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 15 毫秒
1.
Risk assessment of the nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP), 4-chloromethylpyrazole (ClMP), and dicyandiamide (DCD) on nontarget microbial activity in soils was determined by measuring dehydrogenase and dimethyl sulfoxide reductase activity (DHA, DRA, respectively) in three differently textured soils under laboratory conditions. Dehydrogenase activity was measured with standard procedure recommended to evaluate side effects of environmental chemicals on general microbial activity in soils. The kinetic of inhibition were obtained by dose–response relationships and used to calculate the no observable effect levels (NOEL values) and the effective doses at 10% and 50% inhibition (ED10 and ED50), respectively. Negative effects on DHA and DRA, respectively, were observed only at rates approximately 40–100 times higher than the concentrations recommended in the field. Both DHA and DRA were affected more in the sandy than in the silty or clayey soil. Consequently, NOEL, ED10, and ED50 values were considerably higher in the clayey than in the silty or sandy soil. The heterocyclic N compounds DMPP and ClMP, respectively, were more effective in inhibiting DHA and DRA than DCD. At application rates used in the field as well as at concentration up to 25 to 90 times higher, the NIs concerned failed to affect general soil microbial activity in soils. Among the three NIs tested, the not marketed ClMP exhibited the strongest negative effects on soil microbial activity. At recommended application rates, the NIs tested should be considered as enviromentally safe.  相似文献   

2.
The Fe(III)-reduction test - a simple procedure to determine the effects of environmental chemicals on the microbial activity in soils A new simple microorganism test is described. The test is based on the fact that the degree of microbial reduction in waterlogged soils is influenced by the addition of different amounts of toxic chemicals. The microbial activity under reducing conditions can be measured by the degree of the microbial reduction of easily reducable Fe(III)-oxides (ferrihydrites) to soluble Fe2+-ions. The influence of different test parameters, the reproducibility and limitations of the proposed test are described. Toxicity indices of the investigated chemicals are derived graphically from the resulting dose effect curves. Values are determined for those concentrations which cause no (Non Effect Level, NEL) and a 50%-inhibition (ED50) of the microbial activity in soil samples. By representing some results for 2,4-D, 2,4,5-T, LAS, Cd and Hg the scope of the test is described. First results show that the effective toxicity of chemicals is strongly influenced by the adsorption capacity of the soils. Furthermore the relation of toxic substances to nutrients in the soil solution causing competition or antagonistic and synergistic effects during uptake and also within the organisms can substantially influence the toxicity of chemicals.  相似文献   

3.
Nickel pollution may affect microbial communitydevelopment and its activity in soil and, therefore, itsfertility, while organic amendment may affect Ni mobilityand bioavailability. The aim of this research was toascertain the extent to which the addition of sewage sludgeto soil may affect Ni toxicity and to establish theecological dose of this heavy metal. Unamended and amendedsoils with sewage sludge were spiked with differentconcentrations of Ni (0–8000 mg kg-1) and then incubatedfor 3 hours, 12 days and 40 days. Soil dehydrogenaseactivity, ATP content, microbial respiration and microbialbiomass C were measured in the samples containing differentNi concentrations. A mathematical model which describe theinhibition of these soil parameters were used to calculatethe ecological dose of Ni: ED50. Soil microbialbiomass C measurements of all treatments better fitted themodel (r2 = 0.95–0.69 with p < 0.05) than the otherparameters studied; but the ED50 values predicted by the modelhad a high coefficient of variation. For both ATP contentand microbial biomass C, the ED50 values calculatedfor the amended soil were higher than for the unamendedsoil and so that the effect of Ni toxicity on theseparameters of microbial activity may be considered lower inthe former. In this study, an increase in ED50 valueswith the time elapsed was also observed.  相似文献   

4.
Summary The aim of this study was to provide manageable data to help establish permissible limits for the pollution of soil by heavy metals. Therefore the short-and long-term effects of heavy metal pollution on phosphatase activity was studied in five different soil types. The results are presented graphically as logistic dose-response curves. It was possible to construct a curve for sand and silty loam soil but it was more difficult to establish a curve for sandy loam and clay soil and nearly impossible (except for Cu) for peat. The toxicity of the various metals can be compared on the basis of mmol values. In clay soils, for Cd, Cr, Cu, and Zn, the 50% effective ecological dose (ED50) values were comparable (approximately 45 mmol kg–1), but the ED10 values were very different, at 7.4, 41.4, 15.1, and 0.55, respectively. At the ED50 value, toxicity did not decrease with time and, in sandy soils, was approximately 2.6 mmol kg –1 dry soil for Cd, Cu, and Zn. In four out of five soils, the Cd toxicity was higher 1.5 years after the addition of heavy metal salts than after 6 weeks. Toxicity was least in the sandy loam, silty loam, and clay soil, and varied in general between 12 and 88 mmol kg–1. In setting limits, the criteria selected (no-effect level, ED10 or ED50) determine the concentration and also the toxicity of the sequence. It is suggested that the data presented here could be very useful in helping to set permissible limits for heavy metal soil pollution.  相似文献   

5.
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   

6.
Scale-dependent spatial variability of microbiological characteristics in soil of a beech forest The spatial variability of the microbial biomass content (Cmic), the microbial respiration rate (basal respiration) and the metabolic quotient (qCO2) was analyzed in sandy Cambisols and Luvisols in a beech forest in Northern Germany. Highest variability of microbiological features and, thus, the distance of independent samples was around 10 m that is discussed with reference to spatial hierarchy. Structural changes between the 10 m and 50 m grid were suggested for the Ah horizon due to the break of correlations of Cmic content and the contents of Corg and plant-available Ca, Mg, K and Nt. The Cmic content correlated with the Corg content close to tree trunks and ecotones like borders of the forest and clearings. The qCO2 did not generally increase with declining pH value. High H+ concentrations and Corg content in the litter layer near to the tree trunk indicated retarded microbial mineralization rates. High proportion of microorganisms that are resistant to low pH value and adjusted ro readily-degradable substrates seems to dominate in the soil close to the tree.  相似文献   

7.
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   

8.
A comparative study was conducted on the toxicity of Cd to alkaline phosphatase activity (ALP) and dehydrogenase activity (DHA) in 18 top soils with contrasting soil properties representative of 14 major soil types in China. Soil pH and carbonate content, soil organic matter, and cation exchange capacity (CEC) largely affected the Cd toxicity on two enzyme activities; with the soil pH having only minor effect on the median ecological dose values based on total Cd concentrations (ED50 T). The values of ED50 T/ED50 W (based on water-soluble Cd content) of alkaline phosphatase and dehydrogenase were strongly influenced by pH and CEC contents, which explained up to 71% of the variation for alkaline phosphatase, 82% of the variation for dehydrogenase, and also were significantly correlated with the parameter KF derived from Freundlich adsorption isotherms. This study suggests that the values of ED50 T/ED50 W could be useful to evaluate the buffer capacity of soils which protects soil enzymes from harmful effects of heavy metal.  相似文献   

9.
Defining the validity of a biochemical index of soil quality   总被引：2，自引：0，他引：2  
 The native soils of Galicia (NW Spain) exhibit a biochemical equilibrium such that total soil N is a function of five biochemical and microbiological parameters: microbial biomass C, mineralized N, phosphomonoesterase, β-glucosidase and urease activities. To investigate whether the ratio of the total N calculated from biochemical soil properties (Nc) and the total N as measured by the Kjeldahl method (Nk; Nc/Nk) can be used as an index of soil quality, we determined these variables and consequently the ratio in three kinds of disturbed soils: an artificially Cu-contaminated soil, two lignite mine soils, and a number of arable soils. In none of the studied soils did the individual biochemical parameters respond consistently to the factors influencing soil quality, but in all cases soil degradation was reflected by the Nc/Nk value, which differed more or less markedly from 100%. Nc/Nk can therefore be used for the rapid evaluation of soil degradation, since it distinguishes among biochemically balanced soils, soils in a transient state of high microbiological and biochemical activity and degraded soils. It can also serve as a reliable basis for the rapid calculation of the "ecological dose" (ED50) of soil pollutants. The use of Nc/Nk as an objective index of the biochemical quality of soils is recommended. Received: 20 December 1998  相似文献   

10.
《Soil biology & biochemistry》2001,33(4-5):483-489
Two soils of contrasting texture, organic matter content and pH were treated with CdSO4 solutions to give a Cd concentration range of 0–4000 mg kg−1 soil. The content of ATP and dehydrogenase and urease activities of soils were assayed after 3 h, and 7 and 28 days of Cd contamination. The relative ED50 values were calculated by two kinetic models (model 1 and model 2) used by Speir et al. (1995) and by the sigmoidal dose–response model (model 3) employed by Haanstra et al. (1985). Model 1 was the most successful in calculating the ED50 values for the ATP content, urease and dehydrogenase activities when both soils were contaminated by Cd. Similar ED50 values were predicted by model 1 (describing the full inhibition) and model 3 only when the correlation coefficients r2 were higher than 0.9. The ED50 values of ATP calculated by model 1 were markedly higher than those calculated by model 2 (describing partial inhibition) when both models gave correlation coefficients higher than 0.9. This behavior was due to the high asymptote values obtained using model 2. According to model 2, some of the enzyme activities responsible for the ATP synthesis were probably not inhibited at the highest Cd concentrations. The inhibitory effect of Cd on the ATP content and both enzymatic activities was lower in the Castelporziano soil, which had the highest total organic carbon content.  相似文献   

11.
Short-term experiments for the estimation of long-term effects of inorganic pollutants on soil microbial activity The purpose of the present study was to develope a short-term laboratory method to predict long-term effects of inorganic pollutants on soil microbial activity. Experiments were carried out on a sandy cambisol which had been used in a long-term field plot of the Biologische Bundesanstalt in Berlin. The perfusion technique was suitable to prove long-term effects of concentrations of 50 mg Cd/kg and 1000 mg Pb/kg dry soil on dehydrogenase activity of the test soil. 200 mg Cd/kg and 4000 mg Pb/kg caused higher reductions in the perfusion experiment than in the long-term field trial. Due to the desorption of OH-ions and the dissolution of organic material, effects of NaF-additions were partly compensated in the short-term experiment. The lysimeter technique used here seems to be of minor value to simulate long-term effects of cadmium, lead, and fluorine because unadsorbed portions of these elements and their accompanying ions (e.g. Cl, NO3) are washed out of the system too slowly. The dehydrogenase activity was more valid to indicate long-term effects on soil microbial activity than ATP-contents and nitrification measurements did.  相似文献   

12.
Summary The aim of this study was to provide data to evaluate the short- and long-term effects of heavy metals on arylsulphatase activity in five soils. The effects are fitted on a logistic dose-response model and are presented graphically as the ecological dose (heavy metal concentration corresponding to 50% inhibition; ED50) and ecological dose range (heavy metal concentration range corresponding to 10–90% inhibition; EDR). In 7 out of 22 comparable soil-metal combinations the ED50 decreased significantly over 6 weeks to 18 months of incubation and in two cases the ED50 increased. Toxicity (defined as ED50) was highest in sand and sandy loam and lowest in sandy peat. Cd toxicity in sand, silty loam, and clay varied from 1.08 to 9.04 mmol kg-1. Both Cr and Ni toxicity varied strongly and decreased with time in some soils while increasing in others. The Cu toxicity ranged from 4.51 to 2 mmol kg-1 in sand and silty loam, respectively, but remained fairly constant over time. Pb was the least toxic element (14.5 to 59.9 mmol kg-1). The toxicity of Zn ranged from 5.73 to 148 mmol kg-1 in sand and sandy peat, respectively. At critical concentrations set by the Dutch Soil Protection Act, Cr, Cu, Ni, and Zn inhibited arylsulphatase by 53, 35, 48 and 97%, respectively.  相似文献   

13.
ABSTRACT

On the basis of greenhouse bioassays, the sensitivities of root and shoot biomass of barley (Hordeum vulgare L.), corn (Zea mays L.), oilseed rape (Brassica napus L.) and sugar beet (Beta vulgaris L.) to soil-incorporated sulfosulfuron and tribenuron methyl were assessed. Shoot and root biomass production was measured 30 days after emergence. Plant responses, including roots and shoots dry weight per pot, were described by a three parameter log-logistic regression model as a function of sulfosulfuron or tribenuron methyl doses and the relative sensitivities were calculated at the various ED-levels with their associated 95% confidence intervals. The most precise ED-levels were that at ED50 and sensitivity rank was oilseed rape, sugar beet, corn and barley, whatever the chosen response level and herbicide. We calculated relative sensitivities at ED10, ED50 and ED90 for the species of barley, the most tolerant crop, as reference. Comparison of relative sensitivity of crops to both herbicides showed that the sensitivity of these crops was much larger for tribenuron methyl than for sulfosulfuron. Oilseed rape was the most sensitive species (ED50?=?0.202 and 0.179?µg?kg?1 soil for root dry weight (RDW) response to sulfosulfuron and tribenuron methyl, respectively) while barley was the most tolerant one (ED50?=?1.008 and 3.68?µg?kg?1soil for RDW response to sulfosulfuron and tribenuron methyl, respectively). Sugar beet and corn had intermediate sensitivity. Also, we demonstrated how important it is to show the confidence intervals of relative sensitivities. In several instances the relative sensitivities, even numerically large, were not significantly different from 1.00. We demonstrate that classifying biotypes as resistant to a herbicide requires the threshold of resistance/susceptible (R/S) of 4.00 only be accepted if confidence intervals do not cover 1.00.  相似文献   

14.
Soil variability and pesticide behaviour The spatial variability of selected soil characteristics (organic carbon, particle size), pesticide adsorption and leaching was estimated for an agricultural location. Variograms were calculated to describe the spatial dependence of data. All parameters showed a nearly isotropic behaviour. According to variograms a kriging interpolation was done and the spatial variability of parameters was estimated. Leaching of terbuthylazine was calculated (model PRZM) with regard to soil variability and adsorption pattern (Kd-values). Leaching depth in the winter season varied between 10 and 22 cm depending strictly on soil characteristics.  相似文献   

15.
 This study focuses on a comparison of the microbial toxicity of nine metals, including As as a metalloid and two species of Cr. A loess soil [Ap horizon, clay 15.2%, organic C 1.12%, pH(CaCl2) 7.02] was spiked with 8–12 geometrically increasing doses of the metals. The dehydrogenase assay (2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazoliumchloride method) was combined with sorption and solubility experiments. The resulting dose-response curves and sorption isotherms were used to derive total doses that caused definite percentage inhibitions [i.e. effective doses (ED) causing a 10–90% reduction in dehydrogenase activity (dha)] as well as the corresponding toxic solution concentrations causing the same reductions in dha (i.e. effective concentrations; EC10–EC90). Based on total doses, the toxicity decreased in the following order with ED50 values (mg kg–1) given in brackets: Hg (2.0)>Cu (35)>Cr(VI) (71)>Cr(III) (75)>Cd (90)>Ni (100)>Zn (115)>As (168)>Co (582)>Pb (652). With regard to solution concentrations, toxicity decreased in the order (EC50 in mg l–1): Hg (0.003)>Pb (0.04)>Cu (0.05)>Cd (0.14)>Zn (0.19)>Cr(III) (0.62)>Ni (0.69)>Co (30.6)>As (55.5)>Cr(VI) (78.1). The retention of the metals by the soil differed strongly. Pb, Cu, and Hg exhibited the highest and Ni, As, and Cr(VI) the lowest sorption constants (Freundlich K values: 2455, 724, 348, 93, 13, and 0.06 mg kg–1, respectively). The sorptivity of the metals and their microbial toxicity in the aqueous phase were characteristically related: metals with a strong toxic action in the soil solution were adsorbed by the soil to a high degree and vice versa. Therefore, especially for metals with a high inherent toxicity, sorption is an effective way of immobilizing them and temporarily detoxifying soil. Received: 2 July 1998  相似文献   

16.
The fixation of radioactive C was used to mesaure the toxicity of Pb(NO3)2 to five species of freshwater algae. Portions of unialgal cultures were inoculated into low salt medium and were used to test all species at 10, 20 and 30 ppm Pb. This medium approximated the salt concentrations of natural aquatic environments. Three different cell weights were used for each concentration of Pb and for the control to determine a relationship between cell weight and toxicity. The concentration of Pb causing a 50% reduction of14CO2 fixation as compared to the control was called the ED50 (median effective dose). These values were extrapolated from graphs of ppm Pb vs dpm mg?1 dry cell weight. The ED50 for three of the species tested (Anabaena, Chlamydomonas andNavicula) was between 15 and 18 ppm Pb. A desmid,Cosmarium, had an ED50 of 5 ppm. This species has a higher surface: volume ratio than the other species tested and this may account for its increased sensitivity. An ED50 forOchromonas was not obtained. Throughout this experiment the fixation of14CO2 increased with increasing Pb concentrations and is not readily explained.  相似文献   

17.
Field estimation of the microbial biomass of soils derived from natural and anthropogenic parent materials Whereas the estimation and evaluation of physical and chemical soil properties is possible with the use of widely accepted methods, there is still no procedure with respect to microbiological parameters. Therefore, our objective was to develop a field procedure for estimating the integral parameter ”︁microbial biomass”. For this purpose, microbial biomass data (Cmic in dry matter) of soils developed in natural parent materials from 116 sites in Germany and abroad were analyzed. Additionally, Cmic in 33 German soils developed in anthropogenic parent materials was determined. In the soils under consideration, Cmic varied between 100 and 4000 kg ha—1 in the upper 30 cm. For soils of natural substrates statistical relations between Cmic and the humus and clay content as well as pH were derived. From these parameters which are combined as the diagnostic characteristics of humus a simple procedure for estimating Cmic of arable soils was developed. For soils developed in anthropogenic parent materials, however, an estimation procedure was developed that uses the nature of the parent material and the degree of soil development. To evaluate the estimated amount of Cmic, a frame consisting of 6 classes is proposed: < 200 kg ha—1 (= very low), 200—400 kg ha—1 (= low), 400—800 kg ha—1 (= moderate), 800—1600 kg ha—1 (= medium), 1600—3200 kg ha—1 (= high), and > 3200 kg ha—1 (= very high).  相似文献   

18.
Degradation of humic substances by soil microorganisms — a review Humic substances which represent differently extractable fractions of the soil organic matter exert multifarious effects on soil as a site for plant growth and a part of terrestrial environments. Among them especially humic acids and fulvic acids are subject to degradation and/or transformation by soil microorganisms. Several authors demonstrated the participation of different species of fungi, actinomycetes and also of non-mycelial aerobic or anaerobic bacteria in those processes under laboratory conditions. Indications exist that humic substances irrespective of their structure undergo degradation on cell surfaces due to the activity of exoenzymes. In this respect microbial phenoloxidases play an extraordinarily important role. The degradation rate of humic substances can be followed by optical, gravimetric and chemoanalytical methods as well as using biochemical and microbiological procedures (CO2 release, microbial growth, biomass formation). An objective evaluation, however, can be hindered by the adsorption of humic substances on microbial biomass and sometimes also by formation of novel humic-like microbial metabolites. Therefore it is necessary to apply a multifactorial approach in the study of the degradation of humic substances which includes both quantitative and qualitative parameters. To better elucidate how these processes may occur under natural conditions, mixed populations of soil microorganisms should be predominantly involved in future studies.  相似文献   

19.
Calculation of redox potential in soil and groundwater from the curve of the electrode depolarization An inherent problem with redox potential measurements in soil and groundwater is the initial drift of potential readings. This is caused by electrode depolarization. The depolarization kinetics corresponds to a first-order process, mathematically described by an e-function. Based on the depolarization kinetics a method was developed to calculate redox potentials (Eh-values) from only short time (= 10 min) measured depolarization curves. Besides the Eh-value this procedure gives the depolarization constant λ. The method was tested and verified by a number of depolarization measurements in soils and groundwater.  相似文献   

20.
Influence of soil characteristics, agricultural use and soil temperature on the N-mobilization of cultivated soils A new N-mobilization model, which considers also the short term and seasonal N-supplying capacity of soil is presented. At a fixed time the potential mobilizable N (N-MOB) is a sum of difficultly mobilizable N (N-MOBs) originating from the pool of difficultly mobilizable N (Ns) and the easily mobilizable N (N-MOB1) originating from the pool of easily mobilizable N (N1). It is possible to characterize soil according to their M1, N-MOBs and v (N-MOBs per day) values. Usefulness of these parameters in N-nutrition and ground water burden from N has been discussed. Basic parameters of this model have been experimentally determined independently with the help of two different experiments i. e. laboratory incubation and column lysimeter using surface soil samples. The easily mobilizable N pool (N1) values were found in the range of 142 to 814 kg N ha?1 which corresponded to 1.2 to 7.4 % of organic N content of these soils. The difficultly mobilizable N per day (i. e. v = N-MOBs per day) in an incubation experiment (35°C) were found in the range of 1.5 to 24kg N ha?1. However, in the column lysimeter experiment, in contrast, these values at 10°C ranged between 0.05 to 0.9 kg N ha?1. These values correspond to N-MOBs values in the range of 11–182 kg N·ha?1 for a period of 200 days which approximate to a vegetation period. For practical purposes, the N1 and v values could be calculated by just measuring 3–4 points after 14 days of incubation at 35°C. The results show that N-MOBs values strongly correlated compared to N1 values to total N, organic carbon and clay content and non significantly to pH and silt content. The results of an laboratory incubation experiment carried out to assess the effect of temperature on N-mobilization show that even at 0°C there was N-mobilization. The results revealed that in the temperature range of 0–8°C (a range of soil temp. usually observed in winter months) and in the range of 25–40°C (range of summer months temp. for surface arable soil), a small change in the soil temperature would result in enormous increase in the quantity of mobilized N. The highest mobilized N quantity was found above 60°C.  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