Slurry Irrigation Research Articles

Environmental risks in swine biogas slurry-irrigated soils: A comprehensive analysis of antibiotic residues, resistome, and bacterial pathogens

Simple anaerobic digestion is insufficient to completely remove residual parent antibiotics and antibiotic resistance genes (ARGs) from animal manure. ARG prevalence in swine biogas slurry-irrigated soils threatens human health. However, comprehensive analysis of antibiotic residues, high-resolution resistance gene profiles, and pathogenic microbiomes in biogas slurry-irrigated soils is very limited. Here, we comprehensively determined the antibiotics, resistome, and potential pathogens distribution in these soils, using high-performance liquid chromatography-tandem mass spectrometry, high-throughput quantitative PCR, and 16S rRNA gene sequencing. The results revealed a significant enrichment of tetracyclines and fluoroquinolones antibiotics and ARGs in soils with prolonged biogas slurry irrigation, with a total of 12 antibiotics, 175 unique ARGs, and 9 mobile genetic elements (MGEs) detected. Quantification of veterinary antibiotic residues (especially chlortetracycline) showed significant correlations with multiple ARGs. The abundance of ARGs and MGEs was highest in the biogas slurry-irrigated soils, denoting a tight link between the application of biogas slurry and the spread of antibiotic resistance. The presence of 50 potential pathogenic bacterial genera, including 13 with multidrug resistance, was identified. Variation partitioning, combined with hierarchical partitioning analysis, indicated that Firmicutes, MGEs, and tetracyclines were the key drivers shaping the ARG profiles in biogas slurry-irrigated soils. The findings offer insights into the mechanisms of antibiotic residue and ARGs spread from the agricultural practice of biogas slurry irrigation, underscoring the necessity of sustainable soil management to mitigate the spread of antibiotic resistance.

232 In Vitro Digestibility of Dry Matter and Nitrogen of Napier Grass Silage Is Affected By Fertilization with Cow-Dung Bio-Digester Slurry and Fermentable Carbohydrate Additives at Ensiling

Abstract The use of silages during the dry season could ameliorate major nutritional constraints in ruminant livestock production in tropical regions. Napier grass (Pennisetum purpureum) is a tropical forage source that is used for silage in South Africa. The present objective was to determine the effects of fertilization with bio-digester slurry (BDS) and of carbohydrate additives [no additive (control), molasses, brown sugar, and maize meal] at ensiling on in vitro digestibility of Napier grass silage. Fresh Napier grass irrigated weekly with either BDS or water was cut after 12 weeks and ensiled for 90 days in 1 liter glass jars in a 2 (control and slurry irrigation) x 4 (no additive, molasses, maize meal and brown sugar) factorial arrangement replicated three times. The nutrient composition was determined using standard protocols. The in vitro digestibility of dry matter (DM) and crude protein (CP) were determined by the three-stage method after incubation in rumen of steers for 12, 24 and 48-hour incubation. The bags containing rumen undegradable residuals (RURs) were removed from the bags, composited by treatment, and ground through a 1 mm sieve. Approximately 1g samples of RURs of each silage sample were placed in a 0.1 N HCl solution adjusted to pH 1.9 with 1 g ℓ-1 of pepsin, and then in pancreatin solution and rinsed with deionized water and dried at 60°C for 48 h. At 24 h incubation, the no BDS, no additive (control) treatment had the least (P < 0.01) DM degradability. As incubation time progressed to 48 h, fertilization with BDS with molasses inclusion increased (P < 0.05) DM disappearance. However, the BDS fertilization and carbohydrate additive interaction had no effect (P > 0.05) on 12 incubation h, and in vitro digestibility after 12, 24 and 48 h of incubation. Fertilization with BDS reduced (P < 0.05) DM digestibility after 48 hours of rumen incubation. Carbohydrate additives increased (P < 0.01) DM disappearance at 12, 24 and 48 rumen incubation h but did not not influence in vitro DM digestibility after 12, 24, and 48 h of rumen incubation. Fertilization with BDS and carbohydrate additives at ensiling interaction had no effect (P > 0.05) on CP degradability at 12, 24, and 48 h of rumen incubation, and in vitro CP digestibility after 12, 24, and 48 h of incubation. Carbohydrate additives increased (P < 0.01) CP disappearance at 12, 24 and 48 rumen incubation h and reduced (P < 0.01) in vitro CP digestibility after 12 h of rumen incubation but did not have an effect (P > 0.05) on in vitro CP digestibility after 24 and 48 h of rumen incubation.

Comprehensive discovery and migration evaluation of antimicrobial drugs and their transformation products in a swine farm by target, suspect, and nontarget screening

Swine farms contaminated the surrounding environment through manure application and biogas slurry irrigation, hence causing the wide residual of multiple antimicrobial drugs (ADs) and their transformation products (TPs). This study performed target, suspect, and nontarget screening methods to comprehensively investigate the pollution profiles of ADs in a typical swine farm, and characterize the potential transformed pathway of TPs and distinguish specific reactions of different catalog of ADs. Samples of fresh feces, compost, biogas slurry, topsoil, column soil, groundwater and plants were analyzed using the database containing 98 target analytes, 679 suspected parent ADs, and ∼ 107 TPs. In total, 29 ADs were quantitively detected, and tetracyclines (TCs) were mostly frequently detected ADs with the concentrations up to 4251 ng/g in topsoil. Soil column investigation revealed that doxycycline (DOX) and tetracycline (TC) in soil could migrate to depths of approximately 1 m in soil. Suspect screening identified 75 parent ADs, with 10 being reported for the first time in environmental media. Semi-quantification of ADs revealed that one of the less-concerned ADs, clinafloxacin, was detected to exceed 5000 ng/L in biogas slurry, suggesting that significant attentions should be paid to these less-concerned ADs. Moreover, 314 TPs was identified, and most of them were found to undergo microbial/enzymatic metabolism pathways. Overall, our study displays a comprehensive overview of ADs and their TPs in swine farming environments, and provides an inventory of crucial list that worthy of concern. The results emphasize the need to quantify the levels and distribution of previously overlooked ADs and their TPs in livestock farms.

Integrated microbiota and multi-omics analysis reveal the differential responses of earthworm to conventional and biodegradable microplastics in soil under biogas slurry irrigation

As one of the promising alternatives of conventional plastic mulching film (C-PMF), biodegradable plastic mulching films (B-PMF) were employed in agronomy production to alleviate the environmental burden of C-PMF. However, information regarding the potential toxicity effects of biodegradable microplastics (MPs) in soil still in scarcity, and the available findings were found to be controversial. Additionally, little is known about the molecular toxicity effects of conventional and biodegradable MPs on terrestrial organisms. Thus, 5 % (w/w) biodegradable (polylactic acid, PLA) and conventional (polyvinylchloride, PVC; low-density polyvinylchloride, LDPE) MPs were employed to assess the toxicity effects on Eisenia fetida in agricultural soil with biogas slurry irrigation. In the present study, transcriptomic, metabolomic profiles and individual indexes were selected to reveal the toxicity mechanisms from molecular level to the individual response. Furthermore, dysbiosis of bacterial community in gut was also investigated for obtaining comprehensive knowledge on the MPs toxicity. At the end of the exposure, the number of survival earthworms after MPs exposure was significantly reduced. Compared with the initial body weight, PLA and LDPE increased the biomass of earthworms after MPs exposure, while no significant influence on the biomass was observed in PVC treatment. Microbacterium, Klebsiella and Chryseobacterium were significantly enriched in earthworm gut after PLA, PVC and LDPE exposure, respectively (p < 0.05). Transcriptomic and metabolomic analysis revealed that PLA exposure induced neurotransmission disorder and high energetic expenditure in earthworms. However, PVC and LDPE inhibited the nutrient absorption efficiency and activated the innate immunity responses of earthworms. The PLS-SEM results showed that the effects of MPs were dominated by the polymer types, and hence, significantly and directly influence the gut bacterial community of earthworms. This study provides a better understanding of the similarities and discrepancies in toxicity effects of biodegradable and conventional MPs from the perspectives of individual, gut bacterial community, transcriptome and metabolome.

Discussion of the economic benefits of biogas slurry irrigation by analytic hierarchy process (AHP)

In this study, the benefits of Biogas slurry irrigation on farmland were evaluated in the background of circular economy. Biogas slurry irrigation is a worldwide option to promote sustainable agriculture and the policy of biogas slurry irrigation has been implemented nationally for more than five years in Taiwan. As the result, the number of irrigating households has been increasing year by year. In this study, we implemented a questionnaire to apply a two-by-two comparison question to the same group of respondents and used the analytic hierarchy process (AHP) to evaluate the factors including cost of fertilizer, environmental benefits, food safety benefits and operational costs in order to analyze the benefits of irrigation. Accordingly, the evaluation results show that 31% in fertilizer cost, 26% in environmental benefits, 23% in food safety benefits and 20% in operating costs conform to pairwise comparison matrix consistency results after validation that the fertilizer cost which has the highest percentage is the most important issue for farmers. Facing the global climate change and rising raw material prices, farmers will have to pay higher costs for fertilizers in the coming future. Therefore, Biogas slurry substitution is proven to not only solve the problems of chemical fertilizers in environmental damages but also creating a sustainable business model to achieve the circular economy policy encouraged by the government in accordance with the global trend of environmental protection.

Response of earthworms to microplastics in soil under biogas slurry irrigation: Toxicity comparison of conventional and biodegradable microplastics

As a reliable environment-friendly alternative, biodegradable plastic mulching films have been introduced into agricultural practice to reduce the adverse threats posed by conventional plastic products. Information regarding whether potential untoward effects of biodegradable plastics exist in soil and how strong are such effects on terrestrial organisms, however, still remains unknown. This study examined differences in the responses of earthworm, represented by Eisenia fetida, to exposure to biodegradable (PLA: polylactic acid) and conventional microplastics (PVC: polyvinylchloride, LDPE: low-density polyethylene) in soil with biogas slurry irrigation. Mortality, growth, histopathology and biochemical enzymes of the earthworms exposed to different concentrations of microplastics (5, 20 and 50 g/kg wet weight of soil, respectively) were investigated after 28 days of incubation in the experiment. The obtained results showed that the ecotoxicity of microplastics (MPs) to earthworms was time-dependent. Regardless of MPs type, continuous exposure to MPs at the concentration of 50 g/kg induced mucous vacuolization, longitude muscle disorder, and granular lipofuscin-like deposits generation in the epithelium. Moreover, tissue fibrosis and cavity formation were also observed in intestinal tissue. The presence of MPs stimulated the oxidative stress system of the earthworms, as indicated by the enhancement of malonaldehyde (MDA) content in vivo. The antioxidative defense system in earthworms was supposed to collapse at the MPs concentration of 50 g/kg after 28 days of exposure. Interestingly, PLA exhibited similar ecotoxicity effects with LDPE, which might violate the original intention of biodegradable plastics with less harmful or nontoxic influence on the terrestrial biotas. Thus, knowledge regarding the molecular and genetic mechanisms of the earthworms in soil containing biodegradable plastics should be further explored to better understand the risk posed by biodegradable plastics in the agroecosystem.

Response of sunflower to salt and alkali stress induced by biogas slurry irrigation

Response of sunflower to salt and alkali stress induced by biogas slurry irrigation

Response of Earthworms to Microplastics in Soil Under Biogas Slurry Irrigation: Toxicity Comparison of Conventional and Biodegradable Microplastics

Response of Earthworms to Microplastics in Soil Under Biogas Slurry Irrigation: Toxicity Comparison of Conventional and Biodegradable Microplastics

Occurrence and Fate of Steroid Estrogens in a Chinese Typical Concentrated Dairy Farm and Slurry Irrigated Soil.

Animal husbandry is the second largest source of steroid estrogen (SE) pollutants in the environment, and it is significant to investigate the occurrence and fate of SEs discharged from concentrated animal feeding operations. In this research, with a Chinese typical concentrated dairy farm as the object, the concentrations of SEs (E1, 17α-E2, 17β-E2, E3, and E1-S3) in slurry, lagoon water, and slurry-irrigated soil samples in summer, autumn, and winter were determined. The total concentrations of SEs (mainly E1, 17α-E2, and 17β-E2) in slurry were very high in the range of 263.1-2475.08 ng·L-1. In the lagoon water, the removal efficiencies of the aerobic tank could reach up to 89.53%, with significant fluctuation in different seasons. In the slurry-irrigated soil, the maximum concentrations of SEs in the topsoil and subsoil were 21.54 ng·g-1 to 6.82 g·g-1, respectively. Most of the SEs tended to transport downward and accumulate in the soil accompanied with the complex mutual conversion. Correlations and hierarchical clustering analysis showed a variety of intertransformation among SEs, and the concentrations of SEs were correlated with various physicochemical indexes, such as TN and NO3--N of the slurry, chemical oxygen demand of the lagoon water, and the heavy metals of soil. In addition, 17β-estradiol equivalency assessment and risk quotients indicated that the slurry irrigation and discharge of the lagoon water would cause potential estrogenic risks to the environment. Consequently, reasonable slurry irrigation and lagoon water discharge are essential to efficiently control SE pollution in the environment.

Wide-scope screening for pharmaceutically active substances in a leafy vegetable cultivated under biogas slurry irrigation

The use of livestock waste for the production of biogas and the application of biogas slurry to agricultural soil can resolve livestock waste problems and reduce synthetic fertiliser use. However, the migration of veterinary drugs to land and crops resulting from biogas slurry irrigation is a potential food safety concern. This study employed an ultra-performance liquid chromatography coupled with quadrupole-time of flight high-resolution mass spectrometry system for wide-scope suspect screening of pharmaceutically active substances on crop cultivated under biogas slurry irrigation. Briefly, a total of 22 pak choi samples were obtained from a greenhouse farmed in tropical south Taiwan between March 2019 and March 2020. Molecular spectra and fragmented ions (between m/z 70 and 1100) were acquired. Ion features were searched and matched with a library consisting of 1068 compounds. The matrixes in the crop production environment including soil, livestock wastewater, biogas slurry, and groundwater were included in this study to elucidate potential sources of the pharmaceutically active substances. Results demonstrated 23 suspects were matched with high mass accuracy (mass error within ±5.0 ppm) in pak choi. The detection of both bufexamac and nandrolone were confirmed using standards, where a new system of identification points was applied. Nandrolone was detected throughout the pak choi samples as well as livestock wastewater. Tetracycline, macrolide, and sulfonamide antibiotics were presented in biogas slurry and soil but not pak choi. This is the first study to reveal the presence of multiclass pharmaceutically active substances in a crop supplied as food. Such findings suggest that anabolics and antibiotics should be closely monitored in the corps irrigated by biogas slurry in future.

Effects of biogas slurry irrigation DOC/N ratios on the fate of soil nitrogen and GHG emissions: A laboratory study

Following biogas slurry irrigation, high rates of nitrogen (N) leaching have been measured, and testing increased slurry ratios of dissolved organic carbon (DOC) to N as a potential technique to reduce leaching, have been evaluated in previous research. Here, we explored the effects of slurry DOC/N ratios on the fate of soil N and greenhouse gas (GHG) emissions in a laboratory study. Slurries with DOC/N ratios of 0.9, 7.3, and 17.3 were applied to soil columns. Overall, the application of biogas slurry with a DOC/N ratio of 0.9 and increasing the ratio, enhanced soil mineralization, N immobilization and denitrification, and resulted in net mineralization. Additionally, most of the applied N left the soil through gaseous N emissions rather than by N leaching. Increasing the slurry DOC/N ratio from 0.9 to 7.3 or to 17.3 reduced nitrous oxide (N2O) emissions by 13% and 25%, respectively, and reduced methane (CH4) emissions by 1168% and 483%, respectively. In comparison, the respective carbon dioxide (CO2) emissions were 58% and 113% higher. In summary, an increased slurry DOC/N ratio contributes to soil CO2 emissions, but reduces both soil N2O and CH4 emissions. However, the reductions in N2O and CH4 emissions warrant further study.

Ösztrogének és ösztrogénhatású anyagok a növénytermesztésben

Összefoglalás Egy vegyület akkor tekinthető ösztrogén hatásúnak, ha alacsony affinitással is, de az ösztrogén receptorokhoz (ER) kötődni képes, az ösztrogén érzékeny sejtekben, szövetekben biológiai hatást képes kiváltani, melyek hasonlóak a petefészek eredetű ösztrogén hormonok által előidézett folyamatokhoz. Irodalmi adatok alapján a hígtrágyával történő öntözés és intenzív állattartásból származó trágya termőföldre juttatása következtében a szteroid ösztrogének, beleértve az ösztron E1, ösztradiol E2, ösztriol E3, valamint a szintetikus ösztrogén EE2, mindenütt jelen vannak a termőtalajban. A növények felhalmozhatják az ösztrogéneket gyökereikben és hajtásaikban, bekerülve a táplálékláncba akár hatást fejthetnek ki a humán egészségre. A vegyületek ösztrogén potenciálját legtöbbször a 17β-ösztradiol referencia vegyülethez viszonyított relatív potenciálként fejezik ki. Meghatározó szerepe van a vegyületek minőségének, ugyanis az egyes ösztrogénhatású vegyületek különböző hatással lehetnek a receptorokra Ahogy korábban említettük, hígtrágya csak talajtani szakvéleményre alapozott talajvédelmi hatósági engedély birtokában juttatható ki mezőgazdasági területre, melyben az is meghatározásra kerül, hogy a területre milyen mennyiségű hígtrágya helyezhető el. A különböző típusú hígtrágyák nemcsak tápanyag összetételben, hanem EDC tartalomban is különböznek egymástól. A természetes hormon kiválasztódás és a hormonhatású készítmények felhasználása tekintetében fontos az állatállomány ivararányát és korcsoportját figyelembe venni. A jövőre nézve fontos, hogy toxikológiai vizsgálatokat végezzünk, és nagyobb hangsúlyt fektessünk a mezőgazdasági melléktermékek által kijuttatott hormonhatású anyagok mennyiségére és lehetséges hatásaira.

Establishment and Application Demonstration of Standards for Agricultural Biogas Slurry Returning to Field in Citrus Orchard

In this paper, we take citrus orchard as target, evaluate the safety of agricultural biogas slurry by comparing the properties of unfermented manure and biogas slurry from 27 farms in Chongqing. The results indicate that the amount of harmful heavy metal element in biogas slurry completely meets the requirements in China agricultural standards “Biogas Fertilizer” (NY/T 2596) and “Organic Fertilizer” (NY 525), indicating the biogas slurry is safe to use as fertilizer. These results provide data support in formulating a stricter standard about the limitations of harmful heavy metal containment ratio in biogas slurry. Biogas slurry can replace chemical fertilizer partly, and can be popularized as a good new type of liquid fertilizer. A certain amount of biogas slurry irrigation can basically meet the supply of nitrogen and phosphorus nutrition, and zero use of chemical fertilizer (nitrogen and phosphorus) come true. However, the content of biogas slurry varies greatly, the measurement of fertilizer efficiency is complex, and it cannot meet the balanced supply of all mineral nutrients, which will lead to the imbalance of nutrient abundance and deficiency. The nutritional diagnosis should be used to monitor the nutritional level of trees, guide the control of abundance and deficiency, enhance the efficiency of citrus orchards to absorb the effective elements of biogas slurry, and improve the yield and quality of citrus. Through monitoring the runoff quality of the orchard returned with biogas slurry, it is found that the runoff quality of the orchard is inferior V. Total phosphorus and granular phosphorus are the main contaminating sources of the outflow runoff in orchard. This indicates that the problems of nitrogen and phosphorus pollution need to be prevented and controlled in the process of returning the biogas slurry to the orchard. It is necessary to establish the landscape system of fruit grass in the orchard and the interception system of flood interception ditches, sediment pockets and buffer ponds in order to sand, retention and reduction of particulate phosphorus. Based on this, a bunch of agricultural biogas slurry returning technology model suitable for modern ecological citrus orchard planting was summarized. The technical standards for biogas slurry harmlessly returning to citrus orchard and technical specification for formula fertilization of citrus nutrition diagnosis, were formed. It has been applied on a large scale in Chongqing three gorges reservoir area and national modern eco-agricultural demonstration base, and has achieved remarkable socio-economic and ecological environmental benefits. The results of this study provide data and technical support for the formulation of two new national standards of "Agricultural Biogas Slurry" and "Technical Specification for Harmless Treatment of Agricultural Biogas Slurry".

N2O and CO2 emissions, nitrogen use efficiency under biogas slurry irrigation: A field study of two consecutive wheat-maize rotation cycles in the North China Plain

Reuse of biogas slurry (BGS) could reduce fertilizer application rate because this material is an alternative source of nutrients and irrigation that could replace some of applied fertilizer. However, the environmental impacts of BGS irrigation, such as greenhouse gas emissions (GHG) are poorly understood. We investigated the global warming potential (GWP) and greenhouse gas intensity (GHGI) of BGS irrigation by quantifying the nitrous oxide (N2O) and carbon dioxide (CO2) emissions under different BGS irrigation rates in a two-year wheat-maize rotation field in the North China Plain. We found BGS irrigation did not change the patterns and fluxes of CO2 and N2O emission during the entire wheat-maize cropping cycle. In addition, there were no significant difference between BGS treatments (BSL, BSM, and BSH) and conventional fertilizer treatment (CF) in GWP. Further, no significant difference occurred in GHGI between BSM (33% BGS and 67% groundwater were mixed and irrigated during the wintering period and joining stage of wheat and after maize sowing, 315 kg·N·hm−1), BSH (50% BGS and 50% groundwater were mixed and irrigated during the wintering period and joining stage of wheat and after maize sowing, 477 kg·N·hm−1) and CF (conventional NPK fertilizer, 420 kg·N·ha−1), despite a higher value BSL (33% BGS and 67% groundwater were mixed and irrigated during the wintering period of wheat and after maize sowing, 210 kg·N·hm−1).The BSL and BSM treatments significantly increased the nitrogen use efficiency (NUE) compared to the CF treatment (11.3% for BSL and 15.3% for BSM). Despite the lower NUE in the BSH treatment relative to CF, it was not statistically significant. Therefore, BGS reuse can increase NUE and does not cause environmental impacts. According to the results of GHGI and NUE, it can be concluded that BSM should be recommended as an improved recycling management practice for the wheat-maize rotation systems.

Nitrogen leaching losses following biogas slurry irrigation to purple soil of the Three Gorges Reservoir Area

Ammonium (NH4+) in biogas slurries is readily nitrified into very mobile soil nitrate (NO3-) to promote nitrogen (N) leaching concerning which a few studies, however, have been reported. These slurries are regularly applied through irrigation to purple soil in the Three Gorges Reservoir Area, and therefore we explored the consequent N leaching there with a plot experiment. Biogas slurry irrigation was carried out with nitrogen application rates of 0, 48, 144, 240, 336, and 480kgN/ha. As a result, the last two rates have triggered N leaching being detrimental to groundwater safety. In addition, N leaching was negatively correlated with soil microbial biomass, diversity, and respiration, indicating a potential technique to prevent it with soil heterotrophs activated by increased ratios of carbon to nitrogen (C/N) in biogas slurries.

Diversity of the Microbial Community in Rice Paddy Soil with Biogas Slurry Irrigation Analyzed by Illumina Sequencing Technology

In order to explore the variation in soil microbial community diversity in paddy fields with different irrigation periods, we collected in situ rice field soils during different biogas irrigation periods and analyzed the microbial community structures of these soils by high-throughput sequencing. The results showed that as the biogas irrigation period increased, the soil pH decreased gradually, while organic matter, nitrate nitrogen, phosphate, and other nutrients were accumulated. Years of continued biogas irrigation was not conducive to improving rice yields. The results showed that as the biogas irrigation period increased, the richness in microbial species in paddy soils decreased gradually, and the diversity in the microbial communities was also reduced. Proteobacteria accounts for the largest proportion in rice paddy soil with biogas slurry irrigation. With the increase of biogas irrigation years, the proportion of β-Proteobacteria, Bacteroidia, Bacteroidales, Burkholderiales, Bacteroides, and Thiobacillus increased, while the proportion of Gemmatimonadetes and α-Proteobacteria decreased gradually. Dissolved organic carbon (F=2.67, P=0.09) had the greatest effect on microbial community structures in the studied paddy soils.

Soil nitrogen leaching decreases as biogas slurry DOC/N ratio increases

Previous work has measured high rates of nitrogen (N) leaching during biogas slurry irrigation. Here we tested whether increasing the ratio of dissolved organic carbon (DOC) to N in biogas slurry would decrease N leaching by applying biogas slurries with DOC/N ratios of 0.9, 2.3, 7.3, 12.3 and 17.3 to soil columns in the laboratory. Increasing the DOC/N ratio to at least 7.3 reduced N leaching by approximately 91%, likely because denitrification and nitrate (NO3−) consumption were increased in the DOC/N 7.3 treatment and ammonium immobilization increased (and NO3− production decreased) in the DOC/N 12.3 and 17.3 treatments. Additionally, all the detected soil nitrifiers—uncultured Nitrosomonadaceae, Nitrospira, Nitrosospira and Nitrosomonas—were promoted in the DOC/N 0.9–7.3 treatments and inhibited in the DOC/N 12.3 and 17.3 treatments. According to the results of weighted gene co-expression network analysis (WGCNA), it is likely that the soil nitrification was promoted by Acidobacteriaceae (Subgroup_1_uncultured), Rhizomicrobium, Massilia, uncultured Nitrosomonadaceae and Nitrospira but inhibited by Trichococcus.

Effects of Biogas Slurry Irrigation on Growth, Photosynthesis, and Nutrient Status of Perilla frutescens Seedlings

Using biological decomposition of plants in an agroecology system is a good method to reduce biogas slurry pollutions. The effects of biogas slurry irrigation on the growth, photosynthesis, and nutrient status of Perilla frutescens seedlings were investigated. The results indicated that biogas slurry irrigation caused a marked increase in plant height, root length, biomass of shoot and root, photosynthetic pigment content, net photosynthetic rate, transpiration rate, stomatal conductance, intercellular carbon dioxide (CO2) concentration, and water-use efficiency. Biogas slurry irrigation changed the concentration of nutrient elements of various organs.

Study of a Slurry Irrigation System by Methane Fermentation Digestion for Wet Rice Cultivation

We investigated difference in effects between periodic and one-time application of digested slurry (PDS and 1DS, respectively) to wet rice fields by a slurry irrigation system using controlled pot cultivation and actual wet rice field tests. Fertilizer application rates were 120 kgN/ha for PDS and 220 kgN/ha for 1DS. Both experiments gave similar results for growth duration and nitrogen (N) use efficiency. During the tillering stage, plants after PDS had lower stem number and SPAD values (chlorophyll content of leaves) than plants after 1DS, but the values increased during the panicle initial stage and were higher than 1DS during the ripening stage. PDS exhibited significantly higher levels of N uptake, agronomic efficiency, and fertilizer N recovery efficiency than 1DS.

Study of a Slurry Irrigation System by Methane Fermentation Digestion for Wet Rice Cultivation

Study of a Slurry Irrigation System by Methane Fermentation Digestion for Wet Rice Cultivation