首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 765 毫秒
1.
This research aimed to determine whether a diluted nutrient broth (DNB) medium was different from a conventional nutrient broth (NB) medium when counting and isolating denitrifying bacteria in surface and subsurface upland soils. To this end, we investigated populations of denitrifying bacteria isolated from the surface to a depth of 4 m of subsurface upland soil that had received slurry. The DNB medium gave higher viable counts of denitrifying bacteria than the NB medium and a higher isolation ratio of denitrifying bacterial isolates. In total, 74 isolates from the DNB medium (D-isolates) and 26 isolates from the NB medium (N-isolates) were collected. We characterized their denitrifying activity and analyzed the diversity of 16S rDNA and denitrifying-related genes. Seventy-three percent of the D-isolates were oligotrophic denitrifying bacteria. The N2-producing, oligotrophic denitrifying bacteria, largely of α-Proteobacteria, increased in the D-isolates. The D-isolates and the N-isolates had some taxonomic overlapping on a phylogenetic tree based on 16S rDNA. It was not possible to identify the denitrification phenotype (N2-producing or N2O-producing) on the phylogenetic tree. Phylogenetic groups of isolates corresponded to nirK groups, except in some isolates in which horizontal gene transfer might have occurred. The terminal gas emission of the isolates was consistent with the existence of the nosZ gene. The DNB medium may be very useful in isolating N2-producing denitrifying α-Proteobacteria. Its use highlights the ecological significance of oligotrophic isolates and the different viable counts resulting from the selectivity of conventional and diluted media.  相似文献   

2.
We used a laboratory incubation approach to measure rates of net N mineralization and nitrification in forest soils from Fu-shan Experimental Forest WS1 in northern Taiwan. Net mineralization rates in the O horizon ranged from 4.0 to 13.8 mg N kg−1 day−1, and net nitrification rates ranged from 2.2 to 11.6 mg N kg−1 day−1. For mineral (10–20 cm depth) soil, net mineralization ranged from 0.06 to 2.8 mg N kg−1 day−1 and net nitrification rates ranged from 0.02 to 2.8 mg N kg−1 day−1. We did not find any consistent differences in N mineralization or nitrification rates in soils from the upper and lower part of the watershed. We compared the rates of these processes in three soil horizons (to a soil depth of 30 cm) on a single sampling date and found a large decrease in both net N mineralization and nitrification with depth. We estimated that the soil total N pool was 6,909 kg N ha−1. The present study demonstrates the importance of the stock of mineral soil N in WS1, mostly organic N, which can be transformed to inorganic N and potentially exported to surface and ground water from this watershed. Additional studies quantifying the rates of soil N cycling, particularly multi-site comparisons within Taiwan and the East Asia–Pacific region, will greatly improve our understanding of regional patterns in nitrogen cycling.  相似文献   

3.
Abstract. Soil cores from river marginal wetlands from three sites in the UK (Torridge and Severn catchments), sampled and restrained in PVC piping, were flooded with dilute aqueous potassium nitrate. Half of the cores were sterilized prior to flooding to destroy the denitrifying bacteria. The change in nitrate concentration in the flood-water was measured over time. It is argued that the observed nitrate depletion rates (from 1.2 to 4.7 kg ha−1 d−1) is the result of microbially-mediated denitrification. The results show the method to be a simple and direct procedure for the assessment of spatial variation in nitrate-sink capacity. The depth of the denitrifying layer at the soil–water interface was confirmed to be of the order of a few mm only. A one-dimensional model for the diffusive flux in the flooded soil was developed which, on differentiation, gave a predictive expression for denitrification rate in terms of the effective soil diffusion coefficient for nitrate, the flood-water depth and concentration, and the thickness of the microbially active zone.  相似文献   

4.
We observed the presence of reduced sulfur compounds in the buried soil layer of a paddy field on Sado Island, Niigata Prefecture. We sampled the paddy field soil from 0 to 300 cm depth and analyzed the physico-chemical properties of the soil and the numbers of sulfur-oxidizing bacteria and iron-oxidizing bacteria in order to elucidate both the sulfur-oxidizing mechanism and the function of sulfur-oxidizing bacteria in the subsoil. Based on the physico-chemical properties of the soil, layers 4 and 5, which were located below 1 m in depth, were found to be potential acid sulfate soils and to be under semi-anaerobic conditions. However, the concentrations of water-soluble sulfate ions in layers 4 and 5 (88.2 to 444 mg S kg−1) were higher than those in layers 1 and 3 (16.1 and 8.29 mg S kg−1, respectively) and a significant number of sulfur-oxidizing bacteria (102–6 MPN g−1) was detected in layer 4. These results suggested that the oxidation of reduced sulfur compounds by sulfur-oxidizing bacteria had occurred in layer 4. Since no iron-oxidizing bacteria were detected in any layers, and it was reported that sulfur-oxidizing bacteria such as Acidithiobacillus thiooxidans could not oxidize pyrite directly, it was considered that the oxidation of the reduced sulfur compounds in layer 4 occurred through the following processes. At first, reduced sulfur compounds such as pyrite were oxidized chemically by ferric ions to intermediary sulfur compounds such as thiosulfate ions. Subsequently, sulfur-oxidizing bacteria in layer 4 oxidized these intermediary sulfur compounds to sulfate ions. However, it was considered that the oxidation rate of the reduced sulfur compounds in layer 4 was far slower than would occur under aerobic conditions.  相似文献   

5.
(pp. 825–831)
This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L−1.
For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg−1 dry soil or higher in the 0–30 cm layer; 38 kg ha−1 of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg−1 dry soil; 75 kg ha−1 of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg−1 dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L−1 from early harvest time to topping time under these conditions.  相似文献   

6.
The origin of highly acidic (pH<4.5) barren soils in the Klamath Mountains of northern California was examined. Soil parent material was mica schist that contained an average of 2,700 mg N kg−1, which corresponds to 7.1 Mg N ha−1 contained in a 10-cm thickness of bedrock. In situ soil solutions were dominated by H+, labile-monomeric Al3+ and NO3−, indicating that the barren area soils were nitrogen saturated—more mineral nitrogen available than required by biota. Leaching of excess NO3− has resulted in removal of nutrient cations and soil acidification. Nitrogen release rates from organic matter free soil ranged from 0.0163 to 0.0321 mg N kg−1 d−1. Nitrogen release rate from fresh ground rock was 0.0465 mg N kg−1 d−1. This study demonstrates that geologic nitrogen may represent a large and reactive nitrogen pool that can contribute significantly to soil acidification.  相似文献   

7.
To evaluate the selenium (Se) level in agricultural soils in Japan and to investigate its determining factors, 180 soil samples were collected from the surface layer of paddy or upland fields in Japan and their total Se contents were determined. Finely ground soil (50 mg) was wet-digested with HNO3 and HClO4 solution and the released Se was reduced to Se(IV). The concentration of Se(IV) was then determined by high-performance liquid chromatography with a fluorescence detector after treatment with 2,3-diaminonaphthalene and extraction with cyclohexane. The total Se content ranged from 0.05 to 2.80 mg kg−1 with geometric and arithmetic means of 0.43 and 0.51 mg kg−1, respectively. The overall data showed a log-normal distribution. In terms of soil type, volcanic soils and peat soils had relatively high Se content and regosols and gray lowland soils had relatively low Se content. In terms of land use, upland soils had significantly higher Se content than paddy soils. Among regions, soils in the Kanto, Tohoku, Hokkaido and Kyushu regions had relatively high content. The total Se content had a significant positive correlation with the organic carbon content ( P  < 0.01) and the equation for the estimation of total Se content with organic carbon suggested that on average approximately 48% (0.24 mg kg−1) of the total Se was in inorganic forms and approximately 52% (0.25 mg kg−1) was in organic forms. Soil pH, on the contrary, did not show a significant relationship with the total Se content. In conclusion, the organic matter content, in combination with volcanic materials, was the main determining factor of the total Se content of agricultural soils in Japan.  相似文献   

8.
The effect of lime (CaCO3) and phosphate additions on surface charge characteristics and their effect on the leaching of sulphate were examined for two soils (Patua loam and Tokomaru silt loam) which differed in their adsorption capacities for sulphate.
Incubation of soils with either CaCO3 (0–600 mmol kg−1) or phosphate (0-208 mmol kg−1) resulted in a two- to five-fold increase in the net negative charge and a similar decrease in the adsorption of sulphate. The effect of either lime or phosphate addition on both the surface charge and sulphate adsorption was more pronounced for the allophanic Patua soil than for the Tokomaru soil containing mainly vermiculite.
In a column experiment, liming induced the leaching of sulphur either by the desorp-tion of adsorbed sulphate or by the mineralization of organic sulphur. During a miscible displacement study, addition of either CaCO3 or phosphate resulted in an early breakthrough of sulphate in the leachate. In a pulse experiment, in which soils were incubated with sulphate (3.12 mmol kg−1) for 1 week and subsequently leached with water, more added sulphate was lost in the leachate of the soils previously incubated with either CaCO3 or phosphate.  相似文献   

9.
Emissions of nitrous oxide (N2O) and nitrogen gas (N2) from denitrification were measured using the acetylene inhibition method on drained and undrained clay soil during November 1980-June 1981. Drainage limited denitrification to about 65% of losses from undrained soil. Emissions from the undrained soil were in the range 1 to 12 g N ha–1 h–1 while those from the drained soil ranged from 0.5 to 6 g N ha–1 h–1 giving estimated total losses (N2O + N2) of 14 and 9 kgN ha–1.
Drainage also changed the fraction of nitrous oxide in the total denitrification product. During December, emissions from the drained soil (1.8±0.6 gN ha–1 h–1) were composed entirely of nitrous oxide, but losses from the undrained soil (2.7 ± 1.1 g N ha–1 h–1) were almost entirely in the form of nitrogen gas (the fraction of N2O in the total loss was 0.02). In February denitrification declined in colder conditions and the emission of nitrous oxide from drained soil declined relative to nitrogen gas so that the fraction of N2O was 0.03 on both drainage treatments. The delayed onset of N2O reduction in the drained soil was related to oxygen and nitrate concentrations. Fertilizer applications in the spring gave rise to maximum rates of emission (5–12g N ha–1 h–1) with the balance shifting towards nitrous oxide production, so that the fraction of N2O was 0.2–0.8 in April and May.  相似文献   

10.
Phosphate sorption was measured by the method of Barrow (1980) using a laboratory incubation procedure for up to 60 d on four soils which had different mineralogies but medium to high phosphate retention. All the soils had slow reactions where phosphate sorption continued, but at a decreasing rate, with time. The rate of decrease in the slow reactions was similar on all the soils. Phosphate became less available to plants during the slow reactions, and results of a pot trial with white clover showed that, on all the soils, phosphate incubated with the soils for 218 d was about 65% as effective as phosphate incubated for 10d.
When 700 mg P kg−1 was added to allophanic soils (Andisols), about 100 mg kg−1 was strongly adsorbed, about 200 mg kg−1 became unavailable in about 200 days and the remainder was weakly adsorbed. A similar result was obtained on Waiarikiki soil (Inceptisol), which contained ferrihydrite and Al-humus as the predominant reactive species. On the Kerikeri soil (Oxisol) about 150 mg P kg−1 became unavailable with time as a result of reactions with geothite, hematite and Al-humus.
The phosphate uptake by the microbial biomass was similar to the uptake by the clover, and immobilization of phosphate in the biomass can contribute to the loss of availability of phosphate in soils.  相似文献   

11.
  【目的】  反硝化作用导致农田土壤氮素损失和温室气体N2O的排放。研究不同作物茬口对土壤反硝化细菌群落结构的影响,旨在揭示作物茬口影响N2O排放的相关机制。  【方法】  定位试验位于黑龙江省海伦市前进乡光荣村(47°23′N,126°51′E),种植方式包括玉米连作(CC)、大豆连作(SS)以及玉米–大豆轮作,每年一季。取样时,轮作体系玉米已倒茬三次、大豆两次。采集CC、SS以及轮作体系中的大豆茬口(SSC)和玉米茬口(CSC)的表层土壤(0—15 cm)样品,利用实时定量PCR (qPCR)和高通量测序技术,分析土壤中的nirS和nirK型反硝化细菌丰度和群落组成。  【结果】  在4个作物茬口土壤中,CC处理的反硝化速率最高,玉米–大豆轮作体系中SSC和CSC处理的反硝化速率显著高于SS处理。轮作体系两个茬口SSC和CSC处理的nirS和nirK型反硝化细菌基因丰度多显著高于SS处理,而与CC处理多差异不显著。PCoA结果显示,SSC和CSC处理的nirS型反硝化细菌群落间差异显著,而CC和SS处理的nirK型反硝化细菌群落间存在显著差异。RDA分析结果表明,NO3–-N和C/N分别是nirS和nirK型反硝化细菌群落分异的最主要驱动因子。SEM分析结果显示,nirS型反硝化细菌群落与反硝化速率呈显著正相关(R2=0.92),而nirS和nirK型基因丰度与土壤反硝化速率无显著相关关系。  【结论】  作物茬口显著影响黑土农田土壤反硝化细菌群落和丰度组成。反硝化细菌群落组成而非反硝化细菌丰度是反硝化速率变化的决定性因素,nirS型反硝化细菌对土壤反硝化作用贡献更大。  相似文献   

12.
Potassium chlorate is widely used as an active substance for flower induction in longan plantation fields for off-season production of longan fruits in northern Thailand. Contamination of groundwater with residual chlorate in soil is a cause for concern because of its toxicity to human health. Based on our previous finding that the addition of glucose or sucrose to soil was effective for accelerating the disappearance of residual chlorate in soil, the effect of the addition of molasses, which contains a high concentration of sucrose, as a substitute for glucose or sucrose was examined in laboratory and pot experiments. Under laboratory conditions, the addition of molasses to soil at the concentrations of 100 to 200 g kg−1 soil strikingly enhanced the rate of disappearance of chlorate applied at 341 mg kg−1 soil. Addition of diluted molasses was also effective for the accelerated disappearance of chlorate in soil when 33 g kg−1 soil of molasses was added repeatedly. The effect of repeated addition of diluted molasses to soil on the decontamination of residual chlorate in soil was also confirmed in an outdoor pot experiment. These results may lead to the development of a practical method of cleaning-up chlorate-polluted soil in longan plantation fields.  相似文献   

13.
Amelioration of a highly alkaline soil by trees in northern India   总被引：2，自引：0，他引：2  
Abstract. A study was carried out to compare the impact of 6-year-old plantations of Prosopis juliflora (Swartz) D.C., Dalbergia sissoo Roxb. Ex. D.C. and Eucalyptus tereticornis Sm. on the physical and chemical properties of sodic soil in the Indo-Gangetic alluvial plains of Uttar Pradesh, India. Soil properties under the three tree species showed significant improvement through a reduction in the pH, electrical conductivity, exchangeable sodium percentage, CaCO3 and gypsum requirement, and by increase in organic C, total N, and available P and K. The six years of reclamation had achieved a marked reduction in exchangeable sodium (from 11.5 to 4.5 cmolc kg−1) to a depth of 1.5 m in the soil profile, whereas the levels of exchangeable calcium, magnesium and potassium had increased. There was also a significant reduction in soil bulk density (from 1.66 to 1.24 g cm−3) and increases in porosity, water holding capacity, field capacity, permeability and infiltration rate. The equilibrium infiltration rate after 455 min increased from 0.03 cm h−1 in the control to 0.13 cm h−1 under P juliflora and D. sissoo and 0.10 cm h−1 under E. tereticornis . It is concluded that salt-tolerant tree species have a significant impact on soil properties, which could help to rehabilitate the sodic wastelands in the region.  相似文献   

14.
Two field experiments commencing in winter (December) and spring (April) were conducted to determine the fate of nitrogen (N) in cattle slurry following application to grassland. In each experiment three methods of application were used: surface application, and injection ± the nitrification inhibitor, nitrapyrin. Slurry was applied at 80t ha−1, (≡248 kg total N ha−1 in the winter experiment, and 262 kg N ha−1 in the spring experiment). From slurry applied to the surface, total losses of N through NH3 volatilization, measured using a system of wind tunnels, were 77 and 53 kg N ha−1 respectively for the winter and spring experiments. Injection reduced the total NH3 volatilization loss to ∼2 kg N ha −1. Following surface application, loss by denitrification, measured using an adaptation of the acetylene-inhibition technique, was 30 and 5 kg N ha−1 for the two experiments. Larger denitrification losses were observed for the injected treatments; in the winter experiment the loss from the injected slurry without nitrapyrin was 53 kgN ha −1, and with nitrapyrin 23 kgN ha−1. Total denitrification losses for the corresponding injected treatments in the spring experiment were 18 and 14 kg N ha −1. Apparent recoveries of N in grass herbage in both experiments broadly reflected the differences between treatments in total gaseous loss.  相似文献   

15.
The present study aimed to elucidate ammonia (NH3) volatilization loss following surface incorporation (0–15 cm mixing depth) of nitrogen (N) fertilizer in an upland field of light-colored Andosol in central Japan. A dynamic chamber technique was used to measure the NH3 effluxes. Poultry manure, pelleted poultry manure, cattle manure, pelleted cattle manure and ammonium sulfate were used as N fertilizers for basal fertilization to a bare soil with surface incorporation. All three experiments in summer and autumn 2007 and in summer 2008 showed negligible NH3 volatilization losses following the application of all N fertilizers with the same application rate of 120 kg N ha−1 as total N; these negligible losses were primarily ascribed to chemical properties of the soil, that is, its high cation exchange capacity (283 mmolc kg−1 dry soil) and relatively low pH(H2O) (5.9). In addition, the surface incorporation, the very small ratio of ammoniacal N to total N for the manure, and the decrease in soil pH to ≤5.5 following applications of ammonium sulfate were also advantageous to the inhibition of NH3 volatilization loss from the field-applied N fertilizers.  相似文献   

16.
We used neutron radiography (NR), a non-invasive and in situ technique, to study living plant roots in soil. Plant roots have a larger water content than their unsaturated surrounding media. As water strongly attenuates a neutron-beam, NR can identify root structures in detail. We investigated the use of NR to visualize the root growth of lupin in quartz sand and in a loamy sand field soil. Further experiments elucidated the root growth of lupin in the loamy sand heterogeneously contaminated with 10 and 20 mg kg−1 boron (B) and 100 mg kg−1 zinc (Zn). We obtained high-quality images of root growth dynamics in both media with a resolution range of 110–270 μm. The images with quartz sand revealed fine structures such as proteoid roots that are difficult to locate in situ by other methods without destruction of the soil. Though quartz sand provided excellent visibility of roots, it proved to be a poor medium for growing plants, probably because of its bulk density (1.8 Mg m−3). The images with field soil showed normal root growth with slightly less contrast than the quartz sand. The poorer contrast was due to the greater neutron interaction with soil water and soil organic matter. In the heterogeneously contaminated soil, root growth was significantly reduced in the contaminated part of the soil in all B and Zn treatments. This study shows that NR has potential as a non-invasive method to investigate root growth over time as well as the response of roots to various abiotic stress factors.  相似文献   

17.
Gaseous N loss, through denitrification and NH3−volatilization, was monitored throughout the growing season after spring application of 15N labelled urea fertilizer to peaty gley soils supporting N-deficient Sitka spruce. From the 15N data, it was calculated that only about 0.28% of applied N was lost through NH3-volatilization, almost all within the first few days after fertilizer application. Approximately 0.05% of applied N was calculated to be lost through denitrification. Denitrification decreased slowly over a 4-month period after fertilizer application. Rates of NH3-volatilization correlated with available NH4+ in the litter layer, while for the early part of the study when N-losses were highest, denitrification rates correlated with available NO3− in the litter layer. Observations of gaseous N-loss are also discussed in relation to data from lysimetry, changes in soil pH, and the soil moisture regime.  相似文献   

18.
In a field experiment with soil compaction by tractor traffic on a loam soil, the denitrification rate (using the C2H2 inhibition method), the soil structure, and the wheat yield were investigated. Tractor traffic on wet soil (> – 50 mbar matric potential) reduced the pore volume, doubled the percentage of large aggregates (> 20 mm), reduced the wheat yield by about 25%, and increased the N-loss through denitrification by a factor of 3–4. Neither of these parameters were affected by tractor traffic at low soil moisture content. The weight of the tractor (1800 kg vs 4800 kg) did not significantly alter the effect of compaction on the measured parameters. There was a factor of 2–6 between the measured denitrification rate in compacted and that in uncompacted soil, and this factor showed little dependence on the average activity level on each date of measurement. Accumulated values for the measured denitrification during 75 days (May 23-August 9) were 3–5 kg N ha–1 in uncompacted soil and 15–20 kg N ha–1 in soil which was compacted in wet condition.  相似文献   

19.
Abstract. In order to optimize the management of the N-fertilizer inputs with drip fertigation on sandy-silt soil under apple tree orchard cultivation, we observed in situ: (i) the N and water soil transfers, (ii) the N levels in all leaves, fruits and annual shoots, and (iii) the root distribution. Then we used a mechanistic one-dimensional model (WAVE, Vanclooster et al. , 1994) to quantify the annual parameters of the water and nitrogen balance on a daily basis. The horizontal heterogeneity along the row of the tree-soil-dripper system has been treated with two adjacent compartments: one under the dripper and receiving fertigation and the other outside this zone. N transfers in the tree make it impossible to estimate directly N uptake by roots over time.
The simulated N losses were due to equal amounts of N leaching below 0.9 m deep (9 g N tree−1year−1 and denitrification (7 g N tree−1year−1. The simulated losses of gaseous N were localized predominantly in the compartment under the dripper and showed a higher rate of leaching during the period of N input when the wet conditions and the high NO3− concentrations were favourable to denitrification. The N-leaching at 0.9 m depth was greatest outside the growing season and was caused by the extension of the N-inputs after the harvest date. This practice, based on the objective to store nitrogen before the period of dormancy does not seem to be justified.  相似文献   

20.
An experiment was conducted in the laboratory on a cultivated soil incubated in serum bottles with a range of C-to-nitrate concentrations. C was added in form of glucose and nitrate in form of Ca(NO3)2. It was shown that an C-N concentration of respectively 500 μg C (glucose-equivalent, Glc-Eq.) and 36 μg N g− dry soil was optimal for denitrification. Results obtained either in the laboratory, in soil columns or in the field were in good agreement with one another. In particular, the root zone was shown to be favorable for denitrifying activity because the water-soluble C (Glc-Eq.) and N concentrations were more favorable than in bare soil. Furthermore, the water-soluble extractable Glc-Eq. appeared to be closely related to the denitrification rate and is thus likely to represent the energetic C pool supporting denitrification.

This was related to an inhibiting effect of increasing NO3− and NO2− concentrations on NO3− loss and N2O production. Such inhibition can affect short-term measurements of denitrification in the field.  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号