Query: manure denitrification soil

title: Fungi dominate denitrification when Chinese milk vetch green manure is used in paddy soil
abstract: Fungi play an important role in soil nitrous oxide (N2O) emission in many agricultural soil systems. However, the effect of fungi on N2O emission in Chinese milk vetch (CMV) containing soils has not been examined sufficiently. This study investigated the contribution of bacteria and fungi to soil N2O emission in CMV amended soils. We compared soils from an experimental field in the Fujian Academy of Agricultural Sciences that had been treated with 30 000 kg of CMV per 667 m2 per year with one that was not treated with CMV. We incubated soil using cycloheximide and streptomycin to differentiate fungal and bacterial N2O emissions, respectively. Quantitative PCR (qPCR) was performed to investigate bacterial and fungal abundances in the two agricultural soil ecosystems. The contribution of fungi to soil N2O emission in CMV amended soils was greater than that in non CMV amended paddy soils, with fungi accounting for more than 56% of the emissions in CMV amended soils. Quantitative PCR showed that the ratio of the internal transcribed spacer to 16S rDNA was significantly higher in CMV amended soils than in non CMV amended paddy soils. Furthermore, soil properties, such as pH (P<0.05) and NH4+ concentration (P<0.05) significantly and negatively affected N2O emission by fungi in soil, whereas the total organic carbon (P<0.05) and NO3 concentration (P<0.05) showed significant positive effects. Fungi may be important contributors to N2O production in CMV amended soils, which may create challenges for mitigating N2O production.

title: Quantifying soil N2O emissions from soil and anaerobically digested swine manure, nitrification and denitrification using 15N isotope labeling method
abstract: Increasing use of anaerobically digested swine manure in the farmland makes it necessary to understand its impact on N 2 O emissions, regarding the source of N 2 O and the corresponding mechanism of action. We used a 15 N labeled sulfate modifying the soil in order to identify the sources of N 2 O and the pathways of nitrification and denitrification. Three soil moisture contents (50% WHC, 75% WHC, and 100% WHC) along with three levels of anaerobically digested swine manure (0 g*kg 1 10 g*kg 1 and 25 g*kg 1 were tested using randomized block design. Although the combined effect of contents of anaerobically digested swine manure and the soil moisture contents added to the system stimulated the utilization of soil N and promoted denitrification, the process of nitrification dominated. In anaerobically digested swine manure treated soils, the rate of contribution of anaerobically digested swine manure to N 2 O accounted for 68.6 99.8% In the 25 g*kg 1 treatment, the maximum of N 2 O produced by denitrification and nitrification were 14.1% and 93.1%

title: Differences in labile soil organic matter explain potential denitrification and denitrifying communities in a long term fertilization experiment
abstract: Content and quality of organic matter (OM) may strongly affect the denitrification potential of soils. In particular, the impact of soil OM fractions of differing bioavailability (soluble, particulate, and mineral associated OM) on denitrification remains unresolved. We determined the potential N2O and N2 as well as CO2 production for samples of a Haplic Chernozem from six treatment plots (control, mineral N and NP, farmyard manure FYM, and FYM mineral N or NP) of the Static Fertilization Experiment Bad Lauchstadt (Germany) as related to OM properties and denitrifier gene abundances. Soil OM was analyzed for bulk chemical composition (13C CPMAS NMR spectroscopy) as well as water extractable, particulate, and mineral associated fractions. Soils receiving FYM had more total OM and larger portions of labile fractions such as particulate and water extractable OM. Incubations were run under anoxic conditions without nitrate limitation for seven days at 25 degC in the dark to determine the denitrification potential (N2O and N2) using the acetylene inhibition technique. Abundances of nirS, nirK, and nosZ (I II) genes were analyzed before and after incubation. The denitrification potential, defined as the combined amount of N released as N2O N2 over the experimental period, was larger for plots receiving FYM (25.9 27.2 mg N kg 1) than pure mineral fertilization (17.1 19.2 mg N kg 1) or no fertilization (12.6 mg N kg 1) The CO2 and N2O production were well related and up to three fold larger for FYM receiving soils than under pure mineral fertilization. The N2 production differed significantly only between all manured and non manured soils. Nitrogenous gas emissions related most closely to water extractable organic carbon (WEOC) which again related well to free particulate OM. The larger contribution of N2 production in soils without FYM application, and thus, with less readily decomposable OM, coincided with decreasing abundances of nirS genes (NO2 reductase) and increasing abundances of genes indicating complete denitrifying organisms (nosZ I) during anoxic conditions. Limited OM sources, thus, favored a microbial community more efficient in resource use. This study suggests that WEOC, representing readily bioavailable OM, is a straightforward indicator of the denitrification potential of soils.

title: Microbial functional attributes, rather than taxonomic attributes, drive top soil respiration, nitrification and denitrification processes.
abstract: We lack empirical evidence for the relative importance of microbial functional attributes vs taxonomic attributes in regulating specified soil processes related to carbon (C) and nitrogen (N) cycling, which has hindered our ability to predict the responses of ecosystem multifunctionality to environmental changes. Here, we collected soil samples from a long term experimental field with eight inorganic and organic fertilization treatments and evaluated the linkage between microbial functional attributes (abundance of functional genes) taxonomic attributes (microbial taxonomic composition) and soil processes including soil respiration, denitrification and nitrification. Long term fertilization had no significant effect on the bacterial or fungal alpha diversity. The treatments of chicken manure and sewage sludge addition significantly altered the rates of soil respiration, denitrification and nitrification, which were significantly correlated with the abundances of relevant functional genes. Random forest model indicated that the abundance of functional genes was the main diver for the rate of soil processes. The predominant effect of microbial functional attributes in driving soil processes was maintained when simultaneously accounting for multiple abiotic (total C, total N and soil pH) and biotic drivers (bacterial and fungal community structure) indicating that microbial functional attributes were the predominant driver predicting the rate of soil respiration, denitrification and nitrification. Our results suggested the importance of developing a functional gene centric framework to incorporate microbial communities into biogeochemical models, which may provide new insights into the biodiversity functions relationship and have implications for future management of the consequences of biodiversity loss for ecosystem multifunctionality.

title: Soil anammox and denitrification processes connected with N cycling genes co supporting or contrasting under different water conditions.
abstract: The anaerobic ammonium oxidizing bacteria (anammox) are the hidden culprit behind the excessive nitrogen loss under a favorable environment, since their detection and abundance get disturbed by several unknown factors. This study intends to find the gap between actual anammox working capacity under different water conditions and fertilizers in the laboratory. The 15N isotopic tracer technique was used to measure anammox and denitrification rate, and anammox community structure was analyzed through high throughput sequencing with cytochrome cd 1 nitrite reductase functional gene (an_nirS gene, initially found in Candidatus Scalindua) The experiment consisted of four treatments, i.e. (I) CK_ Control, (II) UR_Urea, (III) PM_Pig Manure, and (IV) SRF_ Slow release fertilizer, under two water conditions, i.e. (a) Continuous flooding_ CF, (b) Alternate wetting and drying_ AWD. Results showed that anammox under CF decreased over time by 40.24% and denitrification increased up to 39.25% However, anammox activity under AWD increased up to 10.62% with the availability of NO2 and surprisingly accompanied by the reduction in denitrification loss 31.97% being the most critical factor. We found that soil nifH and AOB genes were strongly favorable for anammox activity, while we observed the presence of anammox and AOB genes co existing at the same time in paddy soil. The high throughput sequencing with an_nirS functional gene showed a much higher diversity of anammox genera ever reported, mostly uncultured and unidentified. We concluded that water management is more prominent than fertilizer for anammox, and the most critical factor is the duration of AWD cycle, because of short term air supply could boost anammox activity and gene abundance, and could reduce denitrifier activity as well as nirK gene abundance.

title: Effect of rice straw and swine manure biochar on N2O emission from paddy soil
abstract: We analyzed the effects of rice straw biochar (RSBC) and swine manure biochar (SMBC) on N2O emission from paddy soil. The biochars were added to soil at the rates of 1% and 5% (w/w) and N2O emission, soil properties and soil enzyme activities were determined at the elongation, heading and maturation stages of rice growth. The N2O flux started within 2 h of adding the biochar, and decreased significantly thereafter during the three growth stages. The cumulative N2O emission was suppressed by 45.14 73.96% following biochar application, and 5% SMBC resulted in the lowest cumulative emission. In addition, biochar application significantly increased soil pH, soil organic carbon (SOC) NO3 levels and urease activity, and decreased soil NH4+ and nitrate reductase activity. Regression analysis indicated that cumulative N2O emission was correlated positively to NH4+ and negatively to soil pH, SOC and NO3 SEM further revealed that biochar application weakened the denitrification process, and the NH4+ level had the most significant impact on N2O emission. Taken together, RSBC and SMBC regulated the nitrogen cycle in paddy soil and mitigated N2O emission by increasing soil pH, decreasing nitrate reductase activity and NH4+ content.

title: Differential response of denitrifying community to the application of green manure and reduced chemical fertilizer in a paddy soil
abstract: Denitrification could lead to N loss from agricultural soil resulting in a low rate of N availability by crops. We investigated the response of nirK and nirS denitrifiers in a paddy soil to the incorporation of green manure and reduced chemical fertilizer. Soil samples were collected from plots of a short term fertilization experiment initiated in 2009. The treatments were no chemical fertilizer, no Chinese milk vetch (Astragalus sinicus L. CK) chemical fertilizer (NPK) Chinese milk vetch (MV) plus 80% chemical fertilizer (MF80) MV plus 60% chemical fertilizer (MF60) and MV plus 40% chemical fertilizer (MF40) Abundance and community composition of nirK and nirS denitrifiers were analyzed using quantitative PCR and Miseq sequencing. Reduced chemical fertilizer did not reduce content of total N and available N in soils amended with green manure. Abundances of nirK and nirS genes in different treatments were 1.04 x108 to 4.89x108 and 1.22 x107 to 7.04 x107 copies g 1 soil, respectively, which were significantly higher in NPK treatment than those in soils with green manure. NirK abundance was positively correlated with the potential denitrifying activity (PDA) (r2 0.827, p 0.01) Green manure combination with reduced chemical fertilizer significantly changed the community structure of nirK denitrifiers but not nirS denitrifiers relative to soils amended with chemical fertilizer and unfertilized soil. Shifts of community structure of nirK denitrifiers were closely associated with soil organic matter (r2 0.623, p 0.003) available N (r2 0.507, p 0.01) pH (r2 0.661, p 0.006) and PDA (r2 0.633, p 0.005) In conclusion, nirK type denitrifying community was more sensitive to the incorporation of green manure and reduced chemical fertilizer and they played a more important role in the denitrification process in this study.

title: [Characteristics of soil nitrogen cycle and mechanisms underlying the increase in rice yield with partial substitution of mineral fertilizers with organic manure in a paddy ecosystem: A review]
abstract: Partial substitution of mineral fertilizers with organic manure is a key strategy for stable and increase crop yield accompanying with zero growth of mineral fertilizers. Based on recent stu dies, we reviewed the effects of partial substitution of mineral fertilizers with organic manure on rice yield, nitrogen utilization efficiency, soil nitrogen fractions, and microbial nitrogen fixation, ammonification, nitrification, and denitrification in rice paddy ecosystems. We further compared the cha racteristics of soil nitrogen cycle of mineral fertilizers alone and partial substitution of mineral fertili zers with organic manure. The partial substitution altered key processes of nitrogen cycling, including enhancement of ammonification, mediation of nitrification and denitrification, reduction of ammonia volatilization and nitrogen loss, improved the status of nitrogen supplements (enriching the supplement of low molecular weight organic nitrogen, adjusting the distribution of inorganic nitrogen components, increasing the amount of microbial biomass nitrogen, and decreasing the loss of total nitrogen) improved soil nitrogen supply (increasing supply of small molecule organic nitrogen, coordinating inorganic nitrogen components and proportions, and increasing soil microbial biomass nitrogen and total nitrogen fixation) which promoted nitrogen uptake and regulated nitrogen allocation in rice plant to realize stability and enhancement of rice yield.

title: Effects of long term pig manure application on antibiotics, abundance of antibiotic resistance genes (ARGs) anammox and denitrification rates in paddy soils.
abstract: Previous studies of long term manure applications in paddy soil mostly focused on the effects on denitrification, occurrence of antibiotics and antibiotic resistance genes (ARGs) without considering the effects on anaerobic ammonium oxidation (anammox) Here, we investigated the potential rates of anammox and denitrification, occurrence of antibiotics and AGRs in response to three fertilization regimes (C, no fertilizer; N, mineral fertilizer; and NM, N plus pig manure) in six long term paddy experiment sites across China. The potential rates of anammox (0.11 3.64 nmol N g 1 h 1) and denitrification (1.5 29.05 nmol N g 1 h 1) were correlated with the abundance of anammox genes (hzsB) and denitrification functional genes (narG, nirK, nirS and nosZ) respectively. The anammox and denitrification rates were affected by soil organic carbon (SOC) and significantly (p 0.05) increased in NM treatments relative to those in N treatments. Although pig manure application increased antibiotic concentrations and abundance of ARGs compared with N treatments, the increased antibiotics did not directly affect the anammox and denitrification rates. Our results suggested that long term pig manure application significantly increased antibiotic concentrations, abundance of ARGs, and rates of anammox and denitrification, and that the effects of pig manure derived antibiotics on anammox and denitrification were marginal. This is the first report that investigates the effects of long term pig manure application on anammox in paddy soils. More attention should be paid to the potential ecological risk of increased ARGs caused by pig manure application in paddy soils.

title: Mechanisms of mitigating nitrous oxide emissions from vegetable soil varied with manure, biochar and nitrification inhibitors
abstract: A clear understanding of the effects of manure, biochar and nitrification inhibitors (NI, nitrapyrin SNI and Sorghum bicolor L. BNI) amendment on nitrous oxide (N2O) production pathways and consumption remains elusive under field conditions. A field experiment using an isotopocule mapping approach (d15NSPN2O and d18ON2O/H2O map) in conjunction with molecular techniques were conducted to understand the mechanisms of these options for N2O mitigation in a Tung choy (Ipomoea aquatic Forssk. vegetable soil. The manure substitution and biochar not only decreased nitrification/fungal denitrification and bacterial denitrification/nitrifier denitrification derived N2O emission, but also stimulated N2O reduction to N2 during the denitrification process as evidenced from the decrease of ammonia oxidizing bacteria (AOB) amoA and the increase of nirS, nosZI, nosZII and fungal nirK transcripts. Biochar had a greater potential to enhance this reduction with decrease of ammonia oxidizing archaea (AOA) amoA transcripts. NIs mitigated the N2O derived from nitrification and/or bacterial denitrification/nitrifier denitrification demonstrated from the simultaneous decrease of soil NO2 and NO3 and increase of soil NH4+ intensity together with the lower AOB amoA transcripts in NIs than in the urea. These results helped explain the observed differences in N2O emissions among these mitigation options, and laid the foundation for a better understanding of N2O production and reduction under field conditions.