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1.
This study aims to determine leaf litter preference, consumption rate, growth rate, food conversion efficiency, and quality
of fecal pellets of two endemic pill millipedes (Arthrosphaera dalyi and Arthrosphaera davisoni) of the Western Ghats of India by laboratory microcosm experiments. Among seven combinations of three plantation leaf litters
offered in 4-day trial, top three preferred combinations were selected for 4-week trial. In 4-week trial, preference of mixed
litter diet was higher than single litter diet, which resulted in enhanced growth as well as food conversion efficiency of
millipedes. Among Hopea
,
Pongamia
, and Areca litters, A. dalyi preferred Hopea + Pongamia, and its consumption was significantly correlated with contents of organic carbon (P < 0.05; r = –0.97) and nitrogen (P < 0.01; r = 0.99), while growth rate with phosphorus content (P < 0.05; r = 0.97) and food conversion efficiency with contents of organic carbon (P < 0.05; r = 0.98) and calcium (P < 0.01; r = –0.99). Among Areca
,
Elettaria
, and Coffea litters, Areca + Elettaria
+ Coffea was most preferred by A. davisoni, which was significantly correlated with organic carbon content (P < 0.05; r = 0.98) and food conversion efficiency with calcium content (P < 0.0001; r = 0.99). The food conversion efficiency, however, was the highest in millipedes fed with Areca
+
Elettaria. The present study demonstrated increased nitrogen and phosphorus contents and decreased phenolic content and C/N ratio in
fecal pellets of pill millipedes fed with plantation litter, and thus, these millipedes play an important role in leaf litter
mineralization and soil enrichment in plantations Western Ghats. 相似文献
2.
3D skeleton reconstructions of natural earthworm burrow systems using CAT scan images of soil cores 总被引:2,自引:0,他引:2
Y. Capowiez A. Pierret O. Daniel P. Monestiez A. Kretzschmar 《Biology and Fertility of Soils》1998,27(1):51-59
Four soil cores (length, 20 cm; diameter, 16 cm) were sampled in a Swiss pre-Alpine meadow with high earthworm abundance
(>400 individuals/m2); two cores were taken in October 1993 and the other two cores in April 1994. The cores were described using computer assisted
tomography which gives a series of section images every 3 mm. A method for reconstructing the three-dimensional (3D) skeleton
of the earthworm burrow system is presented and discussed. This method provides an image of the structural organisation of
the burrow system and was found to be adequately sensitive for use in ecological and functional studies. The seasonal variation
of these 3D skeletons was investigated using two approaches, i.e. the analysis of: (1) global burrow system characteristics,
and (2) individual burrow characteristics. At the scale of the global burrow system no difference was found between seasons
(same number of burrows and same total burrow length) except for the vertical segment distribution, which was homogeneous
in spring and decreased with depth in the fall. The study of individual burrow characteristics revealed that burrows tended
to be more vertical in spring and that their branching intensity was higher in this season.
Received: 10 June 1997 相似文献
3.
Tillage practice influences on the physical protection, bioavailability and composition of particulate organic matter 总被引:7,自引:0,他引:7
This study was conducted to determine whether separation of particulate organic matter (POM) that is biologically labile
from aggregate entrapped material improves the usefulness of POM as an index of soil C and N dynamics. The effects of conventional
(CT) and no-tillage (NT) practices on POM were assessed using soils from three 10-year trials in Illinois. Loose and occluded
POM in the 0–5 cm depth were separated from 1994 samples. Use of NT practices increased C and N contents at 0–5 cm relative
to CT practices and those increases were most apparent in the occluded POM fraction. The correlation between total POM-N and
potentially mineralizable N (PMN) was stronger than that between PMN and either the loose or occluded-POM fractions. In 1995,
both the microbial biomass, estimated as chloroform-labile C (CFEC), and PMN were correlated with POM-C and N, but the relationship
was weak when data (from different tillage and depth combinations) were not treated in aggregate. POM-C and CFEC were most
strongly correlated in surface depths and in CT treatments. In NT 0–5 cm samples, PMN contents were similar (≈27 mg N kg–1 soil) at all sites despite notable differences in POM-N concentrations; PMN was not related to POM-N in CT samples. There
was no consistent relationship between PMN and POM-N contents in 5–30 cm samples. DRFTIR spectra indicated that carbohydrates
were most abundant in POM at 0–5 cm. Relatively low PMN rates and enrichment of polysaccharides in POM in the sicl soil suggest
that physical protection of labile organic substrates was more important at that site than at sites with lighter textured
soils. Improved fractionation and incubation techniques and alleviation of laboratory artifacts will improve our ability to
relate POM quantity, distribution and composition to biologically mediated C and N dynamics occurring in the field.
Received: 2 December 1999 相似文献
4.
Denitrification plays an important role in N-cycling. However, information on the rates of denitrification from horticultural
growing media is rare in literature. In this study, the effects of pH, N, C, and moisture contents on denitrification were
investigated using four moderately decomposed peat types (oligotrophic, mesotrophic, eutrophic, and transitional). Basal and potential denitrification rates (20°C, 18 h) from the unlimed peat samples varied widely from 2.0 to 21.8 and
from 118.9 to 306.6 μg (N2O + N2)–N L−1 dry peat h−1, respectively, with the highest rates from the eutrophic peat and the lowest from the transitional one. Both basal and potential
denitrification rates were substantially increased by 3.6–14- and 1.4–2.3-fold, respectively, when the initial pH (4.3–4.8)
was raised to 5.9–6.5 units. Emissions of (N2O + N2)–N from oligotrophic, mesotrophic, and transitional peats were markedly increased by the addition of 0.15 g NO3–N L−1 dry peat but further additions had no effect. Denitrification rates were increased by increasing glucose concentration suggesting
that the activity of denitrifiers in all peat types was limited by the low availability of easily decomposable C source. Increasing
moisture contents of all peats from 40 to 50% water-filled pore space (WFPS) did not significantly (p > 0.05) increase (N2O + N2)–N emissions. However, a positive effect was observed when the moisture contents were increased from 60% to 70% WFPS in the
eutrophic peat, from 70% to 80% in the transitional, from 80% to 90% in the oligotrophic and from 70% to 90% in the mesotrophic
peat. It can be concluded that liming, N-fertilization, availability of easily decomposable C, and moist condition above 60%
WFPS could encourage denitrification from peats although the rates are greatly influenced by the peat-forming environments
(eutrophic > mesotrophic > oligotrophic > transitional types). 相似文献
5.
The effects of biochar properties on crop growth are little understood. Therefore, biochar was produced from eight feedstocks
and pyrolyzed at four temperatures (300°C, 400°C, 500°C, 600°C) using slow pyrolysis. Corn was grown for 46 days in a greenhouse
pot trial on a temperate and moderately fertile Alfisol amended with the biochar at application rates of 0.0%, 0.2%, 0.5%,
2.0%, and 7.0% (w/w) (equivalent to 0.0, 2.6, 6.5, 26, and 91 t biochar ha−1) and full recommended fertilization. Animal manure biochars increased biomass by up to 43% and corn stover biochar by up
to 30%, while food waste biochar decreased biomass by up to 92% in relation to similarly fertilized controls (all P < 0.05). Increasing the pyrolysis temperature from 300°C to 600°C decreased the negative effect of food waste as well as
paper sludge biochars. On average, plant growth was the highest with additions of biochar produced at a pyrolysis temperature
of 500°C (P < 0.05), but feedstock type caused eight times more variation in growth than pyrolysis temperature. Biochar application rates
above 2.0% (w/w) (equivalent to 26 t ha−1) did generally not improve corn growth and rather decreased growth when biochars produced from dairy manure, paper sludge,
or food waste were applied. Crop N uptake was 15% greater than the fully fertilized control (P < 0.05, average at 300°C) at a biochar application rate of 0.2% but decreased with greater application to 16% below the N
uptake of the control at an application rate of 7%. Volatile matter or ash content in biochar did not correlate with crop
growth or N uptake (P > 0.05), and greater pH had only a weak positive relationship with growth at intermediate application rates. Greater nutrient
contents (N, P, K, Mg) improved growth at low application rates of 0.2% and 0.5%, but Na reduced growth at high application
rates of 2.0% and 7.0% in the studied fertile Alfisol. 相似文献
6.
Manuel Aira Niall P. McNamara Trevor G. Piearce Jorge Domínguez 《Journal of Soils and Sediments》2009,9(1):54-61
Background, aim, and scope Earthworms make a major contribution to decomposition in ecosystems where they are present, mainly acting in the drilosphere,
that is, galleries, burrows, casts, and middens. Earthworm middens are hot-spots of microbial activity and nutrient dynamics
and represent a suitable model for studying earthworm-mediated influences on soil microbial communities by alteration of the
patch structure of the microbial environment. We studied the structure and activity of the microbial communities in the soil
system formed by middens of Lumbricus terrestris and the soil below and surrounding them and the role of earthworms in maintaining these structures through time.
Material and methods We set up an experiment in which middens were either left (control) or removed from their original place (translocated) and
left in a nearby area free of earthworm activity for 2 months. After 1 and 2 months we sampled middens, soil below them, and
surrounding soil. We analyzed the phospholipid fatty acid (PLFA) profiles and measured respiratory fluxes of CO2 and CH4.
Results Microbial communities of middens clearly differed from those of soil below and surrounding soil samples, showing higher bacterial
and fungal PLFAs (p < 0.0001 and p < 0.01, respectively); furthermore, changes in microbial communities were stronger in control middens than in translocated
middens. Moreover, gram positive and negative bacterial PLFAs were greater in translocated than control middens (p < 0.0001 and p < 0.001, respectively), as well as total organic carbon (p < 0.001). Microbial activity was higher in middens than in soil below and surrounding soil samples both for CO2 (p < 0.0001) and CH4 (p < 0.0001).
Discussion Soil bioturbation by the earthworm L. terrestris was strong in their middens, but there was not any effect on soil below and surrounding soil. Microbial communities of middens
maintain their biomass and activity when earthworms were not present, whereas they decreased their biomass and increased their
activity when earthworms were present.
Conclusions Earthworms strongly enhanced microbial activity measured as CO2 production in middens, which indicates that there are hot spots for soil microbial dynamics and increasing habitat heterogeneity
for soil microorganisms. Moreover, our data strongly support the fact that the impact of this earthworm species in this soil
is restricted to their middens and increasing soil heterogeneity.
Recommendations and perspectives Our data indicate that it is not clear if earthworms enhance or depress microbial communities of middens since the microbial
activity increased, but did not modify their biomass and this was not dependent on soil organic C content. These results indicate
no competence for C pools between this anecic earthworm and microorganisms, which has been found for other earthworm species,
mainly endogeics. Conversely, they suggest some type of facilitation due to the release of additional nutrient pools in middens
when earthworms are present, through the digestion of middens' material or the addition of casts produced from other food
sources. 相似文献
7.
Leaves of eupatorium and lantana were separately composted in the laboratory in two phases. The first phase was run for 28
days at 50°C inside a hot-air oven and the second phase at room temperature for more than 5 months. After composting, the
C/N ratio of the dry matter fell from 13.4 and 12.9 to 8.2 and 9.2 in eupatorium and lantana, respectively. The nitrogen contents
of composted materials increased by 43 and 29% in eupatorium and lantana, respectively. In both composts, ammonium contents
were much higher than nitrate contents. The light absorbance at 665 nm by acetone extracts decreased by 39% in eupatorium
in comparison to 87% in lantana. The total extractable lipid phosphate contents decreased in both composts from about 4 μmol
(during the mid-thermophilic phase) to less than 0.5 μmol lipid phosphate g–1 dry matter. After composting, germination bioassays with Chinese cabbage seeds showed nearly complete elimination of allelopathic
potentials of both plant materials. However, the germination index of Dia sorghum indicated that eupatorium, but not lantana,
compost still retained a significant inhibitory potential.
Received: 5 March 1997 相似文献
8.
The evolution of clay soil porosity is currently demonstrated via the shrinkage curves in a large water content domain spreading from a shrinkage limit to a liquidity limit. In fact, the parallel between in situ profiles and the shrinkage curves in such a large water content range is difficult to obtain because of the lack of earth pressure in the laboratory tests and in situ limited water contents. The vertical distribution of porosity throughout a clay-rich marsh soil profile was studied in a grassland field with samples taken from the soil surface characterized by water contents near their shrinkage limit down to 2.00 m deep saturated sediments over their liquidity limit. The depth of the plasticity limit isolates a soil in a solid state characterized by a vertical prism-like structure from a plastic to pseudo-liquid state in depth. The porosity was calculated from the measurements of the density of intact samples by double weighing and image analysis of 100 cm2 polished sections. The initial structure of clay soil was maintained by impregnation based on water–acetone–resin exchange. An ultraviolet photo luminescent pigment added to the resin allowed the capture of images from which shrinkage cracks and microporosity of the clay matrix were easily separated. The distribution of porosity between the shrinkage crack mesoporosity and the clay matrix microporosity was evaluated after the mathematical decomposition of the grey level curves characteristic of each level. Vertical evolution of the porosity distribution from the soil surface in a solid state to the plastic and pseudo-liquid sediment in depth was presented on the shrinkage curve of the clay material. The measurements point out how the clay matrix microporosity and mesoporosity of shrinkage cracks are complementary and the role of the scale effect on the shrinkage curve. The analysis of images captured on an optical microscope under polarized and analyzed light and the SEM observation of freeze-dried samples demonstrated the isotropic arrangement of the clay particles in typical “honey-comb” architecture in the in situ plastic-to-liquid saturated domain. Eventually the distribution of porosity through the profile results from the evolution of the initial “honey-comb” microstructure of the sediment induced by the desiccation phenomenon. It is governed by the depth of plasticity limit of the clay material and by the depth of the water table. 相似文献
9.
Effects of salts and moisture content on N2O emission and nitrogen dynamics in Yellow soil and Andosol in model experiments 总被引:2,自引:0,他引:2
The effects of salt type and its concentration on nitrification, N mineralization and N2O emission were examined under two levels of moisture content in Yellow soil and Andosol samples as simulated to agriculture
under arid/semi-arid conditions and under heavy application of fertilizer in a glass-house, respectively. The salt mixtures
were composed of chlorides (NaCl and NH4Cl) or sulphates [Na2SO4 and (NH4)2SO4] and were added at various concentrations (0, 0.1, 0.2, 0.4 and 0.6 M as in the soil solution). These salts were added to
non-saline Yellow soil at different moisture contents (45 or 40 and 65% of maximum water-holding capacity; WHC) and their
effects on the changes in mineral N (NH4
+-N and NO3
–-N) concentration as well as N2O emission were examined periodically during laboratory incubation. We also measured urease activities to know the effect
of salts on N mineralization. Furthermore, Ca(NO3)2 solution was added at various concentrations (0, 0.1, 0.3, 0.5 and 0.8 M as in the soil solution) to a non-saline Andosol
taken from the subsurface layer in a glass-house and incubated at different moisture contents (50% and 70% of WHC) to examine
their effects on changes in mineral N. Nitrification was inhibited by high, but remained unaffected by low, salt concentrations.
These phenomena were shown in both the model experiments. It was considered that the salinity level for inhibition of nitrification
was an electric conductivity (1 : 5) of 1 dS m–1. This level was independent of the type of salts or soil, and was not affected by soil moisture content. The critical level
of salts for urease activities was about 2 dS m–1. The emission rate of N2O was maximum at the beginning of the incubation period and stabilized at a low level after an initial peak. There was no
significant difference in N2O emission among the treatments at different salt concentrations, while higher moisture level enhanced N2O emission remarkably.
Received: 29 July 1998 相似文献
10.
Long-term experiments on different crop management systems provide essential information about turnover of soil organic matter
and changes in microbial properties over a period of time. A long-term field site trial, which was established in 1967 near
Vienna, Austria, to document the fate of 14C-labelled manure (straw and farmyard) under different crop management systems (crop rotation, spring wheat and bare fallow),
was investigated. Soil samples were taken in 1997 and separated into size fractions (>250 μm, 250–63 μm, 63–2 μm, 2–0.1 μm
and <0.1 μm) after aggregate dispersion using low-energy sonication. Organic C, total N and 14C content were measured in the bulk soil and the size fractions and microbial properties were analysed in the bulk soil. Additionally,
C mineralization in bulk soil samples was monitored at 20 °C over a period of 28 days, and subsequently 14C-CO2 content was analysed. The distribution of organic C and N within the size fractions was similar between crop rotation and
spring wheat; the highest amounts of organic C and N were found in the clay-sized fraction. The amounts of C and N were significantly
smaller in the bare fallow, which was depleted of organic matter in the coarse-sized fractions. 14C distribution differed significantly from unlabelled C distribution, labelled C was accumulated in the silt-sized fraction,
indicating weak humification of the applied manure C. The highest rate of C mineralization was measured in the crop rotation
and spring wheat, whereas the emission rate of the bare fallow was about 40% lower. The higher 14C:C ratio of the bulk soil in comparison to the emitted CO2 indicated that labelled C compounds still remained mineralizable after a period of 30 years. Microbial properties showed
a great difference between crop management systems and bare fallow, particularly regarding urease and xylanase activity.
Received: 31 May 1999 相似文献
11.
Bruno B. Cunha Wander Gustavo Botero Luciana Camargo Oliveira Viviane M. Carlos Marcelo L. M. Pompêo Leonardo F. Fraceto André H. Rosa 《Water, air, and soil pollution》2012,223(1):329-336
The sorption of four endocrine disruptors, bisphenol A (BPA), estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2)
in tropical sediment samples was studied in batch mode under different conditions of pH, time, and sediment amount. Data obtained
from sorption experiments using the endocrine disruptors (EDs) and sediments containing different amounts of organic matter
showed that there was a greater interaction between the EDs and organic matter (OM) present in the sediment, particularly
at lower pH values. The pseudosecond order kinetics model successfully explained the interaction between the EDs and the sediment
samples. The theoretical and experimentally obtained q
e values were similar, and k values were smaller for higher SOM contents. The k
F values, obtained from the Freundlich isotherms, varied in the ranges 4.2–7.4 × 10−2 (higher OM sediment sample, S2) and 1.7 × 10−3–3.1 × 10−2 (lower OM sediment sample, S1), the latter case indicating an interaction with the sediment that increased in the order: EE2 > > E2 > E1 > BPA. These results
demonstrate that the availability of endocrine disruptors may be directly related to the presence of organic material in sediment
samples. Studies of this kind provide an important means of understanding the mobility, transport, and/or reactivity of this
type of emergent contaminant in aquatic systems. 相似文献
12.
Recovering decomposing plant residues from the particulate soil organic matter fraction: size versus density separation 总被引:2,自引:0,他引:2
A detailed size separation of particulate organic matter (POM) from soils amended with straw from Hordeum vulgare or Vicia sativa revealed that the loss of C during the first 56 days of incubation mainly occurred from particles >2,000 μm, without a concomitant
reduction in the size of these large particles. Preliminary studies of POM from non-amended soil had shown that the stable
heavy (>1.4 g cm–3) POM fraction was mainly (>80%) composed of particles <400 μm, whereas the light fraction was dominated by larger particles
(>80%). Therefore we decided to compare the POM <1.4 g cm3 with POM >400 μm. There was a very close relationship between POM>400 μm and POM <1.4 g cm–3 with regard to amounts of C and N, as well as the appearance of these fractions under the microscope. Similarly there was
a close relationship between changes in the C content of the POM fractions and the CO2 respired, and this was also the case when comparing changes in POM-N with net N mineralization. This indicated that the biological
activity during decomposition was actually localized in the POM. Due to the lighter workload and lower expenditure for reagents
in connection with size separation of POM, we recommend the size separation procedure in connection with studies of residue
decomposition in arable systems.
Received: 23 May 2000 相似文献
13.
Soil organic carbon stocks,distribution, and composition affected by historic land use changes on adjacent sites 总被引:1,自引:0,他引:1
Historic alterations in land use from forest to grassland and cropland to forest were used to determine impacts on carbon
(C) stocks and distribution and soil organic matter (SOM) characteristics on adjacent Cambisols in Eastern Germany. We investigated
a continuous Norway spruce forest (F-F), a former cropland afforested in 1930 (C-F), and a grassland deforested in 1953 (F-G).
For C and N stocks, we sampled the A and B horizons of nine soil pits per site. Additionally, we separated SOM fractions of
A and B horizons by physical means from one central soil pit per pedon. To unravel differences of SOM composition, we analyzed
SOM fractions by 13C-CPMAS NMR spectroscopy and radiocarbon analysis. For the mineral soils, differences in total C stocks between the sites
were low (F-F = 8.3 kg m−2; C-F = 7.3 kg m−2; F-G = 8.2 kg m−2). Larger total C stocks (+25%) were found under continuous forest compared with grassland, due to the C stored within the
organic horizons. Due to a faster turnover, the contents of free particulate organic matter (POM) were lower under grassland.
High alkyl C/O/N-alkyl C ratios of free POM fractions indicated higher decomposition stages under forest (1.16) in relation
to former cropland (0.48) and grassland (0.33). Historic management, such as burning of tree residues, was still identifiable
in the subsoils by the composition and 14C activity of occluded POM fractions. The high potential of longer lasting C sequestration within fractions of slower turnover
was indicated by the larger amounts of claybound C per square meter found under continuous forest in contrast to grassland. 相似文献
14.
A study was conducted to determine mineralization rates in the field and in different soil layers under three grassland managements
(viz. a reseeded sward, a permanent sward with a conventional N management, and a long-term grass sward with 0 N (0-N) input).
Potential mineralization rates of soil particles (sand, silt and clay) and macro-organic matter fractions of different sizes
(i.e. 0.2–0.5, 0.5–2.0 and >2 mm) were also determined in the laboratory. In the reseeded plots, net mineralization was unchanged
down to 40 cm depth. In the undisturbed conventional-N swards, mineralization rates were substantially higher in the top layer
(0–10 cm) than in the deeper layers. In plots which had received no fertilizer N, mineralization was consistently low in all
the layers. There was more macro-organic matter (MOM) in the 0-N plots (equivalent to 23 g kg–1 soil for 0–40 cm) than in the two fertilized plots (i.e. conventional-N and reseeded) which contained similar amounts (ca. 15 g kg–1 soil). C and N contents of separated soil particles did not differ amongst the treatments, but there were large differences
with depth. Potential mineralization in the bulk soil was greatest in the 0–10 cm layers and gradually decreased with depth
in all the treatments. Separated sand particles had negligible rates of potential mineralization and the clay component had
the highest rates in the subsurface layers (10–40 cm). MOMs had high potential rate of mineralization in the surface layer
and decreased with soil depth, but there was no clear pattern in the differences between different size fractions.
Received: 17 November 1997 相似文献
15.
Tillage and land use effects on methane oxidation rates and their vertical profiles in soil 总被引:11,自引:0,他引:11
B. W. Hütsch 《Biology and Fertility of Soils》1998,27(3):284-292
The effect of land use and different soil tillage systems on CH4 oxidation was tested in a laboratory incubation study. Intact soil cores were collected from the topsoil (0–12 cm) of a field
site with ploughed, direct-drilled and set-aside treatments, and from an adjacent undisturbed forest site. CH4 oxidation rates were 4.5 to 11 times higher in the direct-drilled than in the continuously ploughed treatment, in the set-aside
soil they were intermediate. The oxidation rates in the forest soil were 11 times the highest rate measured at the field site,
pointing to a distinct land use effect. Vertical profiles of CH4 oxidation activity revealed a very clear zonation in all treatments. CH4 oxidation increased significantly below the plough layer (0–25 cm), and showed a subsurface maximum under direct-drilling
(5–15 cm) and under forest (5–10 cm). The vertical zonation under set-aside was comparable to that under ploughing. Generally,
the maximum CH4 oxidizing activity was in the zone nearest to the soil surface, unless various constraints prevented this.
Received: 1 December 1997 相似文献
16.
Mirjana Stojanović Dragi Stevanović Jelena Milojković Marija L. Mihajlović Zorica Lopičić Tatjana Šoštarić 《Water, air, and soil pollution》2012,223(1):135-144
This work was undertaken to study the influence of soil type and its physical and chemical properties on uranium sorption
and bioavailability, in order to reduce the uncertainty associated with this parameter in risk assessment models and safe
food production. The tests were conducted on three types of Serbian soils: alluvium, chernozem, and gajnjaca, from which 67
samples were taken. Dominant factors of uranium mobilisation: the specific content of total/available form of uranium and
phosphorus, the degree of acidity (pHKCl), and humus content and their correlation, were analysed. Content of available uranium form, according to the type of soil
decreases in the following order: gajnjaca > alluvium > chernozem. It was found the medium correlation between pH values and
available content of uranium in chernozem and gajnjaca, statistically significant at the level of significance of 99% and
the alluvium at the level of significance of 95%. Correlation coefficients in all cases were negative, indicating that the
reduction in pH increases the mobility of uranium and thus its availability for the adoption of the plants. Soil pH was the
only dominant factor that significantly controlled the uranium value with no further significant contribution of other soil
parameters. 相似文献
17.
The vertical distribution of native earthworm species from natural and disturbed savannas in the Oxisols of the Colombian
Llanos was assessed in a native savanna and in a 17-year-old grazed grass-legume pasture during a period of 17 months. Different
patterns of vertical stratification were observed for all species with a strong migration of populations to deeper layers
in the dry season. The correlation between the size of the earthworms and the average depth at which they were found was not
significant (P>0.05), despite the fact that bigger species are located deeper in the soil. The living habits and adaptive strategies of
the smallest species, Ocnerodrilidae n. sp., found in both ecosystems studied are responsible for this pattern. This endogeic
species is associated with organic pools generated by an anecic species and further studies should assess the role of this
species in ecosystem functioning. Mature worms of one anecic species were located deeper than immature ones in the soil (P<0.01). Soil moisture had an important effect on the vertical distribution of earthworms, although differences between immature
and mature worms of the anecic Martiodrilus carimaguensis are likely to be of biotic origin. New data on the biology and ecology of these Neotropical species are shown.
Received: 24 November 1999 相似文献
18.
Donghong Wang Qinghua Shi Xiufeng Wang Min Wei Jinyu Hu Jun Liu Fengjuan Yang 《Biology and Fertility of Soils》2010,46(7):689-696
The effects of cow manure vermicompost on plant growth, metabolite contents, and antioxidant activities of Chinese cabbage
were investigated in pot cultures. Five treatments were designed by mixing vermicompost and soil at ratio of 0:7, 1:7, 2:7,
4:7, 7:0 (w/w). Marketable weight of Chinese cabbage was significantly (p < 0.05) higher in the 2:1 treatment than in the other treatments, while plants grown in the full soil treatment (0:7) showed
the lowest marketable weight (Fig. 1a). Vermicompost application significantly increased the nutrient content of Chinese cabbage leaves (p < 0.05), especially in the 4:7 treatment, with increases in the contents of soluble sugar (Fig. 2a), soluble protein (Fig. 2b), vitamin C (Fig. 3a), total phenols (Fig. 3b), and total flavonoids (Fig. 3c) by 62%, 18%, 200%, 25%, and 17% compared to the full soil treatment, respectively. The antioxidant activities expressed
by 2, 2-Dipenyl-1-picrylhydrazyl-scavenging activity (Fig. 4a), hydroxyl (OH)-scavenging activity (Fig. 4b), and iron (Fe2+)-chelating activity (Fig. 4c) were higher by 92%, 40%, and 36% in the 4:7 than 0:7 the treatment, respectively. Vermicompost application significantly
increased (p < 0.05) the plant contents of 16 essential amino acids (Table 1); the total amino acid content showed the greatest increase in the 4:7 treatment, 90% compared to the full soil treatment. 相似文献
19.
Chun-Chao Chuang Yu-Lin Kuo Chen-Ching Chao Wei-Liang Chao 《Biology and Fertility of Soils》2007,43(5):575-584
Two of 187 fungal isolates (Aspergillus niger 1B and 6A) displaying superior phosphate (P) solubilization and hydrolytic enzyme secretion were studied using P forms of
calcium (Ca-P), iron (Fe-P), and aluminum (Al-P). Phosphate solubilization in a sucrose-basal salt (SB) broth was increased
and pH decreased by both isolates. In Ca-P medium, solubilization for 6A was approximately 322 μg P mL−1 and pH decreased by 4.2 units to 2.3 in 72 h. However, when pH value of the SB broth was lowered to 2.5 using HCl, 65.3 ± 0.4 μg
mL−1 of P was released from Ca-P, whereas trace amounts of P were released from Fe-P and Al-P. Both isolates displayed enhanced
Al-P solubilization using NH4Cl rather than KNO3 as the N source; final pH values were not significantly different. With Ca-P, gluconic acid was predominantly produced by
1B and 6A, whereas oxalic acid predominated with Fe-P and Al-P. Addition of gluconic acid (final concentration of 8.5 μmol
mL−1) to Ca-P-supplemented SB lowered pH (2.9) and solubilized phosphate (146.0 ± 1.0 μg mL−1). Similarly, addition of oxalic acid (final concentration 6.6 μmol mL−1) to Ca-P- and Fe-P-amended media solubilized P (60.2 ± 0.9 and 21.6 ± 2.1 μg mL−1, respectively), although these quantities were significantly lower than those detected in unamended SB. The presence of unidentified
P solubilized compound(s) in the dialyzed (MW>500) supernatant warrants further study. In pot experiments, significant increases
in plant (Brassica chinensis Linn.) dry weight and N and P contents were observed with the addition of isolate 6A, when a small amount of organic fertilizer
together with either rock phosphate (South African apatite) or Ca-P served as the main P sources. 相似文献
20.
Influences of organic fertilization and solarization in a greenhouse on particle-size fractions of a Mediterranean sandy soil 总被引:1,自引:0,他引:1
The effects of a composted organic amendment and solarization on the organic matter (OM) of a sandy soil were determined
by means of particle-size fractionation and analysis of carbon and nitrogen contents. After 2 years, total soil carbon increased
under organic fertilization but did not significantly change with solarization. As a consequence of the climatic conditions
in the greenhouse, the carbon concentrations (g kg–1 fraction) of the particle-size fractions were lower than those found for temperate soils and closer to those for tropical
soils. The carbon amounts (g kg–1 soil) and carbon:nitrogen ratios, which were highest in fractions >200 μm, reflected the short-term influence of the industrially
processed organic amendment, rich in composted coarse plant debris. In contrast, the characteristics of the OM associated
with each fraction were not significantly affected by solarization. In comparison with other coarse-textured temperate or
tropical soils, carbon concentrations in fine silt (2–20 μm) and clay (0–2 μm) fractions were very low. This suggests a "greenhouse
effect", together with a high rate of carbon mineralization affecting fine silt and clay fractions.
Received: 19 November 1999 相似文献