Impacts of different N management regimes on nitrifier and denitrifier communities and N cycling in soil microenvironments     

Kong AY  Hristova K  Scow KM  Six J 《Soil biology & biochemistry》2010,42(9):1523-1533

Real-time quantitative PCR assays, targeting part of the ammonia monooxygenase (amoA), nitrous oxide reductase (nosZ), and 16S rRNA genes were coupled with ¹⁵N pool dilution techniques to investigate the effects of long-term agricultural management practices on potential gross N mineralization and nitrification rates, as well as ammonia-oxidizing bacteria (AOB), denitrifier, and total bacterial community sizes within different soil microenvironments. Three soil microenvironments [coarse particulate organic matter (cPOM; >250 μm), microaggregate (53-250 μm), and silt-and-clay fraction (<53 μm)] were physically isolated from soil samples collected across the cropping season from conventional, low-input, and organic maize-tomato systems (Zea mays L.-Lycopersicum esculentum L.). We hypothesized that (i) the higher N inputs and soil N content of the organic system foster larger AOB and denitrifier communities than in the conventional and low-input systems, (ii) differences in potential gross N mineralization and nitrification rates across the systems correspond with AOB and denitrifier abundances, and (iii) amoA, nosZ, and 16S rRNA gene abundances are higher in the microaggregates than in the cPOM and silt-and-clay microenvironments. Despite 13 years of different soil management and greater soil C and N content in the organic compared to the conventional and low-input systems, total bacterial communities within the whole soil were similar in size across the three systems (∼5.15 × 10⁸ copies g⁻¹ soil). However, amoA gene densities were ∼2 times higher in the organic (1.75 × 10⁸ copies g⁻¹ soil) than the other systems at the start of the season and nosZ gene abundances were ∼2 times greater in the conventional (7.65 × 10⁷ copies g⁻¹ soil) than in the other systems by the end of the season. Because organic management did not consistently lead to larger AOB and denitrifier communities than the other two systems, our first hypothesis was not corroborated. Our second hypothesis was also not corroborated because canonical correspondence analyses revealed that AOB and denitrifier abundances were decoupled from potential gross N mineralization and nitrification rates and from inorganic N concentrations. Our third hypothesis was supported by the overall larger nitrifier, denitrifier, and total bacterial communities measured in the soil microaggregates compared to the cPOM and silt-and-clay. These results suggest that the microaggregates are microenvironments that preferentially stabilize C, and concomitantly promote the growth of nitrifier and denitrifier communities, thereby serving as potential hotspots for N₂O losses.  相似文献   

Soil particle surface electrochemical property effects on abundance of ammonia-oxidizing bacteria and ammonia-oxidizing archaea, NH₄ activity, and net nitrification in an acid soil     

X. Jiang  Y. Ma  A.L. Wright 《Soil biology & biochemistry》2011,43(11):2215-2221

Soil surface electrochemical properties may have a strong influence on nitrifying microorganisms, H⁺ and NH₄⁺ activities, and therefore on the nitrification process. A gradient of surface electrochemical parameters was obtained by amendment of a subtropical acid pine soil (Oxisol) with 0% (control), 3%, 5%, 8%, 10% and 12% pure Ca-Montmorillonite by weight. The H⁺ and NH₄⁺ activities, the abundance of the ammonia-oxidizing bacterial (AOB) and archaeal (AOA) amoA gene copies, and time-dependent kinetics of net nitrification were investigated. Soil particle surface specific area ranged from 53 to 103 m² g⁻¹ and increased with increasing montmorillonite application rate. Similar to specific area, surface charge quantity, surface charge density, electric field strength and surface potential increased after montmorillonite amendment. The H⁺ and NH₄⁺ activities decreased linearly after montmorillonite addition. AOB amoA gene copy number was 1.82 × 10⁵ copies g⁻¹ for unamended soil, and the highest AOB amoA gene copy numbers were found for the 10% montmorillonite amendment (3.11 × 10⁷ g⁻¹ soil), which was more than 150 times higher than unamended soil. AOA amoA gene copy numbers were 9.19 × 10³ copies g⁻¹ dry unamended soil, and the highest AOA amoA gene copy numbers were found in the 8% montmorillonite amendment (1.22 × 10⁵ g⁻¹ soil). Although pH significantly decreased during the first three weeks of incubation, no significant difference was observed between the unamended control and different rates of montmorillonite addition treatments during the whole incubation. The largest net nitrification (103 mg N kg⁻¹) was observed in the 10% montmorillonite amendment and the lowest in unamended soil (62 mg N kg⁻¹). While montmorillonite did not change the kinetic patterns of net nitrification, the highest nitrification potential (275 mg N kg⁻¹) for the 10% montmorillonite treatment was more than 3 times higher than unamended soil from simulation of time-dependent kinetics. Nitrification was significantly stimulated after montmorillonite amendment in acid soil mainly due to an increase in the quantity and activity of AOB and AOA. We concluded that soil particle surface parameters can significantly influence nitrification, especially in acid soils.  相似文献   

Quantification of Wautersia [Ralstonia] basilensis in the mycorrhizosphere of Pinus thunbergii Parl. and its effect on mycorrhizal formation     

Ryota Kataoka  Takeshi Taniguchi 《Soil biology & biochemistry》2009,41(10):2147-2152

The bacterium Wautersia [Ralstonia] basilensis has been shown to enhance the mycorrhizal symbiosis between Suillus granulatus and Pinus thunbergii (Japanese black pine). However, no information is available about this bacterium under field conditions. The objectives of this study were to detect W. basilensis in bulk and mycorhizosphere soils in a Japanese pine plantation in the Tottori Sand Dunes, determine the density of W. basilensis in soil, and determine the optimal cell density of W. basilensis for mycorrhizal formation in pine seedlings. We designed and validated 16S rRNA gene-targeted specific primers for detection and quantification of W. basilensis. SYBR Green I real-time PCR assay was used. A standard curve relating cultured W. basilensis cell density (10³-10⁸ cells ml⁻¹) to amplification of DNA showed a strong linear relationship (R = 0.9968). The specificity of the reaction was confirmed by analyzing DNA melting curves and sequencing of the amplicon. The average cell density of W. basilensis was >4.8 × 10⁷ cells g⁻¹ of soil in the mycorrhizosphere and 7.0 × 10⁶ cells g⁻¹ in the bulk soil. We evaluated the W. basilensis cell density required for mycorrhizal formation using an in vitro microcosm with various inoculum densities ranging from 10² to 10⁷ cells g⁻¹ soil (10⁴-10⁹ cells ml⁻¹). Cell densities of W. basilensis of >10⁶ cells g⁻¹ of soil were required to stimulate mycorrhizal formation. In vivo and in vitro experiments showed that W. basilensis was sufficiently abundant to enhance mycorrhizal formation in the mycorrhizosphere of Japanese black pine sampled from the Tottori Sand Dunes.  相似文献   

Depth-specific distribution and importance of nitrite-dependent anaerobic ammonium and methane-oxidising bacteria in an urban wetland     

《Soil biology & biochemistry》2015

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two recently discovered processes in the nitrogen cycle that are catalysed by anammox bacteria and n-damo bacteria, respectively. Here, the depth-specific distribution and importance of anammox bacteria and n-damo bacteria were studied in an urban wetland, Xixi Wetland, Zhejiang Province (China). Anammox bacteria related to Candidatus Brocadia, Candidatus Kuenenia and Candidatus Anammoxoglobus, and n-damo bacteria related to “Candidatus Methylomirabilis oxyfera” were present in the collected soil samples. The abundance of anammox bacteria (2.6–8.6 × 10⁶ copies g⁻¹ dry soil) in the shallow soils (0–10 cm and 20–30 cm) was higher than that (2.5–9.8 × 10⁵ copies g⁻¹ dry soil) in the deep soils, whereas the abundance of n-damo bacteria (0.6–1.3 × 10⁷ copies g⁻¹ dry soil) in the deep soils (50–60 cm and 90–100 cm) was higher than that (3.4–4.5 × 10⁶ copies g⁻¹ dry soil) in the shallow soils. Anammox activity was detected at all depths, and higher potential rates (12.1–21.4 nmol N₂ g⁻¹ dry soil d⁻¹) were observed at depths of 0–10 cm and 20–30 cm compared with the rates (3.5–8.7 nmol N₂ g⁻¹ dry soil d⁻¹) measured at depths of 50–60 and 90–100 cm. In contrast, n-damo was mainly occurred at depths of 50–60 cm and 90–100 cm with potential rates of 0.7–5.0 nmol CO₂ g⁻¹ dry soil d⁻¹. This study suggested the niche segregation of the anammox bacteria and n-damo bacteria in wetland soils, with anammox bacteria being active primarily in deep soils and n-damo bacteria being active primarily in shallow soils.  相似文献   

Quantification of ammonia-oxidising bacteria in limed and non-limed acidic coniferous forest soil using real-time PCR     

Anna Hermansson  Bo H. Svensson 《Soil biology & biochemistry》2004,36(12):1935-1941

Ammonia-oxidising bacteria (AOB) in limed and non-limed acidic coniferous forest soil were investigated using real-time PCR. Two sites in southern Sweden were studied, 244 Åled and Oxafällan. The primers and probe used earlier appeared to be specific to the 16S rRNA gene of AOB belonging to the β-subgroup of the Proteobacteria [Appl. Environ. Microbiol. 67 (2001) 972]. Plots treated with two different doses of lime, 3 or 6 t ha⁻¹, were compared with non-limed control plots on two occasions during a single growing season. Three different soil depths were analysed to elucidate possible differences in the density of their AOB communities. The only clear effect of liming on the AOB was recorded in the beginning of the growing season at 244 Åled. In samples taken in April from this site, the numbers of AOB were higher in the limed plots than in the control plots. At the end of the growing season the AOB communities were all of a similar size in the different plots at both sites, irrespective of liming. The number of AOB, determined using real-time PCR, ranged between 6×10⁶ and 1×10⁹ cells g⁻¹ soil (dw) at the two sites, and generally decreased with increasing soil depth. The results showed no correlation between community density and potential nitrification. This may indicate a partly inactive AOB community. Furthermore, more than 10⁷ cells g⁻¹ soil (dw) were recorded using real-time PCR in the control plot at 244 Åled, although Bäckman et al. [Soil Biol. Biochem. 35 (2003) 1337] detected no AOB like sequences in the same plots using PCR followed by DGGE. Taken together our results strongly suggest that the primers and probe set used are not well suited for quantifying AOB in acidic forest soils, which is probably due to an insufficient specificity. This shows that it is extremely important to re-evaluate any primers and probe set when used in a new environment. Consideration should be given to the specificity and sensitivity, both empirically and using bioinformatic tools.  相似文献   

Short-term population dynamics of ammonia oxidizing bacteria in an agricultural soil   总被引：2，自引：0，他引：2  

T.R. Cavagnaro  L.E. Jackson  K. Hristova  K.M. Scow 《Applied soil ecology》2008,40(1):13-18

Ammonia oxidizing bacteria (AOB) control the rate limiting step of nitrification, the conversion of ammonia (NH₄⁺) to nitrite (NO₂⁻). The AOB therefore have an important role to play in regulating soil nitrogen cycling. Tillage aerates the soil, stimulating rapid changes in soil N cycling and microbial communities. Here we report results of a study of the short term responses of AOB and net nitrification to simulated tillage and NH₄⁺ addition to soil. The intensively farmed vegetable soils of the Salinas Valley, California, provide the context for this study. These soils are cultivated frequently, receive large N fertilizer inputs and there are regional concerns about groundwater N concentrations. An understanding of N dynamics in these systems is therefore important. AOB population sizes were quantified using a real-time PCR approach. In a 15 day experiment AOB populations, increased rapidly following tillage and NH₄⁺ addition and persisted after the depletion of soil NH₄⁺. AOB population sizes increased to a similar degree, over a 1.5-day period, irrespective of the amount of NH₄⁺ supplied. These data suggest selection of an AOB community in this intensively farmed and C-limited soil, that rapidly uses NH₄⁺ that becomes available. These data also suggest that mineralization may play an especially important role in regulating AOB populations where NH₄⁺ pool sizes are very low. Methodological considerations in the study of soil AOB communities are also discussed.  相似文献   

施用不同生物有机肥对连作黄瓜枯萎病防治效果及其机理初探   总被引：11，自引：4，他引：7  

袁玉娟胡江  凌宁仇美华  沈其荣杨兴明 《植物营养与肥料学报》2014,20(2):372-379

采用营养钵育苗和盆钵试验的方法,研究了以枯草芽孢杆菌SQR9和哈茨木霉T37这两株拮抗菌制成的三种生物有机肥（BIOⅠ、 BIOⅡ和BIOⅢ）对黄瓜生长、 土传枯萎病防治效果及其生防菌株在黄瓜根系中的定殖情况的影响。结果表明, 1）未施用生物有机肥的对照处理（CK）完全发病,有机肥处理（OF）发病率高达88.2%。施用BIO处理都不同程度地降低了黄瓜土传枯萎病的发病率,施用生物有机肥BIOⅠ、 BIOⅡ和BIOⅢ后发病率分别降至51.0%、 19.6%、 13.7%。2）与对照相比,BIOⅠ、 BIO Ⅱ和BIO Ⅲ处理能够显著提高黄瓜生物量,分别是对照的 2.55、 2.46 和 2.58 倍。3）菌株SQR9和T37通过有效的根际定殖降低了病原真菌对根系的侵染,荧光定量PCR（real-time PCR）测定黄瓜根际尖孢镰刀菌数量的结果表明,施用BIOⅡ和BIOⅢ能够将病原菌数量控制在103 copies/g, 土,而对照土壤高达 107 copies/g, 土。  相似文献   

Traceability of ammonia-oxidizing bacteria in compost-treated soils     

Gerd Innerebner  Brigitte Knapp  Martin Romantschuk 《Soil biology & biochemistry》2006,38(5):1092-1100

Composts are increasingly used as environmentally safe biofertilizers in sustainable agriculture all over the world. Although it is well known that composts may contribute to soil vitality and sustainability, and in the enhancement of various soil microbiological processes, little is known about their direct or indirect effects on a microbial-community or population level. Ammonia oxidation by autotrophic ammonia-oxidizing bacteria (AOB) is a key process in agricultural and natural ecosystems and plays an important role in the global nitrogen cycle. Here, we studied the diversity and community composition of ammonia oxidizers in a long-term crop rotation field experiment (>10 years) where four major types of compost (from organic waste, cattle manure, green waste and sewage sludge) had been applied annually. The methods used ranged from PCR-DGGE (denaturing gradient gel electrophoresis) and cloning of 16S rDNA fragments to quantitative real-time PCR. Cluster analysis of DGGE profiles differentiated between the microbial communities of composts, compost-treated soils and mineral-fertilized soils. The community composition of the composts was not reflected in the community composition of the compost-treated soils. Sequencing of screened clones revealed a characteristic AOB community structure for the representative soil sample and the four composts. All AOB-like sequences grouped within the Nitrosospira cluster 3 and 4 and within the Nitrosomonas cluster 6 and 7. The average AOB abundance in compost-treated soils was two times higher than in mineral-fertilized soils (4.3×10⁷ and 1.9×10⁷, respectively). Our data suggest that composts do not leave direct microbial imprints in soils after long-term amendment, but an indirect effect on the AOB community was evident.  相似文献   

两种农田土壤中的氨氧化细菌和氨氧化古菌对硝化抑制剂DCD和DMPP的响应-盆栽试验   总被引：4，自引：0，他引：4  

GONG Ping  ZHANG Li-Li  WU Zhi-Jie  CHEN Zhen-Hu  CHEN Li-Jun 《土壤圈》2013,23(6):729-739

Taking two important agricultural soils with different pH, brown soil （Hap-Udic Luvisol） and cinnamon soil （Hap-Ustic Luvisol）, from Northeast China, a pot culture experiment with spring maize （Zea mays L.） was conducted to study the dynamic changes in the abundance and diversity of soil ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA） populations during maize growth period in response to the additions of nitrification inhibitors dicyandiamide （DCD） and 3,4-dimethylpyrazole phosphate （DMPP） by the methods of real-time polymerase chain reaction （PCR） assay, PCR-denaturing gradient gel electrophoresis （DGGE）, and construction of clone library targeting the amoA gene. Four treatments were established, i.e., no urea （control）, urea, urea plus DCD, and urea plus DMPP. Both DCD and DMPP inhibited growth of AOB significantly, compared to applying urea alone. Soil bacterial amoA gene copies had a significant positive linear correlation with soil nitrate content, but soil archaeal amoA gene copies did not. In both soils, all AOB sequences fell within Nitrosospira or Nitrosospira-like groups, and all AOA sequences belonged to group 1.1b crenaxchaea. With the application of DCD or DMPP, community composition of AOB and AOA in the two soils had less change except that the AOB community composition in Hap-Udic Luvisol changed at the last two growth stages of maize under the application of DCD. AOB rather than AOA likely dominated soil ammonia oxidation in these two agricultural soils.  相似文献   

Quantitative PCR assays to enumerate Rhizobium leguminosarum strains in soil also target non viable cells and overestimate those detected by the plant infection method     

Miet Boonen  Jelle Mertens  Erik Smolders 《Soil biology & biochemistry》2010,42(12):2342-2344

The plant infection method is commonly used to estimate the Most Probable Number (MPN) of soil rhizobia. Here, a qPCR method was set-up and validated with newly developed ANU (strain specific) and RHIZ (more general) primers to quantify the specific Rhizobium leguminosarum bv. trifolii ANU843 strain or general R. leguminosarum strains. Detection limits of qPCR protocols in soil were 1.2 × 10⁴ (ANU) and 4.2 × 10³ (RHIZ) cells per g soil. The qPCR assay appears robust and accurate in freshly inoculated soils but overestimated MPN for indigenous soil rhizobia. An incubation experiment showed that qPCR detected added DNA or non viable cells in soils up to 5 months after addition and incubation at 20 °C in moist conditions.  相似文献   

Development of a real-time PCR method to quantify the PGPR strain Azospirillum lipoferum CRT1 on maize seedlings     

Olivier Couillerot  Marie-Lara Bouffaud  Ezékiel Baudoin  Daniel Muller  Jesus Caballero-Mellado 《Soil biology & biochemistry》2010,42(12):2298-2305

Azospirillum lipoferum CRT1 is a promising phytostimulatory PGPR for maize, whose effect on the plant is cell density-dependent. A nested PCR method is available for detection of the strain but does not allow quantification. The objective was to develop a real-time PCR method for quantification of A. lipoferum CRT1 in the rhizosphere of maize seedlings. Primers were designed based on a strain-specific RFLP marker, and their specificity was verified under qualitative and quantitative PCR conditions based on successful CRT1 amplification and absence of cross-reaction with genomic DNA from various rhizosphere strains. Real-time PCR conditions were then optimized using DNA from inoculated or non-inoculated maize rhizosphere samples. The detection limit was 60 fg DNA (corresponding to 19 cells) with pure cultures and 4 × 10⁴ CFU equivalents g⁻¹ lyophilized sample consisting of mixture of rhizosphere soil and roots. Inoculant quantification was effective down to 10⁴ CFU equivalents g⁻¹. Assessment of CRT1 rhizosphere levels in a field trial was in accordance with estimates from semi-quantitative PCR targeting another locus. This real-time PCR method, which is now available for direct rhizosphere monitoring of A. lipoferum CRT1 in greenhouse and field experiments, could be used as a reference for developing quantification tools for other Azospirillum inoculants.  相似文献   

Effect of green manure Sesbania sesban and nitrification inhibitor encapsulated calcium carbide (ECC) on soil mineral-N,enzyme activity and nitrifying organisms in a rice–wheat cropping system     

《European Journal of Soil Biology》2006,42(3):173-180

Green manure Sesbania sesban (S. sesban) and the nitrification inhibitor encapsulated calcium carbide (ECC) have been used to improve N supply and management in rice–wheat production systems in India. However, the ecological impact of combined use of these materials is largely unknown. We conducted a net-house pot culture experiment for 2 years, to investigate the effects of S. sesban and ECC on mineral N availability (NH₄⁺ and NO₃^–), soil enzyme activities (dehydrogenase and nitrate reductase) and populations (MPN) of nitrifying organisms under a rice–wheat cropping system. Green manure S. sesban and ECC (+ECC or –ECC) were applied along with urea in various combinations to hybrid rice under flooded conditions. For wheat, it was urea alone or urea + ECC. Soil samples were studied at 10 days after top dressing, i.e. 40 days after rice transplanting and 35 days after wheat sowing, for above characteristics. The mineral-N in soil revealed the significant effect of combined use of S. sesban and ECC to enhance NH₄⁺ and total mineral-N (NH₄⁺ + NO₃^–) contents. Dehydrogenase and nitrate reductase activities and population (MPN) of ammonia oxidizing bacteria (AOB) revealed a significant reduction in soils, whereas nitrite oxidizing bacteria (NOB) remained almost unaffected (P > 0.05) in response to application of ECC with S. sesban and urea. Our results suggest that slow release of acetylene (C₂H₂) from ECC has reduced ammonia mono-oxygenase with reducing population of AOB, and has the potential to retard the enzyme activities in favor of C and N conservations in a semi-arid agro-ecosystem.  相似文献   

Population size and specific nitrification potential of soil ammonia-oxidizing bacteria under long-term fertilizer management     

Haiyan Chu  Takeshi Fujii  Sho Morimoto  Xiangui Lin  Kazuyuki Yagi 《Soil biology & biochemistry》2008,40(7):1960-1963

Population size of soil ammonia-oxidizing bacteria (AOB) was quantified by real-time PCR in a long-term (16 years) field experiment under different fertilizer managements. AOB population sizes in mineral nitrogen-fertilized soils and organic manure-fertilized soil were 10.3 and 3.1 times, respectively, that of the control, while phosphorus and potassium fertilization had no significant effect. On the other hand, the AOB specific nitrification potential (soil nitrification potential per AOB cell) was significantly higher (P < 0.05) in organic manure-fertilized soil than in mineral-fertilized soils and the control, indicating that AOB was likely more metabolically active in organic manure-fertilized soils than in mineral nitrogen-fertilized soils after long-term application.  相似文献   

亚热带4种典型森林植被土壤固碳细菌群落结构及数量特征   总被引：2，自引：0，他引：2  

刘茗  曹林桦  刘彩霞  梁辰飞  秦华  陈俊辉  邵帅  徐秋芳 《土壤学报》2021,58(4):1028-1039

为研究亚热带不同森林植被类型土壤固碳微生物特征及其影响因子,选取毛竹林(Moso banboo groves)、阔叶林(Broad-leaved forest)、杉木林(Chinese fir forest)和马尾松林(Masson pine forest)等4种森林植被为研究对象,以 cbbL为固碳细菌指示基因,利用实时荧光定量PCR (Real-time quantitative PCR)和MiSeq高通量测序为研究手段。结果表明,4种林分土壤的细菌16S rRNA基因和固碳细菌cbbL基因丰度范围分别是5.40×10~(10)～2.81×10~(11) copies·g~(-1)干土和4.55×10~8～3.53×10~9 copies·g~(-1)干土,其中毛竹林显著高于其他三种林分(P0.05);基因丰度显著关联的环境因子是阔叶林土壤的有效磷、不同土层的pH(P0.05)。杉木林土壤固碳细菌多样性显著低于其他3种林分(P0.05),其亚表层土壤高于表层(P0.05);双因子分析表明,林型、土层之间土壤固碳细菌多样性均存在显著或极显著差异。所有土壤具有相似的优势属但相对丰度不同,其中毛竹林和杉木林土壤的甲基化石油杆菌属(Methylibium)和诺卡菌属(Nocardia)占比明显高于阔叶林和马尾松林。冗余分析结果显示,不同林分土壤pH、土壤有机碳、有效磷、全氮差异是影响土壤固碳细菌群落特征形成的主要因素。综上,4种植被对土壤固碳微生物数量及群落结构多样性影响明显,从土壤理化性质、固碳细菌基因丰度、多样性以及结构特征等多维度结果证明,毛竹林对土壤肥力以及固碳细菌影响效果最好,固碳微生物对毛竹林土壤有机质积累贡献大于阔叶林,定量结论有待进一步研究。  相似文献   

Non-symbiotic bacterial diazotrophs in crop-farming systems: can their potential for plant growth promotion be better exploited?     

Ivan R Kennedy  A.T.M.A Choudhury  Mihály L Kecskés 《Soil biology & biochemistry》2004,36(8):1229-1244

Biological N₂ fixation (BNF) by associative diazotrophic bacteria is a spontaneous process where soil N is limited and adequate C sources are available. Yet the ability of these bacteria to contribute to yields in crops is only partly a result of BNF. A range of diazotrophic plant growth-promoting rhizobacteria participate in interactions with C₃ and C₄ crop plants (e.g. rice, wheat, maize, sugarcane and cotton), significantly increasing their vegetative growth and grain yield. We review the potential of these bacteria to contribute to yield increases in a range of field crops and outline possible strategies to obtain such yield increases more reliably. The mechanisms involved have a significant plant growth-promoting potential, retaining more soil organic-N and other nutrients in the plant-soil system, thus reducing the need for fertiliser N and P. Economic and environmental benefits can include increased income from high yields, reduced fertiliser costs and reduced emission of the greenhouse gas, N₂O (with more than 300 times the global warming effect of CO₂), as well as reduced leaching of NO₃⁻-N to ground water. Obtaining maximum benefits on farms from diazotrophic, plant growth promoting biofertilisers will require a systematic strategy designed to fully utilise all these beneficial factors, allowing crop yields to be maintained or even increased while fertiliser applications are reduced.  相似文献   

Potato cultivar type affects the structure of ammonia oxidizer communities in field soil under potato beyond the rhizosphere     

《Soil biology & biochemistry》2012

The effects of plants on the microbiota involved in the oxidation of ammonia in soils have been controversial. Here, we investigated the dynamics in the abundances and community structures of the bacterial and archaeal ammonia oxidizers (AOB and AOA, respectively) in two fields that were cropped with potato. Six different potato cultivars were used, including a genetically-modified one, in a fourfold replicated experimental set-up. On the basis of bulk and rhizosphere soil extracted microbial community DNA, AOB and AOA quantitative PCR as well as PCR-DGGE were performed. In addition, samples were used for the production and analysis of amoA gene fragment based clone libraries. Regardless of sample type (bulk versus rhizosphere soil) and across soils, the population sizes of AOA (of the order 10⁴–10⁸ amoA gene copies g⁻¹ dry soil), were generally higher than those of AOB in the same samples (about 10⁴–10⁵ g⁻¹ dry soil), resulting in ratio's of log-transformed values > 1.0. Whereas the AOB numbers were generally raised in the rhizosphere versus bulk soils in both soils, the opposite was true for the AOA numbers. Moreover, significant effects of cultivar type on both the AOB and AOA community structures were found in both soils, and these extended to beyond the rhizospheres. The effects were found across the whole growth season. Soil type did not significantly affect the community structures of AOA, but had a small effect on the community structure of AOB. Analysis of the structures of the AOB communities revealed a prevalence of AOB subgroups 2, 3a, 3b and 4 in one field soil and of 2 and 4 in the other one. With respect to the AOA, soil/sediment clusters (SS) I, II, III and IV were found to prevail.  相似文献   

Stimulated activity of the soil nitrifying community accelerates community adaptation to Zn stress     

Stefan Ruyters  Jelle Mertens  Dirk Springael  Erik Smolders 《Soil biology & biochemistry》2010,42(5):766-772

Field data have shown that soil nitrifying communities gradually adapt to zinc (Zn) after a single contamination event with reported adaptation times exceeding 1 year. It was hypothesized that this relatively slow adaptation relates to the restricted microbial diversity and low growth rate of the soil nitrifying community. This hypothesis was tested experimentally by recording adaptation rates under varying nitrification activities (assumed to affect growth rates) and by monitoring shifts in community composition. Soils were spiked at various Zn concentrations (0-4000 mg Zn kg⁻¹) and two NH₄⁺-N doses (N1, N2) were applied to stimulate growth. A control series receiving no extra NH₄⁺-N was also included. Soils were incubated in pots under field conditions with free drainage. The pore water Zn concentration at which nitrification was halved (EC50, mg Zn l⁻¹) did not change significantly during 12 months in the control series (without NH₄⁺-N applications), although nitrification recovered after 12 months at the highest Zn dose only. The EC50 after 12 months incubation increased by more than a factor 10 with increasing NH₄⁺-N dose (p < 0.05) illustrating that increased activity accelerates adaptation to Zn. Zinc tolerance tests confirmed the role of Zn exposure, time and NH₄⁺-N dose on adaptation. Zinc tolerance development was ascribed to the AOB community since the AOB/AOA ratio (AOB = ammonia oxidizing bacteria; AOA = ammonia oxidizing archaea) increased from 0.4 in the control to 1.4 in the most tolerant community. Moreover, the AOB amoA DGGE profile changed during Zn adaptation whereas the AOA amoA DGGE profile remained unaffected. These data confirm the slow but pronounced adaptation of nitrifiers to Zn contamination. We showed that adaptation to Zn was accelerated at higher activity and was associated with a shift in soil AOB community that gradually dominated the nitrifying community.  相似文献   

Nitrification, ammonia-oxidizing communities, and N2O and CH4 fluxes in an imperfectly drained agricultural field fertilized with coated urea with and without dicyandiamide     

Hiroko Akiyama  Sho Morimoto  Masahito Hayatsu  Atsushi Hayakawa  Shigeto Sudo  Kazuyuki Yagi 《Biology and Fertility of Soils》2013,49(2):213-223

Agricultural soil is a major source of nitrous oxide (N₂O), and the application of nitrogen and soil drainage are important factors affecting N₂O emissions. This study tested the use of polymer-coated urea (PCU) and polymer-coated urea with the nitrification inhibitor dicyandiamide (PCUD) as potential mitigation options for N₂O emissions in an imperfectly drained, upland converted paddy field. Fluxes of N₂O and methane (CH₄), ammonia oxidation potential, and ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) abundances were monitored after the application of PCU, PCUD, and urea to upland soil. The results showed that urea application increased the ammonia oxidation potential and AOB and AOA abundances; however, the increase rate of AOB (4.6 times) was much greater than that of AOA (1.8 times). These results suggested that both AOB and AOA contributed to ammonia oxidation after fertilizer application, but the response of AOB was greater than AOA. Although PCU and PCUD had lower ammonia oxidation potential compared to urea treatment, they were not effective in reducing N₂O emissions. Large episodic N₂O emissions (up to 1.59 kg N ha^?1 day^?1) were observed following heavy rainfall 2 months after basal fertilizer application. The episodic N₂O emissions accounted for 55–80 % of total N₂O emissions over the entire monitoring period. The episodic N₂O emissions following heavy rainfall would be a major source of N₂O in poorly drained agricultural fields. Cumulative CH₄ emissions ranged from ?0.017 to ?0.07 kg CH₄ ha^?1, and fertilizer and nitrification inhibitor application did not affect CH₄ oxidation.  相似文献   

Response of soil enzymes to Linear Alkylbenzene Sulfonate (LAS) addition in soil microcosms     

María del Mar Sánchez-Peinado  María Victoria Martínez-Toledo  Jesús González-López  Clementina Pozo 《Soil biology & biochemistry》2009,41(1):69-76

Soil enzymatic activities (phosphatases, arylsulphatase and dehydrogenase) were measured in microcosm systems designed for the study of the impact of a commercial mixture of Linear Alkylbenzene Sulphonate (LAS) homologues on a xerofluvent agricultural soil. The soil microcosms consisted of glass columns filled with 800 g of dry soil which were fed with sterile commercial LAS solutions at concentrations of 10 or 50 mg l⁻¹ for periods of time up to 21 days. A soil microcosm fed with sterile distilled water was included in this study and considered as control. Our results showed that the continuous application of the anionic surfactant to soil increased the values of the enzymes acid and alkaline phosphatases and arylsulphatase. On the contrary, the dehydrogenase activity was decreased by the continuous application of 10 or 50 mg l⁻¹ LAS when compared with control microcosms. In addition, a statistically negative correlation was found between this enzymatic activity in the upper portion of the soil columns amended with LAS and the viable counts of heterotrophic aerobic microorganisms. Moreover, in order to test the influence of LAS on nutrient availability and, consequently, on bacteria populations and soil biological activities, phosphate concentration was regularly determined in the microcosm leachates. The phosphate concentration tested in the leachate of the microcosm continuously amended with 50 mg l⁻¹ LAS solution was significantly lower than the concentrations detected in the leachate of the microcosms continuously amended with 10 mg l⁻¹ LAS throughout the experiment.  相似文献   

Grazing by nematodes on rhizosphere bacteria enhances nitrate and phosphorus availability to Pinus pinaster seedlings     

Usman Irshad  Cécile Villenave  Claude Plassard 《Soil biology & biochemistry》2011,43(10):2121-2126

The microbial loop is thought to play a major role in the mineralization of nutrients such as nitrogen (N) and phosphorus (P) in terrestrial ecosystems. This microbial loop is based on the grazing of bacteria by predators such as bacterial-feeding nematodes. However, little is known about the impact of grazing by nematodes on the mineral nutrition of woody plants. This study was undertaken to quantify the effect of nematode grazing on bacteria in the rhizosphere on the root architecture, growth and mineral nutrition (N and P) of a woody species (Pinus pinaster). Young P. pinaster seedlings were cultivated for 35 days in a simplified sterile experimental system with bacteria (Bacillus subtilis) and bacterivorous nematodes (Rhabditis sp.) isolated from soil samples collected from a 15-year old stand of maritime pine. To check the hypothesis that bacteria could be a source of nutrients, especially N, two N sources were supplied in the medium: (i) bacterial N labeled with ¹⁵N and (ii) nitrate. Phosphorus was supplied as insoluble inorganic tri-calcium phosphate (TCP). The results showed that the ¹⁵N flow from the bacteria to the plant shoots was only significant when nematodes were present, with an average accumulation of 14 ± 5 μg plant⁻¹ of ¹⁵N. Plants cultivated with nematodes also accumulated significantly more total N in their shoots than sterile ones or inoculated with bacteria, resulting in a net average increase in N of 700 μg plant⁻¹. The same result was observed for the total P accumulation in the shoots, as plants with nematodes accumulated an average of 300 μg plant⁻¹ more P than sterile ones or inoculated with bacteria. However, the presence of bacteria, whether alone or with nematodes, did not modify the root architecture. These results demonstrated that the presence of bacterial-feeding nematodes significantly enhanced N and P availability to P. pinaster seedlings, probably by improving plant use of nitrate and insoluble P supplied in the medium.  相似文献