The impacts of inorganic nitrogen application on mineralization of C-labelled maize and glucose, and on priming effect in saline alkaline soil     

E. Conde 《Soil biology & biochemistry》2005,37(4):681-691

Organic matter dynamics and nutrient availability in saline alkaline soil of the former lake Texcoco will determine the success of a planned reforestation program. Uniformly labelled ¹⁴C-maize (MAI-treatment) and glucose (GLU-treatment) with or without 200 mg  kg⁻¹ soil (MAI-N treatment and GLU-N treatment, respectively) were added to soils with electrolytic conductivity (EC) 56 dS m⁻¹ (soil A) and 12 dS m⁻¹ (soil B) to investigate the importance of N availability on decomposition of organic material. Production of CO₂ and and inorganic N dynamics were monitored. The amount of ¹⁴C-glucose mineralized increased 1.8-times in the soil A, but had no effect in the soil B when 200 mg  kg⁻¹ soil was added, while the amount of ¹⁴C-maize mineralized increased 1.7 and 1.3-times when 200  kg⁻¹ soil was added in the soils A and B, respectively. Application of increased priming effect 3.7-times in the MAI-treatment of the soil A and 3.4-times in the GLU-treatment, while in the soil B the increase of priming effect was 4.1-times in the MAI-treatment and 3.7-times in the GLU-treatment. Of the 200 mg  kg⁻¹ added to both soils less than 10 mg NH₃-N kg⁻¹ was volatilized within one day, while 22 and 44 mg  kg⁻¹ soil was fixed on the soil matrix in the soil A and the soil B, respectively. Therefore more than 100 mg −N kg⁻¹ was immobilized into the microbial biomass within the first day. Concentration of nitrite increased sharply in all the treatments of soil A at the onset of the incubation followed by a decrease. A similar pattern was observed in the GLU-N and MAI-N treatments of the soil B, but not in the other treatments. A decrease in concentration of was observed in both soils followed by an increase in the MAI-N and GLU-N treatments of the soil B. It was found that application of had a stimulating effect on the decomposition of maize and glucose, and on the priming effect, while assimilatory reduction of resulted in an increase of in the soil A, and nitrification in the soil B.  相似文献   

Emission of N₂O, N₂ and CO₂ from soil fertilized with nitrate: effect of compaction, soil moisture and rewetting     

R. Ruser  H. Flessa  G. Schmidt  J.C. Munch 《Soil biology & biochemistry》2006,38(2):263-274

Soil compaction and soil moisture are important factors influencing denitrification and N₂O emission from fertilized soils. We analyzed the combined effects of these factors on the emission of N₂O, N₂ and CO₂ from undisturbed soil cores fertilized with (150 kg N ha⁻¹) in a laboratory experiment. The soil cores were collected from differently compacted areas in a potato field, i.e. the ridges (ρ_D=1.03 g cm⁻³), the interrow area (ρ_D=1.24 g cm⁻³), and the tractor compacted interrow area (ρ_D=1.64 g cm⁻³), and adjusted to constant soil moisture levels between 40 and 98% water-filled pore space (WFPS).High N₂O emissions were a result of denitrification and occurred at a WFPS≥70% in all compaction treatments. N₂ production occurred only at the highest soil moisture level (≥90% WFPS) but it was considerably smaller than the N₂O-N emission in most cases. There was no soil moisture effect on CO₂ emission from the differently compacted soils with the exception of the highest soil moisture level (98% WFPS) of the tractor-compacted soil in which soil respiration was significantly reduced. The maximum N₂O emission rates from all treatments occurred after rewetting of dry soil. This rewetting effect increased with the amount of water added. The results show the importance of increased carbon availability and associated respiratory O₂ consumption induced by soil drying and rewetting for the emissions of N₂O.  相似文献   

Land use effects on gross nitrogen mineralization, nitrification, and N₂O emissions in ephemeral wetlands     

Angela Bedard-Haughn  Amanda L. Matson  Dan J. Pennock 《Soil biology & biochemistry》2006,38(12):3398-3406

Stable ¹⁵N isotope dilution and tracer techniques were used in cultivated (C) and uncultivated (U) ephemeral wetlands in central Saskatchewan, Canada to: (1) quantify gross mineralization and nitrification rates and (2) estimate the relative proportion of N₂O emissions from these wetlands that could be attributed to denitrification versus nitrification-related processes. In-field incubation experiments were repeated in early May, mid-June and late July. Mean gross mineralization and nitrification rates (10.3 and 3.1 mg kg⁻¹ d⁻¹, respectively) did not differ between C and U wetlands on any given date. Despite these similarities, the mean NH₄⁺ pool size in the U wetlands (17.2 mg kg⁻¹) was two to three times that of the C wetlands (6.7 mg kg⁻¹) whereas the mean NO₃⁻ pool size in U wetlands (2.2 mg kg⁻¹) was less than half that of C wetlands (5.8 mg kg⁻¹). Mean N₂O emissions from the C wetlands decreased from 112.8 to 17.0 ng N₂O m² s⁻¹ from May to July, whereas mean U-wetland N₂O emissions ranged only from 31.8 to 51.1 ng N₂O m² s⁻¹ over the same period. This trend is correlated to water-filled pore space in C wetlands, demonstrating a soil moisture influence on emissions. Denitrification is generally considered the dominant emitter of N₂O under anaerobic conditions, but in the C wetlands, only 49% of the May emissions could be directly attributed to denitrification, decreasing to 29% in July. In contrast, more than 75% of the N₂O emissions from the U wetlands arose from denitrification of the soil NO₃⁻ pool throughout the season. These land use differences in emission sources and rates should be taken into consideration when planning management strategies for greenhouse gas mitigation.  相似文献   

Nitrite production by Nitrosomonas europaea and Nitrosospira sp. AV in soils at different solution concentrations of ammonium     

Anne E. Taylor  Peter J. Bottomley 《Soil biology & biochemistry》2006,38(4):828-836

Although it remains unclear why NH₃-oxidizing bacteria (AOB) of the genus Nitrosospira dominate soil environments, and why Nitrosomonas spp. are less common, virtually no studies have compared their behavior in soil. In this study, the NH₃ oxidation rates of Nitrosomonas europaea (ATCC 19718) and Nitrosospira sp. AV were compared in three differently textured soils containing a range of extractable contents (2-11 μg soil). Soils were adjusted to pH 7.0-7.4 with CaCO₃ and sterilized with γ-radiation. Cell suspensions of each bacterium were inoculated into the soils to bring them to two-third of water-holding capacity and cell densities ∼2.5×10⁶ g⁻¹ soil. In virtually all cases, rates of production for both N. europaea and Nitrosospira sp. AV were linear over 48 h, and represented between 13 and 75%, respectively, of the maximum rates achieved in soil-free bacterial suspensions. Soil solution concentrations that supported these rates ranged between 0.2 and 1.5 mM. Addition of 21-36 μg soil raised soil solution levels to 1.8-2.5 mM and stimulated production to a greater extent in N. europaea (3.3-6.6-fold) than in Nitrosospira sp. AV (1-2.1-fold). Maximum rates of production were obtained by raising soil solution levels to 3-4 mM with a supplement of ∼80-90 μg soil. K_s values in soil for Nitrosospira sp. AV and N. europaea were estimated as 0.14 and 1.9 mM , respectively, and estimates of V_max were about 3.5-times higher for N. europaea (0.007 pmol h⁻¹ cell⁻¹) than for Nitrosospira sp. AV (0.002 pmol h⁻¹ cell⁻¹). The cell density of N. europaea increased in sterile Steiwer soil independent of supplemental . In the case of treatments receiving supplemental , growth yields of N. europaea calculated from either produced or consumed were similar to those reported in literature (3.5×10⁶-6×10⁶ cells μmol⁻¹). A higher growth yield was measured in the case of zero added (2.7×10⁷ cells μmol⁻¹), indicating that use of organic carbon compounds might have occurred and resulted in some energy sparing. Our results suggest that Nitrosospira spp. with a K_s similar to Nitrosospira sp. AV may have an advantage for survival in soil environments where soil solution levels are less than 1 mM. However, it is apparent that AOB like N. europaea are poised to take advantages of modest increases in extractable that raise soil solution levels to about 2.0-2.5 mM.  相似文献   

Acceleration of N mineralization by release of enzymes and substrates from soil mineral particles with phosphates     

Anni Kokkonen  Martti Esala  Erkki Aura 《Soil biology & biochemistry》2006,38(3):504-508

A study was conducted to develop an improved method for measuring organic N (net) mineralization in which chemical extraction takes place in combination with suspension incubation in ammonia-absorbing membrane bottles. To obtain direct evidence of the extent to which extracted organic N is mineralizable, the extraction suspension was further incubated immediately after the extraction procedure with mild and selective extractants. In this ‘extraction incubation’ method, extraction continues during the incubation but only relatively easily mineralizable organic matter is released. Standard incubation is usually carried out in sealed N₂-flushed bottles. However, when phosphate or pyrophosphate soil suspensions are incubated, mineralization is much higher than in soil water suspensions. Further, accumulation of ammonia+(ammonium) and other gases, i.e. CO_2, can affect the reaction rate and final reaction equilibrium in the sealed incubation flask. It was to avoid these effects that the membrane method was developed. With this procedure, the flask is closed with an ammonia-absorbing membrane permeable to other gases. Water, phosphate and pyrophosphate suspensions were incubated at 37 °C in sealed bottles (SB), in sealed N₂ gas-flushed bottles (SBN₂), and in bottles with ammonia-trapping filters (MB). The maximum amount of released during 10 days' incubation was 133.0 mg kg⁻¹ in the water, 208.0 mg kg⁻¹ in the phosphate and 454.1 mg kg⁻¹ in the pyrophosphate suspension (soil total C content 6.2% and N 0.25%). During incubation in phosphate and pyrophosphate suspensions, the mobilization was nearly linear in membrane bottles. The variation between replicates was also smallest in these bottles. It was concluded that membrane bottles were best suited to incubation when mobilization reactions were accelerated with phosphate or pyrophosphate extractants. The method was easy to perform and gave results with good replicability.  相似文献   

Attempts to derive EC₅₀ values for heavy metals from land-applied Cu-, Ni-, and Zn-spiked sewage sludge     

Tom W. Speir  Andrew P. van Schaik  Janine L. Ryburn 《Soil biology & biochemistry》2007,39(2):539-549

We established a field trial to assess the impacts on soil biological properties of application of heavy metal-spiked sewage sludge, with the aim of determining toxicity threshold concentrations of heavy metals in soil. Plots were treated with sludges containing increasing concentrations of Cu, Ni and Zn in order to raise the metal concentrations in the soil by 0-200 mg Cu kg⁻¹, 0-60 mg Ni kg⁻¹ and 0-400 mg Zn kg⁻¹, and were then cultivated and sown in ryegrass-clover pasture and monitored annually for 6 years. All biological properties measured (soil basal respiration, microbial biomass C, and sulphatase enzyme activities), except phosphatase activity, increased in all plots over the duration of the experiment. Consequently, it was only possible to assess effects of heavy metals across time if, each year, all data for each metal were normalised by expressing them as percentages of the activities measured in an un-sludged control plot. When this was done, no significant effects of increasing heavy-metal concentrations on basal respiration, microbial biomass C or respiratory quotient (qCO₂) were observed, although total Cu and soil solution Cu were significantly negatively related to microbial biomass C when it was expressed as a proportion of soil total C. None of the properties measured were affected by increasing Ni concentrations. Phosphatase and sulphatase activities were significantly negatively related to increasing Zn concentrations, but not usually to increasing Cu unless they were expressed as a proportion of total C. A sigmoidal dose-response model was used to calculate EC₂₀ and EC₅₀ values using the normalised data, but generally, the model parameters had very large 95% confidence intervals and/or the fits to the model had small R² values. The factors primarily responsible for confounding these results were site and sample variations not accounted for by the normalisation process and the absence of any data points at metal concentrations beyond the calculated EC₅₀ values. In the few instances where reasonable EC₂₀ values could be calculated, they were relatively consistent across properties, e.g., EC₂₀ for total Zn and phosphatase (330 mg kg⁻¹), total Zn and sulphatase (310 mg kg⁻¹), and EC₂₀ for total Cu and sulphatase (140 mg kg⁻¹) and total Cu and microbial biomass C (140 mg kg⁻¹), when both sulphatase and microbial biomass C were expressed as a proportion of total C. Our results suggest that Cu and Zn at the upper concentrations used in this experiment were possibly having adverse effects on some soil biological properties. However, much higher metal concentrations will be needed to accurately calculate EC₂₀ and EC₅₀ and this may not be easily achievable without many applications of sewage sludge, even if the sludge is spiked with heavy metals.  相似文献   

Survival of rhizobia in soil is sensitive to elevated zinc in the absence of the host plant     

K. Broos  H. Beyens  E. Smolders 《Soil biology & biochemistry》2005,37(3):573-579

The survival of free-living rhizobia in soil is sensitive to elevated heavy metals in soil and can explain adverse effects of metals on symbiotic nitrogen fixation in soils. A survival experiment was set-up to derive critical cadmium (Cd) and zinc (Zn) concentrations in a range of field-contaminated soils in the absence of their host plant (Trifolium repens L.). Soils applied with metal salts or sewage sludge >10 years ago were sampled and were inoculated with Rhizobium leguminosarum bv. trifolii (10⁸ cells g⁻¹ soil) and incubated outdoors for up to 6 months. The most probable number (MPN) decreased 1-2 orders of magnitude in uncontaminated soils during the incubation. There was no significant effect of total metal concentrations on rhizobia survival in soils contaminated with Cd salts or with high Ni/Cd sewage sludge with highest Cd concentrations between 18 and 118 mg Cd kg⁻¹. In contrast, survival was strongly affected in soils contaminated by sewage sludge, where Zn was the principal metal contaminant. Neither total Cd nor soil solution Cd was large enough to attribute these effects to Cd when compared with the soil series, where Cd salts had been applied. The MPN decreased at least one order of magnitude above total Zn concentrations of 233 mg Zn kg⁻¹ (soil pH 5.6) and 876 mg Zn kg⁻¹ (soil pH 6.3). The EC50s of log MPN were 204 and 604 mg Zn kg⁻¹, respectively, and were lower than those for the symbiotic nitrogen fixation measured in the pot trial on the same soils (respectively 602 and 737 mg Zn kg⁻¹). This study corroborates the evidence that symbiotic nitrogen fixation is affected by Zn in the field when Zn decreases the free-living population of rhizobia to below a critical threshold.  相似文献   

Microbial activity in pig slurry-amended soils under semiarid conditions     

C. Plaza  D. Hernández  J.C. García-Gil  A. Polo 《Soil biology & biochemistry》2004,36(10):1577-1585

Soil amendment with manures from intensive animal industries is nowadays a common practice that may favorably or adversely affect several soil properties, including soil microbial activity. In this work, the effect of consecutive annual additions of pig slurry (PS) at rates of 30, 60, 90, 120 and 150 m³ ha⁻¹ y⁻¹ over a 4-year period on soil chemical properties and microbial activity was investigated and compared to that of an inorganic fertilization and a control (without amendment). Field plot experiment conducted under a continuous barley monoculture and semiarid conditions were used. Eight months after the fourth yearly PS and mineral fertilizer application (i.e. soon after the fourth barley harvest), surface soil samples (Ap horizon, 0-15 cm depth) from control and amended soils were collected and analysed for pH, electrical conductivity (EC), contents of total organic C, total N, available P and K, microbial biomass C, basal respiration and different enzymatic activities. The control soil had a slightly acidic pH (6.0), a small EC (0.07 dS m⁻¹), adequate levels of total N (1.2 g kg⁻¹) and available K (483 mg kg⁻¹) for barley growth, and small contents of total organic C (13.2 g kg⁻¹) and available P (52 mg kg⁻¹). With respect to the control and mineral fertilized soils, the PS-amended soils had greater pH values (around neutrality or slightly alkaline), electrical conductivities (still low) and contents of available P and K, and slightly larger total N contents. A significant decrease of total organic C was observed in soils amended at high slurry rate (12.3 g kg⁻¹). Compared with the control and mineral treatments, which produced almost similar results, the PS-amended soils were characterized by a higher microbial biomass C content (from 311 to 442 g kg⁻¹), microbial biomass C/total organic C ratio (from 2.3 to 3.6%) and dehydrogenase (from 35 to 173 μg INTF g⁻¹), catalase (from 5 to 24 μmol O₂ g⁻¹ min⁻¹), BAA-protease (from 0.7 to 1.9 μmol  g⁻¹ h⁻¹) and β-glucosidase (from 117 to 269 μmol PNP g⁻¹ h⁻¹) activities, similar basal respirations (from 48 to 77 μg C-CO₂ g⁻¹ d⁻¹) and urease activities (from 1.5 to 2.2 μmol  g⁻¹ h⁻¹), and smaller metabolic quotients (from 6.4 to 7.7 ng C-CO₂ μg⁻¹ biomass C h⁻¹) and phosphatese activities (from 374 to 159 μmol PNP g⁻¹ h⁻¹). For example, statistical analysis of experimental data showed that, with the exception of metabolic quotient and total organic C content, these effects generally increased with increasing cumulative amount of PS. In conclusion, cumulative PS application to soil over time under semiarid conditions may produce not only beneficial effects but also adverse effects on soil properties, such us the partial mineralization of soil organic C through extended microbial oxidation. Thus, PS should not be considered as a mature organic amendment and should be treated appropriately before it is applied to soil, so as to enhance its potential as a soil organic fertilizer.  相似文献   

Zinc toxicity on N₂O reduction declines with time in laboratory spiked soils and is undetectable in field contaminated soils     

K. De Brouwere  S. Hertigers  E. Smolders 《Soil biology & biochemistry》2007,39(12):3167-3176

Denitrification assays in soils spiked with zinc salt have shown inhibition of the N₂O reduction resulting in increased soil N₂O fluxes with increasing soil Zn concentration. It is unclear if the same is true for environmentally contaminated soils. Net production of N₂O and N₂ was monitored during anaerobic incubations (25 °C, He atmosphere) of soils freshly spiked with ZnCl₂ and of corresponding soils that were gradually enriched with metals (mainly Zn) in the field by previous sludge amendments or by corrosion of galvanized structures. Total denitrification activity (i.e. the sum of N₂O+N₂ production rate) was not inhibited by freshly added Zn salts up to 1600 mg Zn kg⁻¹, whereas N₂O reduction decreased by 50% (EC₅₀) at total Zn concentrations of 231 mg Zn kg⁻¹ (ZEV soil) and 368 mg Zn kg⁻¹ (TM soil). In contrast, N₂O reduction was not reduced by soil Zn in any of the field contaminated soils, even at total soil Zn or soil solution Zn concentrations exceeding more than 5 times corresponding EC₅₀'s of the freshly spiked soil. The absence of adverse effects in the field contaminated soils was unrelated to soil NO₃ or organic matter concentration. Ageing (2-8 weeks) and soil leaching after spiking reduced the toxicity of Zn on N₂O reduction, either expressed as total Zn or soil solution Zn, suggesting adaptation reactions. However, no full recovery after spiking was identified at the largest incubation period in one soil. In addition, the denitrification assay performed with sewage sludge showed elevated N₂O release in Zn contaminated sludges (>6000 mg Zn kg⁻¹ dry matter) whereas this was not observed in low Zn sludge (<1000 mg Zn kg⁻¹ dry matter) suggesting limits to adaptation reactions in the sludge particles. It is concluded that the use of soils spiked with Zn salts overestimates effects on N₂O reduction. Field data on N₂O fluxes in sludge amended soils are required to identify if metals indeed promote N₂O emissions in sludge amended soils.  相似文献   

CH₄ oxidation and N₂O emissions at varied soil water-filled pore spaces and headspace CH₄ concentrations     

M.I. Khalil  E.M. Baggs 《Soil biology & biochemistry》2005,37(10):1785-1794

Emission of N₂O and CH₄ oxidation rates were measured from soils of contrasting (30-75%) water-filled pore space (WFPS). Oxidation rates of ¹³C-CH₄ were determined after application of 10 μl ¹³C-CH₄ l⁻¹ (10 at. % excess ¹³C) to soil headspace and comparisons made with estimates from changes in net CH₄ emission in these treatments and under ambient CH₄ where no ¹³C-CH₄ had been applied. We found a significant effect of soil WFPS on ¹³C-CH₄ oxidation rates and evidence for oxidation of 2.2 μg ¹³C-CH₄ d⁻¹ occurring in the 75% WFPS soil, which may have been either aerobic oxidation occurring in aerobic microsites in this soil or anaerobic CH₄ oxidation. The lowest ¹³C-CH₄ oxidation rate was measured in the 30% WFPS soil and was attributed to inhibition of methanotroph activity in this dry soil. However, oxidation was lowest in the wetter soils when estimated from changes in concentration of ¹²⁺¹³C-CH₄. Thus, both methanogenesis and CH₄ oxidation may have been occurring simultaneously in these wet soils, indicating the advantage of using a stable isotope approach to determine oxidation rates. Application of ¹³C-CH₄ at 10 μl ¹³C-CH₄ l⁻¹ resulted in more rapid oxidation than under ambient CH₄ conditions, suggesting CH₄ oxidation in this soil was substrate limited, particularly in the wetter soils. Application of and (80 mg N kg soil⁻¹; 9.9 at.% excess ¹⁵N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N₂O emissions. The highest N₂O emission (119 μg ¹⁴⁺¹⁵N-N₂O kg soil⁻¹ over 72 h) was measured from the 75% WFPS soil and was mostly produced during denitrification (18.1 μg ¹⁵N-N₂O kg soil⁻¹; 90% of ¹⁵N-N₂O from this treatment). Strong negative correlations between ¹⁴⁺¹⁵N-N₂O emissions, denitrified ¹⁵N-N₂O emissions and ¹³C-CH₄ concentrations (r=−0.93 to −0.95, N₂O; r=−0.87 to −0.95, denitrified ¹⁵N-N₂O; P<0.05) suggest a close relationship between CH₄ oxidation and denitrification in our soil, the nature of which requires further investigation.  相似文献   

Heterotrophic and autotrophic nitrification in two acid pasture soils   总被引：1，自引：0，他引：1  

A. Islam  R.E. White 《Soil biology & biochemistry》2007,39(4):972-975

Laboratory incubation experiments, using ¹⁵N-labeling techniques and simple analytical models, were conducted to measure heterotrophic and autotrophic nitrification rates in two acid soils (pH 4.8-5.3; 1/5 in H₂O) with high organic carbon contents (6.2-6.8% in top 5 cm soil). The soils were from pastures located near Maindample and Ruffy in the Northeast Victoria, Australia. Gross rates of N mineralization, nitrification and immobilization were measured. The gross rates of autotrophic nitrification were 0.157 and 0.119 μg N g⁻¹ h⁻¹ and heterotrophic nitrification rates were 0.036 and 0.009 μg N g⁻¹ h⁻¹ for the Maindample and Ruffy soils, respectively. Heterotrophic nitrification accounted for 19% and 7% of the total nitrification in the Maindample and Ruffy soils, respectively. The heterotrophic nitrifiers used organic N compounds and no as the substrate for nitrification.  相似文献   

Short-term effects of single or combined application of mineral N fertilizer and cattle slurry on the fluxes of radiatively active trace gases from grassland soil     

K. Dittert  C. Lampe  K. Butterbach-Bahl  H. Papen  F. Taube 《Soil biology & biochemistry》2005,37(9):1665-1674

After implementation of legislative measures for the reduction of environmental hazards from nitrate leaching and ammonia volatilisation when using organic manures and fertilizers in Europe, much attention is now paid to the specific effects of these fertilizers on the dynamics of global warming-relevant trace gases in soil. Particularly nitrogen fertilizers and slurry from animal husbandry are known to play a key role for the CH₄ and N₂O fluxes from soils. Here we report on a short-term evaluation of trace gas fluxes in grassland as affected by single or combined application of mineral fertilizer and organic manure in early spring. Methane fluxes were characterised by a short methane emission event immediately after application of cattle slurry. Within the same day methane fluxes returned to negative, and on average over the 4-day period after slurry application, only a small but insignificant trend to reduced methane oxidation was found. Nitrous oxide emissions showed a pronounced effect of combined slurry and mineral fertilizer application. In particular fresh cattle slurry combined with calcium ammonium nitrate (CAN) mineral fertilizer induced an increase in mean N₂O flux during the first 4 days after application from 10 to 300 μg N₂O-N m⁻² h⁻¹. ¹⁵N analysis of emitted N₂O from ¹⁵N-labelled fertilizer or manure indicated that easily decomposable slurry C compounds induced a pronounced promotion of N₂O-N emission derived from mineral CAN fertilizer. Fluxes after application of either mineral fertilizer or slurry alone showed an increase of less than 5-fold. The NO_x sink strength of the soil was in the range of −6 to −10 μg NO_x-N m⁻² h⁻¹ and after fertilization it showed a tendency to be reduced by no more than 2 μg NO_x-N m⁻² h⁻¹, which was a result of both, increased NO emission and slightly increased NO₂ deposition. Associated determination of the N₂O:N₂ emission ratio revealed that after mineral N application (CAN) a large proportion (c. 50%) was emitted as N₂O, while after application of slurry with easily decomposable C and predominantly -N serving as N-source, the N₂O:N₂ emission ratio was 1:14, i.e. was changed in favour of N₂. Our work provides evidence that particularly the combination of slurry and nitrate-containing N fertilizers gives rise to considerable N₂O emissions from mineral fertilizer N pool.  相似文献   

Influence of selenium on oxidoreductive enzymes activity in soil and in plants     

Janina Nowak  Krzysztof Kaklewski 《Soil biology & biochemistry》2004,36(10):1553-1558

The aim of this greenhouse experiment was the assessment of the influence of H₂SeO₃ at soil concentrations of 0.05, 0.15 and 0.45 mmol kg⁻¹, on the activity of selected oxidoreductive enzymes in wheat (Triticum aestivum). The wheat plants were grown in 2 dm³ pots filled with dust-silt black soil of pH 7.7. Applied H₂SeO₃ caused activation of plant nitrate reductase at all concentrations, but activation of plant polyphenol oxidase at only two lower concentrations. The highest concentration caused inhibition of polyphenol oxidase and peroxidase. Plant catalase activity decreased under the influence of 0.15 and 0.45 mmol kg⁻¹ concentration. After the final analysis Se was quantified in plants and soil. The amounts in plants were: control (unamended soil) 1.95 mg kg⁻¹; I dose (0.05 mmol kg⁻¹) 18.27 mg kg⁻¹; II dose (0.15 mmol kg⁻¹) 33.20 mg kg⁻¹ and III dose (0.45 mmol kg⁻¹) 38.37 mg kg⁻¹, in soil: 0.265 mg kg⁻¹; 3.61 mg kg⁻¹; 10.53 mg kg⁻¹; 30.53 mg kg⁻¹; respectively. Simultaneously, a laboratory experiment was performed, where the activity of soil catalase and peroxidase were tested after 1, 3, 7, 14, 28, 56, and 112 days after Se treatment. Peroxidase activity in soil decreased with increasing Se content, over the whole experiment. The lowest dose of Se caused activation a significant 10% increase in catalase activity, but the influence of others doses was unclear.  相似文献   

Cyanobacterial inoculation of heated soils: effect on microorganisms of C and N cycles and on chemical composition in soil surface   总被引：2，自引：0，他引：2  

M.J Acea  A Prieto-FernándezN Diz-Cid 《Soil biology & biochemistry》2003,35(4):513-524

Physiological groups of soil microorganisms, total C and N and available nutrients were investigated in four heated (350 °C, 1 h) soils (one Ortic Podsol over sandstone and three Humic Cambisol over granite, schist or limestone) inoculated (1.5 μg chlorophyll a g⁻¹ soil or 3.0 μg chlorophyll a g⁻¹ soil) with four cyanobacterial strains of the genus Oscillatoria, Nostoc or Scytonema and a mixture of them.Cyanobacterial inoculation promoted the formation of microbiotic crusts which contained a relatively high number of NH₄⁺-producers (7.4×10⁹ g⁻¹ crust), starch-mineralizing microbes (1.7×10⁸ g⁻¹ crust), cellulose-mineralizing microbes (1.4×10⁶ g⁻¹ crust) and NO₂⁻ and NO₃⁻ producers (6.9×10⁴ and 7.3×10³ g⁻¹ crust, respectively). These crusts showed a wide range of C and N contents with an average of 293 g C kg⁻¹ crust and 50 g N kg⁻¹ crust, respectively. In general, Ca was the most abundant available nutrient (804 mg kg⁻¹ crust), followed by Mg (269 mg kg⁻¹ crust), K (173 mg kg⁻¹ crust), Na (164 mg kg⁻¹ crust) and P (129 mg kg⁻¹ crust). There were close positive correlations among all the biotic and abiotic components of the crusts.Biofertilization with cyanobacteria induced great microbial proliferation as well as high increases in organic matter and nutrients in the surface of the heated soils. In general, cellulolytics were increased by four logarithmic units, amylolytics and ammonifiers by three logarithmic units and nitrifiers by more than two logarithmic units. C and N contents rose an average of 275 g C kg⁻¹ soil and 50 g N kg⁻¹ soil while the C:N ratio decreased up to 7 units. Among the available nutrients the highest increase was for Ca (315 mg kg⁻¹ soil) followed by Mg (189 mg kg⁻¹ soil), K (111 mg kg⁻¹ soil), Na (109 mg kg⁻¹ soil) and P (89 mg kg⁻¹ soil). Fluctuations of the microbial groups as well as those of organic matter and nutrients were positively correlated.The efficacy of inoculation depended on both the type of soil and the class of inoculum. The best treatment was the mixture of the four strains and, whatever the inoculum used, the soil over lime showed the most developed crust followed by the soils over schist, granite and sandstone. In the medium term there were not significant differences between the two inocula amounts tested.These results showed that inoculation of burned soils with alien N₂-fixing cyanobacteria may be a biotechnological means of promoting microbiotic crust formation, enhancing C and N cycling microorganisms and increasing organic matter and nutrient contents in heated soils.  相似文献   

The role of plant residues in pH change of acid soils differing in initial pH     

J.M. Xu  C. Tang  Z.L. Chen 《Soil biology & biochemistry》2006,38(4):709-719

Reports on the effect of plant residues on soil pH have been contradictory. The conflicting accounts have been suggested to result from differences in compositions and types of plant residues and characteristics of soils. This incubation study examined the effect of plant residues differing in concentrations of N (3-49 g kg⁻¹) and of alkalinity (excess cations) (220-1560 mmol kg⁻¹) on pH change of three soils differing in initial pH (3.9-5.1 in 0.01 M CaCl₂). The addition of plant residues at a rate of 15 g kg⁻¹ soil weight increased the pH of all soils by up to 3.4 units and the pH reached the maximum at day 42 after incubation for Wodjil (initial pH 3.87) and Bodallin (pH 4.54) soils and day 14 for Lancelin soil (pH 5.1). The amount of pH buffering was decreased by residue addition in Wodjil soil, increased in Bodallin soil and remained unchanged in Lancelin soil, which closely related to changes of soil pH. Residue addition increased concentration and the increase in concentration generally correlated positively with the concentration of residue N. The concentration increased with time, reached the peak at Days 42-105 for Wodjil soil, Days 14-105 for Bodallin soil and Days 14-42 for Lancelin soil, and then decreased only in Lancelin soil. The concentration of was kept minimal in Wodjil and Bodallin soils. In Lancelin soil, concentrations increased with incubation time from days 14-28. Irrespective of plant residue and incubation time, the amounts of alkalinity produced due to residue addition correlated highly with the sum of the alkalinity added as plant residues (excess cations) and those resulting from mineralization of residue N, with the slope of regression lines decreasing with increase of the initial soil pH. Direct shaking of soil with the residues at the same rate of alkalinity (excess cations) under sterile conditions increased the pH of the Wodjil soil but decreased it in the Lancelin soil. It is suggested that the decarboxylation of organic anions (as indicated by excess cations) of added plant residues and ammonification of the residue N causes soil pH increase whereas nitrification of mineralised residue nitrogen causes soil pH decrease, and that the association/dissociation of organic compounds also plays a role in soil pH change, depending initial pH of the soil. The overall effect on soil pH after addition of plant residues would therefore depend on the extent of each of these processes under given conditions.  相似文献   

Heavy metal accumulation by two earthworm species and its relationship to total and DTPA-extractable metals in soils   总被引：1，自引：0，他引：1  

Jun Dai  Thierry Becquer  Georges Reversat  Johanne Nahmani 《Soil biology & biochemistry》2004,36(1):91-98

The concentrations of Zn, Cd, Pb and Cu in earthworm tissues were compared with the total and DTPA-extractable contents of these heavy metals in contaminated soils. Samples were taken from a pasture polluted by waste from a metallurgic industry over 70 y ago. Three individuals of Aporrectodea caliginosa and Lumbricus rubellus and soil samples were collected at six points along a gradient of increasing pollution. Total metal contents of earthworms, soil, and metals extracted by DTPA from the soil were measured. Total heavy metal contents of the soils ranged from 165.7 to 1231.7 mg Zn kg⁻¹, 2.7 to 5.2 mg Cd kg⁻¹, 45.8 to 465.5 mg Pb kg⁻¹ and 30.0 to 107.5 mg Cu kg⁻¹. Their correlations with metals extracted by DTPA were highly significant. Contents of the metals in earthworm tissues were higher in A. caliginosa than in L. rubellus, with values ranging from 556 to 3381 mg Zn kg⁻¹, 11.6 to 102.9 mg Cd kg⁻¹, 1.9 to 182.8 mg Pb kg⁻¹ and 17.9 to 35.9 mg Cu kg⁻¹ in A. caliginosa, and from 667.9 to 2645 mg Zn kg⁻¹, 7.7 to 26.3 mg Cd kg⁻¹, 0.5 to 37.9 mg Pb kg⁻¹ and 16.0 to 37.6 mg Cu kg⁻¹ in L. rubellus, respectively. Correlations between body loads in earthworms with either total or DTPA-extractable contents of soil metals were significant, except for Cd in L. rubellus and Cu in A. caliginosa. Considering its simple analytical procedure, DTPA-extractable fraction may be preferable to total metal content as a predictor of bio-concentrations of heavy metals in earthworms. Biota-to-Soil Accumulation Factor (BSAF) of these four metals are Cd>Zn>Cu>Pb, with range of mean values between: Cd (6.18-17.02), Zn (1.95-7.91), Cu (0.27-0.89) and Pb (0.08-0.38) in A. caliginosa, and Cd (3.64-6.34), Zn (1.5-6.35), Cu (0.29-0.87) and Pb (0.04-0.13) in L. rubellus. The BSAF of Ca, Fe and Mn are Ca>Mn>Fe, with mean values of: Ca (0.46-1.31), Mn (0.041-0.111), Fe (0.017-0.07) in A. caliginosa and Ca (0.98-2.13), Mn (0.14-0.23), Fe (0.019-0.048) in L. rubellus, respectively. Results of principal component analysis showed that the two earthworm species differ in the pattern of metal bioaccumulation which is related to their ecological roles in contaminated soils.  相似文献   

Immobilization and remineralization of N following addition of wheat straw into soil: determination of gross N transformation rates by N-ammonium isotope dilution technique     

H. Shindo  T. Nishio 《Soil biology & biochemistry》2005,37(3):425-432

N dynamics in soil where wheat straw was incorporated were investigated by a soil incubation experiment using ¹⁵N-labelled nitrate or ¹⁵N-labelled wheat straw. The incubated soils were sampled after 7, 28, 54 days from the incorporation of wheat straw, respectively, and gross rates of N transformations including N remineralization and temporal changes in the amount of microbial biomass were determined.Following the addition of wheat straw into soils, rapid decrease of nitrate content in soil and increase of microbial biomass C and N occurred within the first week from onset of the experiment. Both the gross rates of mineralization and immobilization determined by ¹⁵N-ammonium isotope dilution technique were remarkably enhanced by the addition of wheat straw, and gradually decreased with time. Remineralization rate of N derived from ¹⁵N-labelled nitrate, and mineralization rate of N derived from ¹⁵N-labelled wheat straw was estimated by ¹⁵N isotope dilution technique using non-labelled ammonium. Remineralization rates of N derived from ¹⁵N-labelled nitrate were calculated to be 0.71 mg N kg⁻¹ d⁻¹ after 7 days, 0.55 mg N kg⁻¹ d⁻¹ after 28 days, and 0.29 mg N kg⁻¹ d⁻¹ after 54 days.Nearly 10% of the ¹⁵N-labelled N originally contained in the wheat straw was held in the microbial biomass irrespective of the sampling time. The amount of inorganic N in soil which was derived from ¹⁵N-labelled wheat straw ranged between 1.93 and 2.37 mg N kg⁻¹.Rates of N transformations in soil with ¹⁵N-labelled wheat straw were obtained by assuming that the k value was equal to the ¹⁵N abundance of biomass N, and the obtained values were considered to be valid.  相似文献   

Denitrification enzyme activity and potential of subsoils under grazed grasslands assayed by membrane inlet mass spectrometer     

M.I. Khalil  K.G. Richards 《Soil biology & biochemistry》2011,43(9):1787-1797

The importance of subsoil denitrification on the fate of agriculturally derived nitrate (NO₃) leached to groundwater is crucial for budgeting N in an ecosystem and for identifying areas where the risk of excess NO₃ is reduced. However, the high atmospheric background of di-nitrogen (N₂) causes difficulties in assessing denitrification enzyme activity (DEA) and denitrification potential (DP) in soils directly. Here, we apply Membrane Inlet Mass Spectrometry (MIMS) technique to investigate indirectly DEA and DP in soils by measuring N₂/Ar ratio changes in headspace water over soil. Soils were collected from 0-10, 15-25 and 60-70 cm depths of a grazed ryegrass and grass-clover. The samples were amended with helium-flushed deionized water containing ranges of NO₃ and carbon (glucose-C) and were incubated for six hours in the dark at 21 °C. The peaks for N₂/Ar ratio, declined with increasing soil depth, indicating a reduced substrate requirements to initiate DEA en-masse (15-30 mg NO₃-N alone or with 60-120 mg glucose-C, kg⁻¹ soil). The dissolved N₂O concentrations were very small (0.004-0.269 μg N kg⁻¹ soil) but responded well to the added N and C, showing a reduction in DEA with soil depth. In three separate studies, only subsoils were incubated for 3 days at 12 °C with 20-30 mg NO₃-N ± 40-60 mg glucose-C, kg⁻¹ soil. Denitrification capacity (DC, NO₃ only treatment) was not statistically different to the control (no amendment) within a land use (0.03-0.05 vs. 0.07-0.22 mg N kg⁻¹ soil d⁻¹), the highest being in ryegrass subsoils receiving groundwater. The DP was significantly (P < 0.0001) higher in subsoils under ryegrass than under grass-clover (0.50-0.71 vs. 1.15 mg N kg⁻¹ soil d⁻¹). The rates of DP (NO₃ + glucose-C) increased significantly (P < 0.0001) in unsaturated and saturated subsoils (0.92 and 2.19 mg N kg⁻¹ soil d⁻¹, respectively) of grass-clover, due to the higher reductive state resulting from the 10 day pre-incubation. Available C accelerated denitrification in soils and superseded the temporary elevation in oxidative state due to NO₃ addition. The substrates load differences between the land uses regulated the degree of denitrification rates. Results suggest that both dissolved N₂O measured by gas chromatography and N₂/Ar ratio measured by MIMS to indirectly determine DEA, and the latter to quantify total DC/DP in soils can be used. However, interference of oxygen in the MIMS system should be considered if available C is added or is naturally elevated in soil or groundwater.  相似文献   

Enzyme activities and microbial biomass in coastal soils of India   总被引：1，自引：0，他引：1  

Sudipta Tripathi  Ashis Chakraborty  Bimal Kumar Bandyopadhyay 《Soil biology & biochemistry》2007,39(11):2840-2848

Soil salinity is a serious problem for agriculture in coastal regions, wherein salinity is temporal in nature. We studied the effect of salinity, in summer, monsoon and winter seasons, on microbial biomass carbon (MBC) and enzyme activities (EAs) of the salt-affected soils of the coastal region of the Bay of Bengal, Sundarbans, India. The average pH of soils collected from different sites, during different seasons varied from 4.8 to 7.8. The average organic C (OC) and total N (TN) content of the soils ranged between 5.2-14.1 and 0.6-1.4 g kg⁻¹, respectively. The electrical conductivity of the saturation extract (ECe) of soils, averaged over season, varied from 2.2 to 16.3 dSm⁻¹. The ECe of the soils increased five fold during the summer season (13.8 dSm⁻¹) than the monsoon season (2.7 dSm⁻¹). The major cation and anion detected were Na⁺ and Cl⁻, respectively. Seasonality exerted considerable effects on MBC and soil EAs, with the lowest values recorded during the summer season. The activities of β-glucosidase, urease, acid phosphatase and alkaline phosphatase were similar during the winter and monsoon season. The dehydrogenase activity of soils was higher in monsoon than in winter. Average MBC, dehydrogenase, β-glucosidase, urease, acid phosphatase and alkaline phosphatase activities of the saline soils ranged from 125 to 346 mg kg⁻¹ oven dry soil, 6-9.9 mg triphenyl formazan (TPF) kg⁻¹ oven dry soil h⁻¹, 18-53 mg p-nitro phenol (PNP) kg⁻¹ oven dry soil h⁻¹, 38-86 mg urea hydrolyzed kg⁻¹ oven dry soil h⁻¹, 213-584 mg PNP kg⁻¹ oven dry soil h⁻¹ and 176-362 mg PNP g⁻¹ oven dry soil h⁻¹, respectively. The same for the non-saline soils were 274-446 mg kg⁻¹ oven dry soil, 8.8-14.4 mg TPF kg⁻¹ oven dry soil h⁻¹, 41-80 mg PNP kg⁻¹ oven dry soil h⁻¹, 89-134 mg urea hydrolyzed kg⁻¹ oven dry soil h⁻¹, 219-287 mg PNP kg⁻¹ oven dry soil h⁻¹ and 407-417 mg PNP kg⁻¹ oven dry soil h⁻¹, respectively. About 48%, 82%, 48%, 63%, 40% and 48% variation in MBC, dehydrogenase activity, β-glucosidase activity, urease activity, acid phosphatase activity and alkaline phosphatase activity, respectively, could be explained by the variation in ECe of saline soils. Suppression of EAs of the coastal soils during summer due to salinity rise is of immense agronomic significance and needs suitable interventions for sustainable crop production.  相似文献   

Nitrous oxide production of heavy metal contaminated soil     

M.S. Vásquez-Murrieta  N. Trujillo-Tapia  B. Govaerts  L. Dendooven 《Soil biology & biochemistry》2006,38(5):931-940

Arsenic (As), lead (Pb), copper (Cu) and zinc (Zn) can be found in large concentrations in mine spills of central and northern Mexico. Interest in these heavy metals has increased recently as they contaminate drinking water and aquifers in large parts of the world and severely affect human health, but little is known about how they affect biological functioning of soil. Soils were sampled in seven locations along a gradient of heavy metal contamination with distance from a mine in San Luis Potosí (Mexico), active since about 1800 AD. C mineralization and N₂O production were monitored in an aerobic incubation experiment. Concentrations of As in the top 0-10 cm soil layer ranged from 8 to 22,992 mg kg⁻¹, from 31 to 1845 mg kg⁻¹ for Pb, from 27 to 1620 mg kg⁻¹ for Cu and from 81 to 4218 mg kg⁻¹ for Zn. There was a significant negative correlation between production rates of CO₂ and concentrations of As, Pb, Cu and Zn, and there was a significant positive correlation with pH, water holding capacity (WHC), total N and soil organic C. There was a significant negative correlation (P<0.05) between production rate of nitrous oxide (N₂O) attributed to nitrification by the inhibition method in soil incubated at 50% WHC and total concentrations of Pb and Zn, and there was a significant positive correlation (P<0.05) with pH and total N content. There was a significant negative correlation (P<0.05) between the production rate of N₂O attributed to denitrification by the inhibition method in soil incubated at 100% WHC and total concentrations of Pb, Cu and Zn, and a significant positive correlation (P<0.01) with pH; there was a significant positive correlation (P<0.05) between the production of N₂O attributed to other processes by the inhibition method and WHC, inorganic C and clay content. A negative value for production rate of N₂O attributed to nitrifier denitrification by the inhibition method was obtained at 100% WHC. The large concentrations of heavy metals in soil inhibited microbial activity and the production rate of N₂O attributed to nitrification by the inhibition method when soil was incubated at 50% WHC and denitrification when soil was incubated at 100% WHC. The inhibitor/suppression technique used appeared to be flawed, as negative values for nitrifier denitrification were obtained and as the production rate of N₂O through denitrification increased when soil was incubated with C₂H₂.  相似文献