Ammonia Nitrogen Concentration Research Articles

Bioefficiency of microencapsulated hemp leaf phytonutrient-based extracts to enhance in vitro rumen fermentation and mitigate methane production.

The objective was to assess the supplementation with microencapsulation of hemp leaf extract (mHLE) utilized as a rumen enhancer on in vitro rumen fermentation and to enhance the bioavailability of active compounds for antimicrobial action, particularly in protozoa and methanogen populations. The feed treatments were totally randomized in the experimental design, with different levels of mHLE diet supplemented at 0, 4, 6 and 8% of total DM substrate and added to an R:C ratio of 60:40. During fermentation, gas kinetics production, nutrient degradability, ammonia nitrogen concentration, volatile fatty acid (VFA) profiles, methane production, and the microbial population were measured. The supplemented treatment at 6% of total DM substrate affected reductions in gas kinetics, cumulative gas production, and volatile fatty acid profiles, especially the acetate and acetate to propionate ratio. Whereas propionate proportion and total volatile fatty acid concentration were enhanced depending on the increase of nutrients in vitro dry matter degradability (IVDMD) after 12 h of post-fermentation at a R:C ratio of 60:40 (P < 0.05). Consequently, mHLE addition resulted in optimal ruminal pH and increased nutrient degradability, followed by ammonia nitrogen concentrations (P < 0.05), which were enhanced by dominant cellulolytic bacteria, particularly Ruminococcus albus and Ruminococcus flavefaciens, which showed the highest growth rates in the rumen ecology. Therefore, mHLE, a rich phytonutrient feed additive, affected the methanogen population, reduced the calculated methane production and can be a potential supplement in the ruminant diet.

A synthetic bacterial community engineered from Miscanthus floridulus roots enhances ammonia nitrogen removal in ionic rare earth mine tailings.

Ammonium sulfate, as the primary leaching agent, has caused significant nitrogen pollution in rare earth elements (REEs) mining areas. Phytoremediation is a promising remediation method, relying on the synergistic relationships between plants and their root-associated microbiome. Nevertheless, harnessing the microbiome to accelerate nitrogen transformation and absorption by plants is challenging. Here, we investigated the composition, activities and culturable fraction of the root bacterial microbiome of the pioneer plant Miscanthus floridulus grown in a REEs tailing soil containing a high ammonia nitrogen (AN) concentration at 344.35mgkg-1. Based on this, we constructed a simplified synthetic microbial community (SynCom) derived from the roots of M. floridulus, possessing nitrification and denitrification capabilities, to help REEs mine plants efficiently convert pollutant AN into nutrients, thereby enhancing plant growth and AN removal. This SynCom, consisting of 10 bacterial strains, included species of the genera Burkholderia (5) Paraburkholderia (1), Curtobacterium (1), Leifsonia (1) and Sinomonas (2). As a result, this SynCom alone achieved a significant reduction of 24.8% in AN content in tailing soil. When the SynCom inoculated with plants, the reduction in AN was even more significant (32.6%), surpassing the reduction achieved solely by plants (25.5%). Moreover, live SynCom inoculation significantly increased shoot and root biomass by 39.8% and 49.7%, respectively, compared to dead SynCom inoculation. These results indicate that the reduction in AN can be attributed to the SynCom's nitrification and denitrification capabilities, as well as its ability to enhance plant nitrogen absorption by stimulating their growth. Notably, seven nitrifying and denitrifying strains of the SynCom are particularly enriched, suggesting that plant roots selectively recruit nitrogen cycle-related bacteria to accelerate nitrogen transformation and absorption. These results provide a practical solution for harnessing the synergistic relationships between plants and their root microbiome in environmental remediation efforts.

Soil Properties and Rhizosphere Microbes Community Structure Reveal Nitrogen Uptake Preferences and Nitrogen Use Efficiency of Two Ecotypes of Paphiopedilum micranthum

Paphiopedilum micranthum, an IUCN Red List species, is discontinuously distributed in the karst limestone mountain of southwest China and exhibits ecological specialization, typically through lithophytic and terrestrial ecotypes. Whether the distribution of rhizosphere bacteria and fungi in these different habitats is random or reflects soil preferences requires further investigation. A total of 73 samples from the core distribution areas in China, representing all habitats in two sites, were analyzed for soil differences by comparing edaphic properties and microbial community structure based on high-throughput sequencing of bacterial 16S rRNA genes and fungal ITS region sequences, alongside soil physiochemical data. The results showed no significant differences in microbial community richness and diversity across the heterogeneous habitats. However, significant differences in taxa were observed across various habitats. Dominant bacterial phyla included Actinobacteriota, Proteobacteria and Acidobacteriota, with dominant genera such as Crossiella, Pseudonocardia, 67-14, Mycobacterium and RB41. The primary fungal phyla were Basidiomycota and Ascomycota, featuring prominent genera such as Phlegmacium, Archaeorhizomyces, Trechispora, and Lepiota. There were 16 bacterial genera and 13 fungal genera associated with nitrogen transformation and fixation. Alkali-hydrolyzed nitrogen (AN) was identified as a main driver of soil bacterial and fungal community variation. Based on an analysis of soil physicochemical properties, ammonium nitrogen content was consistently higher than nitrate nitrogen across different habitats. Furthermore, across all heterogeneous habitats, P. micranthum showed no significant differences in nitrate nitrogen, ammonium nitrogen, or their ratio. The nitrogen-use efficiency of P. micranthum ranged from 7.73% to 9.87%, with the highest efficiency observed in the terrestrial habitat of Shedu. These results suggest that P. micranthum prefers habitats rich in organic matter and nitrogen, showing a preference for ammonium nitrogen uptake in natural conditions. Heterogeneous habitats affect plant nitrogen-use efficiency as well as changes in microbial community composition.

Advantageous effects of rumen-protected phytonutrients from tropical plant extracts on rumen fermentation efficiency and methane mitigation using in vitro fermentation technique.

Tropical plants are composed of phytonutrients (PTNs) and are utilized for their capacity to manipulate rumen fermentation characteristics and methane production. The aim of this experiment was to determine the impact of microencapsulated phytonutrients-extracted from lemongrass and mangosteen peel (M-LEMANGOS), as well as crude protein levels on nutrient degradability, rumen ecology, microbial population, and methane emission in an in vitro study. The treatments were randomly assigned in a 2 × 4 Factorial arrangement in a Completely randomized design. The two factors consisted of crude protein (CP) percentage in the concentrate diet (16% and 18% CP) and the levels of M-LEMANGOS addition (0%, 2%, 4%, and 6% of the total substrate). The results showed that nutrient degradability both 12 and 24 h were significantly increased with M-LEMANGOS at 4% total substate. In part of volatile fatty acids (VFAs), particularly propionate and total VFA, these were enhanced by %CP and M-LEMANGOS combination. The %CP increased ruminal ammonia-nitrogen concentration (NH3-N), while M-LEMANGOS supplementation reduced such concentration. Methane production and Methanobacteriales population at 12 and 24 h were reduced when supplemented with M-LEMANGOS at 4% total substate. The population of Fibrobacter succinogenes, Ruminococcus flavefaciens, and Megasphaera elsdenii were increased with the interaction between %CP and M-LEMANGOS addition. M-LEMANGOS indicates promising potential as a plant-based PTN for dietary modulation of rumen fermentation and mitigation of methane production.

Novel Venturi injector reactor design and application in ammonia nitrogen wastewater treatment

The Venturi injector reactor has a robust and durable design and is highly efficient and reliable. The flow field control in the Venturi reactor is an effective way to enhance gas−liquid mass transfer. In this study, a novel Venturi injector reactor with an expandable self-priming air inlet and a second water inlet in the diffusion section was designed by combining particle image velocimetry (PIV) experiments with a computational fluid dynamics simulation. This novel design increased the gas holdup, generated smaller and more uniform bubbles, and enhanced mass transfer. Furthermore, we applied the novel Venturi device to the biological degradation of ammonia nitrogen wastewater. The total gas holdup in the novel Venturi was higher than in the conventional Venturi injector reactor by 0.0056 on average. The minimum bubble diameter was approximately 0.71 mm. Moreover, the ammonia nitrogen removal efficiency of the novel Venturi equipment with the second inlet was 2 and 1.1 times higher than that of conventional aeration and conventional Venturi device, respectively. This study provides a theoretical basis and practical significance for improving the performance and efficient degradation of the ammonia nitrogen concentration in Venturi injector reactors.

The quality of snaplage from an early ripening corn hybrid with biological inoculant and chemical preservatives

The article presents the results of experiments on studying the preservative effect of various additives in the production of snaplage from early-ripening corn hybrids in the conditions of the Central region of the Russian Federation. After opening the containers with feed, its quality indicators were assessed by the content and ratio of organic acids, the degree of acidification, the content of ammonia nitrogen, the preservation of sugars and essential nutrients. In physiological experiments on Romanov wethers, the digestibility of nutrients was determined. It was found that in all variants, the acidity of the feed was optimal (pH 4.2 and below), which excluded the development of undesirable microbiota. At the same time, in the snaplage with chemical preservatives, acidification occurred due to formic and propionic acids introduced with the preparations and (partially) due to the fermentation of sugars. The results of the physiological experiment showed that the digestibility of dry matter of snaplage from the early-ripening hybrid corn Emelin was high (over 70.2%) in all variants, which also affected the energy value (over 11 MJ NE). Thus, for high-moisture snaplage from early-ripening corn hybrids in the Central region of Russia, it is possible to use both chemical preservatives based on organic acids and biological inoculants intended for the preservation of wet flattened grain, containing active strains of lactic acid bacteria.

Mechanisms of Irrigation Water Levels on Nitrogen Transformation and Microbial Activity in Paddy Fields

Nitrogen is a vital nutrient for rice growth; however, its inefficient use often results in nutrient loss, environmental degradation, and the emission of greenhouse gases. In this study, a rice paddy simulation was conducted under different water levels (1–4 cm), incorporating a comprehensive analysis of nitrogen dynamics, environmental factors, and microbial communities to evaluate the impact of water levels on nitrogen concentrations and microbial composition. The results indicated that the water level had a greater impact on nitrogen concentrations in surface water than in soil water. Compared to low water level conditions (1 cm), the average concentrations of ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen in surface water under 2–4 cm water levels decreased by approximately 53.8%, 36.7%, and 78.9%, respectively. Water levels also influenced the microbial composition and nitrogen cycling in paddy soil, with lower water levels promoting aerobic processes such as nitrification, while higher water levels facilitated anaerobic processes such as denitrification and dissimilatory nitrate reduction to ammonium. Correspondingly, microbial composition shifted, with aerobic bacteria predominating in shallow water conditions and anaerobic bacteria flourishing under deeper water. These findings suggest that optimized water management, particularly through shallow irrigation, may mitigate nitrogen loss and improve nitrogen use efficiency. Nevertheless, additional field studies are necessary to validate these results and explore their interaction with other agricultural practices.

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

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

Spatiotemporal Variation Characteristics and Source Identification of Nitrogen in the Baiyangdian Lake Water, China

To study the characteristics and sources of nitrogen in the Baiyangdian Lake, this research conducted water quality monitoring during three hydrological periods (normal period, flood period, and dry period), and 165 pieces of routine water quality monitoring data were collected from the three national control sections for Baiyangdian Lake and its inflow rivers. By integrating water chemical analysis with multivariate statistical techniques, the study comprehensively investigated the spatiotemporal variation patterns of nitrogen in Baiyangdian Lake and identified the sources of nitrogen pollution. The results showed that the concentration of total nitrogen (TN) was highest during the dry period, reaching an average of 0.924 mg/L, and 31.3% of the sites exceeded the national Grade III surface water quality standard, reflecting a potential risk of nitrogen pollution. Based on the ion ratio method and principal component analysis (PCA), the main sources of nitrogen pollution in Baiyangdian Lake were identified as manure and domestic sewage, with agricultural fertilizers also having a certain impact on water nitrogen pollution. In addition, the study also compared the nitrogen concentration in Baiyangdian Lake with several important lakes in China. The results showed that the concentrations of TN and ammonium nitrogen (NH4+-N) in Baiyangdian Lake are lower than those in lakes in areas with similar human activity intensity, indicating that the water quality of Baiyangdian is relatively good. This study can provide a scientific basis for water quality management and pollution prevention for Baiyangdian Lake.

Patterns and Drivers of Greenhouse Gas Emissions in a Tropical Rubber Plantation from Hainan, Danzhou

The intensification of global climate change has made the study of greenhouse gas (GHG) emissions increasingly important. To gain a deeper understanding of the emission characteristics and driving factors of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) from rubber plantation soils, this study conducted a 16-month continuous observation in a rubber plantation in Danzhou, Hainan, employing the static chamber method for the monthly sampling and measurement of GHG emissions while analyzing the soil’s physical and chemical properties. The results indicated that the N2O flux exhibited no significant diurnal variation between the dry and rainy seasons, with an average emission rate of 0.03 ± 0.002 mg·m−2·h−1. A clear seasonal trend was observed, with higher emissions in summer than in winter, resulting in an annual flux of 3 kg·hm−2·a−1 (equivalent to 1.9 kg N·hm−2·a−1). N2O emissions were significantly correlated with soil temperature and moisture, explaining 46% and 40% of the variations, respectively, while soil ammonium nitrogen content also significantly influenced N2O and CO2 emissions. The rubber plantation soil acted as a source of N2O and CO2 emissions and a sink for CH2, with lower emissions of N2O and CO2 during the daytime compared to nighttime, and higher CH4 uptake during the daytime. In the dry season, there was a significant positive correlation between N2O and CO2 emissions (R2 = 0.74, p &lt; 0.001). This study reveals the diurnal and seasonal patterns of GHG emissions from rubber plantation soils in Hainan and their interrelationships, providing a scientific basis for the low-carbon management of rubber plantations and GHG mitigation strategies, thereby contributing to attempts to reduce the impact of rubber cultivation on climate change.

Fertilization shapes microbial life strategies, carbon and nitrogen metabolic functions in Camellia oleifera soil

Mineral, organic and microbial fertilizers are crucial for maintaining and improving soil quality, ecosystem functions, and fruit yield in Camellia oleifera plantations. However, how the application of these fertilizers shapes the life strategies and functions of soil microbial communities is unclear. Here, we conducted a one-year field experiment with three types of fertilizers: mineral (NPK), manure (Man), and microbial (MicrF), and analyzed soil properties, bacterial and fungal communities to assess microbial life strategies, functional traits and their determinants. The application of MicrF strongly increased the diversity of both soil bacterial (by 6.4%) and fungal communities (by 23%). Organic matter inputs from Man and MicrF had greater effects on the life strategies of bacteria than fungi: the dominant r-strategy bacteria (Proteobacteria, Bacteroidetes, and Actinobacteria) increased with Man and MicrF, but K-strategists (Acidobacteria) decreased. Conversely, the abundance of r-strategy fungi (Ascomycota) decreased, but that of K-fungi (Basidiomycota) increased. Predictions of the functions indicated that microbial fertilization accelerated the bacterial carbohydrates, carbon and nitrogen metabolism, while also increasing the prevalence of wood saprotrophic fungi. The changes in the taxonomic and functional characteristics of the microbial communities induced co-metabolism priming effects, which were mainly regulated by soil organic carbon, available phosphorus, ammonium nitrogen contents, and carbon-nitrogen ratio. The application of MicrF is an effective approach to increase the diversity and multifunctionality of soil microbial communities in Camellia oleifera plantations, including organic matter decomposition, carbon and nitrogen metabolism. These findings provide valuable insights into the fertilizer regimes based on microbial ecological strategies and functional profiles in Camellia oleifera plantations.

Enhancing soybean yield stability and soil health through long-term mulching strategies: Insights from a 13-year study

Sustainable agriculture systems incorporate important stabilizing mechanisms, such as mulching, for increasing yield and improving soil health. However, the synergistic effects of different long-term mulching practices on soybean yield stability and soil health remain unexplored. In this study, we conducted a 13-year long-term investigation to evaluate the impacts of various mulching methods—no mulching (CK), straw mulching (SM), plastic mulching (PM), and ridged and plastic mulching (RM)—over a 13-year period on soil nutrients, and soybean yield, stability, and sustainability. Our findings revealed that SM, PM, and RM treatments significantly increased the average yields by 28.02 %, 20.49 %, and 51.56 %, respectively. Moreover, SM and RM treatments significantly enhanced yield stability (SM +107.90 %, RM +98.82 %) and sustainability (SM +47.85 %, RM +37.14 %). Additionally, compared to CK, the SM treatment significantly increased the average soil organic carbon (SOC) and total nitrogen (STN) content by 16.78 % and 16.23 %, respectively. Meanwhile, mulching practices also improved soil reactive carbon and nitrogen pools. Compared to CK, plastic mulch reduced microbial biomass carbon (MBC) content (PM −8.85 %, RM −0.73 %) and soil ammonium nitrogen (AN) content (PM −8.19 %, RM −1.20 %), while increasing microbial biomass nitrogen (MBN) content (PM +8.73 %, RM +9.47 %). The SM treatment increased MBC, AN, and MBN contents by 0.24 %, 7.23 %, and 8.94 %, respectively. Additionally, SM and RM treatments significantly increased β-1,4-glucosidase (BG) activity (SM +98.74 %, RM +128.25 %) and decreased and β-1,4- n -acetamido-glucosidase (NAG) + 1-leucine aminopeptidase (LAP) (NAG + LAP) activity (SM −28.74 %, RM −25.33 %) compared to CK. Furthermore, SM, PM, and RM treatments significantly increased the Chao1 index by 35.30 %, 68.08 %, and 52.23 %, respectively, compared to CK. Finally, results of the Mantel test and random forest model indicated that the increases in yield and stability were due to improved soil temperature (ST), active carbon and nitrogen pools, enzyme activity, and diazotrophic bacterial diversity. In summary, our findings suggest that ridged and plastic mulching enhances soil nutrient effectiveness by maintaining soil moisture and regulating diazotrophic bacterial community structure, thereby increasing soybean yields. Conversely, straw mulching continuously supplies nutrients to the soil, enhancing soil quality and diazotrophic bacterial community structure, thus improving yield stability. Over all, our findings provides new insights into global long-term agricultural sustainability.

Bifunctional system constructed by NiCu-F/DSA electrode self-coupling for efficient removal of ammonia nitrogen from landfill leachate

ABSTRACT Landfill leachates containing high concentrations of ammonia nitrogen, due to its strong toxicity, large discharge and great environmental hazard, is in urgent need of efficient cleaning treatment. In this work, Ni1Cu0.25-F/DSA catalytic electrode was prepared via electrodeposition by means of fluorination-induced surface reconstruction. The surface of electrode was determined to be a porous sponge-like structure by physical characterizations. The electrode exhibited a superior ammonia oxidation reaction (AOR) activity and stability by a series of electrochemical tests. On this basis, a Ni1Cu0.25-F/DSA || Ni1Cu0.25-F/DSA bifunctional system was developed for efficient removal of ammonia nitrogen in landfill leachate. The results of denitrification experiment indicated that the removal efficiency of NH4 +-N and TN were 99.89% and 68.9%, respectively, when the electrolytic cell potential was 1.7 V, pH was 13 and the initial ammonia concentration was 600 mg L−1. The NH4 +-N removal efficiency remained above 95% after the cyclic denitrification experiment lasting for 6 days, which validates the robust stability of the electrode.

Effects of Different Weeding Methods on Soil Physicochemical Properties, Root Morphology, and Fruit Economic Traits in Camellia oleifera Abel. Plantations

Soil physicochemical properties, root characteristics, and fruit economic traits were determined in Camellia oleifera plantations under spontaneous vegetation + mowing (W1), spontaneous vegetation + glyphosate (W2), and no weeding (CK) treatments. Compared with CK, W1 reduced soil bulk density and increased total nitrogen, total phosphorus, ammonium nitrogen, nitrate nitrogen, and effective potassium content. W2 treatment resulted in higher bulk density than W1 and lower water-holding capacity, total nitrogen, total phosphorus, total potassium, ammonium nitrogen, nitrate nitrogen, and available potassium of the soil. Generally, both W1 and W2 inhibited weed morphological traits while favoring the C. oleifera root system, with the W1 treatment resulting in the greatest increase. Fruit transverse diameter, longitudinal diameter, yield, and oil yield were higher in W1 than in CK and W2 treatments. Weed root systems and C. oleifera root systems ultimately affect oil production and yield by affecting bulk density, ammonium nitrogen, nitrate nitrogen, fruit transverse diameter, seed yield, and seed kernel oil content. In summary, W1 treatment improved the physicochemical properties, root growth, fruit growth, and soil quality in C. oleifera plantations.

Investigation of Nitrogen Removal in Flue Gas Desulfurization and Denitrification Wastewater Utilizing Halophilic Activated Sludge.

In the process of flue gas desulfurization and denitrification, the generation of high-sulfate wastewater containing nitrogen is a significant challenge for biological wastewater treatment. In this study, halophilic activated sludge was inoculated in a Sequencing Batch Reactor to remove nitrogen from wastewater with a high sulfate concentration (60 g/L). With the influent concentration of 180 mg/L, the removal rate of total nitrogen was more than 96.7%. The effluent ammonium nitrogen concentration was lower than 1.94 mg/L, and the effluent nitrate nitrogen and nitrite nitrogen concentrations were even lower than 0.77 mg/L. The salt tolerance of activated sludge is mainly related to the increase in the content of ectoine in microbial cells. The Specific Nitrite Oxidation Rate is quite low, while the Specific Nitrite Reduction Rate and Specific Nitrate Reduction Rate are relatively strong. In the system, there are various nitrogen metabolic processes, including aerobic nitrification, anaerobic denitrification, and simultaneous nitrification-denitrification processes. By analyzing the nitrogen metabolic mechanisms and microbial community structure of the reaction system, dominate bacteria can be identified, such as Azoarcus, Thauera, and Halomonas, which have significant nitrogen removal capabilities.

The Effect of Adding Green and Black Tea Waste Extracts on Rumen Fermentation Parameters by In Vitro Techniques

The increase in global temperatures over the past few decades due to greenhouse gas emissions has raised concerns and necessitated further research in climate change mitigation and adaptation. Methane is a prominent greenhouse gas that significantly contributes to climate change, with a substantial amount generated through fermentation processes occurring in the rumen of ruminant animals. The potential of plant secondary metabolites, especially those derived from tannin-rich plants, warrants investigation to modify rumen fermentation and mitigate methane emissions in livestock diets. The objective of this study was to assess the impact of extracts obtained from green and black tea waste on rumen fermentation dynamics and gas (methane) production, utilizing in vitro methods. For this purpose, rumen fluid was collected from two fistulated sheep and subjected to three treatments: (1) a basal diet (control), (2) a basal diet + green tea waste extract (5% of dry matter), (3) a basal diet + black tea waste extract (5% of dry matter). The study assessed the effects of incorporating extracts from green and black tea waste on various parameters, including digestibility, protozoa population, ammonia nitrogen levels, volatile fatty acids, and methane gas production following a 24-h incubation period. Statistical analysis of the data was conducted using SAS software within a completely randomized design framework. The findings indicated that the addition of green and black tea waste extracts significantly decreased methane gas production (p &lt; 0.05), protozoa count (p &lt; 0.05), and ammonia nitrogen concentrations in rumen fluid (p &lt; 0.05) when compared to the control group. The addition of green and black tea waste extracts has significantly altered the concentration of VFAs in rumen fluid (p &lt; 0.05). Specifically, the addition of green tea waste extract has led to a highly significant reduction in acetic acid, (p &lt; 0.01) and the addition of both extracts has resulted in a significant increase in propionic acid (p &lt; 0.05). Consequently, the results suggest that the inclusion of green and black tea waste extracts in livestock diets may effectively mitigate methane emissions in the rumen, thereby reducing feed costs and reducing environmental pollution.

Effects of Chitosan-Based Additive on Rumen Fermentation and Microbial Community, Nutrients Digestibility and Lactation Performance in Goats.

Recently, the potential of using chitosan (CHI) as a feed additive to enhance ruminal fermentation and improve animal performance has gained increasing attention in ruminant nutrition. This study was undertaken to investigate the effect of dietary supplementation with increasing doses of CHI on rumen fermentation attributes and microbial composition, digestibility and milk performance in Dhofari goats. Twenty-four lactating goats (27 ± 1.8 kg of initial live body weight) were fed a control diet comprising of Rhodes grass hay plus a concentrate feed mixture. Goats were assigned to one of three experimental treatments (n = 8 per treatment) as: (1) control diet with no supplement (CTRL), (2) control diet with 0.300 g/day CHI (CHI0.3) and (3) control diet supplemented with 0.600 g/day CHI (CHI0.6) for a 45-day experimental period. Dietary supplementation with increasing doses of CHI decreased (p < 0.05) linearly ruminal pH (p = 0.023), total short chain fatty acids concentrations (p = 0.011), acetate (p = 0.013) and butyrate (p = 0.042) proportions, acetate to propionate ratio (p < 0.001), estimated methane (CH4) production (p < 0.001), ammonia nitrogen concentrations (p = 0.003) and protozoa abundance (p = 0.003). However, the ruminal propionate proportion augmented (p = 0.002) linearly with increasing doses of CHI in the diet. Increasing doses of CHI linearly increased the abundance of the ruminal propionate-producing bacteria, while diminished acetate and CH4-producing bacteria (p < 0.05). Serum total protein (p = 0.037) and glucose (p = 0.042) levels linearly increased as CHI doses increased in the diet. However, serum UREA levels decreased linearly (p = 0.002) by 21% with increasing CHI amounts in the diet. The digestibility of organic matter, crude protein and neutral detergent fibre increased linearly with the increasing CHI doses (p < 0.05). Neither linear nor quadratic responses (p > 0.05) were observed in daily milk yield and feed efficiency by supplementing the diet with CHI. In conclusion, supplementing the diet with CHI at a dose of 0.600 g/day as a feed additive for dairy goats reduced estimated CH4 generation and improved fibre and protein digestion, with no influence on feed intake, milk yield or composition.

Fixing collapsed dry anaerobic digestion system of kitchen waste caused by severe VFAs accumulation

Severe inhibition by volatile fatty acids (VFAs) frequently occurs during the dry anaerobic digestion of kitchen waste at high organic load rate (OLR), leading to decreased biogas production and even the collapse of the anaerobic digestion system. In this study, VFAs accumulation was significantly reduced by adding powder-activated carbon (PAC) or alkaline additives (AA), thus restoring the collapsed system to a stable operating state. With the addition of PAC or AA, the maximal OLR reached 11.14 g VS/(L·d), which was 30 % higher than observed without any additives (control group), while the VFAs concentration was maintained below 3000 mg/L. At this OLR, the volumetric biogas production rate stabilized at 5.1 L/(L·d) in the presence of PAC and AA, while that of the control group gradually decreased to zero. The VFAs concentration with PAC addition was 86 % lower than that of the control group, possibly because PAC might stimulate the formation of direct interspecies electron transfer between syntrophic bacteria and methanogens (Methanosarcina), thereby promoting VFAs degradation. The addition of AA, which resulted in a 95 % decrease in ammonia-nitrogen concentration, can provide a good growth environment for the microorganisms involved in acidogenesis and hydrogenotrophic methanogenesis.

Performance of vertical flow wetland in the treatment of medium organic strength synthetic wastewater

Treatment wetlands have been used for decades to treat wastewaters with low organic strength, but little information is available on the treatment of wastewaters with high organic strength. The objective of this study was to evaluate the efficiency of a vertical flow wetland in the primary treatment of synthetic wastewater with medium organic strength (1976 mg COD/L). Alternatives in the reuse of the resulting treated wastewater were also considered. The wetland consisted of several layers of sand and gravel of different granulometry and was planted with the helophyte Eryngium horridum, a species rarely used in treatment wetlands. The wetland was fed with synthetic wastewater by a single feed pulse, with a hydraulic retention time of 24 h. The treatment removed 81% of TSS and 70% of COD. The concentrations of ammonium nitrogen and soluble reactive phosphorus increased due to partial mineralization of organic matter. Total phosphorus and total nitrogen removal were 28% and 5%, respectively. Wastewater suitability for reuse in irrigation increased after treatment. However, a later stage is recommended to further reduce COD and nutrient concentration and disinfect the water.

Effects of Vegetable Planting Ages on Community Structure of Ammonia-oxidizing Archaea and Ammonia-oxidizing Bacteria in Greenhouse Vegetable Fields

The ammonia oxidation process driven by microorganisms is a dominant source for nitrous oxide （N2O） emissions. Here, we examined the influence of greenhouse vegetable planting ages on soil ammonia-oxidizing archaea （AOA） and ammonia-oxidizing bacteria （AOB）, which is of great significance for assessing the soil quality status and greenhouse gas transformations. A field study was conducted at different times （1, 5, 10, and 20 a） in greenhouse vegetable soils of Gaoyi, Hebei Province. Chemical analysis and Illumina NovaSeq high-throughput sequencing were used to analyze the soil physicochemical properties and community structures and diversity of AOA and AOB. The variation in AOA and AOB communities and the driving factors in greenhouse soils at different ages were also investigated. The results showed that the contents of total nitrogen, organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium first increased and then decreased with the prolongation of growth. The contents of nitrate nitrogen, ammonium nitrogen, and electrical conductivity first decreased and then increased with the prolongation of growth. The pH value of soils decreased with the prolongation of growth. The abundance and diversity index of AOA and AOB first decreased and then increased with the prolongation of growth. Nitrososphaeria, unclassified Thaumarchaeota, and Candidatus Nitrosocaldus were the dominant species of AOA, while Betaproteobacteria and Nitrosospira were the dominant species of AOB. The composition of the soil AOA community varied greatly compared to that of AOB with the prolongation of growth. Correlation analysis showed that the changes in soil nutrient factors had a significant correlation with AOA and AOB communities. Redundancy analysis indicated that ammonium nitrogen, alkali-hydrolyzable nitrogen, and nitrate nitrogen were key factors of AOA communities, while electrical conductivity, available potassium, and nitrate nitrogen were key factors for AOB. In summary, long-term planting of greenhouse vegetables significantly affected the abundance and composition of soil AOA and AOB communities. Our results provide a theoretical basis for further studies on the greenhouse gas transformation and microbial mechanisms of the nitrogen cycle in greenhouse soils.