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1.
PurposeNitrification and denitrification in the N cycle are affected by various ammonia oxidizers and denitrifying microbes in intensive vegetable cultivation soils, but our current understanding of the effect these microbes have on N2O emissions is limited. The nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP), acts by slowing nitrification and is used to improve fertilizer use efficiency and reduce N losses from agricultural systems; however, its effects on nitrifier and denitrifier activities in intensive vegetable cultivation soils are unknown. Materials and methodsIn this study, we measured the impacts of DMPP on N2O emissions, ammonia oxidizers, and denitrifying microbes in two intensive vegetable cultivation soils: one that had been cultivated for a short term (1 year) and one that had been cultivated over a longer term (29 years). The quantitative PCR technique was used in this study. Three treatments, including control (no fertilizer), urea alone, and urea with DMPP, were included for each soil. The application rates of urea and DMPP were 1800 kg ha?1 and 0.5% of the urea-N application rate. Results and discussionThe application of N significantly increased N2O emissions in both soils. The abundance of ammonia-oxidizing bacteria (AOB) increased significantly with high rate of N fertilizer application in both soils. Conversely, there was no change in the growth rate of ammonia-oxidizing archaea (AOA) in response to the applied urea despite the presence of larger numbers of AOA in these soils. This suggests AOB may play a greater role than AOA in the nitrification process, and N2O emission in intensive vegetable cultivation soils. The application of DMPP significantly reduced soil NO3?-N content and N2O emission, and delayed ammonia oxidation. It greatly reduced AOB abundance, but not AOA abundance. Moreover, the presence of DMPP was correlated with a significant decrease in the abundance of nitrite reductase (nirS and nirK) genes. ConclusionsLong-term intensive vegetable cultivation with heavy N fertilization altered AOB and nirS abundance. In vegetable cultivation soils with high N levels, DMPP can be effective in mitigating N2O emissions by directly inhibiting both ammonia oxidizing and denitrifying microbes. 相似文献
2.
Purpose Nitrous oxide (N 2O) is a potent greenhouse gas and, in grazed grassland systems where animals graze outdoor pastures, most of the N 2O is emitted from animal urine nitrogen (N) deposited during grazing. Recently, ammonia-oxidizing archaea (AOA) were found
to be present in large numbers in soils as well in the ocean, suggesting a potentially important role for AOA, in addition
to ammonia-oxidizing bacteria (AOB), in the nitrogen cycle. The relationship between N 2O emissions and AOB and AOA populations is unknown. The objective of this study was to determine the quantitative relationship
between N 2O emissions and AOB and AOA populations in nitrogen-rich grassland soils. 相似文献
3.
A field experiment was conducted on Chinese cabbage (Brassica campestris L. ssp. pekinensis (Lour.) Olsson) in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates: zero chemical fertilizer N (CK); urea at rates of 300 kg N ha^-1 (U300) and 600 kg N ha^-1 (U600), both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha^-1 (PCU180) as a basal application. The acetylene inhibition technique was used to measure denitrification (N2 + N2O) from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to (3K total denitrification losses were significantly greater (P ≤ 0.05) in the PCU180, U300, and U600 treatments,while N2O emissions in the U300 and U600 treatments were significantly higher (P ≤ 0.05) than (3K. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment (PCU180) during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant (P ≤0.01) positive correlation occurred between denitrification (r = 0.872) or N2O emission (r = 0.781) flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season. 相似文献
4.
Purpose Boreal peat soils comprise about 3% of the terrestrial environments, and when drained, they become sources of the greenhouse
gas nitrous oxide (N 2O). Ammonia oxidation can result in N 2O emissions, either directly or by fuelling denitrification, but we know little about the ecology of ammonia-oxidizing bacteria
(AOB) and archaea (AOA) in peat soils. Our aim was to determine temporal alterations in abundance and composition of these
communities in a drained and forested peat soil in relation to N 2O emissions and ammonia oxidation activity. 相似文献
5.
Nitrous oxide (N 2O) is a greenhouse gas that contributes to the destruction of stratospheric ozone, and agricultural soil is an important source of N 2O. Aerobic soils are sinks for atmospheric methane (CH 4), a greenhouse gas. Ammonia monooxygenase (AMO) can oxidize CH 4, but CH 4 is mostly oxidized by methane monooxygenase (MMO), and CH 4 oxidation by AMO is generally negligible in the soil. We monitored the N 2O and CH 4 fluxes after urea application in fields containing different soils using an automated sampling system to determine the effects of environmental and microbial factors on the N 2O and CH 4 fluxes. The soil types were Low-humic Andosol (Gleyic Haplic Andosol), yellow soil (Gleyic Haplic Alisol) and gray lowland soil (Entric Fluvisol). Cumulative N 2O emissions from the yellow soil were higher than those from other soil types, although the difference was not significant. The CH 4 uptake level by Andosol was one order of magnitude higher than that by other soils. There were significant relationships between the ammonia oxidation potential, AOB and AOA amoA copy numbers, and the CH 4 uptake. In contrast, the gene copy numbers of methane-oxidizing bacteria (MOB) pmoA were below the detection limit. Our results suggested that the AMOs of AOB and AOA may have more important roles than those previously considered during CH 4 oxidation in agricultural soils treated with N fertilizers. 相似文献
6.
Soil moisture and nitrogen (N) are two important factors influencing N 2O emissions and the growth of microorganisms. Here, we carried out a microcosm experiment to evaluate effects of soil moisture level and N fertilizer type on N 2O emissions and abundances and composition of associated microbial communities in the two typical arable soils. The abundances and community composition of functional microbes involved in nitrification and denitrification were determined via quantitative PCR (qPCR) and terminal restriction length fragment polymorphism (T-RFLP), respectively. Results showed that N 2O production was higher at 90% water-filled pore (WFPS) than at 50% WFPS. The N 2O emissions in the two soils amended with ammonium were higher than those amended with nitrate, especially at relatively high moisture level. In both soils, increased soil moisture stimulated the growth of ammonia-oxidizing bacteria (AOB) and nitrite reducer ( nirK). Ammonium fertilizer treatment increased the population size of AOB and nirK genes in the alluvial soil, while reduced the abundances of ammonia-oxidizing archaea (AOA) and denitrifiers ( nirK and nosZ) in the red soil. Nitrate addition had a negative effect on AOA abundance in the red soil. Total N 2O emissions were positively correlated to AOB abundance, but not to other functional genes in the two soils. Changed soil moisture significantly affected AOA rather than AOB community composition in both soils. The way and extent of N fertilizers impacted on nitrifier and denitrifier community composition varied with N form and soil type. These results indicate that N 2O emissions and the succession of nitrifying and denitrifying communities are selectively affected by soil moisture and N fertilizer form in the two contrasting types of soil. 相似文献
7.
PurposePaddy fields are an important source of nitrous oxide (N2O) emission. The application of biochar or the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) to paddy soils have been proposed as technologies to mitigate N2O emissions, but their mechanisms remain poorly understood. MethodsAn experiment was undertaken to study the combined and individual effects of biochar and DMPP on N2O emission from a paddy field. Changes in soil microbial community composition were investigated. Four fertilized treatments were established as follows: fertilizer only, biochar, DMPP, and biochar combined with DMPP; along with an unfertilized control. ResultsThe application of biochar and/or DMPP decreased N2O emission by 18.9–39.6% compared with fertilizer only. The combination of biochar and DMPP exhibited higher efficiency at suppressing N2O emission than biochar alone but not as effective as DMPP alone. Biochar promoted the growth of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), while DMPP suppressed AOB and increased AOA. Applying biochar with DMPP reduced the impact of DMPP on AOB. The nirS-/nirK- denitrifiers were decreased and nosZ-N2O reducers were increased by DMPP and the combination of DMPP and biochar. The abundance of the nirK gene was increased by biochar at the elongation and heading stages of rice development. Compared with fertilizer only, the application of biochar and/or DMPP promoted the abundance of nosZ genes. ConclusionThese results suggest that applying biochar and/or DMPP to rice paddy fields is a promising strategy to reduce N2O emissions by regulating the dynamics of ammonia oxidizers and N2O reducers. 相似文献
8.
Literature reports on N 2O and NO emissions from organic and mineral agricultural soil amended with N-containing fertilizers have reached contradictory conclusions. To understand the influence of organic manure (OM) and chemical fertilizer application on N 2O and NO emissions, we conducted laboratory incubation experiments on an agricultural sandy loam soil exposed to different long-term fertilization practices. The fertilizer treatments were initiated in 1989 at the Fengqiu State Key Agro-ecological Experimental Station and included a control without fertilizer (CK), OM, mineral NPK fertilizer (NPK), mineral NP fertilizer (NP), and mineral NK fertilizer (NK). The proportion of N emitted as NO and N 2O varied considerably among fertilizer treatments, ranging from 0.83% to 2.50% as NO and from 0.08% to 0.36% as N 2O. Cumulative NO emission was highest in the CK treatment after NH 4 + -N was added at a rate of 200 mg N kg ?1 soil during the 612-h incubation period, whereas the long-term application of fertilizers significantly reduced NO emission by 54–67%. In contrast, the long-term application of NPK fertilizer and OM significantly enhanced N 2O emission by 95.6% and 253%, respectively, compared to CK conditions. The addition of NP fertilizer (no K) significantly reduced N 2O emission by 25.5%, whereas applications of NK fertilizer (no P) had no effect. The difference among the N-fertilized treatments was due probably to discrepancies in the N 2O production potential of the dominant ammonia-oxidizing bacteria (AOB) species rather than AOB abundance. The ratio of NO/N 2O was approximately 24 in the CK treatment, significantly higher than those in the N-fertilized treatments (3–11), and it decreased with increasing N 2O production potential in N-fertilized treatments. Our data suggests that the shift in the dominant AOB species might produce reciprocal change in cumulative NO and N 2O emissions. 相似文献
9.
Increasing lines of evidence have suggested the functional importance of ammonia-oxidizing archaea (AOA) rather than bacteria (AOB) for nitrification in upland soils with low pH. However, it remains unclear whether niche specialization of AOA and AOB occurs in rice paddy wetlands constrained by oxygen availability. Using DNA-based stable isotope probing, we conclude that AOA dominated nitrification activity in acidic paddy soils (pH 5.6) while AOB dominated in alkaline soils (pH 8.2). Nitrification activity was stimulated by urea fertilization and accompanied by a significant increase of AOA in acid soils and AOB in alkaline soils. DNA-based stable isotope probing indicated significant assimilation of 13CO 2 for AOA only in acidic paddy soil, while AOB was the solely responsible for ammonia oxidation in the alkaline paddy soil. Phylogenetic analysis further indicated that AOA members within the soil group 1.1b lineage dominated nitrification in acid soils. Ammonia oxidation in the alkaline soil was catalyzed by Nitrosospira cluster 3-like AOB, suggesting that the physiological diversity of AOA is more complicated than previously thought, and soil pH plays important roles in shaping the community structures of ammonia oxidizers in paddy field. 相似文献
10.
Nitrous oxide (N 2O) is a potent greenhouse gas, which is mainly produced from agricultural soils. Ammonia oxidation is the rate‐determining step in N 2O production, and the process is carried out by ammonia oxidizers, bacteria and archaea. Soil aggregate size has been shown to alter soil properties, which affect N 2O emissions and bacterial communities. However, the effect of aggregate size on temporal and total N 2O emissions and ammonia‐oxidizing bacteria (AOB) and archaea (AOA) is not fully understood. This incubation study investigated the effect of three different soil aggregate sizes on N 2O emissions and ammonia oxidizer abundance under high urine‐N concentrations and the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), at reducing N 2O emissions in different aggregate soils. It was found that temporal patterns of N 2O emissions were affected by aggregate size with higher peak emissions in the large and medium aggregates. However, the total emissions were the same due to a ‘switch’ in emissions at day 66, after which smaller aggregates produced higher N 2O emissions. It is suggested that the switch was caused by an increase in aggregate disruption in the small aggregates, following the urine application, due to their higher surface area to volume ratio. AOB and AOA abundances were not significantly affected by aggregate size. DCD was effective in reducing N 2O emissions in all aggregate sizes by an average of 79%. These results suggest that similar ammonia oxidizer abundance is found in soils of different aggregate sizes, and the efficacy of DCD in reducing N 2O emissions was not affected by aggregate size of the soil. 相似文献
11.
Abstract Field experiments were designed to quantify N 2O emissions from corn fields after the application of different types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and given either urea (200 kg ha ?1), urea (170 kg ha ?1) + dicyandiamide ([DCD] 20 kg ha ?1) or controlled-release fertilizer LP-30 (214 kg ha ?1) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatment was equivalent to 90 kg N ha ?1. Plots without chemical N fertilizer were also prepared as a control. The field was designed to have three replicates for each treatment with a randomized block design. Nitrous oxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA). Total N 2O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions from the urea + DCD plots did not differ from those from the control plots. The N 2O emission from the urea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizer type had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigation option among the tested fertilizer applications for N 2O emission from corn fields in Kalimantan, Indonesia. 相似文献
12.
Agricultural fields, including rice ( Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH 4) and nitrous oxide (N 2O). Organic matter application, such as straw and organic fertilizer, enhances CH 4 emission from paddy fields. In addition, rice straw management after harvest regulates CH 4 emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH 4 and N 2O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH 4 and N 2O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH 4 emission and the emission factor for CH 4 (EF CH4) in the rice-growing season, suggesting that the substrate for CH 4 production was reduced by autumn and spring tillage in the fallow season. Higher EF CH4 [1.8–2.0 kg carbon (C) ha ?1 d ?1] was observed when more straw was applied (6.9–7.2 Mg ha ?1) in the second year. Organic fertilizer application induced higher CH 4 emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EF CH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N 2O efflux during the rice-growing season in the second year, but N 2O emissions were not affected by winter tillage. Although paddy fields can act as an N 2O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N 2O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N 2O (EF N2O) can be applied, and EF N2O of organic fertilizer should be considered during the estimation of N 2O emission in the paddy field. 相似文献
13.
Purpose Nitrous oxide (N 2O) is a potent greenhouse gas which is mainly produced from agricultural soils through the processes of nitrification and denitrification. Although denitrification is usually the major process responsible for N 2O emissions, N 2O production from nitrification can increase under some soil conditions. Soil pH can affect N 2O emissions by altering N transformations and microbial communities. Bacterial (AOB) and archaeal (AOA) ammonia oxidisers are important for N 2O production as they carry out the rate-limiting step of the nitrification process. Material and methods A field study was conducted to investigate the effect of soil pH changes on N 2O emissions, AOB and AOA community abundance, and the efficacy of a nitrification inhibitor, dicyandiamide (DCD), at reducing N 2O emissions from animal urine applied to soil. The effect of three pH treatments, namely alkaline treatment (CaO/NaOH), acid treatment (HCl) and native (water) and four urine and DCD treatments as control (no urine or DCD), urine-only, DCD-only and urine + DCD were assessed in terms of their effect on N 2O emissions and ammonia oxidiser community growth. Results and discussion Results showed that total N 2O emissions were increased when the soil was acidified by the acid treatment. This was probably due to incomplete denitrification caused by the inhibition of the assembly of the N 2O reductase enzyme under acidic conditions. AOB population abundance increased when the pH was increased in the alkaline treatment, particularly when animal urine was applied. In contrast, AOA grew in the acid treatment, once the initial inhibitory effect of the urine had subsided. The addition of DCD decreased total N 2O emissions significantly in the acid treatment and decreased peak N 2O emissions in all pH treatments. DCD also inhibited AOB growth in both the alkaline and native pH treatments and inhibited AOA growth in the acid treatment. Conclusions These results show that N 2O emissions increase when soil pH decreases. AOB and AOA prefer different soil pH environments to grow: AOB growth is favoured in an alkaline pH and AOA growth favoured in more acidic soils. DCD was effective in inhibiting AOB and AOA when they were actively growing under the different soil pH conditions. 相似文献
14.
【目的】氨氧化微生物是氨氧化过程的主要驱动者,氨氧化过程作为硝化作用的限速步骤对氮循环具有重要作用。本研究以沈阳农业大学棕壤含氯化肥长期定位试验的土壤为研究对象,探讨了连续34年施用高氯和低氯化肥对棕壤硝化作用及氨氧化微生物的影响。【方法】该长期试验在等量氮、磷、钾条件下,设置高氯和低氯处理,共8个处理:T1(不施肥);T2(单施尿素);T3(尿素+氯化钾);T4(尿素+过磷酸钙);T5(尿素+过磷酸钙+氯化钾);T6(尿素+磷酸一铵+氯化钾);T7(尿素+氯磷铵+氯化钾);T8(硝酸磷肥+过磷酸钙+氯化钾),T7为高氯处理。采集0—20cm土壤样品,利用荧光定量PCR技术测定氨氧化细菌(AOB)和古菌(AOA)丰度,并结合土壤硝化潜势和基本化学性质,分析长期施用含氯化肥对棕壤硝化作用及氨氧化微生物丰度的影响及影响氨氧化微生物丰度的主要环境因素。【结果】长期施肥降低了土壤pH值,高氯处理降低得最多,显著低于其他处理;高氯处理的土壤硝化潜势也显著低于其他处理,且除高氯处理外,配施磷肥的处理土壤硝化潜势显著高于不施磷处理。各处理土壤中AOA丰度均显著高于AOB,高氯处理土壤中AOA、AOB丰度均显著低于其他处理,土壤硝化潜势与AOA和AOB均呈显著正相关关系。【结论】连续施用高氯化肥34年显著降低了棕壤AOA和AOB丰度,抑制了硝化潜势。该结果可为通过含氯化肥的合理施用来调节土壤AOA和AOB,进而调控土壤氮素循环提供参考。 相似文献
15.
PurposeAmmonia oxidation is the limiting step in soil nitrification and critical in the global nitrogen cycle. The discovery of ammonia-oxidizing archaea (AOA) has improved our knowledge of microbial mechanisms for ammonia oxidation in complex soil environments. However, the relative contributions of AOA and ammonia-oxidizing bacteria (AOB) to ammonia oxidation remain unclear. Materials and methodsIn this study, through large geographical scale sampling in China, totally nine samples representing various types of arable land soils were selected for analyzing the ammonia oxidation activity. The AOA and AOB activities were separately determined by using the dicyandiamide and 1-octyne inhibition method. High-throughput pyrosequencing and DNA stable-isotope probing (DNA-SIP) analysis were applied to investigate the distribution and activity of Candidatus Nitrosocosmicus franklandus in the arable land soils. Results and discussionIn this study, AOA abundance (3.2?×?107–3.4?×?109 copies g?1) and activity (0.01–1.33 mg N kg?1 dry soil day?1) were evaluated for nine selected arable land soils and accounted for 4–100% of ammonia oxidation. By separately determining AOA and AOB rates, we observed that archaeal ammonia oxidation dominated the ammonia oxidation process in six soils, revealing a considerable contribution of AOA in ammonia oxidation in arable land soils. Based on high-throughput pyrosequencing analysis, the AOA species Ca. N. franklandus with relatively low abundance (0.6–13.5% in AOA) was ubiquitously distributed in all the tested samples. Moreover, according to the DNA-SIP analysis for Urumqi sample, the high activity and efficiency of Ca. N. franklandus in using CO2 suggests that this species plays an important role in archaeal ammonia oxidation in arable land soils. ConclusionsThrough determining the AOA activity and analyzing the potential predominant functional AOA species, this study greatly improves our understanding of ammonia oxidation in arable land soils. 相似文献
16.
Purpose Ammonia oxidation—as the rate-limiting step of nitrification—has been found to be performed by both ammonia-oxidizing archaea (AOA) and bacteria (AOB). However, how ammonium content and oxidation–reduction status regulate the distribution of ammonia oxidizers in constructed wetlands and their contribution to potential ammonia oxidation rate are still in dispute. This study aimed to explore the effects of ammonium content and oxidation–reduction status on the abundances of AOA/AOB and examine the contributions of AOA and AOB populations to ammonia oxidation rates in the plant-bed/ditch system of a constructed wetland. Materials and methods Sampling was carried out in the plant-bed/ditch system of the Shijiuyang Constructed Wetland, China. Three plant-bed soil cores were collected using a soil auger and sampled at depths of 0, 20, and 50 cm in 5-cm increments. Five ditch surface sediments (0–5 cm) were collected along the water flow direction. The abundances of AOA and AOB were investigated by quantitative polymerase chain reaction based on amoA genes. The potential ammonia oxidation rate was determined using the chlorate inhibition method. Results and discussion The results showed that AOA outnumbered AOB in the plant-bed surface soil which had lower ammonium content (4.67–7.63 mg kg ?1), but that AOB outnumbered AOA in the ditch surface sediment which had higher ammonium content (14.0–22.9 mg kg ?1). Ammonium content was found to be the crucial factor influencing the relative abundances of AOA and AOB in the surface samples of the plant-bed/ditch system. In the deep layers of the plant bed, AOA abundance outnumbered AOB, though much lower oxidation–reduction potential occurred along the water flow direction. Thus, the oxidation–reduction potential may be another factor influencing the distributions of AOA and AOB in the deep layers of the plant bed without significant difference in ammonium content ( p?<?0.05). Moreover, the potential ammonia oxidation rate was significantly dominated by AOB rather than AOA in the plant-bed/ditch system. Conclusions The high ammonium content in the ditch sediment likely favored AOB. AOA seemed to persist more readily even under low oxidation–reduction potential in the deep layers of the plant bed. Ammonium content and the oxidation–reduction potential were important parameters influencing the distribution of AOA and AOB in the plant-bed/ditch system of Shijiuyang Constructed Wetland. AOB contributed more to ammonia oxidation than AOA, both in the plant-bed soils ( r?=?0.592, p?=?0.0096) and in the ditch sediments ( r?=?0.873, p?=?0.0002). 相似文献
17.
Bio-organic fertilizers enriched with plant growth-promoting microbes(PGPMs)have been widely used in crop fields to promote plant growth and maintain soil microbiome functions.However,their potential effects on N 2O emissions are of increasing concern.In this study,an in situ measurement experiment was conducted to investigate the effect of organic fertilizer containing Trichoderma guizhouense(a plant growth-promoting fungus)on soil N 2O emissions from a greenhouse vegetable field.The following four treatments were used:no fertilizer(control),chemical fertilizer(NPK),organic fertilizer derived from cattle manure(O),and organic fertilizer containing T.guizhouense(O+T,referring to bio-organic fertilizer).The abundances of soil N cycling-related functional genes(amoA)from ammonium-oxidizing bacteria(AOB)and archaea(AOA),as well as nirS,nirK,and nosZ,were simultaneously determined using quantitative PCR(qPCR).Compared to the NPK plot,seasonal total N 2O emissions decreased by 11.7%and 18.7%in the O and O+T plots,respectively,which was attributed to lower NH 4+-N content and AOB amoA abundance in the O and O+T plots.The nosZ abundance was significantly greater in the O+T plot,whilst the AOB amoA abundance was significantly lower in the O+T plot than in the O plot.Relative to the organic fertilizer,bio-organic fertilizer application tended to decrease N 2O emissions by 7.9%and enhanced vegetable yield,resulting in a significant decrease in yield-scaled N 2O emissions.Overall,the results of this study suggested that,compared to organic and chemical fertilizers,bio-organic fertilizers containing PGPMs could benefit crop yield and mitigate N 2O emissions in vegetable fields. 相似文献
18.
PurposeIntensive agricultural practices have enhanced problems associated with the competing use of limited water resources. Nitrous oxide (N2O) is a major contributor to global warming. It is important for researchers to ascertain the relationship between irrigation and soil N2O emissions in order to identify mitigation strategies to reduce nitrous oxide emissions. Different irrigation amounts affect soil water dynamics and nitrogen turnover. The effect of three lower limits of irrigation on soil N2O emissions, influencing factors, and abundance of genes involved in nitrification and denitrification were investigated in tomato irrigated in a greenhouse.Materials and methodsObservations were performed between April and August 2015 in a long-term irrigated field subjected to different lower limits of irrigation: 20 kPa (D20), 30 kPa (D30), and 40 kPa (D40) from greenhouse soil during the tomato crop season. Soil N2O fluxes were monitored using the static chamber-gas chromatograph method. Copy numbers of genes were determined using the real-time quantitative polymerase chain reaction (real-time PCR) technique. Characteristics of soil N2O emissions were analyzed, and differences between irrigation regimes were determined. The effects of influencing factors on soil N2O emissions were analyzed, including soil temperature, soil moisture, soil pH, and soil mineral nitrogen, as well as changes in the abundance of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) based on amoA genes and denitrifier genes (nosZ, nirK, and cnorB).Results and discussionOur results showed that peaks in N2O emissions occurred 1–5 days after each irrigation. During the whole tomato growth period, soil N2O fluxes were lowest under D30 treatment compared with those under D20 and D40 treatments. Soil NO3 ?-N concentrations were significantly higher than NH4 +-N concentrations. Soil N2O fluxes were significantly related to soil moisture, NH4 +-N concentrations (P < 0.01), soil pH, and AOA copy numbers (P < 0.05). There was no consistent correlation between soil N2O emissions, soil temperature, and soil NO3 ?-N concentrations. Different irrigation regimes significantly affected AOA copy numbers but did not affect the expression of other genes. AOA copy numbers were higher than those of AOB. Soil N2O fluxes significantly affected the AOA copy numbers and potential nitrification rates (P < 0.05).ConclusionsSoil moisture, pH, and NH4 +-N concentration were important factors affecting soil N2O emissions. Compared with other genes associated with nitrification and denitrification, AOA plays an important role in N2O emissions from greenhouse soils. Selecting a lower limit of irrigation of 30 kPa could effectively reduce N2O emissions from vegetable soils. 相似文献
19.
In recent years, identification of the microbial sources responsible for soil N 2O production has substantially advanced with the development of isotope enrichment techniques, selective inhibitors, mathematical models and the discoveries of specific N-cycling functional genes. However, little information is available to effectively quantify the N 2O produced from different microbial pathways (e.g. nitrification and denitrification). Here, a 15N-tracing incubation experiment was conducted under controlled laboratory conditions (50, 70 and 85% water-filled pore space (WFPS) at 25 and 35 °C). Nitrification was the main contributor to N 2O production. At 50, 70 and 85% WFPS, nitrification contributed 87, 80 and 53% of total N 2O production, respectively, at 25 °C, and 86, 74 and 33% at 35 °C. The proportion of nitrified N as N 2O ( P N2O) increased with temperature and moisture, except for 85% WFPS, when P N2O was lower at 35 °C than at 25 °C. Ammonia-oxidizing archaea (AOA) were the dominant ammonia oxidizers, but both AOA and ammonia-oxidizing bacteria (AOB) were related to N 2O emitted from nitrification. AOA and AOB abundance was significantly influenced by soil moisture, more so than temperature, and decreased with increasing moisture content. These findings can be used to develop better models for simulating N 2O from nitrification to inform soil management practises for improving N use efficiency. 相似文献
20.
It is still not clear which group of ammonia-oxidizing microorganisms plays the most important roles in nitrification in soils. Change in abundances and community compositions of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) under long-term different nitrogen (N) fertilization rates were investigated in an acidic luvisols soil using real-time polymerase chain reaction and denaturing gradient gel electrophoresis, respectively, based on the ammonia monooxygenase a-subunit gene. The experimental plan included the following treatments: control without N fertilization (N CK), low N fertilization rate, middle N fertilization rate, and high N fertilization rate as 0, 100, 150, and 250?kg urea-N?ha ?1, respectively. Long-term different N fertilization rates did not significantly alter the total C and N contents of soil while it significantly decreased soil pH, which ranged from 5.60 to 5.20. The AOB abundance was more abundant in the N fertilization treatments than the N CK treatment; the AOA abundance decreased by the increasing N fertilization rates, as did the ratios of AOA/AOB. The large differences in the potential nitrification rates among four treatments depended on the changes in AOA abundance but not to changes in AOB abundance. Phylogenetic analysis showed that the AOB communities were dominated by Nitrosospira clusters 1, 3, and 9 while all AOA sequences were grouped into soil/sediment cluster except for one sequence. Taken together, these results indicated that AOB and AOA preferred different soil N conditions and AOA were functionally more important in the nitrification than AOB in the acidic luvisols soil. 相似文献
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