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1.
The ecological dose (ED50) of Cd on alkaline and acid phosphatase activity and the ATP content of three contrasting forest soils was measured with or without Cu and Zn to assess the additive toxic effects of these two metals. Soils polluted with Cu and/or Zn were treated with increasing Cd concentrations to give the following metal combinations: Cd, Cd+Cu, Cd+Zn and Cd+Cu+Zn. Alkaline and acid phosphatase activities and ATP content of the three soils were analysed 4 h, 7 and 28 days after the metal additions. The ED50 values were obtained by interpolating the enzyme activities or ATP data with a kinetic model and the goodness of fit was satisfactory.Generally, the ED50 values of both acid and alkaline phosphatase activities for Cd were lower (higher toxicity) with than without Cu and Zn and the effect of Cu and Zn was particularly adverse when these two metals were both added to soils. The alkaline phosphatase was more sensitive in the acid and neutral soil whereas the acid phosphatase was more sensitive in the alkaline soil. Both phosphatase activities and the ATP content were more sensitive in the sandy than in the finer textured soils. The ATP content was less sensitive to the additive effects. Increasing toxicity was observed during the incubation.Analysis of 1 M NH4NO3-extractable Cd, Cu and Zn revealed that Cd competed with Zn for the adsorption sites but not with Cu. However, the lower ED50 values for Cd of the two phosphatase activities and of the ATP content in the presence of heavy metal combinations could be not explained by the heavy metal solubility data. It is concluded that the ED50 may be a sensitive tool for assessing additve toxic effects to soil biochemical parameters.  相似文献   

2.
The bioremediation effects of three biostimulants (BS): WCDS, wheat condensed distillers soluble; PAHE, hydrolyzed poultry feathers; and RB, rice bran extract in a soil polluted with two rates of benzo(a)pyrene (BaP) (50 or 100 mg kg−1 soil, respectively) over 90 days were studied. Their effects on the soil biochemical properties (ATP and urease and phosphatase activities) and ergosterol were determined. Also, extractable BaP in soils was determined during the incubation period. An non-polluted and non-organic-amended soil was used as control. The results indicated that at the end of the incubation period and compared with the control soil, the ATP, ergosterol, urease and phosphatase activities decreased 29.4%, 24.8%, 44.7% and 42.9%, respectively in the non-organic amended soil polluted with polluted 100 mg BaP kg−1 soil. The application of biostimulants to unpolluted soil increased the biochemical parameters. However, this stimulation was higher in the soil amended with PAHE, followed by RB and WCDS. The application of BaP in organic-amended soils decreased the biochemical properties. However, this decrease was lower than for the non-amended BaP polluted soil. Possibly the low molecular weight protein content easily assimilated by soil microorganisms is responsible for less inhibition of these soil biochemical parameters.  相似文献   

3.
The effects of adding a crushed cotton gin compost (CCGC) and poultry manure (PM) on the biological properties of a Typic Xerofluvent soil contaminated with Ni were studied in the laboratory. Urease, BBA-protease, alkaline phosphatase, β-glucosidase and arylsulfatase activities were measured in soils containing seven concentrations (100, 250, 500, 1000, 2500, 5000 and 8000 mg kg−1 soil) of Ni after four incubation times (1 day, 7 days, 15 days and 45 days). The resulting inhibition was compared with that of the enzymatic activities in the same soil containing similar concentrations of the Ni but amended with crushed cotton gin compost and poultry manure. The 50% ecological dose (ED50) values were calculated by the two kinetic models used by Speir et al. [T.W. Speir, H.A. Kettles, A. Parshotam, P.L. Searle, L.N.C. Vlaar, A simple kinetic approach to derive the ecological dose value, ED50, for the assessment of Cr(VI) toxicity to soil biological properties, Soil Biol. Biochem. 27 (1995) 801–810] and by the sigmoidal dose–response model used by Haanstra et al. [L. Haanstra, P. Doelman, J.H. Oude Voshaar, The use of sigmoidal dose response curves in soil ecotoxicological research, Plant Soil 84 (1985) 293–297]. The urease, BBA-protease, β-glucosidase, alkaline phosphatase and arylsulfatase activities were higher in the organic amended soils (76%, >99.7%, >95.7%, >27.6% and >87.2%, respectively) than in the control soil. Also, the enzymatic activities were higher in CCGC-amended soils than in the PM-amended soils (51%, 20%, 11.2%, and 11.3% increase for urease, BBA-protease, β-glucosidase and alkaline phosphatase, respectively). For all soil enzymatic activities and at the end of the period of incubation, the ED50 values were lowest in control soil, followed by PM and CGCC-amended soils. This may have been due to the adsorption capacity of Ni being higher in the humic acid (CGCC) than in the fulvic acid-amended soil (PM).  相似文献   

4.
The ultimate goal of soil remediation is to restore soil health. Soil microbial parameters are considered to be effective indicators of soil health. The aim of this study was to determine the effects of phytoextraction on microbial properties through the measurement of soil microbial biomass carbon, soil basal respiration and enzyme activities. For this purpose, a pre-stratified rhizobox experiment was conducted with the Cd hyperaccumulator Sedum alfredii H. for phytoextraction Cd from an artificial contaminated soil (15.81 mg kg−1) under greenhouse conditions. The plant and soil samples were collected after growing the plant for three and six months with three replications. The results indicated that the ecotype of S. alfredii H. originating from an ancient silver mining site was a Cd-hyperaccumulator as it showed high tolerance to Cd stress, the shoot Cd concentration were as high as 922.6 mg kg−1 and 581.9 mg kg−1 at the two samplings, and it also showed high BF (58.4 and 36.8 after 3 and 6 months growth), and TF (5.8 and 5.1 after 3 and 6 months growth). The amounts of Cd accumulated in the shoots of S. alfredii reached to an average of 1206 μg plant−1 after 6 months growth. Basal respiration, invertase and acid phosphatase activities of the rhizosphere soil separated by the shaking method were significantly higher (P < 0.01) than that of the near-rhizosphere soil and the unplanted soil after 3 months growth, so were microbial biomass carbon, urease, invertase and acid phosphatase activities of the rhizosphere soil after 6 months growth. Acid phosphatase activity of the 0–2 mm sub-layer rhizosphere soil collected by the pre-stratified method after 3 months growth was significantly higher (P < 0.05) than that of other sub-layer rhizosphere soils and bulk soil, and so were microbial biomass carbon, basal respiration, urease, invertase and acid phosphatase activities of the 0–2 mm sub-layer rhizosphere soil after 6 months growth. It was concluded that phytoextraction by S. alfredii could improve soil microbial properties, especially in rhizosphere, and this plant poses a great potential for the remediation of Cd contaminated soil.  相似文献   

5.
Mineral fertilizers, organic amendments, and pesticides are inputs commonly used in conventional farming practices. The aim of this study was to evaluate the effects of single or combined applications of spent grape marc-vermicompost, urea, and/or diuron on soil-enzyme activities and the persistence of this herbicide in soils with low organic carbon content. The application of vermicompost enhanced dehydrogenase (DHase) enzyme activity over time but altered soil urease activity to a very limited extent. The reduction in diuron concentrations and the increase in DHase activity indicated that the soil microorganisms were capable of degrading the ureic herbicide. Treatment with vermicompost and diuron had a stimulatory effect on soil microbial activity. On the whole, the application of diuron and urea to the vermicompost-amended soil raised DHase and urease activity to maximum levels (>3 μg INTF g?1 h?1 and >47 μg NH4+ g?1 h?1, respectively). The application of urea to the unamended and vermicompost-amended soil decreased diuron persistence from 18.8 and 33 d to 12.5 and 15 d, respectively. Our findings show that although vermicompost additions reduce diuron availability, this boosts diuron degradation when combined with urea. These additions, under different soil management conditions, minimize the bioavailability and persistence of diuron and consequently the risk of leaching and seepage into aquifers. Compared with untreated soils, these types of treated soils could also improve agricultural sustainability and the quality of the environment.  相似文献   

6.
Arbuscular mycorrhizal fungus (AMF) can enhance plant growth and resistance to toxicity produced by heavy metals (HMs), affect the bioavailability of HMs in soil and the uptake of HMs by plants, and thus has been emerged as the most prominent symbiotic fungus for contribution to phytoremediation. A greenhouse pot experiment was conducted to assess the effect of Glomus versiforme BGC GD01C (Gv) on the growth and Cd accumulation of Cd-hyperaccumulator Solanum nigrum in different Cd-added soils (0, 25, 50, 100 mg Cd kg−1 soil). Mycorrhizal colonization rates were generally high (from 71% to 82%) in Gv-inoculated treatments at all Cd levels. Gv colonization enhanced soil acid phosphatase activity, and hence elevated P acquisition and growth of S. nigrum at all Cd levels. Moreover, the presence of Gv significantly increased DTPA-extractable (phytoavailable) Cd concentrations in 25 and 50 mg Cd kg−1 soils, but did not affect phytoavailable Cd in 100 mg Cd kg−1 soil. Similarly, inoculation with Gv significantly increased Cd concentrations of S. nigrum in 25 and 50 mg Cd kg−1 soils, but decreased Cd concentrations of the plants in 100 mg Cd kg−1 soil. Overall, inoculation with Gv greatly improved the total Cd uptakes in all plant tissues at all Cd levels. The present results indicated that S. nigrum associated with Gv effectively improved the Cd uptake by plant and would be a new strategy in microbe-assisted phytoremediation for Cd-contaminated soils.  相似文献   

7.
《Applied soil ecology》2010,46(3):144-151
Soil microbial activity plays a crucial role in soil microbiological processes, which can be used as a useful indicator to determine the ecological effects of heavy metal pollution on soils. The objective was to determine the effects of heavy metal pollution on mining soils at the Lawu mine of central Tibet, China on soil enzyme activities (sucrase, urease and acid phosphatase), microbial biomass C, N and P (MBC, MBN, and MBP), basal respiration, metabolic quotients, and N mineralization. Sixteen soil samples around the mine were sampled, and one soil sample, 2 km from the mine center, was taken as the control. Compared to the control, mining soils were polluted by heavy metals, Cu, Zn, Pb and Cd, resulting in decreases of sucrase activities, urease activities, acid phosphatase activities, MBC, MBN, MBP, and N mineralization, and increases of basal respiration and qCO2. Multivariate analysis (cluster analysis [CA], principle component analysis [PCA] and canonical correlation analysis [CCA]) indicated nine microbial variables were only reduced to one principal component explaining 72% of the original variances, and MBC (R2 = 0.93) had the highest positive loadings on the principal component. Mining soils polluted by heavy metals were perfectly clustered into four groups, which were highly distinguished by MBC. There were significant canonical correlations between soil heavy metals and microbial indexes on two canonical variates (R1 = 0.99, p < 0.001; R2 = 0.97, p < 0.01), which further demonstrated significant correlations between soil heavy metal contents and microbial characteristics. Hence, our results suggested that MBC may be used a sensitive indicator for assessing changes in soil environmental quality in metal mine of central Tibet.  相似文献   

8.
Earthworms and arbuscular mycorrhizal fungi (AMF) are known to independently affect soil microbial and biochemical properties, in particular soil microbial biomass (SMB) and enzymes. However, less information is available about their interactive effects, particularly in soils contaminated with heavy metals such as cadmium (Cd). The amount of soil microbial biomass C (MBC), the rate of soil respiration (SRR) and the activities of urease and alkaline phosphatase (ALP) were measured in a calcareous soil artificially spiked with Cd (10 and 20 mg Cd kg−1), inoculated with earthworm (Lumbricus rubellus L.), and AMF (Glomus intraradices and Glomus mosseae species) under maize (Zea mays L.) crop for 60 days. Results showed that the quantity of MBC, SRR and enzyme activities decreased with increasing Cd levels as a result of the elevated exchangeable Cd concentration. Earthworm addition increased soil exchangeable Cd levels, while AMF and their interaction with earthworms had no influence on this fraction of Cd. Earthworm activity resulted in no change in soil MBC, while inoculation with both AMF species significantly enhanced soil MBC contents. However, the presence of earthworms lowered soil MBC when inoculated with G. mosseae fungi, showing an interaction between the two organisms. Soil enzyme activities and SRR values tended to increase considerably with the inoculation of both earthworms and AMF. Nevertheless, earthworm activity did not affect ALP activity when inoculated with G. mosseae fungi, while the presence of earthworm enhanced urease activity only with G. intraradices species. The increases in enzyme activities and SRR were better ascribed to changes in soil organic carbon (OC), MBC and dissolved organic carbon (DOC) contents. In summary, results demonstrated that the influence of earthworms alone on Cd availability is more important than that of AMF in Cd-polluted soils; and that the interaction effects between these organisms on soil microorganism are much more important than on Cd availability. Thus, the presence of both earthworms and AMF could alleviate Cd effects on soil microbial life.  相似文献   

9.
The purpose of this study was to investigate the effects of high cadmium and nickel soil concentrations on selected physiological parameters of Arundo donax L. A 2-year pot experiment was held in the field and the pots were irrigated with aqueous solutions of Cd and Ni in concentrations of 5, 50 and 100 ppm, against the control (tap water). At the end of the cultivation periods the pots soil was divided into three equal zones and total and NH4OAc extractable Cd and Ni concentrations were determined. The top zone exhibited the highest metal content. Cadmium and nickel total concentrations at the end of the experiment were up to 973.8 mg kg−1 and 2543.3 mg kg−1 respectively, while NH4OAc extractable Cd was up to 291.7 mg kg−1 and Ni up to 510.3 mg kg−1. Stomatal conductance ranged between 0.3 and 0.8 mol CO2 m−2 s−1, intercellular CO2 concentration ranged between 212.9 and 243.0 ppm CO2, stomatal resistance between 0.6 and 1.3 s cm−1, chlorophyll content (SPAD values) between 46.3 and 57.0 and chlorophyll fluorescence (Fv/Fm) ranged between 0.8 and 0.9. All studied physiological parameters did not show statistically significant differences among control and heavy metal treated plants for both years; therefore, high soil cadmium and nickel concentration did not inhibit stomatal opening and did not affect the function of the photosynthetic machine of A. donax plants.  相似文献   

10.
Meat and bone meal (MBM) utilization for animal production was banned in the European Union since 2000 as a consequence of the appearance of transmissive spongiform encephalopathies. Soil application could represent a lawful and effective strategy for the sustainable recycling of MBM due to its relevant content of nutritive elements and organic matter. The effectiveness of MBM as organic fertilizer needs to be thoroughly investigated since there is a lack of knowledge about the mineralization dynamics of MBM in soil and the impact of such residues, in particular the high content of lipids, on soil biochemical and microbiological properties. For this aim, a defatted (D) and the correspondent non-defatted (ND) MBM were added at two rates (200 and 400 kg N ha?1) to two different moist soils and incubated at 15 and 20 °C for 14 d. MBM mineralization dynamics was studied by measuring CO2 evolution. Water extractable organic C, K2SO4-extractable NO3? and NH4+, microbial biomass ninhydrin-reactive N, enzymatic activities (FDA, urease, protease, alkaline phosphatase) and microbial composition (aerobic and anaerobic bacteria, fungi) were measured 2 and 14 d after MBM addition to the soil. The rate of CO2 evolution showed a maximum 2–3 d after the addition of MBM, followed by a decrease approaching the control. MBM mineralization was fast with, on average, 54% of total CO2 evolved in the first 4 d of incubation at 20 °C. The percentage of added C which was evolved as CO2 at the end of the incubation period ranged between 8% and 16% and was affected by temperature, soil type and MBM treatment (ND > D). Soil amendment with MBM caused a noteworthy increase in both extractable NH4+ and NO3? (about 50% of added N) which was higher for ND. The addition of MBM also enhanced microbial content and activity. Microbial biomass increased as a function of the rate of application and was higher for ND with respect to D. The increase in numbers of aerobic and anaerobic bacteria and fungi caused by MBM addition was, in general, more pronounced with ND. Enzymatic activity in amended soils showed an enhancement in nutrient availability and element cycling. At the rate of application of present work, lipids did not cause adverse effects on soil microorganisms.The potential of MBM as effective organic fertilizer was supported by the large increase in available N and the enhancement of the size and activity of soil microorganisms.  相似文献   

11.
《Applied soil ecology》2006,34(3):258-268
The potential negative impact of agricultural practices on soil and water quality is of environmental concern. The associated nutrient transformations and movements that lead to environmental concerns are inseparable from microbial and biochemical activities. Therefore, biochemical and microbiological parameters directing nitrogen (N) transformations in soils amended with different animal manures or inorganic N fertilizers were investigated. Soils under continuous corn cultivation were treated with N annually for 5 years at 56, 168, and 504 kg N ha−1 in the form of swine effluent, beef manure, or anhydrous ammonia. Animal manure treatments increased dehydrogenase activity, microbial biomass carbon (Cmic) and N (Nmic) contents, and activities of amidohydrolases, including l-asparaginase, urease, l-glutaminase, amidase, and β-glucosaminidase. Soils receiving anhydrous ammonia demonstrated increased nitrate contents, but reduced microbiological and biochemical activities. All treatments decreased Cmic:organic C (Corg) ratios compared with the control, indicating reduced microbial C use efficiency and disturbance of C equilibrium in these soil environments. Activities of all enzymes tested were significantly correlated with soil Corg contents (P < 0.001, n = 108), but little correlation (r = 0.03, n = 36) was detected between Cmic and Corg. Activities of amidase and β-glucosaminidase were dominated by accumulated enzymes that were free of microbial cells, while activities of asparaginase and glutaminase were originated predominately from intracellular enzymes. Results indicated that soil microbial and biochemical activities are sensitive indicators of processes involved in N flow and C use efficiency in semiarid agroecosystems.  相似文献   

12.
Soil urease is crucial for the nitrogen cycle and its association with humic acids (HAs) is a fundamental requirement for its stability. In this work, the chemical characteristic of two HA fractions (HA1, ≥50 kDa; HA2, 10–50 kDa) extracted from lignite was evaluated, and their effects on the activity and stability of Jack Bean urease were also studied. HA1 and HA2 exhibited different structural properties in the micro-FT-IR and 13C NMR spectra and influences on urease stability during 12 days of incubation: HA1 stabilized the urease activity. After 12 days, the residual activity of urease, at pH 6.0, 7.0 and 8.0, was 2.1, 2.6 and 3.9 times higher in the treatment of HA1-urease than in the free urease, respectively. With pH values increasing, the stability of free urease decreased and that of HA1-urease increased, which indicated that HA1 improved the stability of urease in the solution, especially at the alkaline condition.  相似文献   

13.
Contradictory effects of simultaneous available organic C and N sources on nitrous oxide (N2O), carbon dioxide (CO2) and nitric oxide (NO) fluxes are reported in the literature. In order to clarify this controversy, laboratory experiments were conduced on two different soils, a semiarid arable soil from Spain (soil I, pH=7.5, 0.8%C) and a grassland soil from Scotland (soil II, pH=5.5, 4.1%C). Soils were incubated at two different moisture contents, at a water filled pore space (WFPS) of 90% and 40%. Ammonium sulphate, added at rates equivalent to 200 and 50 kg N ha?1, stimulated N2O and NO emissions in both soils. Under wet conditions (90% WFPS), at high and low rates of N additions, cumulative N2O emissions increased by 250.7 and 8.1 ng N2O–N g?1 in comparison to the control, respectively, in soil I and by 472.2 and 2.1 ng N2O–N g?1, respectively, in soil II. NO emissions only significantly increased in soil I at the high N application rate with and without glucose addition and at both 40% and 90% WFPS. In both soils additions of glucose together with the high N application rate (200 kg N ha?1) reduced cumulative N2O and NO emissions by 94% and 55% in soil I, and by 46% and 66% in soil II, respectively. These differences can be explained by differences in soil properties, including pH, soil mineral N and total and dissolved organic carbon content. It is speculated that nitrifier denitrification was the main source of NO and N2O in the C-poor Spanish soil, and coupled nitrification–denitrification in the C-rich Scottish soil.  相似文献   

14.
《Soil biology & biochemistry》2001,33(7-8):1077-1093
We studied soil moisture dynamics and nitrous oxide (N2O) fluxes from agricultural soils in the humid tropics of Costa Rica. Using a split-plot design on two soils (clay, loam) we compared two crop types (annual, perennial) each unfertilized and fertilized. Both soils are of andic origin. Their properties include relatively low bulk density and high organic matter content, water retention capacity, and hydraulic conductivity. The top 2–3 cm of the soils consists of distinct small aggregates (dia. <0.5 cm). We measured a strong gradient of bulk density and moisture within the top 7 cm of the clay soil. Using automated sampling and analysis systems we measured N2O emissions at 4.6 h intervals, meteorological variables, soil moisture, and temperature at 0.5 h intervals. Mean daily soil moisture content at 5 cm depth ranged from 46% water filled pore space (WFPS) on clay in April 1995 to near saturation on loam during a wet period in February 1996. On both soils the aggregated surface layer always remained unsaturated. Soils emitted N2O throughout the year. Mean N2O fluxes were 1.04±0.72 ng N2O-N cm−2 h−1 (mean±standard deviation) from unfertilized loam under annual crops compared to 3.54±4.31 ng N2O-N cm−2 h−1 from the fertilized plot (351 days measurement). Fertilization dominated the temporal variation of N2O emissions. Generally fluxes peaked shortly after fertilization and were increased for up to 6 weeks (‘post fertilization flux’). Emissions continued at a lower rate (‘background flux’) after fertilization effects faded. Mean post-fertilization fluxes were 6.3±6.5 ng N2O-N cm−2 h−1 while the background flux rate was 2.2±1.8 ng N2O-N cm−2 h−1. Soil moisture dynamics affected N2O emissions. Post fertilization fluxes were highest from wet soils; fluxes from relatively dry soils increased only after rain events. N2O emissions were weakly affected by soil moisture during phases of low N availability. Statistical modeling confirmed N availability and soil moisture as the major controls on N2O flux. Our data suggest that small-scale differences in soil structure and moisture content cause very different biogeochemical environments within the top 7 cm of soils, which is important for net N2O fluxes from soils.  相似文献   

15.
We used natural gradients in soil and vegetation δ13C signatures in a savannah ecosystem in Texas to partition soil respiration into the autotrophic (Ra) and heterotrophic (Rh) components. We measured soil respiration along short transects from under clusters of C3 trees into the C4 dominated grassland. The site chosen for the study was experiencing a prolonged drought, so an irrigation treatment was applied at two positions of each transect. Soil surface CO2 efflux was measured along transects and CO2 collected for analysis of the δ13C signature in order to: (i) determine how soil respiration rates varied along transects and were affected by localised change in soil moisture and (ii) partition the soil surface CO2 efflux into Ra and Rh, which required measurement of the δ13C signature of root- and soil-derived CO2 for use in a mass balance model.The soil at the site was unusually dry, with mean volumetric soil water content of 8.2%. Soil respiration rates were fastest in the centre of the tree cluster (1.5 ± 0.18 μmol m?2 s?1; mean ± SE) and slowest at the cluster–grassland transition (0.6 ± 0.12 μmol m?2 s?1). Irrigation produced a 7–11 fold increase in the soil respiration rate. There were no significant differences (p > 0.5) between the δ13C signature of root biomass and respired CO2, but differences (p < 0.01) were observed between the respired CO2 and soil when sampled at the edge of the clusters and in the grassland. Therefore, end member values were measured by root and soil incubations, with times kept constant at 30 min for roots and 2 h for soils. The δ13C signature of the soil surface CO2 efflux and the two end member values were used to calculate that, in the irrigated soils, Rh comprised 51 ± 13.5% of the soil surface CO2 efflux at the mid canopy position and 57 ± 7.4% at the drip line. In non-irrigated soil it was not possible to partition soil respiration, because the δ13C signature of the soil surface CO2 efflux was enriched compared to both the end member values. This was probably due to a combination of the very dry porous soils at our study site (which may have been particularly susceptible to ingress of atmospheric CO2) and the very slow respiration rates of the non-irrigated soils.  相似文献   

16.
Four biostimulants (BS): WCDSs, wheat condensed distiller solubles; PA-HE, hydrolyzed poultry feathers; CGHE, carob germ enzymatic extract; and RB, rice bran extract were applied annually at 4.7 t organic matter (OM) ha−1 for a 3-year period to a Xerollic Calciorthid soil to evaluate their efficiency in soil restoration. Their effects on the plant cover, soil enzymatic activities and the structure of the soil microbial community by analysing phospholipid fatty acids (PLFAs) were determined. Application of BS that contain higher amounts of protein and higher percentage of peptides under 3 kDa had a greater effect on the soil biological properties, possibly due to the low molecular weight protein content can be easily assimilated by soil microorganisms. Following 3 years of successive soil amendment, the dehydrogenase activity was 4.6, 9.6, and 17.6% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The urease activity was 5.3, 14.5, and 28.8% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The phosphatase activity was 8, 15.3, and 20.2% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The arylsulfatase activity was 16, 21.1, and 27.2% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. Total soil phospholipid fatty acid (PLFA) concentration was significantly (p < 0.05) higher in BS-amended soil than control soil. Principal component analysis discriminated between the BS-amended soils, mainly based on content of lower molecular weight peptides. Thus, PA-HE and RB were grouped and differentiated from CGHE and WCDS, respectively. After 3 years of treatment, vegetal cover was 11.4, 17.7, 24.1, and 85.8% higher in PA-HE-amended soils than in the RB, CGHE, WCDS treatments and control soil. These results suggested that under semiarid climatic conditions the application of BS with higher amounts of protein (>50%) and a higher percentage of peptides under 0.3 kDa (>60%) notably increased the soil enzymatic activities, induced changes in microbial community because the protein with lower molecular weight can be more easily absorbed by soil microorganisms, and also favoured the establishment of vegetation, which will protect the soil against erosion and will contribute to its restoration.  相似文献   

17.
Soil of the former lake Texcoco is alkaline saline with pH often >10 and electrolytic conductivity (EC) >70 dS m?1 with rapidly changing water contents. Little is known how fertilizing this area with urea to vegetate the soil would affect emissions of carbon dioxide (CO2) and dynamics of N. Texcoco soil with electrolytic conductivity (EC) 2.3 dS m?1 and pH 8.5 (TEXCOCO A soil), EC 2.0 dS m?1 and pH 9.0 (TEXCOCO B soil) and 200 dS m?1 and pH 11.2 (TEXCOCO C soil) was amended with or without urea and incubated at 40% of water holding capacity (WHC), 60% WHC, 80% WHC and 100% WHC, while emissions of nitrous oxide (N2O) and CO2 and dynamics of ammonium (NH4+), nitrite (NO2?) and nitrate (NO3?) were monitored for 7 days. An agricultural soil served as control (ACOLMAN soil). The emission of CO2 increased in the urea amended soil 1.5 times compared to the unamended soil, it was inhibited in TEXCOCO C soil and was >1.2 larger in soil incubated at 40%, 60% and 80% WHC compared to soil incubated at 100% WHC. The emission of N2O increased in soil added with urea compared to the unamended soil, was similar in TEXCOCO A and B soils, but was <0.2 mg N kg?1 soil day?1 in TEXCOCO C soil and generally larger in soil incubated at 60% and 80% WHC compared to soil incubated at 40% and 100% WHC. The water content of the soil had no significant effect on the mean concentration of NH4+, but addition of urea increased it in all soils. The concentration of NO2? was not affected by the water content and the addition of urea except in TEXCOCO A soil where it increased to values ranging between 20 and 40 mg N kg?1. The concentration of NO3? increased in the ACOLMAN, TEXCOCO A and TEXCOCO B soil amended with urea compared to the unamended soil, but not in the TEXCOCO C soil. It decreased with increased water content, but not in TEXCOCO C soil. It was found that the differences in soil characteristics, i.e. soil organic matter content, pH and EC between the soils had a profound effect on soil processes, but even small changes affected the dynamics of C and N in soil amended with urea.  相似文献   

18.
《Applied soil ecology》2005,28(3):247-257
Carbon dioxide emissions from soils beneath canopies of two Mediterranean plants, Artemisia absinthium L. and Festuca pratensis Huds. cv. Demeter, were monitored over a 7-day period that included an artificial precipitation event of 4 cm. The experiments were conducted using 0.2 m3 soil microcosms inside greenhouses with CO2 concentrations of either 360 or 500 μmol mol−1. Carbon dioxide flux from the soil surface, as calculated using a diffusive transport model agreed well with CO2 flux measurements made using a dynamic flow system. Soil CO2 emissions did not differ significantly between the 360 and 500 μmol mol−1 CO2 treatments when soils were dry (volumetric soil moisture content ≤9%). A simulated precipitation event caused an immediate exhalation of CO2 from soil, after which CO2 emissions declined slightly and remained constant for approximately 36 h. CO2 emissions from soil microcosms with F. pratensis plants growing in 500 μmol mol−1 CO2 then rose to levels that were significantly greater than CO2 emissions from soils in the microcosms exposed to 360 μmol mol−1 CO2. For A. absinthium growing in 500 μmol mol−1 CO2, the rise in soil CO2 emissions following the wetting event was not significantly greater than emissions from soils with A. absinthium growing under 360 μmol mol−1 CO2. A. absinthium above ground biomass increased by 46.1 ± 17.9% (mean ± S.E., n = 4, P ≤ 0.05). Above ground biomass did not significantly increase for F. pratensis (14.4 ± 6.5%, P ≥ 0.10). Root biomass, on the other hand, increased for both species; by 50.6 ± 17.9% (P ≤ 0.05) for A. absinthium and by 55.9 ± 12.7% (P ≤ 0.05) for F. pratensis. Our results demonstrate two events following precipitation onto dry soils, an immediate release of CO2 followed by a gradual increase from enhanced biological activity The gradual increase was greater for the herbaceous ruderal perennial F. pratensis under elevated CO2.  相似文献   

19.
《Soil biology & biochemistry》2001,33(12-13):1797-1804
Sulphur transformations were monitored in a unique set of arable, grassland and woodland soils from the Broadbalk Classical Experiment, which started in 1843. In an open incubation experiment with periodic leaching, 14–35 mg SO42−-S kg−1 was mineralised in 28 weeks at 25°C, equivalent to 4.4–8.3% soil organic S. Cumulative amounts of S mineralised increased linearly during the 28 weeks, indicating constant rates of mineralisation. The rate of mineralisation was the greatest in the woodland soil (170 μg SO4-S kg−1 day−1), followed by the grassland (120 μg SO4-S kg−1 day−1) and the arable soil from the farmyard manure (FYM) plot (110 μg SO4-S kg−1 day−1). Three soils from arable plots receiving different inorganic fertiliser treatments but no FYM had similar rates of S mineralisation (~70 μg SO4-S kg−1 day−1). In an incubation experiment with 35SO42−, addition of glucose greatly enhanced S immobilisation. In 132 days, the woodland and grassland soils immobilised more S than the arable soils, with or without glucose amendment. Immobilisation and mineralisation of S occurred concurrently, and both were stimulated by glucose addition. The results show that S mineralisation and immobilisation were influenced strongly by the type of land-use and long-term organic manuring, whereas annual application of sulphate-containing fertilisers for over 150 years had few effects on short-term S transformations.  相似文献   

20.
M. Jalali  Z.V. Khanlari 《Geoderma》2008,143(1-2):26-40
This study was conducted to investigate the effect of time on lead (Pb), zinc (Zn), cadmium (Cd) and copper (Cu) availability in some calcareous soils of Iran. Heavy metals were added to soils at the rate of 500 mg kg? 1 of Pb, Zn, and Cu and 8 mg kg? 1 of Cd as chloride. The samples were incubated for 3 h, 1, 3, 7, 14, 21, and 28 days at 25 °C and constant moisture. After incubation, metals in amended and control soils were fractionated by the sequential extraction procedure. There were changes in the proportional distribution of heavy metals in all five studied soils during 28 days of incubation with spiked heavy metals. In general the proportions of heavy metals associated with the most weakly bound fraction (EXCH) tended to decrease, with corresponding increases in the other five more strongly binding fractions during the incubation. The distribution of added heavy metals into different solid phase fractions appears to be consisted of two phases involving the initial rapid retention followed by a slow continuous retention. Three kinetic equations were used to fit the experimental data. The parabolic equation fits well the data used in this work. The transformation rate of EXCH fraction for soils was estimated by parabolic equation for above incubation periods. There were differences in the rates at which redistribution took place between soils and heavy metals. The constant b in parabolic equation was defined as the transformation rate, which were in the order Cu > Zn ≥ Pb ? Cd. The higher proportions of EXCH fraction of spiked Cd in these calcareous soils indicates its higher potential of downward leaching and runoff transport especially at the early stage of pollution.  相似文献   

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