body, chemical analysis of water, toxic substances, ecological condition.

Antibiotic resistant genes profile in the surface water of subtropical drinking water river-reservoir system

To comprehensively understand antibiotic resistant genes (ARGs) profile in the subtropical drinking water river-reservoir system, this study selected Dongzhen river-reservoir system in Mulan Creek as object to investigate the spatial-temporal characteristics of ARGs diversity, bacterial host and resistance mechanism, and to analyze the key environmental factors driving ARGs profile variation. The results indicated that a total of 440 ARGs were detected in the target system, and the ARGs distribution pattern in the reservoir was attributed to autologous evolution or the comprehensive influence of feeding river system. The predominant bacterial host at different sites showed similar variations to dominated ARGs, and Proteobacteria, Actinobacteria and Bacteroidetes harbored most ARGs at phylum level, which showed the highest proportions of 74%, 37% and 35%, respectively. Antibiotic efflux was the primary resistance mechanism in all samples from wet season (45%–60%), yet the samples from dry season exhibited multiple resistance mechanisms, including inactivation (37%–52%), efflux (44%), and target alteration (43%). The total relative abundances of ARGs in the target system ranged from 0.89 × 10−2 to 1.71 × 10−2, and seasonal variation had a more significant influence on ARGs abundance than spatial variation (R = 0.68, P < 0.01). Environmental factors analysis indicated that the concentrations of nitrite nitrogen and total organic carbon were significant factors explaining ARGs number and various resistance mechanism proportions (P < 0.01), accounting for 48.7% and 61.1% of the variation, respectively; ammonia nitrogen concentration, total organic carbon concentration, temperature and pH were the significant influence factors on the relative abundance of ARGs (P < 0.05), with standardized regression weights of 0.700, 1.414, 1.447, and 1.727, respectively. In summary, in the surface water of the target system, ARGs diversity was primarily driven by ARGs horizontal transfer and antibiotics biosynthesis. Nutrients mainly promoted ARGs abundance by providing abundant energy, rather than increasing bacterial reproductive capacity.

Inoculation of cold-adapted microbial consortium screened from alpine meadows promotes the growth of mixed grasses by changing soil properties and enzyme activity

The objective of this study was to investigate the effect of co-inoculation of three PGPR strains and inoculation ratio on the growth characteristics and soil properties of mixed grasses. In this study, we used 3 strains of PGPR for the material, which were Acinetobacter calcoaceticus called HMAJ1, Pseudomonas piscium called HMAJ5, and Pseudarthrobacter psychrotolerans called NCZ1, with nitrogen fixation and phosphorus solubilization ability. By mixing the bacteria in a different ratio, the effect of inoculating with a microbial consortium on the plant and soil properties of mixed grasses (Elymus nutans Griseb, Festuca sinensis, and Poa pratensis L.) was evaluated and the best microbial inoculants ratio was selected. The results showed that inoculating with a microbial consortium increased the soil organic carbon , available phosphorus, ammonium and nitrate nitrogen content, and the activities of soil alkaline phosphatase, sucrase, peroxidase, and urease, which promoted the plant height and biomass of mixed grasses. Pearson correlation analysis showed that plant characteristics were differently correlated with soil properties. Grey correlation analysis of plant biomass, soil properties, and soil enzyme activity revealed that T7 (HMAJ1:NCZ1 = 3:7) was the most effective in improving mixed-grasses biomass and soil quality. Our results indicated that the positive interaction of nitrogen-fixing bacteria with phosphorus-solubilizing strains may become a novel and effective bio-inoculant to achieve sustainable pulse productivity.

Does stand density affect understory vegetation and soil properties of differently aged Robinia pseudoacacia plantations?

Robinia pseudoacacia is the most important tree species used for afforestation on the Chinese Loess Plateau. However, most R. pseudoacacia plantations face environmental problems due to inappropriate initial densities. The sustainable development of R. pseudoacacia plantations is challenging due to significant knowledge gaps regarding the appropriate stand densities for maximizing ecological benefits. Herein, R. pseudoacacia plantations of three age classes—young, middle-aged, and mature—were sampled in the loess hilly-gully region of northern Shaanxi Province, China. Based on stand density, R. pseudoacacia plantations in each age class were categorized as low (<1000 trees ha−1), medium (1000–1500 trees ha−1), and high (>1500 trees ha−1) density. We analyzed the effects of stand density on soil physicochemical properties, understory vegetation community structure, and ecosystem multifunctionality. In young stands, a medium stand density significantly increased the Shannon-Wiener index, species richness, and above-ground biomass of herbaceous communities. In middle-aged stands, stand density had no significant effects on understory diversity, whereas medium-density stands showed increased understory above-ground biomass. In mature stands, low-density stands significantly increased understory above-ground biomass and species richness of herbaceous communities. In all age classes, stand density did not significantly affect shrubby community composition, but herbaceous communities shifted compositionally towards shade-tolerant and drought-tolerant species as stand density increased. In the soils of young and middle-aged stands, organic carbon, ammonium nitrogen, nitrate nitrogen, available phosphorus, and water content were highest in medium-density stands, whereas in mature stands, these variables were highest in low-density plantations. In young, middle-aged, and mature stands, the ecosystem multifunctionality indices were highest at densities of 1000–1500, 1000–1500, and < 1000 trees ha−1, respectively. We concluded that the effects of stand density on ecosystem functions in R. pseudoacacia plantations varied with stand age. Our findings highlight a need to implement age-based stand density management strategies for R. pseudoacacia plantations to improve their ecological benefits.

Quantitative Analysis of the Driving Factors of Water Quality Variations in the Minjiang River in Southwestern China

The Minjiang River is an important first-level tributary of the Yangtze River. Understanding the driving factors of water quality variations in the Minjiang River is crucial for future policy planning of watershed ecology protection of the Yangtze River. The water quality of the Minjiang River is impacted by both meteorological factors and anthropogenic factors. By using wavelet analysis, machine learning, and Shapley analysis approaches, the impacts of meteorological factors and anthropogenic factors on the permanganate index (CODMn) and ammonia nitrogen (NH3-N) concentrations at the outlet of the Minjiang River Basin were quantified. The observed CODMn and NH3-N concentration data in the Minjiang River from 2016 to 2020 were decomposed into long-term trend signals and periodic signals. The long-term trends in water qualities showed that anthropogenic factors were the major driving factors, accounting for 98.38% of the impact on CODMn concentrations and 98.18% of the impact on NH3-N concentrations. The periodic fluctuations in water qualities in the Minjiang River Basin were mainly controlled by meteorological factors, with an impact of 68.89% on CODMn concentrations and 63.94% on NH3-N concentrations. Compared to anthropogenic factors, meteorological factors have a greater impact on water quality in the Minjiang River Basin during both the high-temperature and rainy seasons from July to September and during the winter from December to February. The separate quantification of impacts of driving factors on the varying water quality signals contributed to the originality in this work, providing more intuitive insights for the assessment of the influences of policies and the climate change on the water quality.

Ammonia nitrogen stress damages the intestinal mucosal barrier of yellow catfish (Pelteobagrus fulvidraco) and induces intestinal inflammation.

Nitrogen from ammonia is one of the most common pollutants toxics to aquatic species in aquatic environment. The intestinal mucosa is one of the key mucosal defenses of aquatic species, and the accumulation of ammonia nitrogen in water environment will cause irreversible damage to intestinal function. In this study, histology, immunohistochemistry, ultrastructural pathology, enzyme activity analysis and qRT-PCR were performed to reveal the toxic effect of ammonia nitrogen stress on the intestine of Pelteobagrus fulvidraco. According to histological findings, ammonia nitrogen stress caused structural damage to the intestine and reduced the number of mucous cells. Enzyme activity analysis revealed that the activity of bactericidal substances (Lysozyme, alkaline phosphatase, and ACP) had decreased. The ultrastructure revealed sparse and shortened microvilli as well as badly degraded tight junctions. Immunohistochemistry for ZO-1 demonstrated an impaired intestinal mucosal barrier. Furthermore, qRT-PCR revealed that tight junction related genes (ZO-1, Occludin, Claudin-1) were downregulated, while the pore-forming protein Claudin-2 was upregulated. Furthermore, as ammonia nitrogen concentration grew, so did the positive signal of Zap-70 (T/NK cell) and the expression of inflammation-related genes (TNF, IL-1β, IL-8, IL-10). In light of the above findings, we conclude that ammonia nitrogen stress damages intestinal mucosal barrier of Pelteobagrus fulvidraco and induces intestinal inflammation.

The relationship between mountain wetland health and water quality: A case study of the upper Hanjiang River Basin, China

This study investigates the degradation process of mountain wetlands in the upper Hanjiang River Basin (HRB) over a 30-year span from 1990 to 2020. In particular, the landscape development intensity (LDI) index was employed to conduct a comprehensive assessment of the wetland health. This was subsequently combined with the spatio-temporal changes of water quality in the basin to explore the potential correlations between the health status of mountain wetlands and the associated watershed water quality. The results show that over the past three decades, wetland ecosystems have shrunk by 18% due to conversion into farmland, grass, construction land and forest land. This was significant between 2010 and 2020, as shown by a land use dynamic index of −1.121% during 2010–2020, which was significantly higher than that in the preceding two decades (0.003%, 0.367%) (p < 0.05). LDI values for individual sub-watersheds across different years ranged from 2.39 to 4.93, demonstrating an increasing trend since 2010. This indicates a heightened level of human interference in mountain wetlands. Although the water quality within the basin generally adhered to the Class II surface water quality standard, total nitrogen (TN) (primarily from farming) was a concern. Areas with relatively more human activity were observed to exhibit increased pollution levels, as demonstrated by a positive correlation between LDI and the concentrations of total phosphorus (TP), ammonium nitrogen (NH4+-N), and chemical oxygen demand (COD) in the basin. The LDI of the mountain wetland exhibited a consistent positive correlation with the water quality comprehensive function, both during the flood (r = 0.77–0.81) and non-flood (r = 0.61–0.70) seasons (p < 0.05). This indicates the significant impact of the wetland landscape structure on the water quality within a 1000 m radius on either side of the river. Special attention should be paid to the management and allocation of wetland landscapes within this 1000 m buffer zone. Furthermore, efforts to control upstream pollutant emission should be strengthened.

Mitigating the adverse effect of warming on rice canopy and rhizosphere microbial community by nitrogen application: An approach to counteract future climate change for rice

The adverse impact of climate change on crop production continues to increase, necessitating the development of suitable strategies to mitigate these effects and improve food security. Several studies have revealed how global warming negatively impacts the grain-filling stage of rice and that this effect could be mitigated by nitrogen; however, the impact of nitrogen application on rice canopy and rhizosphere microbial communities remains unclear. We conducted a study using an open-field warming system. Results showed that warming influenced rice canopy by decreasing aboveground biomass and harvest index, whereas nitrogen application had positive effect on rice production under warming conditions by increasing the plant nitrogen content, biomass, harvest index and soil fertilities. Moreover, soil ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) contents were significantly decreased under warming, which were higher after nitrogen application. Notably, warming and nitrogen fertilizer caused 19 % (P < 0.01) and 7 % (P < 0.05) variations, respectively, in the β diversity of the microbial community, respectively. The impact of warming was significant on NH4+-N-related microorganisms; however, this impact was weakened by nitrogen application for microbes in the rhizosphere. This study demonstrated that enhanced nitrogen fertilizer can alleviate the adverse impact of warming by weakening its effects on rhizosphere microbes, improving soil fertility, promoting rice nitrogen uptake, and increasing the aboveground biomass and harvest index. These findings provide an important theoretical basis for developing practical, responsive cultivation strategies.

Simulated nitrogen deposition alters the ectomycorrhizal fungal community structure in northern Korean pine plantations

Northern temperate forests are sensitive to nitrogen deposition. Korean pines are the zonal dominant vegetation in these forest ecosystems and a typical obligate ectomycorrhizal (ECM) tree. However, the impact of varying nitrogen additions on the ectomycorrhizal fungal (ECMF) community structure in Korean pine plantations remains unclear. In this experiment, nitrogen deposition was simulated (CK = 0 kg N ha−1 yr−1, LN = 20 kg N ha−1 yr−1, MN = 40 kg N ha−1 yr−1, HN = 80 kg N ha−1 yr−1), and soil biochemical indicators, ECMF community composition, and diversity were measured. The results showed that high nitrogen addition led to increased ECMF colonization, decreased ECMF community diversity and richness, and altered the occurrence of biomarkers. The MN treatment significantly increased the Simpson index compared to the LN treatment (P < 0.05), with Amphinema sp, Tuber sp, and Tylospora asterophora identified as biomarkers in the CK, LN, and HN treatments, respectively. The HN treatment significantly reduced the Chao1 index (P < 0.05), with Inocybe quietiodor, Tarzetta catinus, Inocybe giacomi, and Russula viscida serving as biomarkers in the CK, LN, MN, and HN treatments, respectively. Nitrogen addition led to decreased soil pH and available phosphorus content, increased ammonium nitrogen content, and affected ectomycorrhiza colonization by altering the soil ECMF community structure. Among these factors, ammonium nitrogen was the most influential in changing the ECMF community structure. This research offers valuable data to help predict changes in ECMF community structure in Korean pine plantations as nitrogen additions increase.

Sub-lethal Ammonia Toxicity in Fingerlings of &lt;i&gt;Catla catla&lt;/i&gt; (ham.) and &lt;i&gt;Labeo rohita&lt;/i&gt; (ham.): Effect on Certain Haematological Parameters and Enzymes Activities

Fingerlings of catla and rohu were exposed to ambient sub-lethal total ammonia-nitrogen concentrations of 1, 2, 4, 8, 11.8 and 16 mg/l for 96 hours to study the toxic effect. Haematological parameters such as TEC and TLC increased in both species in lower concentration of ambient ammonia but decreased in higher concentration while haemoglobin and serum protein content decreased and blood glucose level increased with increasing ammonia concentration. Elevation of LDH, ALAT and ASAT activities were observed in serum and different tissues while inhibition was recorded in AChE activity in brain and liver with increasing ammonia concentration. Comparison of the haematological responses of the two major carps revealed catla to exhibit significant alteration in almost all haematological parameters at relatively lower ammonia concentrations compared to that of rohu. The study on enzymes also revealed lower alteration in AChE, LDH, ALAT and ASAT activities in rohu suggesting better tolerance of the species to higher ambient ammonia than catla, corroborating catla to be more susceptible to environmental stress than rohu.

Effects of freeze–thaw cycles and the soil water content on carbon and nitrogen changes in different soil types of Heilongjiang Province, China

AbstractTo reveal the influence of freeze–thaw cycles (FTCs) on soil carbon and nitrogen changes, six typical soils in Northeast China were selected as the research objects to conduct a FTC simulation test in an artificial climate chamber. Three soil volumetric water contents (10%, 20%, 30%) and eight FTCs (0, 2, 4, 6, 8, 10, 15, 20) were set. The results showed that the soil organic carbon (SOC) and microbial biomass carbon (MBC) contents of different soil types under the FTCs initially exhibited a downward and then an upward trend, while the dissolved organic carbon (DOC) content exhibited an upward and then a downward trend. Otherwise, the fourth and sixth FTCs were the key points of change. The SOC, MBC and DOC contents in paddy fields were higher than those in dry fields, showing upward and then downward trends spatially from northeast to southwest. The SOC and MBC contents in each soil type were the highest at the 20% water content, and the DOC content gradually increased with increasing water content. The ammonium nitrogen (NH4+‐N) content in different soil types at different water contents under the FTCs showed an upward trend first, then a downward trend and finally an upward trend. The NH4+‐N content in paddy fields was higher than that in dry fields. The nitrate nitrogen (NO3‒‐N) content showed a downward trend first, then an upward trend and finally a downward trend. The NO3‒‐N content in dry fields was higher than that in paddy fields. The NH4+‐N contents in the three soil types on the Sanjiang Plain were significantly higher than those on the Songnen Plain. The NH4+‐N and NO3‒‐N contents showed upward trends with increasing water content, but the differences were not significant. The results have implications for the study of different types of soils and provide references for research on the mechanism of soil carbon and nitrogen transformation in typical farming areas in Northeast China.

Evaluation of Associative Effects of In Vitro Gas Production and Fermentation Profile Caused by Variation in Ruminant Diet Constituents

This study aimed to investigate the associative effects caused by changes in the proportions of feed ingredients (forage-to-concentrate ratio) and the forage source in ruminant diets on in vitro gas production and fermentation parameters. The study consisted of two assays conducted in a completely randomized design with a 3 × 10 factorial arrangement consisting of three forages (pineapple crop waste silage [PS], corn silage [CS], and Tifton hay [TH]) associated with concentrate feed (C) (binary mixture) in 11 proportions, with triplicates of each combination. For the first assay, the asymptotic volume of gas did not show any difference among (p = 0.059) CS and PS (p = 0.464) and their proportions. We evaluated the associative effect among forages and their proportions and noticed there was an effect on gas production between the combination of forage and concentrate for the CS (p = 0.003) and PS (p = 0.003). In the second assay, volatile fatty acids (VFA) and ammonia nitrogen (p &lt; 0.05) were affected by the forage source and concentrate inclusion. In conclusion, forages with a high content of soluble carbohydrates presented the lowest gas production, as well as higher concentrations of propionic acid and ammonia nitrogen. The associative effect on in vitro gas production was more pronounced in the first 12 h incubation. The different forage sources and the inclusion of concentrate change fermentation parameters.

Waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis promote tomato seedlings growth by benefiting properties, enzyme activities and rhizosphere bacterial community in coastal saline soil of Yellow River Delta, China

This study investigated the effects of waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis HCH2-3 on the tomato seedlings growth in coastal saline soils and chemical properties, enzyme activities, microbial communities of rhizosphere soil. Microcosmic experiment showed that the seaweed compost and rhizosphere bacteria (SC + HCH2-3) significantly alleviated the negative effects of salinity on the growth of tomato seedlings. SC + HCH2-3 amendment significantly increased the plant height and root fresh biomass of tomato seedling by 105.59% and 55.60% in the coastal saline soils, respectively. The soil properties and enzyme activities were also dramatically increased, indicating that the nutrient status of coastal saline soil was improved by SC + HCH2-3 amendment. In addition, Proteobacteria, Actinobacteriota and Firmicutes were the dominant phyla in the rhizosphere soil after adding seaweed compost and rhizosphere bacteria P. koreensis HCH2-3. The relative abundances of Massilia, Azospira, Pseudomonas and Bacillus increased in treatment SC + HCH2-3. Especially, the beneficial bacteria genera, such as Pseudomonas, Bacillus and Azospira, were significantly correlated with the increases of contents of total nitrogen, nitrate nitrogen and ammonium nitrogen in tomato rhizosphere soil samples. Consequently, adding waste seaweed compost and rhizosphere bacteria P. koreensis HCH2-3 into coastal saline soil was suggested as an effective method to relieve salt stress of tomato plants.

From the perspective of rumen microbiome and host metabolome, revealing the effects of feeding strategies on Jersey Cows on the Tibetan Plateau.

Previous studies have discussed the effects of grazing and house feeding on yaks during the cold season when forage is in short supply, but there is limited information on the effects of these feeding strategies on Jersey cows introduced to the Tibetan Plateau. The objective of this study was to use genomics and metabolomics analyses to examine changes in rumen microbiology and organism metabolism of Jersey cows with different feeding strategies. We selected 12 Jersey cows with similar body conditions and kept them for 60 days under grazing (n=6) and house-feeding (n=6) conditions. At the end of the experiment, samples of rumen fluid and serum were collected from Jersey cows that had been fed using different feeding strategies. The samples were analyzed for rumen fermentation parameters, rumen bacterial communities, serum antioxidant and immunological indices, and serum metabolomics. The results of the study were examined to find appropriate feeding strategies for Jersey cows during the cold season on the Tibetan plateau. The results of rumen fermentation parameters showed that concentrations of acetic acid, propionic acid, and ammonia nitrogen in the house-feeding group (Group B) were significantly higher than in the grazing group (Group G) (P<0.05). In terms of the rumen bacterial community 16S rRNA gene, the Chao1 index was significantly higher in Group G than in Group B (P=0.038), while observed species, Shannon and Simpson indices were not significantly different from the above-mentioned groups (P>0.05). Beta diversity analysis revealed no significant differences in the composition of the rumen microbiota between the two groups. Analysis of serum antioxidant and immune indices showed no significant differences in total antioxidant capacity between Group G and Group B (P>0.05), while IL-6, Ig-M , and TNF-α were significantly higher in Group G than in Group B (P<0.05). LC-MS metabolomics analysis of serum showed that a total of 149 major serum differential metabolites were found in Group G and Group B. The differential metabolites were enriched in the metabolic pathways of biosynthesis of amino acids, protein digestion and absorption, ABC transporters, aminoacyl-tRNA biosynthesis, mineral absorption, and biosynthesis of unsaturated fatty acids. These data suggest that the house-feeding strategy is more beneficial to improve the physiological state of Jersey cows on the Tibetan Plateau during the cold season when forages are in short supply.

Dietary Neutral Detergent Fiber Levels Impacting Dairy Cows' Feeding Behavior, Rumen Fermentation, and Production Performance during the Period of Peak-Lactation.

This study investigated the impact of dietary neutral detergent fiber (NDF) levels (25.49%, 28.65%, 31.66%, and 34.65%, respectively) on the feeding behavior, rumen fermentation, cellulolytic bacteria, and production performance of dairy cows during peak lactation. A feeding experiment was conducted using four fistulated Holstein dairy cows (600 ± 25 kg) with days in milk (50 ± 15 days), employing a 4 × 4 Latin square design to assign the cows to four groups. The results demonstrated that increasing NDF levels in the diet had the following effects: (1) A linear decrease in dry matter intake (DMI), NDF intake, and physically effective NDF8.0 (peNDF8.0) intake; a linear increase in the average time spent eating and ruminating, as well as the time spent eating and ruminating per kilogram of dry matter (DM); a quadratic response in the time spent ruminating per kilogram of NDF and peNDF8.0. (2) A linear increase in average pH value, acetate concentration, and the proportions of Fibrobacter succinogenes and Ruminococcus flavefaciens among total bacteria; a linear decrease in ammonia nitrogen (NH3-N) concentration, microbial crude protein (MCP), total volatile fatty acid (TVFA), propionate, butyrate, and lactate. (3) A linear decrease in milk yield, milk protein percentage, and nitrogen efficiency of dairy cows; a linear increase in milk fat percentage and milk urea nitrogen (MUN) concentration. Based on the combined results, it was found that diets with 25% and 34% NDF had detrimental effects on the feeding behavior, rumen fermentation, and production performance of dairy cows. However, the diet with 28% NDF showed superior outcomes in production performance compared to the one with 31% NDF. Therefore, it is strongly recommended to include a diet containing 28% NDF during the critical peak lactation period for dairy cows.

Different rotation years change the structure and diversity of microorganisms in the nitrogen cycle, affecting crop yield

Crop rotation is a common farmland management measure, which can effectively improve soil permeability and soil fertility, reduce crop diseases and pests, and affect microbial activity and community structure to a certain extent. However, the effects of long-term crop rotation pattern on nitrogen cycle microorganisms and crop yield are still unclear. Using monocrop rice as a control (CK), this study looked at the effects of different rotation years of tobacco rice (rotation years 10–20 (T10), 20–40 (T20), and >40 years of rotation) on nitrogen cycling microorganisms, soil nitrogen content, and crop yield. The results showed that compared with CK, crop rotation mode improved soil fertility and increased soil nitrogen content. Among them, the ammonium nitrogen content of farmland under T20 treatment (increased by 32.27 % compared with CK), and the yields of tobacco and rice were the highest (increased by 43.12 % compared with CK; Compared with T10 and T40 treatment, the tobacco content was increased by 3.59 % and 1.82 %, respectively). In addition, crop rotation also changed the structure and diversity of nitrogen-cycling microorganisms. This study found that Proteobacteria contributed significantly to the increase of soil nitrogen content, and Geobacter, Nitrosospira, Frankia, and Burkholderia Cupriavidus were the key groups to increase soil nitrogen content and crop yield. Therefore, tobacco rice rotation increases soil fertility and crop yield, but the effect decreases after >40 years. This study provides a reference for ensuring soil nitrogen transformation and sustainable agricultural production. The research results laid a solid theoretical foundation for the efficient transformation and utilization of soil nitrogen and grain increase.

Evaluation of activated pyrochar for boosting anaerobic digestion: Performances and microbial community

In this study, the effects of CO2-activated/non-activated pyrochars (PCs) from cornstalk, cotton straw, and rice straw on anaerobic digestion (AD) performances and microbial characteristics were investigated. The maximum biogas production rate (2.2 L/L/d) with a methane content of 73% was obtained from the AD with CO2-activated cotton straw PC. The activated PC mainly played a strengthening role in the early and middle stages of AD. Specifically, the cornstalk PC could greatly relieve acid inhibition, and cotton straw PC had a significantly positive effect on the regulation of ammonia nitrogen concentration. The rare genera like Verrucomicrobia had obvious differences among groups of AD with PCs. Regarding differential metabolites, cornstalk PC-N2 displayed a positive correlation with isoleucyl-alanine, while exhibiting a negative correlation with deoxyinosine, and the corresponding relative expression levels were + 3.0 and −2.4, respectively. Overall, gas-activated PCs could promote methane production and affect the composition of microbial community.

Effects of Balanced Fertilization and Straw Mulching on Soil Nutrients and Stoichiometry in Purple Soil Slope

To explore the effects of long-term balanced fertilization and straw mulching on soil nutrients and stoichiometric ratios in purple soil sloping cropland, nine plots (length 7 m×width 3 m) were established in Dianjiang County as the research sample area of long-term farmland nitrogen and phosphorus loss monitoring. The following three treatments were set up:conventional mode (CK), balanced fertilization mode (M1), and balanced fertilization+straw mulching mode (M2), with three replications for each treatment to compare the contents of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) and their stoichiometric changes under different treatments from 2018 to 2020. The results showed:K contents showed significant differences among the three treatments in 2018, in the order of CK>M2>M1. NO3--N and NH4+-N contents showed significant differences among the three treatments in 2019, both in the order of M1>M2>CK. Other nutrient contents showed no significant difference among different treatments each year. Soil C and N contents showed non-significant differences among different years. The total K contents of CK, M1, and M2 in 2018 were significantly higher than that in other years and were 78.26% and 98.79%, 19.13% and 35.4%, and 54.49% and 41.76% higher than that in 2019 and 2020, respectively. The total P content in the CK and M2 treatments decreased with years, and that of CK and M2 in 2018 was 20.29% and 10.67% and 39.68% and 17.33% higher than that in 2019 and 2020, respectively. The available potassium (AK) content of the three treatments showed non-significant differences among different years, whereas the contents of nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), and available phosphorus (AP) showed significant differences among the different treatments, with all being the highest in 2020. Soil C:P, C:K, N:P, N:K, and P:K ratios of each treatment showed significant differences among different years (P<0.05). Soil C:K, N:K, and AN:AP ratios all showed significant differences among different fertilization modes in 2018 and 2019, respectively (P<0.05). There was a significantly linearly positive relationship between soil C and N concentration and soil P and K concentration. There were very significant linear positive correlations between soil C:K and C:P, N:K, N:P, and P:K; N:K with C:P, P:K, and N:P; and N:P with C:P, N:P, and C:P. Soil P concentration was highly significantly linearly negatively correlated with C:K and N:K ratios. There were significant positive correlations between soil NO3--N, NH4+-N, AN:AP, and AN:AK; NH4+-N, AN:AP, and AN:AK; and AN:AP and AN:AK. The results suggested that balanced fertilization and straw mulching was a more suitable management mode for purple soil sloping cropland.

Integrating anaerobic acidification with two-stage forward osmosis concentration for simultaneously recovering organic matter, nitrogen and phosphorus from municipal wastewater

In order to meet the demand of municipal wastewater for low-carbon treatment and resource recovery, a novel process of anaerobic acidification membrane bioreactor (AAMBR) assisted with a two-stage forward osmosis (FO) (FO-AAMBR-FO) was developed for simultaneously recovering organic matter and nutrients from municipal wastewater. The results indicated that the first FO process concentrated the municipal wastewater to one tenth of the initial volume. The corresponding chemical oxygen demand (COD), ammonia nitrogen (NH4+-N) and total phosphorus (TP) concentration reached up to 2800, 200 and 33 mg/L, respectively. Subsequently, the AAMBR was operated at pH value of 10 for treating the concentration of municipal wastewater, in which the organic matter was successfully converted to acetic acid and propionic acid with a total volatile fatty acids (VFAs) concentration of 1787 mg COD/L and a VFAs production efficiency of 62.36 % during 47 days of stable operation. After that, the NH4+-N and TP concentration in the effluent of the AAMBR were further concentrated to 175 and 36.7 mg/L, respectively, by the second FO process. The struvite was successfully recovered with NH4+-N and TP recovery rate of 94.53 % and 98.59 %, respectively. Correspondingly, the VFAs, NH4+-N and TP concentrations in the residual solution were 2905 mg COD/L, 11.8 and 7.92 mg/L, respectively, which could be used as the raw material for the synthesis of polyhydroxyalkanoate (PHA). Results reported here demonstrated that the FO-AAMBR-FO is a promising wastewater treatment technology for simultaneous recovery of organic matter (in form of VFAs) and nutrients (in form of struvite).

Different responses of soil fungal and bacterial communities to nitrogen addition in a forest grassland ecotone.

Continuous nitrogen deposition increases the nitrogen content of terrestrial ecosystem and affects the geochemical cycle of soil nitrogen. Forest-grassland ecotone is the interface area of forest and grassland and is sensitive to global climate change. However, the structure composition and diversity of soil microbial communities and their relationship with soil environmental factors at increasing nitrogen deposition have not been sufficiently studied in forest-grassland ecotone. In this study, experiments were carried out with four nitrogen addition treatments (0 kgN·hm-2·a-1, 10 kgN·hm-2·a-1, 20 kgN·hm-2·a-1 and 40 kgN·hm-2·a-1) to simulate nitrogen deposition in a forest-grassland ecotone in northwest Liaoning Province, China. High-throughput sequencing and qPCR technologies were used to analyze the composition, structure, and diversity characteristics of the soil microbial communities under different levels of nitrogen addition. The results showed that soil pH decreased significantly at increasing nitrogen concentrations, and the total nitrogen and ammonium nitrogen contents first increased and then decreased, which were significantly higher in the N10 treatment than in other treatments (N:0.32 ~ 0.48 g/kg; NH4+-N: 11.54 ~ 13 mg/kg). With the increase in nitrogen concentration, the net nitrogen mineralization, nitrification, and ammoniation rates decreased. The addition of nitrogen had no significant effect on the diversity and structure of the fungal community, while the diversity of the bacterial community decreased significantly at increasing nitrogen concentrations. Ascomycetes and Actinomycetes were the dominant fungal and bacterial phyla, respectively. The relative abundance of Ascomycetes was negatively correlated with total nitrogen content, while that of Actinomycetes was positively correlated with soil pH. The fungal community diversity was significantly negatively correlated with nitrate nitrogen, while the diversity of the bacterial community was significantly positively correlated with soil pH. No significant differences in the abundance of functional genes related to soil nitrogen transformations under the different treatments were observed. Overall, the distribution pattern and driving factors were different in soil microbial communities in a forest-grassland ecotone in northwest Liaoning. Our study enriches research content related to factors that affect the forest-grassland ecotone.