[Effects of Application of Different Organic Materials on Phosphorus Accumulation and Transformation in Vegetable Fields].

Presently, the improvement of soil organic matter is the basis to ensure food security, but the accumulation and transformation characteristics of soil phosphorus (P) as affected by organic matter remain unclear. The accumulation, transformation, and migration characteristics of soil P in different soil layers of vegetable fields were researched under the application of organic materials. Six treatments were set up in the experiment:control (no fertilization), traditional fertilizer application by farmers, biochar, chicken manure, food waste, and straw application. Available phosphorus (Olsen-P), water-soluble phosphorus (CaCl2-P) content, soil phosphorus forms, soil organic matter (SOM), and pH were determined during the pepper harvest period. In the 0-5 cm and 5-10 cm soil layers, the available phosphorus content of traditional fertilization of farmers was higher, and the available phosphorus content of the four organic materials was in the order of straw > biochar > chicken manure > food waste. Compared to that with food waste, the straw and biochar treatments increased soil available phosphorus by 59.6%-67.3% and 29.1%-36.9%, respectively. The straw treatment could easily enhance the soil labile P pool, and soil labile P in the 0-5 cm soil layer increased by 47.3% and 35.1% compared with that under the chicken manure and food waste treatments, respectively. With the increase in soil depth, the proportion of available phosphorus in the chicken manure treatment decreased the least, and available phosphorus of the 20-30 cm soil layer accounted for 55.9% of the topsoil layer but only accounted for 16.0%-34.0% under treatment with the other three materials. Compared with that under the traditional fertilization of farmers, the pH significantly increased by 0.18-0.36 units after the application of organic fertilizer, and the pH of the chicken manure and food waste treatments was significantly higher than that of biochar and straw (P < 0.05). SOM content under the biochar treatment significantly increased by 7.7%-17.6% compared to that under the other three organic materials. Among the four organic materials, the straw treatment boosted the labile P pool the most, which was conducive to the rapid increase in plant-available P. Phosphorus was most likely to migrate downward under the chicken manure treatment. In the field management based on soil fertility enhancement, the application of biochar could not only improve soil pH and SOM but also avoid excessive accumulation of phosphorus in the surface layer, which decreases environmental risks.

Green manure (Crotalaria juncea L.) enhances Origanum vulgare L. biomass accumulation, essential oil yield, and phytochemical properties.

Green manure (GM) may reduce the use of chemical fertilizers, been an ecologically appropriate strategy to cultivation of medicinal plants. Crotalaria juncea, is one of the most used because it adapts to different climatic and high nitrogen content. Origanum vulgare. is widely used in cooking, pharmaceutical, cosmetic industries and food products. The objectives of this study were to evaluate the GM on biomass, essential oil (EO), phenolic and antioxidant. The experiment consisted: control; 150, 300, 450, and 600 g (Sh= leaves+steam) more 200 g roots (R); 600 g aerial part; 200 g roots; and soil with 300 g cattle manure per pot. The highest dry weights were observed in the presence of GM and cattle manure (90 days). The control had an EO production 75% lower in relation to the dose of 450 g GM (Sh+R). Principal component analysis showed that GM and cattle manure positively influenced the dry weight, content, yield, and EO constituents, and total flavonoids. The GM contributed to the accumulation of the major EO compounds (trans-sabinene hydrate, thymol, terpinen-4-ol). The GM management may be beneficial for cultivating, because it can increase the production of biomass and the active components, in addition to being an inexpensive resource.

Preparation of high-temperature and low-temperature-resistant solid microbial agent for cattle manure fermentation and effect on composting.

We used microbiology and molecular biology techniques to screen out high-temperature and low-temperature-resistant saprobiotics for compost and prepared a compound fermentation bacteria agent to rapidly ferment cattle manure into high-quality organic fertilizer in low-temperature season. Conventional composting and high-throughput techniques were used to analyze the changes of physical and chemical indexes and biodiversity in the process of composting, from which high and low-temperature-resistant strains were obtained, and high-temperature and low-temperature-resistant solid composite bactericides were prepared and added to composting to verify the effects of composite bactericides on composting. The conventional composting cycle took 22 days, and the diversity of microflora increased first and then decreased. Composting temperature and microbial population were the key factors for the success or failure of composting. Two strains of high-temperature-resistant bacteria and six strains of low-temperature-resistant bacteria were screened out, and they were efficient in degrading starch, cellulose, and protein. The high-temperature and low-temperature-resistant solid bacterial agent was successfully prepared with adjuvant. The preparation could make the compost temperature rise quickly at low temperature, the high temperature lasted for a long time, the water content, C/N, and organic matter fell quickly, the contents of total phosphorus and total potassium were increased, and the seed germination index was significantly improved. Improve the composting effect. The solid composite bacterial agent can shorten the composting time at low temperature and improve the composting efficiency and quality.

Effect of manure co-digestion on methane production, carbon retention, and fertilizer value of digestate.

Anaerobic digestion can provide benefits not only from the perspective of renewable energy production but also in the form of fertilization effect and increased retention of C in soils after digestate application. This study consisted of two phases, where the first phase assessed the suitability of carbon-rich co-feedstocks for methane production via laboratory testing. The second phase assessed the balance and stability of C before and after anaerobic digestion by systematic digestate characterization, and by evaluating its carbon retention potential using a modeling approach. The results indicated that pyrolysis chars had a negligible effect on the methane production potential of cattle manure, while wheat straw expectedly increased methane production. Thus, a mixture of cattle manure and wheat straw was digested in pilot-scale leach-bed reactors and compared with undigested manure and straw. Although the total amount of C in the digestate was lower than in the untreated feedstocks, the digestion process stabilized C and was modeled to be more effective in retaining C in the soil than untreated cattle manure and wheat straw. In addition, digestion converted 23-27 % of the C into valuable methane, increasing the valorization of the total C in the feedstock. Considering anaerobic digestion processes as a strategy to optimize both carbon and nutrient valorization provides a more holistic approach to addressing climate change and improving soil health.

Promoting nitrogen conversion in aerobic biotransformation of swine slurry with the co-application of manganese sulfate and biochar.

This study aimed to explore the co-application of MnSO4 (Mn) and biochar (BC) in nitrogen conversion during the composting process. A 70-day aerobic composting was conducted using swine slurry, supplemented with different levels of Mn (0, 0.25%, and 0.5%) and 5% BC. The results demonstrated that the treatment with 0.5MnBC had the highest levels of NH4+-N (3.07 g kg-1), TKN (29.90 g kg-1), and NO3--N (1.94 g kg-1) among all treatments. Additionally, the 0.5MnBC treatment demonstrated higher urease, protease, nitrate reductase, and nitrite reductase activities than the other treatments, with the peak values of 18.12, 6.96, 3.57, and 15.14 mg g-1 d-1, respectively. The addition of Mn2+ increased the total organic nitrogen content by 29.59%-47.82%, the acid hydrolyzed ammonia nitrogen (AN) content by 13.84%-57.86% and the amino acid nitrogen (AAN) content by 55.38%-77.83%. The richness of Chloroflexi and Ascomycota was also enhanced by the simultaneous application of BC and Mn. Structural equation modeling analysis showed that Mn2+ can promote the conversion of Hydrolyzed Unknown Nitrogen (HUN) into AAN, and there is a positive association between urease and NH4+-N according to redundancy analysis. Firmicutes, Basidiomycota, and Mortierellomycota showed significant positive correlations with ASN, AN, and NH4+-N, indicating their crucial roles in nitrogen conversion. This study sheds light on promoting nitrogen conversion in swine slurry composting through the co-application of biochar and manganese sulfate.

Phosphorus fractions and speciation in an alkaline, manured soil amended with alum, gypsum, and Epsom salt.

Snowmelt runoff is a dominant pathway of phosphorus (P) losses from agricultural lands in cold climatic regions. Soil amendments effectively reduce P losses from soils by converting P to less soluble forms; however, changes in P speciation in cold climatic regions with fall-applied amendments have not been investigated. This study evaluated P composition in soils from a manured field with fall-amended alum (Al2(SO4)3·18H2O), gypsum (CaSO4·2H2O), or Epsom salt (MgSO4·7H2O) using three complementary methods: sequential P fractionation, scanning electron microscopy with energy-dispersive X-rays (SEM-EDX) spectroscopy, and P K-edge X-ray absorption near-edge structure spectroscopy (XANES). Plots were established in an annual crop field in southern Manitoba, Canada, with unamended and amended (2.5 Mg ha-1) treatments having four replicates in 2020 fall. Soil samples (0-10 cm) taken from each plot soon after spring snowmelt in 2021 were subjected to P fractionation. A composite soil sample for each treatment was analyzed using SEM-EDX and XANES. Alum- and Epsom salt-treated soils had significantly greater residual P fraction with a higher proportion of apatite-like P and a correspondingly lower proportion of P sorbed to calcite (CaCO3) than unamended and gypsum-amended soils. Backscattered electron imaging of SEM-EDX revealed that alum- and Epsom salt-amended treatments had P-enriched microsites frequently associated with aluminum (Al), iron (Fe), magnesium (Mg), and calcium (Ca), which was not observed in other treatments. Induced precipitation of apatite-like species may have been responsible for reduced P loss to snowmelt previously reported with fall application of amendments.

Arbuscular mycorrhizal fungi, phosphorus and organic residues in Peltophorum dubium (Spreng.) Taub. seedlings.

Studies have underscored a growingdemand for innovative practices in the cultivation of seedlings from forest species, with a notable emphasis on the utilization of organic waste, inoculation with arbuscular mycorrhizal fungi (AMF), and phosphate fertilization. This study aimed to evaluate the impact of organic residues, inoculation with AMF, and phosphorus on the growth and quality of Peltophorum dubium (Spreng.) Taub. seedlings. Two independent experiments were conducted. In Experiment I, treatments included inoculation with various AMF species: control (without inoculation), Clareoideoglomus etunicatum, Rhizophagus heterosporum, Rhizophagus clarum, and MIX (a combination of the three AMF species), all in conjunction with varying doses of phosphorus (0, 60, 120, 180, and 240 mg kg-1 soil). In Experiment II, treatments comprised a control group (without AMF) and inoculation with Glomus clarum, Gigaspora margarita, Gigaspora albida, Clareoideoglomus etunicatum, and MIX (a combination of the four AMF species), each associated with four substrates: S1) soil + coarse sand - SCS, S2) SCS + poultry manure, S3) SCS + cattle manure, and S4) SCS + sheep manure. Peltophorum dubium seedlings exhibited heightened growth with the inoculation of R. heterosporum, R. clarum, and MIX. Positive responses were observed in seedlings when exposed to organic residues, particularly sheep manure, resulting in increased biomass production and enhanced Dickson quality index. The AMF inoculation, specifically with R. heterosporum, R. clarum, and MIX, provided optimal growth conditions for P. dubium seedlings. Remarkably, the utilization of organic residues, notably substrates with chicken manure and cattle manure, exerted substantial positive effects on both growth and quality of P. dubium seedlings.

The biotic effects of lignite on humic acid components conversion during chicken manure composting.

Targeted regulation of composting to convert organic matter into humic acid (HA) holds significant importance in compost quality. Owing to its low carbon content, chicken manure compost often requires carbon supplements to promote the humification progress. The addition of lignite can increase HA content through biotic pathways, however, its structure was not explored. The Parallel factor analysis revealed that lignite can significantly increase the complexity of highly humified components. The lignite addition improved phenol oxidase activity, particularly laccase, during the thermophilic and cooling phases. The abundance and transformation functions of core bacteria also indicated that lignite addition can influence the activity of microbial transformation of HA components. The structural equation model further confirmed that lignite addition had a direct and indirect impact on enhancing the complexity of HA components through core bacteria and phenol oxidase. Therefore, lignite addition can improve HA structure complexity during composting through biotic pathways.

Effect of microbial inoculum on composting efficiency in the composting process of spent mushroom substrate and chicken manure.

This work aimed to investigate the microbial mechanisms for the improvement of composting efficiency driven by the compound microbial inoculum (MI) (Bacillus subtilis SL-44, Enterobacter hormaechei Rs-189 and Trichoderma reesei) during co-composting of spent mushroom substrate (SMS) and chicken manure (CM). The treatments used in the study were as follows: 1) MI (inoculation with microbial inoculum), 2) CI (inoculation with commercial microbial inoculum), and 3) CK (without inoculation). The results demonstrated that MI increased the seed germination index (GI) by 25.11%, and contents of humus, humic acid (HA) and available phosphorus (AP) were correspondingly promoted by 12.47%, 25.93% and 37.16%, respectively. The inoculation of MI increased the temperature of the thermophilic stage by 3-7 °C and achieved a cellulose degradation rate of 52.87%. 16S rRNA gene analysis indicated that Actinobacteria (11.73-61.61%), Firmicutes (9.46-65.07%), Proteobacteria (2.86-32.17%) and Chloroflexi (0.51-10.92%) were the four major phyla during the inoculation composting. Bacterial metabolic functional analysis revealed that pathways involved in amino acid and glycan biosynthesis and metabolism were boosted in the thermophilic phase. There was a positive correlation between bacterial communities and temperature, humification and phosphorus fractions. The average dry weight, fresh weight and seedling root length in the seedling substrates adding MI compost were 1.13, 1.23 and 1.06 times higher than those of the CK, respectively. This study revealed that biological inoculation could improve the composting quality and efficiency, potentially benefiting the resource utilization of agricultural waste resources.

Manure derived hydrochar reduced phosphorus loss risk via an alteration of phosphorus fractions and diversified microbial community in rice paddy soil.

Phosphorus (P) loss caused by the irrational use of manure organic fertilizer has become a worldwide environmental problem, which has caused a potential threat to water safety and intensified agricultural non-point source pollution. Hydrothermal carbonization is method with a low-energy consumption and high efficiency to deal with environmental problems. Application of pig manure-derived hydrochar (PMH) to soil exhibited potential of sustainable development compared with the pristine pig manure (PM). However, the effects of PMH on the distribution of P among the fractions/forms and the interaction between microorganisms and P forms and its relevance to the potential loss of P in paddy fields has not been clarified. Therefore, in this study, a soil column experiment was conducted using the untreated soil (control), and the PM, PMH1 (PMH derived at 180 °C), and PMH2 (PMH derived at 260 °C) treated soils (at the dose of 0.05 %) and rice was cultivated to investigate the effects of PM and PMH on the P fractions, mobilization, ad potential loss via the induced changes on soil microbial community after a complete growing season of rice. The trend of P utilization was evaluated by P speciation via continuous extraction and 31P NMR. The addition of PMH reduced the proportion of residual P in soil by 23.8-26.3 %, and increased the proportion of HCl-P and orthophosphate by 116.2-158.6 % and 6.1-6.8 % compared to PM. The abundance of gcd gene developed after the application of PMH2, which enhanced the mobile forms of soil P utilization via secreting gluconic acid. The network diagram analysis concluded that the changes in various P forms were mainly related to Proteobacteria, Bacteroides, Firmicutes and Acidobacteria. The results illustrated that PMH mitigate the potential risk of P loss more than PM by altering P fractions and affecting soil microbial community.

Manure nutrient cycling in US animal agriculture basins-North Carolina case study.

Nutrient cycling in crop-animal production is impacted by changes in both systems, with imbalance hotspots in concentrated animal production regions severely impacting water quality. This study assesses manure-crop nutrient balances in five river basins in North Carolina and demonstrates a new approach for partial nutrient balances along hydrological boundaries. County-level crop production data were combined with crop-type spatial distribution data to derive spatially referenced nutrient uptake and removal. Similarly, spatially referred animal production inventory data were used to derive excreted and recovered manure nutrients. Partial nutrient balances were developed for both N and P in basins and hydrologic units. Excreted manure N and P were 139% and 159% of respective plant N and P removal at harvest across the five basins. Finer geographical scales revealed hotspots for manure surplus, particularly within the Cape Fear basin (up to 96% N and 97% P). Despite N hotspots, plant-available manure N met only 38% of crop N demand due to significant losses during storage. Plant-available manure P exceeded crop P removal by 54% over the entire area. Cape Fear showed the greatest P excess, 76% greater than crop removal. This study contributes to nutrient cycling improvements by connecting crop-animal nutrient budgets to hydrologic resources. Furthermore, we show the value of finer spatial scales to identify hotspots that play a significant role in nutrient losses. We conclude that nutrient-surplus basins require, in addition to manure nutrient conservation, a basin-wide redistribution and export strategies to address nutrient excesses and water quality impacts.

Effects of Bacillus-based inoculum on odor emissions co-regulation, nutrient element transformations and microbial community tropological structures during chicken manure and sawdust composting.

This study aims to evaluate whether different doses of Bacillus-based inoculum inoculated in chicken manure and sawdust composting will provide distinct effects on the co-regulation of ammonia (NH3) and hydrogen sulfide (H2S), nutrient conversions and microbial topological structures. Results indicate that the Bacillus-based inoculum inhibits NH3 emissions mainly by regulating bacterial communities, while promotes H2S emissions by regulating both bacterial and fungal communities. The inoculum only has a little effect on total organic carbon (TOC) and inhibits total sulfur (TS) and total phosphorus (TP) accumulations. Low dose inoculation inhibits total potassium (TK) accumulation, while high dose inoculation promotes TK accumulation and the opposite is true for total nitrogen (TN). The inoculation slightly affects the bacterial compositions, significantly alters the fungal compositions and increases the microbial cooperation, thus influencing the compost substances transformations. The microbial communities promote ammonium nitrogen (NH4+-N), TN, available phosphorus (AP), total potassium (TK) and TS, but inhibit nitrate nitrogen (NO3--N), TP and TK. Additionally, the bacterial communities promote, while the fungal communities inhibit the nitrite nitrogen (NO2--N) production. The core bacterial and fungal genera regulate NH3 and H2S emissions through the secretions of metabolic enzymes and the promoting or inhibiting effects on NH3 and H2S emissions are always opposite. Hence, Bacillus-based inoculum cannot regulate the NH3 and H2S emissions simultaneously.

Effect of nitrogen reduction by chemical fertilization with green manure (Vicia sativa L.) on soil microbial community, nitrogen metabolism and and yield of Uncaria rhynchophylla by metagenomics.

Uncaria rhynchophylla is an important herbal medicine, and the predominant issues affecting its cultivation include a single method of fertilizer application and inappropriate chemical fertilizer application. To reduce the use of inorganic nitrogen fertilization and increase the yield of Uncaria rhynchophylla, field experiments in 2020-2021 were conducted. The experimental treatments included the following categories: S1, no fertilization; S2, application of chemical NPK fertilizer; and S3-S6, application of chemical fertilizers and green manures, featuring nitrogen fertilizers reductions of 0%, 15%, 30%, and 45%, respectively. The results showed that a moderate application of nitrogen fertilizer when combined with green manure, can help alleviate soil acidification and increase urease activity. Specifically, the treatment with green manure provided in a 14.71-66.67% increase in urease activity compared to S2. Metagenomics sequencing results showed a decrease in diversity in S3, S4, S5, and S6 compared to S2, but the application of chemical fertilizer with green manure promoted an increase in the relative abundance of Acidobacteria and Chloroflexi. In addition, the nitrification pathway displayed a progressive augmentation in tandem with the reduction in nitrogen fertilizer and application of green manure, reaching its zenith at S5. Conversely, other nitrogen metabolism pathways showed a decline in correlation with diminishing nitrogen fertilizer dosages. The rest of the treatments showed an increase in yield in comparison to S1, S5 showing significant differences (p < 0.05). In summary, although S2 demonstrate the ability to enhance soil microbial diversity, it is important to consider the long-term ecological impacts, and S5 may be a better choice.

The fate of Cu and Zn along the feed-animal-excreta-effluent continuum in swine systems according to feed and effluent treatment strategies.

Copper (Cu) and zinc (Zn) have negative environmental impacts as they accumulate in the soil after pig manure is spread. Cu and Zn are essential elements in pig nutrition but due to their low retention rate, more than 90% of ingested Cu and Zn are excreted. A better understanding of the behaviour of these elements throughout the animal-manure-soil continuum according to feed composition and manure management chain is thus required to propose alternative ways to reduce these environmental impacts. The aim of this study was to determine the fate of Cu and Zn throughout this continuum by studying the effect of Cu and Zn contents in animal feed and in the manure management chain based on anaerobic digestion and composting. Faeces were collected from 24 finishing pigs fed with 4 different Cu and Zn dietary levels and sources of supplementation. Samples of faeces were exposed to mesophilic anaerobic digestion or to 5-week composting with straw. Concentrations of Cu and Zn in the faeces were highly dependent on dietary supplies and ranged from 38 to 188 mg Cu/kg DM and from 191 to 728 mg Zn/kg DM. Degradation of a significant fraction of organic matter during treatment led to a significant increase in Cu and Zn concentration relative to the product's dry matter (DM) content, which. Cu and Zn concentrations relative to DM content were twice as high after treatment whatever the content and the form of Cu and Zn dietary supplementation. Otherwise, effluent treatment tended to reduce the possible availability of Cu and Zn in final organic products according to water-extractible contents. This study clearly shows that feed management is the main lever for reducing the amount of Cu and Zn amount in pig effluents and hence in the soil. Appropriate treatment could also facilitate the supply of organic fertilisers to areas with soil deficiency, but feed strategies need to be adapted to the treatment chain to enable the production of good quality organic products that respect EU regulations.

New phosphorus losses via tile drainage depend on fertilizer form, placement, and timing.

Agricultural phosphorus (P) losses are harmful to water quality, but knowledge gaps about the importance of fertilizer management practices on new (recently applied) sources of P may limit P loss mitigation efforts. Weighted regression models applied to subsurface tile drainage water quality data enabled estimating the new P losses associated with 155 P applications in Ohio and Indiana, USA. Daily discharge and dissolved reactive P (DRP) and total P (TP) loads were used to detect increases in P loss following each application which was considered new P. The magnitude of new P losses was small relative to fertilizer application rates, averaging 79.3 g DRP ha-1 and 96.1 g TP ha-1 , or <3% of P applied. The eight largest new P losses surpassed 330 g DRP ha-1 or 575 g TP ha-1 . New P loss mitigation strategies should focus on broadcast liquid manure applications; on average, manure applications caused greater new P losses than inorganic fertilizers, and surface broadcast applications were associated with greater new P losses than injected or incorporated applications. Late fall applications risked having large new P losses applications. On an annual basis, new P contributed an average of 14% of DRP and 5% of TP losses from tile drains, which is much less than previous studies that included surface runoff, suggesting that tile drainage is relatively buffered with regard to new P losses. Therefore old (preexisting soil P) P sources dominated tile drain P losses, and P loss reduction efforts will need to address this source.

Biochar application can enhance phosphorus solubilization by strengthening redox properties of humic reducing microorganisms during composting.

Phosphorus (P) in nature mostly exists in an insoluble state, and humic reducing microorganisms (HRMs) can dissolve insoluble substances through redox properties. This study aimed to investigate the correlations between insoluble P and dominant HRMs amenable to individual culture during biochar composting. These analyses revealed that, in comparison to the control, biochar addition increased the relative abundance of dominant HRMs by 20.3% and decreased redox potential (Eh) levels by 15.4% hence, enhancing the moderately-labile-P and non-labile-P dissolution. The pathways underlying the observed effects were additionally assessed through structural equation modeling, revealing that biochar addition promoted insoluble P dissolution through both the direct effects of bacterial community structure as well as the direct effects of HRMs community structure and indirect effects based on Eh of HRMs community structure. This research offers a better understanding of the effect of HRMs on insoluble P during the composting process.

Analysis of microbial communities in solid and liquid pig manure during the fertilization process.

Utilizing livestock manure as organic fertilizer in sustainable agriculture is crucial and should be developed through an appropriate manufacturing process. Solid-liquid separation contributes to reducing odor, managing nutrients in livestock excretions, and lowering the cost of transporting manure to arable soil. To investigate the impact of fermentation after solid-liquid separation, we examined the specific correlation between chemical properties and bacterial communities in solid-liquid manures before and after the fermentation process. In terms of chemical properties before fermentation, the levels of electrical conductivity, nitrogen, ammonium nitrogen (NH4+-N), potassium, sodium, and chloride were higher in the liquid sample than in the solid sample. However, the chemical components of the liquid sample decreased during fermentation, which could be attributed to the low organic matter content. Many chemical components increased in the solid samples during fermentation. Fifty-six bacterial species were significantly correlated with NH4+-N and phosphorus. Following fermentation, their abundance increased in the solid samples and decreased in the liquid samples, indicating the potential for NH4+-N release or phosphorus mineralization from organic matter. These results provide information regarding changes in nutrient and bacterial formation when applying the fermentation process after solid-liquid separation.

Intramuscular therapeutic doses of enrofloxacin affect microbial community structure but not the relative abundance of fluoroquinolones resistance genes in swine manure.

Livestock manure is a major source of veterinary antibiotics and antibiotic resistance genes (ARGs). Elucidation of the residual characteristics of ARGs in livestock manure following the administration of veterinary antibiotics is critical to assess their ecotoxicological effects and environmental contamination risks. Here, we investigated the effects of enrofloxacin (ENR), a fluoroquinolone antibiotic commonly used as a therapeutic drug in animal husbandry, on the characteristics of ARGs, mobile genetic elements, and microbial community structure in swine manure following its intramuscular administration for 3 days and a withdrawal period of 10 days. The results revealed the highest concentrations of ENR and ciprofloxacin (CIP) in swine manure at the end of the administration period, ENR concentrations in swine manure in groups L and H were 88.67 ± 45.46 and 219.75 ± 88.05 mg/kg DM, respectively. Approximately 15 fluoroquinolone resistance genes (FRGs) and 48 fluoroquinolone-related multidrug resistance genes (F-MRGs) were detected in swine manure; the relative abundance of the F-MRGs was considerably higher than that of the FRGs. On day 3, the relative abundance of qacA was significantly higher in group H than in group CK, and no significant differences in the relative abundance of other FRGs, F-MRGs, or MGEs were observed between the three groups on day 3 and day 13. The microbial community structure in swine manure was significantly altered on day 3, and the altered community structure was restored on day 13. The FRGs and F-MRGs with the highest relative abundance were qacA and adeF, respectively, and Clostridium and Lactobacillus were the dominant bacterial genera carrying these genes in swine manure. In summary, a single treatment of intramuscular ENR transiently increased antibiotic concentrations and altered the microbial community structure in swine manure; however, this treatment did not significantly affect the abundance of FRGs and F-MRGs.

Study of two approaches for the process water management from hydrothermal carbonization of swine manure: Anaerobic treatment and nutrient recovery.

Hydrothermal carbonization (HTC) is a promising alternative to transform biomass waste into a solid carbonaceous material (hydrochar) and a process water with potential for material and energy recovery. In this study, two alternatives for process water treatment by conventional and acid-assisted HTC of swine manure are discussed. Process water from conventional HTC at 180 °C showed high biodegradability (55% COD removal) and methane production (∼290 mL STP CH4 g-1 CODadded) and the treatment in an upflow anaerobic sludge blanket reactor allowed obtaining a high methane production yield (1.3 L CH4 L-1 d-1) and COD removal (∼70%). The analysis of the microbiota showed a high concentration of Synergistota and Firmicutes phyla, with high degradation of organic nitrogen-containing organic compounds. Acid-assisted HTC proved to be a viable option for nutrient recovery (migration of 83% of the P to the process water), which allowed obtaining a solid salt by chemical precipitation with Mg(OH)2 (NPK of 4/4/0.4) and MgCl2 (NPK 8/17/0.5), with a negligible content of heavy metals. The characteristics of the precipitated solid complied with the requirements of European Regulation (2019)/1009 for fertilizers and amendments in agricultural soils, being a suitable alternative for the recycling of nutrients from wastes.

Cytogenotoxicity of raw and treated dairy manure slurry by two-stage chemical and electrocoagulation: An application of the Allium cepa bioassay.

Livestock farming is an essential agricultural practice. However, the improper management of livestock wastes and discharge of untreated or partially treated livestock manure slurry poses significant environmental problems. In this study, we aimed to compare the cytogenotoxic potential of untreated and treated dairy manure slurry treated with a two-stage chemical and electrocoagulation (EC) using the Allium cepa bioassay. The A. cepa bioassay is a well-established standard tool for assessing the cytogenotoxic effects of environmental contaminants, especially those that are occurred as complex contaminant mixtures. The dairy manure slurry was subjected to chemical treatment utilizing polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) at optimized conditions, followed by EC utilizing either aluminum (Al) or steel anodes. The treated and untreated samples were then evaluated for their potential cytogenotoxicty using the A. cepa bioassay, by measuring the nuclear abnormalities (NAs) and chromosomal aberrations (CAs), along with the mitotic indices (MIs). Our findings revealed a significant reduction in cytogenotoxic indicators in the treated liquid fraction compared to the untreated dairy manure slurry. Specifically, the frequency of total NAs showed a significant reduction from 154 ‰ to 37 ‰ when the dairy manure slurry was treated with chemical coagulation followed by EC utilizing an Al anode. Moreover, the MI exhibited a significant improvement from 7 ‰ to 123 ‰, suggesting the mitigation of toxic effects. These results collectively demonstrate the effectiveness of the two-stage chemical and EC treatment under optimal conditions in treating diary manure slurry while reducing its cytogenotoxicity for living systems. The A. cepa bioassay proved to be a sensitive and reliable method for assessing the toxicity of the treated samples. The efficient solid-liquid separation and the reduction of toxicity in the liquid fraction for biological systems achieved through this treatment process highlight its potential for sustainable management of livestock waste and the preservation of water quality. Nevertheless, further studies are required to assess the toxicity of solid fraction.