Nitrogen Conservation Research Articles

Addition of oyster shell to enhance organic matter degradation and nitrogen conservation during anaerobic digestate composting.

Anaerobic digested residue (DR) is the main by-product from biogas plants, and it is predominantly used as organic fertilizer after composting. To resolve the problems of long duration and nitrogen loss in conventional composting, bulking agents are always added during the composting process. In this study, oyster shell (OS) was used as a bulking agent for DR composting. Four treatments were conducted by mixing DR and OS at different concentrations (0%, 10%, 20% and 30%, based on wet weight) and then composting the mixtures for 40 days. The results showed that the organic matter (OM) degradation efficiency was enhanced by 5.62%, 12.15% and 16.98% with increasing amounts of OS addition. The increased content of microbial biomass carbon in the compost indicated a suitable living environment for aerobic microbes with added OS, which could explain the increased OM degradation efficiency. Compared with the control, the NH3 emissions in the treatments with 10%, 20% and 30% OS were decreased by 13.81%, 33.33% and 53.76%, respectively. The increase in total nitrogen content in the compost is probably due to the absorption of NH3 by OS. Results indicated that OS is a suitable bulking agent for DR composting and that the addition of 20-30% OS can significantly enhance composting performance.

P0915PROTEIN ENERGY WASTING IS ASSOCIATED WITH A DECLINE IN MUSCLE PROTEIN SYNTHESIS IN CKD PATIENTS

Abstract Background and Aims Skeletal muscle is a highly adaptive tissue, however even small imbalances between protein synthesis and degradation can lead to substantial protein loss. Althought proteolysis plays a major role in the development of cachexia in CKD (chronic kidney disease), the responses of muscle protein metabolism to malnutrition had not been completely elucidated. We evaluated retrospectively the results of kinetic studies of protein turnover estimated by the forearm perfusion method associated with H2phenylalanine kinetic, obtained in CKD patients and controls in the last 25 years. Method We analyzed 59 forearm H2phenylalanine kinetic studies obtained in 14 controls (C) (M 11, F 3) and 45 patients with CKD, of whom 15 (M 10, F 5) were on conservative treatment (CKD stage IV-V), 16 (M 14, F 2) under maintenance hemodialysis (HD), 14 (M 12, F 2) in peritoneal dialysis (DP); all subjects were on non-restricted protein/calorie (0.8-1.1 g/kg and 28-32 kcal/kg, respectively) diets. Ten (M 9, F 1) HD patients had Protein Energy Wasting. Acidosis was corrected in all patients (HCO3 24.2±1.9 mmol/L) and studies were performed in the post-absorptive overnight fasted state at rest. Results Overall, Muscle protein synthesis and degradation were similar (p=NS) in patients and controls. Protein net balance was reduced in patients with PD and those with CKD Stage IV-V (p <0.003 - p <0.014) indicating a reduced catabolic state and nitrogen conservation. However PEW HD patients showed reduced rates of protein synthesis and degradation (p <0.048 and p <0.04 respectively). In addition the efficiency of muscle protein turnover, a parameter expressing muscle's ability to reuse amino acids derived from degradation into protein synthesis, was significantly reduced in HD PEW patients vs. controls (55.5 vs. 61.2 %, p <0.018, respectively) and vs. not malnourished patients in conservative treatment (70.1 % p <0.0025) or in PD (74.6 % p <0.005). Conclusion In CKD patients, in absence of acidosis, muscle is able to increase the efficiency of protein metabolism for the maintenance of nitrogen balance. However, in PEW patients, combined alterations of protein synthesis and degradation proceed together to a reduced efficiency of amino acids recycled into protein synthesis and contribute to maintaining wasting. These data also suggest that calorie/protein requirements of CKD patients with PEW may be higher than currently theorized.

Effects of Biochar to Excessive Compost-Fertilized Soils on the Nutrient Status

Positive effects of a biochar–compost mix on soil nutrient status in infertile soil have been reported, but the potential effect of biochar amendments in excessive compost-fertilized soils has not been extensively studied. Excessive application of compost can result in the accumulation of nutrients and heavy metals (Cu and Zn). Thus, the objective of this study is to investigate the effect of biochar–excessive compost co-application on soil nutrient status. We hypothesized that biochar co-application could have positive effects on the absorption of excessive nutrients of Cu and Zn. A 371-day laboratory incubation study was conducted to evaluate the effects of the lead tree (Leucaena leucocephala (Lam.) de. Wit) biochar produced at 750 °C on the dynamics of the soil nutrients. Three Taiwan rural soils were selected, including slightly acidic Oxisols (SAO), mildly alkaline Inceptisols (MAI), and slightly acid Inceptisols (SAI). The biochar treatments include control (0%) and 0.5%, 1.0%, and 2.0% (w/w). In each treatment, 5% (w/w) poultry-livestock manure compost was added to test excessive application. The results indicated that the biochar treatments had a significant increase effect on soil pH, total carbon (TC), total nitrogen (TN), C:N ratio, and available K concentration. The effect of biochar on electrical conductivity (EC) and available P, Ca, Mg, Fe, Mn, Cu, Pb, and Zn was insignificant. The effect of biochar, with relatively low application rates (<2% by wt), low surface area, and less surface function group, was eliminated by excessive compost (5% by wt). In addition to carbon sequestration and nitrogen conservation, biochar addition has no effect on the absorption of the excessive nutrients Cu and Zn in three studied soils.

Net Primary Productivity and Budget of Nitrogen and Phosphorus in the Herbaceous Layer of a Tropical Dry Deciduous Forest in Rajasthan in Northwest India

The net primary productivity and budget of total nitrogen and available phosphorus in the herbaceous layer was studied in a tropical dry deciduous thorn forest in Rajasthan state of north-western India. The average net primary productivity of the herbaceous layer was 242 g m-2yr-1, it was the highest (257 g m-2 yr-1) at the top and the lowest (218 g m-2 yr-1) at the middle of the hill slope. Out of the herbaceous species present in the study site, 29 species contributed more than 1 g m-2 biomass with the highest contribution by Brachiaria ramosa (54%) and Achyranthes aspera (44%). The herbs allocated about 10 and 90% of total biomass to roots and above-ground parts, respectively. The highest content of nitrogen in the soil, biomass, and litter was 181, 3.4, and 1.7 g m-2, respectively, during the rainy season in July. A similar pattern was observed for phosphorus. The annual uptake of nitrogen and phosphorus by vegetation was 3.84 g m-2 and 0.76 g m-2 ; 19 and 16%, respectively, return to the soil through litterfall. Before the litterfall occurred, the nitrogen, a vital element was translocated into below-ground parts. This is a strong strategy for the conservation of nitrogen. Phosphorus, however, did not show such a trend. This interesting observation of the study strongly indicated that a sufficient amount of nutrients are retained in the litter during the dry summer period.

Optimization of biochar additions for enriching nitrogen in active phase low-temperature composting

This paper examines the effectiveness of combining biochar and compost to test if organic fertilizers can be enhanced by the addition of biochar in the active phase of composting high-nitrogen source materials. Therefore, a small-scale experiment was conducted for 40 days to investigate the effects of nitrogen conservation. Four composting piles including a control without biochar were prepared with 18 kg of shredded immature Panicum maximum grass and 2 kg of Gliricidia sepium leaves. Biochar additions were 3%, 6%, and 9% calculated on dry weight basis. There was no significant difference between treatments for temperature (~ 29.5 °C) and pH (~ 9). A novel material balance approach based on total fixed solids provided the means to determine the actual volatile solid contents, i.e., nitrogen levels during the decomposition process. According to this, the actual nitrogen content of 6% biochar mixed pile (16.203 mg/g) was significantly different to the others by having a higher mean value. Similarly, the mean nitrogen loss was lower (− 5.66%) than measured in the other treatments. Nitrogen loss is low in the biochar mixed piles because of nitrogen adsorption compared with 24% loss in control. The kinetic study on nitrogen postulates entrapping ammonia production and increasing enzyme urease activities. First-order rate kinetics could be used to predict the reduction of C/N ratio of 30 to 9 in 65 days. Hence, 6% biochar treatment was discovered to be the optimum to prevent excessive oxidation or volatilization of ammonia during the active phase low-temperature composting and fix atmospheric nitrogen.

Mulching techniques: An approach for offsetting soil moisture deficit and enhancing manure mineralization during maize cultivation

Mulching is an effective technique for soil moisture conservation and increasing mineralization. Four mulching practices (i.e. no-mulch, canola residue, transparent and blue plastic) and five nitrogen (N) treatments (i.e. no-N, 100, 70, 50, 0 % from farmyard manure (FYM) with remaining from urea) to supply a total of 250 kg N ha−1 were assessed under field and lab conditions for soil moisture conservation and quantification of soil organic matter (SOM), total nitrogen (TN) and mineral nitrogen (min-N) contents in 2013-14. A total of 40 % added water to the soil was lost in no-mulching compared to 7 % been lost in plastic mulching during first week in open shed. Based on moisture losses, three moisture regimes were developed and used in a 56 days incubation experiment. The 60 % relative water holding capacity (RWHC) corresponding to plastic mulching had lowered SOM (1.0 %), and TN (1.6 %) but increased min-N (5.9%) than 40% RWHC (corresponding to no-mulch). Among the nitrogen treatments, 100% FYM had improved SOM and TN, but mineralization was higher in 50% FYM/urea. In field studies, the canola residue mulching had increased the SOM (8.4%), TN (1.2%), min-N (5.2%) and moisture contents (5.7%) over no-mulching. The 100% FYM had higher SOM (2.25 folds), TN (2.79 folds) and moisture content (11.3%) than control. In conclusion, soil fertility was improved with 100% FYM and mineral N with 50% FYM/urea. Thus, 100% FYM or 50 %FYM + 50 % urea sources to provide 250 kg N ha-1 should be used with plastic mulching in weed infested area or residue mulch in weeds free field conditions for improving mineralization and water conservation.

A Mechanistic Model of Macromolecular Allocation, Elemental Stoichiometry, and Growth Rate in Phytoplankton.

We present a model of the growth rate and elemental stoichiometry of phytoplankton as a function of resource allocation between and within broad macromolecular pools under a variety of resource supply conditions. The model is based on four, empirically-supported, cornerstone assumptions: that there is a saturating relationship between light and photosynthesis, a linear relationship between RNA/protein and growth rate, a linear relationship between biosynthetic proteins and growth rate, and a constant macromolecular composition of the light-harvesting machinery. We combine these assumptions with statements of conservation of carbon, nitrogen, phosphorus, and energy. The model can be solved algebraically for steady state conditions and constrained with data on elemental stoichiometry from published laboratory chemostat studies. It interprets the relationships between macromolecular and elemental stoichiometry and also provides quantitative predictions of the maximum growth rate at given light intensity and nutrient supply rates. The model is compatible with data sets from several laboratory studies characterizing both prokaryotic and eukaryotic phytoplankton from marine and freshwater environments. It is conceptually simple, yet mechanistic and quantitative. Here, the model is constrained only by elemental stoichiometry, but makes predictions about allocation to measurable macromolecular pools, which could be tested in the laboratory.

Nitrogen economy of alpine plants on the north Tibetan Plateau: Nitrogen conservation by resorption rather than open sources through biological symbiotic fixation.

Nitrogen (N) is one of the most important factors limiting plant productivity, and N fixation by legume species is an important source of N input into ecosystems. Meanwhile, N resorption from senescent plant tissues conserves nutrients taken up in the current season, which may alleviate ecosystem N limitation. N fixation was assessed by the 15N dilution technique in four types of alpine grasslands along the precipitation and soil nutrient gradients. The N resorption efficiency (NRE) was also measured in these alpine grasslands. The aboveground biomass in the alpine meadow was 4–6 times higher than in the alpine meadow steppe, alpine steppe, and alpine desert steppe. However, the proportion of legume species to community biomass in the alpine steppe and the alpine desert steppe was significantly higher than the proportion in the alpine meadow. N fixation by the legume plants in the alpine meadow was 0.236 g N/m2, which was significantly higher than N fixation in other alpine grasslands (0.041 to 0.089 g N/m2). The NRE in the alpine meadows was lower than in the other three alpine grasslands. Both the aboveground biomass and N fixation of the legume plants showed decreasing trends with the decline of precipitation and soil N gradients from east to west, while the NRE of alpine plants showed increasing trends along the gradients, which indicates that alpine plants enhance the NRE to adapt to the increasing droughts and nutrient‐poor environments. The opposite trends of N fixation and NRE along the precipitation and soil nutrient gradients indicate that alpine plants adapt to precipitation and soil nutrient limitation by promoting NRE (conservative nutrient use by alpine plants) rather than biological N fixation (open sources by legume plants) on the north Tibetan Plateau.

Comprehensive Biogeochemical Analysis of Nitrogen Transformation Parameters

The potential for nitrogen attenuation in anoxic groundwater by examining the concentration and distribution patterns of electron acceptors, electron donors and microbiological parameters was assessed. Research was carried out for 25 monitoring bores in two anoxic alluvial aquifers Kovin-Dubovac and Knicanin-Centa during the four years monitoring period (2010–2013). Nitrate and nitrite concentrations were mostly undetectable while ammonium, ferrous and total organic carbon concentrations were increased with sporadic sulfide appearance. Piper diagrams qualified these groundwaters as predominantly Ca2+(Mg2+)–$${\text{HCO}}_{3}^{ - }$$ type. By Alekin classification waters belong to $${\text{C}}_{{\text{I}}}^{{{\text{Ca}}}}$$ type. The multiple electron donors (organic carbon, iron minerals and sulfide) and spatial and temporal variability of alternative electron acceptors proved to be determining factors of dominant nitrogen reduction path way. Concentrations trends of chemical and microbiological parameters revealed the conditions suitable for nitrogen conservation and they are presented via developed maps and BART test results. Statistical analysis was evaluated by Principal Component Analysis and Cluster Dendograms.

Improved nitrogen conservation capacity during composting of dairy manure amended with oil shale semi-coke as the porous bulking agent

Oil shale semi-coke is the solid waste produced from the retorting process of oil shale, which may cause pollution to the environment without reasonable disposing. In this study, semi-coke was used as the bulking agent during composting to accelerate biodegradation of the organics as well as decrease the nitrogen loss. Results showed that the addition of semi-coke could accelerate biodegradation of the organics, with a raise in the organic matter loss from 44.99 % to 47.05 % compared with the control. Furthermore, the nitrogen loss significantly decreased from 40.00%–14.70 % in the treatment added with semi-coke due to less emission of NH3 and much more transformation of NH4+-N to NO3−-N by nitrification, which could be explained by the increasing abundance of ammonia-oxidizing bacteria and archaea at the late composting stage and drastic shift of the microbial community like Chloroflexi, Firmicutes and Actinobacteria. After the composting cycle, the maturity of the produced compost was elevated greatly in the treatments amended with semi-coke. The result of PAHs detection suggested that there were low PAHs content in the raw oil shale semi-coke and they could be removed effectively to within the range for land application by composting especially when the surfactant was added.

Addition of zeolite and superphosphate to windrow composting of chicken manure improves fertilizer efficiency and reduces greenhouse gas emission

This study investigated the impact of adding zeolite (F), superphosphate (G), and ferrous sulfate (L) in various combinations on reducing greenhouse gas (GHG) emission and improving nitrogen conservation during factory-scale chicken manure composting, aimed to identify the combination that optimizes the performance of the process. Chicken manure was mixed with F, G, FL, or FGL and subjected to windrow composting for 46 days. Results showed that global warming potential (GWP) was reduced by 21.9% (F), 22.8% (FL), 36.1% (G), and 39.3% (FGL). Further, the nitrogen content in the final composting product increased by 27.25%, 9.45%, and 21.86% in G, FL, and FGL amendments, respectively. The fertilizer efficiency of the compost product was assessed by measuring the biomass of plants grown in it, and it was consistent with the nitrogen content. N2O emission was negligible during composting, and 98% of the released GHGs comprised CO2 and CH4. Reduction in GHG emission was mainly achieved by reducing CH4 emission. The addition of FL, G, and FGL caused a clear shift in the abundance of dominant methanogens; particularly, the abundance of Methanobrevibacter decreased and that of Methanobacterium and Methanocella increased, which was correlated with CH4 emissions. Meanwhile, the changes in moisture content, NH4+-N content, and pH level also played an important role in the reduction of GHG emission. Based on the effects of nitrogen conservation, fertilizer efficiency improvement, and GHG emission reduction, we conclude that G and FGL are more beneficial than F or FL and suggest these additives for efficient chicken manure composting.

Limited survival strategy in starving subterranean termite colonies

Termites feed on a carbon-rich but nitrogen-poor diet and evolved efficient nitrogen conservation strategies. It was previously suggested that during time of low access to resources (i.e., starvation), subterranean termites (Rhinotermitidae) colonies would adopt an energy conservation strategy by cannibalizing soldiers, a dependent caste. However, such hypothesis was tested with relatively small groups of foragers, which may not have reflected how resources are reallocated in whole colonies when food (carbon) is scarce. The current study subjected 2-year-old colonies (≈ 3000 termites with all castes and instars) to starvation, in order to reexamine if cannibalism is part of an active energy conservation strategy. Within 12 days of starvation, eggs and larvae were all cannibalized, followed by young workers. Soldiers then died marginally faster than old workers. By 22 days, cannibalism was no longer observed, and the king and queen were among the last individuals to die. Termites that engaged in the process of ecdysis with no energetic resources, failed to molt, died in the process, and the subsequent cannibalism was a passive mortality-driven process. Therefore, cannibalism was primarily the result of the inherent termite behavior for recycling nitrogen resources. The hemimetabolous developmental pathway, the difference of timing in the molting cycle of termite instars and the relatively rapid exhaustion of soldiers, indirectly determined the sequence of starvation-induced mortality and subsequent cannibalism. Although termites have evolved efficient nitrogen conservation strategies, they have not evolved an efficient carbon conservation strategy, which is essentially limited to keeping the primary reproductives alive as long as possible.

The Characteristics of Carbon, Nitrogen and Sulfur Transformation During Cattle Manure Composting-Based on Different Aeration Strategies.

This study aimed to investigate the characteristics of gaseous emission (methane—CH4, carbon dioxide—CO2, nitrous oxide—N2O, nitric oxide—NO, hydrogen sulfide—H2S and sulfur dioxide—SO2) and the conservation of carbon (C), nitrogen (N), and sulfur (S) during cattle manure composting under different aeration strategies. Three aeration strategies were set as C60, C100, and I60, representing the different combinations of aeration method (continuous—C or intermittent—I) and aeration rate (60 or 100 L·min−1·m−3). Results showed that C, N, S mass was reduced by 48.8–53.1%, 29.8–35.9% and 19.6–21.9%, respectively, after the composing process. Among the three strategies, the intermittent aeration treatment I60 obtained the highest N2O emissions, resulting in the highest N loss and greenhouse gas (GHG) emissions when the GHG emissions from power consumption were not considered. Within two continuous aeration treatments, lower aeration rates in C60 caused lower CO2, N2O, NO, and SO2 emissions but higher CH4 emissions than those from C100. Meanwhile, C and N losses were also lowest in the C60 treatment. H2S emission was not detected because of the more alkaline pH of the compost material. Thus, C60 can be recommended for cattle manure composting because of its nutrient conservation and mitigation of major gas and GHG emissions.

Evaluation of integrated biochar with bacterial consortium on gaseous emissions mitigation and nutrients sequestration during pig manure composting

This study focused on evaluate the effectiveness of biochar alone compare integrated with bacterial consortium amendment on the gaseous emissions mitigation as well as carbon and nitrogen sequestration during pig manure composting. Six additive treatments were performed based on uniform mixing pig manure with wheat straw [bacterial consortium (T2), 12%wood biochar (T3), 12%wood biochar + bacterial consortium (T4), 12%wheat straw biochar (T5), 12%wheat straw biochar + bacterial consortium (T6), while T1 without any additive]. The results obviously indicated that integrated use of biochar and bacterial consortium could remarkably relieved gaseous emissions, improved carbon and nitrogen conservation as well as accelerated maturity of composting. Notably the optimum combination was existed in T6 owing to lowest nutrient losses (nitrogen and carbon losses were 9.91 g/kg and 189.54 g/kg) and gas emissions (30.16 g/kg) as well as supreme maturity (germination index > 100%); it’s an economic-practical and environmental protection novel disposal approach for solid waste.

Respond of clay amendment in chicken manure composts to understand the antibiotic resistant bacterial diversity and its correlation with physicochemical parameters

Abstract Clay has a positive influence on organic matter degradation and nitrogen conservation during chicken manure composting, but its effects on the diversity of antibiotic-resistant bacterial are unclear. The impact of the clay amendment (0% (T1), 2% (T2), 4% (T3), 6% (T4), 8% (T5) and 10% (T6) on the environmental risk of antibiotic-resistant bacteria abundance during chicken manure composting was investigated. The results showed that 4% clay increased the relative abundances of antibiotic-resistant bacterial, while 8% and 10% clay additions significantly reduced the total relative abundances of antibiotic-resistant bacterial in the compost, where the relative abundances of antibiotic-resistant bacterial was 0.46 log lower than the control. Clay mainly affects the distribution of antibiotic-resistant bacterial by influencing the relative abundances of Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes phylum. The maximum dosage of the clay amendment had a more persistent impact on the antibiotic-resistant bacterial community. However, bacterial abundance could be classified according to the composting time under diverse treatments. In the present study, the abundance of the antibiotic-resistant bacterial has a considerable impact on the alteration of the physicochemical parameters during composting. The correlations between the physicochemical parameters (temperature, carbon/nitrogen ratio, and gaseous emissions) and antibiotic-resistant bacterial were more significant than pH and germination index.

Effect of Different Amendments on Nitrogen Conservation During Simulated Composting

Effect of Different Amendments on Nitrogen Conservation During Simulated Composting

Influence of FeONPs amendment on nitrogen conservation and microbial community succession during composting of agricultural waste: Relative contributions of ammonia-oxidizing bacteria and archaea to nitrogen conservation

Composting amended with iron oxide nanoparticles (FeONPs, α-Fe2O3 and Fe3O4 NPs) were conducted to study the impacts of FeONPs on nitrogen conservation and microbial community. It was found that amendment of FeONPs, especially α-Fe2O3 NPs, reduced total nitrogen (TN) loss, and reserved more NH4+-N and mineral N. Pearson correlation analysis revealed that decrease of ammonia-oxidizing bacteria (AOB) in FeONPs treatments played more important role than ammonia-oxidizing archaea (AOA) in reserving more NH4+-N and mineral N, and reducing TN loss. Bacterial community composition at phylum level did not shift with addition of FeONPs. Firmicutes, Actinobacteria, and Proteobacteria were the three most dominant phyla in all treatments. Overall, this study provides a method to reduce TN loss and improve mineral N reservation during composting, and gives a deep insight into the role of AOB and AOA in nitrogen transformation.

Improvement of cleaner composting production by adding Diatomite: From the nitrogen conservation and greenhouse gas emission

In order to investigate the improvement of Diatomite (DM) on the production of cleaner composting, reflected by emission of NH3 and greenhouse gases (GHGs), three dosages of DM (0%, 5% and 10%) were added into mixture of pig manure and sawdust for 42 days composting. Addition of DM promoted the transformation of organic matter and improved the quality of end product. Meanwhile, it was confirmed by the increase of NO3−-N formation and nitrogen conservation. Besides, adding DM aided on reducing emission of CH4, N2O and NH3 by 18.27%−30.41%, 26.89%−84.16% and 10.41%−23.70%, respectively. Furthermore, the DM had a positive effect on the maturity of compost products, reflecting by GI value and HA/FA. Consequently, through the factor analysis, 10% was suggested to improve the quality of end product and reduce nitrogen loss as well as GHGs emission.

Buffering phosphate mitigates ammonia emission in sewage sludge composting: Enhanced organics removal coupled with microbial ammonium assimilation

Ammonia emission is a challenge for sewage sludge composting, causing odor issues, indirect greenhouse gas emission and nitrogen loss in the mature compost. This study investigated the effectiveness of applying K2HPO4KH2PO4 buffer to mitigate ammonia emission in sewage sludge composting. During the 34-day aerated composting experiment, adding 7.5 mg P·g−1 DM (dry matter) K2HPO4KH2PO4 buffer reduced the ammonia emission and total nitrogen loss by 45.4% and 41.8%, respectively. The enhanced nitrogen conservation by phosphate additive resulted from two complementary mechanisms: (1) phosphate buffering effect and (2) accelerated sludge extracellular polymeric substance (EPS) decomposition, thus improving microbial ammonium assimilation to convert ammonia-N to cell-protein. The extent of nitrogen conservation was found to be positively associated with activities of the key enzymes for microbial ammonium assimilation and relative abundance of the ammonium-assimilating Bacillus. In a summary, K2HPO4KH2PO4 addition was proved as an effective strategy to reduce ammonia emission, promote organics removal and conserve nitrogen nutrients in the final compost product.

Insights into functional microbial succession during nitrogen transformation in an ectopic fermentation system

The ectopic fermentation system (EFS) is an advanced technology for treating farm wastewater, and it reduces ammonia nitrogen emission and nitrogen loss of fermentation products. This study observed the functional bacteria succession related to nitrogen metabolism in EFS by high throughput sequencing, and evaluated their associations with environmental factors. Results revealed that with the changes of temperature, pH, moisture content, and nitrogen content during fermentation, the species richness and diversity of ammonia oxidizing bacteria (AOB) with amoA increased, but those of denitrifying bacteria carrying nirK and nosZ decreased. During the fermentation process, the dominant bacterial populations of AOB and denitrifying bacteria changed significantly, and different bacterial populations showed different positive/negative correlations with the environmental factors. This study revealed the role of functional bacteria in ammonia removal and nitrogen conservation of EFS, and provided a theoretical basis for the improvement of microbial agents and EFS application.