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 31 毫秒
1.
Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha?1 in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton (Gossypium hirsutum L.) residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO2) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level.  相似文献   

2.
设施蔬菜栽培长期施用过量化肥,往往导致土壤质量退化及作物产量降低等问题。因此,采用生态友好的农业生产方式已成为农业可持续发展的趋势。本研究在野外调控试验的第3年采集作物和土壤,研究了施用不同有机物料条件下,接种赤子爱胜蚓(Eisenia foetida)对设施菜地土壤性质和作物生长的影响。结果表明,在不同有机物料施用下接种赤子爱胜蚓均显著地提高了黄瓜和菠菜的产量,其中在施用腐熟牛粪+食用菌渣条件下接种赤子爱胜蚓效果最显著。此外,在腐熟牛粪和腐熟牛粪+食用菌渣施用条件下,接种赤子爱胜蚓显著地提高土壤的硝态氮(NO3–-N)、团聚体平均重量直径(MWD)、微生物生物量碳(MBC)、微生物生物量氮(MBN)和代谢熵(q CO2),而在施用商品有机肥的处理中,接种赤子爱胜蚓仅显著地提高了土壤NO3–-N和q CO2。本研究促进了对蚯蚓在设施农业生态系统中服务功能的理解,并为设施农业生产提供了理论基础。  相似文献   

3.
In this work we studied the influence of Pb, Zn, and Tl on microbial biomass survival and activity during a laboratory incubation of soil. In comparison to uncontaminated soil, the microbial biomass C decreased sharply in soil contaminated with Zn and Tl, whereas the addition of Pb did not have any significant inhibitory effect on the level of microbial biomass C. Zn displayed the greatest biocidal effect, confirmed by the measurement of the death rate quotient (q D). The microbial activity, measured as CO2 evolution, increased significantly in contaminated soils, emphasizing the need of living organisms to expend more energy to survive. The greater demand for energy by microorganisms in order to cope with the toxicity of pollutants was also confirmed by measurement of the metabolic quotient (q CO2). In order to determine whether soil microorganisms affect the bioavailability of these metals through their mobilization and release, we studied the relationships between available Pb, Zn, and Tl, and microbial biomass C. The water-soluble fraction of Tl, available Tl, and Zn, and microbial biomass C were related significantly, but not Pb.  相似文献   

4.
ABSTRACT

The response of potted pear trees grafted on quince (Cydonia oblonga Mill.) Sydo stock to increasing concentrations (0, 50, 100, 200, 400, 600, 800, and 1000 mg kg?1) of copper (Cu) in sandy and clay-loam soils were evaluated and crop toxicity thresholds and symptoms were determined. Reductions of shoot growth and leaf area were observed only for pear grown in sandy soil with more than 400 mg Cu/kg. During the growing season, carbon assimilation and soil microbial biomass were reduced as concentration of soil Cu increased. However, the effect was always stronger in sandy than clay-loam soil. Copper accumulated in roots, with response to soil Cu additions described by a linear and a quadratic function for sandy and clay-loam soil, respectively. A possible antagonism was observed between Cu and zinc (Zn) in the roots. Root Zn concentration decreased as soil Cu concentration increased.  相似文献   

5.
Two soils, one a sandy loam and the other of relatively high clay content, were incubated with [14C(U)]gtucose and [15N](NH4)2SO4 for 101 days, either under continuously moist conditions, or with intermittent drying of soils. Rates of evolution of 14CO2, decline in residual organic 14C, and net immobilization and mineralization of N and 15N in the sandy loam soil were more rapid than in the clay soil. First order decay rates for the decomposition of residual 14C, after 10 days, were consistently twice as fast in the sandy loam soil. By contrast, the efficiency with which glucose was utilized within the first few days, and the amounts of C, 14C, N and 15N present as soil biomass throughout the incubation, were greater in the clay soil than in the sandy loam. Biomass 14C as a percentage of residual organic 14C, was consistently 1.5 times greater in the clay soil. Compared with soils held continuously moist, soils which were intermittently dried and remoistened contained smaller amounts of isotope-labelled biomass C and N, but overall similar amounts of total residual organic 14C and 15N. Remoistening of dried soils caused a temporary (4 days) flush in C and N mineralization rates.A simulation model describes C and N behaviour in the two soils. Three features of the model are proposed to expain short-term differences between soils in the rates of C and N turnover, viz. the clay soil (a) has a greater capacity to preserve biomass C and N (b) holds a higher proportion of microbial decay products in the near vicinity of surviving cells, and, to a lesser extent, (c) utilizes glucose and metabolic products more efficiently for biosynthetic reactions.  相似文献   

6.
Abstract

There is limited knowledge about the differences in carbon availability and metabolic quotients in temperate volcanic and tropical forest soils, and associated key influencing factors. Forest soils at various depths were sampled under a tropical rainforest and adjacent tea garden after clear-cutting, and under three temperate forests developed on a volcanic soil (e.g. Betula ermanii and Picea jezoensis, and Pinus koraiensis mainly mixed with Tilia amurensis, Fraxinus mandshurica and Quercus mongolica), to study soil microbial biomass carbon (MBC) concentration and metabolic quotients (qCO2, CO2-C/biomass-C). Soil MBC concentration and CO2 evolution were measured over 7-day and 21-day incubation periods, respectively, along with the main properties of the soils. On the basis of soil total C, both CO2 evolution and MBC concentrations appeared to decrease with increasing soil depth. There was a maximal qCO2 in the 0–2.5 cm soil under each forest stand. Neither incubation period affected the CO2 evolution rates, but incubation period did induce a significant difference in MBC concentration and qCO2 in tea soil and Picea jezoensis forest soil. The conversion of a tropical rainforest to a tea garden reduced the CO2 evolution and increased the qCO2 in soil. Comparing temperate and tropical forests, the results show that both Pinus koraiensis mixed with hardwoods and rainforest soil at less than 20 cm depth had a larger MBC concentration relative to soil total C and a lower qCO2 during both incubation periods, suggesting that microbial communities in both soils were more efficient in carbon use than communities in the other soils. Factor and regression analysis indicated that the 85% variation of the qCO2 in forest soils could be explained by soil properties such as the C:N ratio and the concentration of water soluble organic C and exchangeable Al (P < 0.001). The qCO2 values in forest soils, particularly in temperate volcanic forest soils, decreased with an increasing Al/C ratio in water-soluble organic matter. Soil properties, such as exchangeable Ca, Mg and Al and water-soluble organic C:N ratio, were associated with the variation of MBC. Thus, MBC concentrations and qCO2 of the soils are useful soil parameters for studying soil C availability and microbial utilization efficiency under temperate and tropical forests.  相似文献   

7.
The present review is focused on microbiological methods used in agricultural soils accustomed to human disturbance. Recent developments in soil biology are analyzed with the aim of highlighting gaps in knowledge, unsolved research questions, and controversial results. Activity rates (basal respiration, N mineralization) and biomass are used as overall indices for assessing microbial functions in soil and can be supplemented by biomass ratios (C : N, C : P, and C : S) and eco‐physiological ratios (soil organic C : microbial‐biomass C, qCO2, qNmin). The community structure can be characterized by functional groups of the soil microbial biomass such as fungi and bacteria, Gram‐negative and Gram‐positive bacteria, or by biotic diversity. Methodological aspects of soil microbial indices are assessed, such as sampling, pretreatment of samples, and conversion factors of data into biomass values. Microbial‐biomass C (µg (g soil)–1) can be estimated by multiplying total PLFA (nmol (g soil)–1) by the FPLFA‐factor of 5.8 and DNA (µg (g soil)–1) by the FDNA‐factor of 6.0. In addition, the turnover of the soil microbial biomass is appreciated as a key process for maintaining nutrient cycles in soil. Examples are briefly presented that show the direction of human impact on soil microorganisms by the methods evaluated. These examples are taken from research on organic farming, reduced tillage, de‐intensification of land‐use management, degradation of peatland, slurry application, salinization, heavy‐metal contamination, lignite deposition, pesticide application, antibiotics, TNT, and genetically modified plants.  相似文献   

8.
The effect of endogeic earthworms (Octolasion tyrtaeum) and the availability of clay (Montmorillonite) on the mobilization and stabilization of uniformly 14C-labelled catechol mixed into arable and forest soil was investigated in a short- and a long-term microcosm experiment. By using arable and forest soil the effect of earthworms and clay in soils differing in the saturation of the mineral matrix with organic matter was investigated. In the short-term experiment microcosms were destructively sampled when the soil had been transformed into casts. In the long-term experiment earthworm casts produced during 7 days and non-processed soil were incubated for three further months. Production of CO2 and 14CO2 were measured at regular intervals. Accumulation of 14C in humic fractions (DOM, fulvic acids, humic acids and humin) of the casts and the non-processed soil and incorporation of 14C into earthworm tissue were determined.Incorporation of 14C into earthworm tissue was low, with 0.1 and 0.44% recovered in the short- and long-term experiment, respectively, suggesting that endogeic earthworms preferentially assimilate non-phenolic soil carbon. Cumulative production of CO2-C was significantly increased in casts produced from the arable soil, but lower in casts produced from the forest soil; generally, the production of CO2-C was higher in forest than in arable soil. Both soils differed in the pattern of 14CO2-C production; initially it was higher in the forest soil than in the arable soil, whereas later the opposite was true. Octolasion tyrtaeum did not affect 14CO2-C production in the forest soil, but increased it in the arable soil early in the experiment; clay counteracted this effect. Clay and O. tyrtaeum did not affect integration of 14C into humic fractions of the forest soil. In contrast, in the arable soil O. tyrtaeum increased the amount of 14C in the labile fractions, whereas clay increased it in the humin fraction.The results indicate that endogeic earthworms increase microbial activity and thus mineralization of phenolic compounds, whereas clay decreases it presumably by binding phenolic compounds to clay particles when passing through the earthworm gut. Endogeic earthworms and clay are only of minor importance for the fate of catechol in soils with high organic matter, clay and microbial biomass concentrations, but in contrast affect the fate of phenolic compounds in low clay soils.  相似文献   

9.
The roles of microbial biomass (MBC) and substrate supply as well as their interaction with clay content in determining soil respiration rate were studied using a range of soils with contrasting properties. Total organic C (TOC), water-soluble organic carbon, 0.5 M K2SO4-extractable organic C and 33.3 mM KMnO4-oxidisable organic carbon were determined as C availability indices. For air-dried soils, these indices showed close relationship with flush of CO2 production following rewetting of the soils. In comparison, MBC determined with the chloroform fumigation-extraction technique had relatively weaker correlation with soil respiration rate. After 7 d pre-incubation, soil respiration was still closely correlated with the C availability indices in the pre-incubated soils, but poorly correlated with MBC determined with three different techniques—chloroform fumigation extraction, substrate-induced respiration, and chloroform fumigation-incubation methods. Results of multiple regression analyses, together with the above observations, suggested that soil respiration under favourable temperature and moisture conditions was principally determined by substrate supply rather than by the pool size of MBC. The specific respiratory activity of microorganisms (CO2-C/MBC) following rewetting of air-dried soils or after 7 d pre-incubation was positively correlated with substrate availability, but negatively correlated with microbial pool size. Clay content had no significant effect on CO2 production rate, relative C mineralization rate (CO2-C/TOC) and specific respiratory activity of MBC during the first week incubation of rewetted dry soils. However, significant protective effect of clay on C mineralization was shown for the pre-incubated soils. These results suggested that the protective effect of clay on soil organic matter decomposition became significant as the substrate supply and microbial demand approached to an equilibrium state. Thereafter, soil respiration would be dependent on the replenishment of the labile substrate from the bulk organic C pool.  相似文献   

10.
The increase in microbial C content, cumulative respiration and changes in ”︁available” C were determined after adding glucose (2 mg glucose-C (g soil)—1, ”︁C”), glucose + nitrogen (”︁C+N”) or glucose + nitrogen + phosphorus (”︁C+N+P”) to four soils. In two sandy soils, one agricultural and the other from a beech forest in Germany, available C was still present approximately 7 days after C addition. The supplement N and N+P decreased the content of available C and stimulated respiration rate and microbial growth. In two loamy forest soils from Italy, which had a high native content of microbial C, available C was present in the beech soil but not in a silver fir soil treated with C+N. In the Italian beech and fir soil, microbial growth was highest with C+N+P and C+N addition respectively. Available C remaining in the soil was related to some extent to the native microbial C content. However, microbial growth and respiration response varied between soil and treatment. The respiratory coefficient, that is the ratio of assimilated to respired C, varied between 0.0 and 1.45 μg Cmic (μg CO2-C)—1 and was generally higher when a large amount of native biomass was present. The eco-physiological strategy of the soil microbiota in using C seemed to shift according to the biomass content, the added concentration and composition of available substrates, and emergent system properties.  相似文献   

11.
The aim of this study was to determine the effects of plant absence or presence on microbial properties and enzyme activities at different levels of salinity in a sandy clay soil. The treatments involved five salinity levels—0.5 (control), 2.5, 5, 7.5, and 10 dS m?1 which were prepared using a mixture of chloride salts—and three soil environments (unplanted soil, and soils planted with either wheat or clover) under greenhouse conditions. Each treatment was replicated three times. At the end of the experiment, soil microbial respiration, substrate-induced respiration (SIR), microbial biomass C (MBC), and enzyme activities were determined after plant harvest. Increasing salinity decreased soil microbial properties and enzyme activities, but increased the metabolic quotient (qCO2) in both unplanted and planted soils. Most microbial properties of planted soils were greater than those of unplanted soils at low to moderate salinity levels, depending upon plant species. There was a small or no difference in soil properties between the unplanted and planted treatments at the highest salinity level, indicating that the indirect effects of plant presence might be less important due to significant reduction of plant growth. The lowered microbial activity and biomass, and enzyme activities were due to the reduction of root activity and biomass in salinized soils. The lower values of qCO2 in planted than unplanted soils support the positive influence of plant root and its exudates on soil microbial activity and biomass in saline soils. Nonetheless, the role of plants in alleviating salinity influence on soil microbial activities decreases at high salinity levels and depends on plant type. In conclusion, cultivation and growing plant in abandoned saline environments with moderate salinity would improve soil microbial properties and functions by reducing salinity effect, in particular planting moderately tolerant crops. This helps to maintain or increase the fertility and quality of abandoned saline soils in arid regions.  相似文献   

12.
Metabolic quotients for CO2C (qCO2C) and microbial-C-loss (qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO2C (unit CO2C unit−1 Cmic h−1) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO2qCO2CC as compared to 0.645 μg CO2C of microbial biomasses from 19 CR systems. The 1.7 times higher CO2C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level.In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher (P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils).These differences were not related to soil texture, Corg or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed.  相似文献   

13.
蚯蚓与黑麦草相互作用对土壤中荧蒽去除的影响   总被引：1，自引：0，他引：1  
Earthworms can promote the bioremediation of contaminated soils through enhancing plant growth and microorganism development. The individual and combined effects of earthworms and ryegrass (Lolium multiflorum Lam.) on the removal of fluoranthene from a sandy-loam alluvial soil were investigated in a 70-d microcosm experiment. The experiment was set up in a complete factorial design with treatments in four replicates: without earthworms or ryegrass (control, CK), with earthworms only (E), with ryegrass only (P), and with both earthworms and ryegrass (EP). The residual fluoranthene, microbial biomass C, and polyphenol oxidase activity in the soil changed significantly (P<0.01) with time. In general, the residual concentration of fluoranthene in the soil decreased sharply from 71.8-88.7 to 31.7-37.4 mg kg 1 in 14 d, and then decreased gradually to 19.7-30.5 mg kg 1 on the 70th d. The fluoranthene concentration left in the soil was the least with both earthworms and ryegrass, compared to the other treatments at the end of the experiment. Half-life times of fluoranthene in the E, P, and EP treatments were 17.8%-36.3% smaller than that of CK. More fluoranthene was absorbed by earthworms than ryegrass. However, the total amounts of fluoranthene accumulated in both the ryegrass and earthworms were small, only accounting for 0.01%-1.20% of the lost fluoranthene. Therefore, we assumed that microbial degradation would play a dominant functional role in fluoranthene removal from soil. We found that earthworms significantly increased microbial biomass C and polyphenol oxidase activity (P<0.01) in the presence of ryegrass at the end of the experiment. Furthermore, microbial biomass C and polyphenol oxidase activity were significantly (P<0.05) and negatively related to the residual fluoranthene concentration. This implied that earthworms might promote the removal of fluoranthene from soil via stimulating microbial biomass C and polyphenol oxidase activity.  相似文献   

14.
The turnover of native and applied C and N in undisturbed soil samples of different texture but similar mineralogical composition, origin and cropping history was evaluated at −10 kPa water potential. Cores of structurally intact soil with 108, 224 and 337 g clay kg−1 were horizontially sliced and 15N-labelled sheep faeces was placed between the two halves of the intact core. The cores together with unamended treatments were incubated in the dark at 20 °C and the evolution of CO2-C determined continuously for 177 d. Inorganic and microbial biomass N and 15N were determined periodically. Net nitrification was less in soil amended with faeces compared with unamended soil. When adjusted for the NO3-N present in soil before faeces was applied, net nitrification became negative indicating that NO3-N had been immobilized or denitrified. The soil most rich in clay nitrified least N and 15N. The amounts of N retained in the microbial biomass in unamended soils increased with clay content. A maximum of 13% of the faeces 15N was recovered in the microbial biomass in the amended soils. CO2-C evolution increased with clay content in amended and unamended soils. CO2-C evolution from the most sandy soil was reduced due to a low content of potentially mineralizable native soil C whereas the rate constant of C mineralization rate peaked in this soil. When the pool of potentially mineralizable native soil C was assumed proportional to volumetric water content, the three soils contained similar proportions of potentially mineralizable native soil C but the rate constant of C mineralization remained highest in the soil with least clay. Thus although a similar availability of water in the three soils was ensured by their identical matric potential, the actual volume of water seemed to determine the proportion of total C that was potentially mineralizable. The proportion of mineralizable C in the faeces was similar in the three soils (70% of total C), again with a higher rate constant of C mineralization in the soil with least clay. It is hypothesized that the pool of potentially mineralizable C and C rate constants fluctuate with the soil water content.  相似文献   

15.
《Applied soil ecology》2007,35(2):319-328
The effects of salinity on the size, activity and community structure of soil microorganisms in salt affected arid soils were investigated in Shuangta region of west central Anxi County, Gansu Province, China. Eleven soils were selected which had an electrical conductivity (EC) gradient of 0.32–23.05 mS cm−1. There was a significant negative exponential relationship between EC and microbial biomass C, the percentage of soil organic C present as microbial biomass C, microbial biomass N, microbial biomass N to total N ratio, basal soil respiration, fluorescein diacetate (FDA) hydrolysis rate, arginine ammonification rate and potentially mineralizable N. The exponential relationships with EC demonstrate the highly detrimental effect that soil salinity had on the microbial community. In contrast, the metabolic quotient (qCO2) was positively correlated with EC, and a quadratic relationship between qCO2 and EC was observed. There was an inverse relationship between qCO2 and microbial biomass C. These results indicate that higher salinity resulted in a smaller, more stressed microbial community which was less metabolically efficient. The biomass C to biomass N ratio tended to be lower in soils with higher salinity, reflecting the bacterial dominance in microbial biomass in saline soils. Consequently, our data suggest that salinity is a stressful environment for soil microorganisms.  相似文献   

16.
Biochar is a carbon-rich product obtained by biomass pyrolysis and considered a mean of carbon sequestration. In this research, a sandy calcareous soil from the Farm of the College of Food & Agriculture Sciences, King Saud University, Saudi Arabia, was amended with either woody waste of Conocarpus erectus L.(CW) or the biochar(BC) produced from CW at rates of 0(control), 10, 30 and 50 g kg-1. The effects of the amendments on soil p H, dissolved organic carbon(DOC), microbial biomass carbon(MBC), CO2 emission and metabolic quotient(q CO2) of the sandy calcareous soil were studied in a 60-d incubation experiment. The results showed that the addition of CW led to a significant decrease in soil p H compared to the control and the addition of BC. The CO2-C emission rate was higher in the first few days of incubation than when the incubation time progressed. The cumulative CO2-C emission from the soil amended with CW, especially at higher rates, was higher(approximately 3- to 6-fold) than that from the control and the soil amended with BC. The BC-amended soil showed significant increases in CO2-C emission rate during the first days of incubation as compared to the non-amended soil, but the increase in cumulative CO2-C emission was not significant after 60 d of incubation. On the other hand, CW applications resulted in considerably higher cumulative CO2-C emission, MBC and DOC than the control and BC applications. With the exception of 0 day(after 1 h of incubation), both CW and BC applications led to lower values of q CO2 as compared to the control. The power function kinetic model satisfactorily described the cumulative CO2-C emission. Generally, the lowest values of CO2 emission were observed in the soil with BC, suggesting that the contribution of BC to CO2 emission was very small as compared to that of CW.  相似文献   

17.
 N transfer from 15N-labelled decomposing material into the microbial biomass and inorganic N forms was studied for more than 2 years at three experimental sites differing in climatic conditions and earthworm abundance. The 15N-labelled decomposing material was mixed with low-elevation soil (LES), mid-elevation soil (MES) and high-elevation soil (HES). The amended soils were put into two kinds of plastic cylinders closed on both sides with nets preventing (0.1 cm mesh) and allowing (0.5 cm mesh) access by earthworms, and were buried in soil (20 cm depth) to monitor the transfer of N from the 15N-labelled decomposing material. Climate and soil type play an important role in the release of N from decomposing material. LES transplanted to more humid sites (mid- and high-elevation sites) showed an increase in most of its biological activities (N atom % excess, and microbial biomass C and N). Furthermore, LES was a sandy soil in which the 15N-labelled decomposing material was less bound than in MES and HES, which contained more silt and clay. This resulted in faster organic matter turnover when climatic conditions were favourable. The presence of earthworms greatly increased the quantity of inorganic N (mainly NH4 +) in the soils and enhanced the release of N from the 15N-labelled decomposing material and the native organic matter, compared to soil without earthworms. Received: 21 January 1999  相似文献   

18.
Interactions between microbial communities and organic matter were analyzed for soils from the project regions ’︁Ecosystem Research in the Agricultural Landscape/FAM, Munich’ in southern Germany and ’︁Ecosystem Research in the Bornhöved Lake district’ from northern Germany using ratios between microbial biomass content (Cmic), microbial metabolic quotient (qCO2) and organic carbon content (Corg). In the agricultural soils in southern Germany, the qCO2/Corg ratio differed significantly with respect to agricultural management in contrast to ecophysiological Cmic/Corg ratio. In addition, Cmic/Corg ratio decreased from 39 to 21 mg Cmic g—1 Corg and qCO2/Corg ratio increased from 72 to 180 mg CO2‐C g—1 Cmic h—1 (g Corg g—1 soil)—1 with increasing soil depth. For the upper soil horizons from the landscape in northern Germany the two quotients differed significantly with reference to land use showing highest microbial colonization under grassland and lowest under beech forest. In contrast, C use efficiency was lowest in arable field under maize monoculture and highest in a wet grassland having a high organic C content.  相似文献   

19.
Biochar application to arable soils could be effective for soil C sequestration and mitigation of greenhouse gas (GHG) emissions. Soil microorganisms and fauna are the major contributors to GHG emissions from soil, but their interactions with biochar are poorly understood. We investigated the effects of biochar and its interaction with earthworms on soil microbial activity, abundance, and community composition in an incubation experiment with an arable soil with and without N-rich litter addition. After 37 days of incubation, biochar significantly reduced CO2 (up to 43 %) and N2O (up to 42 %), as well as NH4 +-N and NO3 ?-N concentrations, compared to the control soils. Concurrently, in the treatments with litter, biochar increased microbial biomass and the soil microbial community composition shifted to higher fungal-to-bacterial ratios. Without litter, all microbial groups were positively affected by biochar × earthworm interactions suggesting better living conditions for soil microorganisms in biochar-containing cast aggregates after the earthworm gut passage. However, assimilation of biochar-C by earthworms was negligible, indicating no direct benefit for the earthworms from biochar uptake. Biochar strongly reduced the metabolic quotient qCO2 and suppressed the degradation of native SOC, resulting in large negative priming effects (up to 68 %). We conclude that the biochar amendment altered microbial activity, abundance, and community composition, inducing a more efficient microbial community with reduced emissions of CO2 and N2O. Earthworms affected soil microorganisms only in the presence of biochar, highlighting the need for further research on the interactions of biochar with soil fauna.  相似文献   

20.
We investigated Cd, Zn, and Cd + Zn toxicity to soil microbial biomass and activity, and indigenous Rhizobium leguminosarum biovar trifolii, in two near neutral pH clay loam soils, under long-term arable and grassland management, in a 6-month laboratory incubation, with a view to determining the causative metal. Both soils were amended with Cd- or Zn-enriched sewage sludge, to produce soils with total Cd concentrations at four times (12 mg Cd g−1 soil), and total Zn concentrations (300 mg Zn kg−1 soil) at the EU upper permitted limit. The additive effects of Cd plus Zn at these soil concentrations were also investigated. There were no significant differences in microbial biomass C (B C), biomass ninhydrin N (B N), ATP, or microbial respiration between the different treatments. Microbial metabolic quotient (defined as qCO2 = units of CO2–C evolved unit−1 biomass C unit−1 time) also did not differ significantly between treatments. However, the microbial maintenance energy (in this study defined as qCO2-to-μ ratio value, where μ is the growth rate) indicated that more energy was required for microbial synthesis in metal-rich sludge-treated soils (especially Zn) than in control sludge-treated soils. Indigenous R. leguminosarum bv. trifolii numbers were not significantly different between untreated and sludge-treated grassland soils after 24 weeks regardless of metal or metal concentrations. However, rhizobial numbers in the arable soils treated with metal-contaminated sludges decreased significantly (P < 0.05) compared to the untreated control and uncontaminated sludge-treated soils after 24 weeks. The order of decreasing toxicity to rhizobia in the arable soils was Zn > Cd > Cd + Zn.  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