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At least 433 records · Page 24Linked to original sources
PubMed2004

[Effect of incorporating corn residues into soil on nitrogen transformation in soil-plant ecosystem].

Appropriate field management of crop residues can help to enhance soil productivity and nutrient recycling, and to minimize greenhouse gas emission. In this paper, a 15N tracer pot experiment was installed to study the effect of incorporating corn stalk and stubble into black soil on the nitrogen transformation in soil-plant ecosystem. The results indicated that compared with single application of N fertilizer, incorporation of corn stalk and stubble could increase soil nitrogen content and enhance its availability, and increase soil microbial nitrogen content. It also promoted the transfer of nitrogen in corn into its kernel, so as to increase the nitrogen use efficiency. Simultaneously, it reduced the content of soil NO3(-)-N, and decreased the fertilizer nitrogen loss by 4.7-5.6%.

Ecosystem↗
PubMed2004

[Dynamics of organic C in black soil of Northeast China, simulated by CENTURY model I. Accumulation of soil organic carbon under natural conditions].

By using CENTURY model, this paper simulated the dynamics of organic carbon and its fractions, including active, slow and passive pools, in black soils under natural condition at Nenjiang, Beian, Hailun and Harbin in Heilongjiang Province and at Gongzhuling in Jilin Province. The results showed that soil organic carbon had increased for a long time, and tended to reach the steady state. In the steady state, soil organic carbon reached 7914.72-11672.78 g x m(-2), which decreased from north to south in geperal. The active, slow and passive fractions were 3.36%-4.62%, 50.54%-55.47% and 36.47%-41.95% of soil organic carbon pool, respectively, which indicated that slow and passive fraction were the main body of soil organic carbon in native ecosystem. The simulated results were in agreement with some observed results, which can be used as the original data in the study on the dynamics of soil organic matter after cultivation.

Biodegradation, Environmental↗
PubMed2005

[Accumulation of phenolic acids in continuously cropped cucumber soil and their effects on soil microbes and enzyme activities].

The study showed that in solar greenhouse continuously cropped cucumber soil, phenolic acids p-hydroxybenzoic acid, ferulic acid and benzoic acid had an obvious accumulation with increasing cropping year, and their contents were significantly higher after continuously cropped for 5 approximately 9 years than for 1 approximately 3 years. With the increasing concentration of treated exogenous phenolic acids, the amounts of bacteria, actinomycetes, total microbes, ammonibacteria, and nitrifying bacteria in cucumber root area increased first, but decreased then. Soil bacteria and actinomycetes had the largest amount at the concentration of 80 microg phenolic acids x g(-1) soil, while soil fungi (including Fusarium and Phytophthora) increased rapidly when the concentration of phenolic acids was lower than 120 microg x g(-1) soil. With increasing phenolic acids concentration, soil enzyme activities also increased first but decreased then, with the peak values differed in different treatments.

Bacteria↗
PubMed2026

Antarctic Peninsula soil carbon stock and efflux: A complex interplay of soil properties and heavy metals.

This study establishes a quantitative framework for understanding surface soil carbon dynamics and ecosystem connectivity in Fildes Peninsula and Ardley Island, King George Island, South Shetland Islands, Antarctic Peninsula. The mean soil organic carbon (SOC) stock across all study sites was 1.10 ± 1.93 kg C/m². Restricting net carbon balance analysis to Fildes Peninsula, where soil respiration (Rs) data were available, yielded a site-specific SOC stock of 0.45 ± 0.45 kg C/m². Scaling Rs to a realistic 120-day active season and assuming stable SOC stocks resulted in estimated annual carbon loss of 15 g C/(m2·yr), equivalent to 3.3 % of standing SOC. Comprehensive sensitivity analyses spanning plausible winter respiration (0 %-20 % of summer rates) and annual change in SOC stocks (-1 %-2 %) consistently supported a net carbon sink, with turnover rates constrained to 3.3 %/yr-4.7 %/yr. Principal component analysis showed that ornithogenic processes as the dominant control on SOC, total nitrogen (TN), zinc (Zn), copper (Cu), and cadmium (Cd) provide a clear multivariate signature of marine-derived nutrient, while Pb was decoupled from this gradient and associated instead with fine-particle size controls. These results reveal dual but independent drivers of soil metal enrichment in this region. Despite their limited spatial extent, ornithogenic soils store disproportionately large carbon pools. Overall, this integrated analysis reveals how marine-terrestrial subsidies regulate Antarctic carbon cycling and provides a quantitative and reproducible framework for assessing carbon dynamics under ongoing climate change.

Antarctic Regions↗
PubMed2004

Enumeration of soil bacteria with the green fluorescent nucleic acid dye Sytox green in the presence of soil particles.

Total counts in soils are usually determined using fluorescent dyes, such as DAPI or Sybr green, due to fluorescence enhancement if they are bound to nucleic acids. Unfortunately, these commonly used dyes stain soil particles as well. Therefore, besides fluorescence enhancement, sufficient spectral differentiation is also required. We present a new procedure that overcomes the problems of visualising bacteria on surfaces in soil and avoids the separation of soil particles to a large extent. Spectral differentiation between bacteria and soil matrix is achieved by using Sytox green and a suboptimal excitation wavelength. Bacteria exhibit a bright green fluorescence, while soil particles fluoresce blue or red. Slight homogenisation and sedimentation of the sand and coarse silt that were too big for microscopic investigations were the only separation steps required. We compared the proposed Sytox green staining with Sybr green staining. The recovery of Sybr green-stained cells amounted to 38%, whereas in samples stained by Sytox green 81% of the spiked cells were counted. Sytox green can also be combined with fluorescence in situ hybridisation (FISH) using deep red dyes such as Cy5.

Aluminum Silicates↗
PubMed2005

Isolation and identification of an EPS-producing Rhizobium strain from arid soil (Algeria): characterization of its EPS and the effect of inoculation on wheat rhizosphere soil structure.

The production of exopolysaccharides (EPSs) by bacterial populations in the rhizosphere has been demonstrated to contribute to water and nutrient uptake by plant roots through the modification of the physical properties of rhizosphere soil. We report here the characterization of a new EPS produced by a bacterial strain (KYGT207) isolated from an arid soil in southern Algeria (Gassi Touil), and the effect of inoculation of this strain on soil physical properties in the rhizosphere of Triticum durum L. Strain KYGT207 was assigned to the genus Rhizobium by 16S ribosomal DNA sequencing and belongs to a new species closely related to Rhizobium sullae. The EPS produced by this strain was found to be composed of glucose (Glc), galactose (Gal), and mannuronic acid (ManA) in a molar ratio of 2:1:1. The primary structure of the EPS was determined by sugar analysis, 1D and 2D NMR spectroscopy, consisting of a tetrasaccharide repeating unit with the following original structure: [structure: see text]. A rheological analysis showed that this EPS could be considered as a thickening agent with polyelectrolyte properties. Inoculation of wheat plantlets with strain KYGT207 caused significant promotion of plant growth (+85% for shoot dry mass and +56% for root dry mass), a significant increase in root-adhering soil (RAS) dry mass (dm) per root dm (RAS/RT) up to 137%, and in RAS aggregate water stability. We demonstrate that EPS-producing bacteria were present in sandy soils subjected to water stress and that EPS-producing Rhizobium populations play an important role in the rhizosphere through their contribution to soil aggregation.

Algeria↗
PubMed2002

Effect of soil properties on bioavailability and extractability of phenanthrene and atrazine sequestered in soil.

Sixteen soils with markedly different properties were analyzed to determine their porosity in the range of 7 nm-10 microm, cation-exchange capacity (CEC), surface area and clay mineralogy. The extent of sequestration of phenanthrene and atrazine has been shown to differ markedly among these soils. Correlations were sought between soil characteristics and four methods of measuring sequestration. Simple correlation analysis showed that some but not all measures of phenanthrene and atrazine sequestration were highly correlated with organic C content, nanoporosity or CEC but not other properties of the soils. Multiple linear-regression analysis suggested an interaction of organic C content with soil texture, CEC or surface area in determining the extent of atrazine or phenanthrene sequestration. We conclude that organic C content, CEC and other properties of soil may be useful predictors of sequestration of some compounds.

Aluminum Silicates↗
PubMed2002

Soil phosphorus quantity-intensity relationships to predict increased soil phosphorus loss to overland and subsurface flow.

Soil phosphorus (P) quantity-intensity (q-i) relationships, based on common extraction methods, may potentially be used to estimate the risk of P loss in overland flow and subsurface drainage water. Some workers have used nonlinear q-i relationships to derive thresholds in soil test P (STP; a quantity factor) above which the risk of P loss increases, while others find linear relationships and no threshold. We present here a simple modelling exercise (based on Langmuir adsorption theory) along with data from literature to explain the behaviour of q-i relationships, and to give an explanation for this apparent discrepancy. The data indicate that q-i relationships are dependent upon the soil to solution ratio of the P intensity parameter, adsorption capacity (Qmax) and strength (K) of the soil, and the total range in STP. In turn, this affects the calculation of a threshold in STP. The q-i relationship tends towards linearity under conditions of a narrow total range of STP and/or when using a wide soil to solution ratio for estimating the P intensity parameter. Under such conditions, a threshold is difficult to detect, and uncertain. We conclude that the sensitivity of thresholds to experimental conditions and soils needs to be considered if thresholds are to be successful in environmental management to decrease P loss to surface waters.

Phosphorus↗
PubMed2003

Estimation of adsorbed amounts of volatile chlorinated organic compounds to wet soil based on the properties of the compounds and soils.

The adsorption equilibriums of 7 volatile organic chlorinated compounds to 10 wet soils were investigated by continuous flow adsorption experiments. The adsorption equilibriums for the wet soils could be expressed by the Henry equation. The most part of the adsorbed amount existed on the organic substances in the soil, and the soil-water adsorption equilibrium constant could be estimated from the organic carbon content of the soil. The adsorption coefficient to the organic carbon of the chloroethylenes and chloroethanes could be expressed by the functions of the n-octanol/water partition coefficient, respectively. The adsorbed amounts could be estimated using equations relating the organic content and the water content of each soil, and the n-octanol/water partition coefficient and the Henry constant for the gas-water equilibrium of each compound. The estimated results agreed well with the measured data.

Adsorption↗
PubMed2003

Effect of industrial pollution on the distribution of 137Cs in soil and the soil-to-plant transfer in a pine forest in SW Finland.

The objective of this study was to evaluate the effect of industrial pollution on the distribution of radiocaesium in soil and on its transfer from soil to plants. The study was started in September 2000 in four Scots pine stands located at distances of 0.5, 2, 4 and 8 km along a transect running SE from the Cu-Ni smelter at Harjavalta in SW Finland. Annual emissions from the smelter in 1990 were 80 t of Cu, 31 t of Ni and 9000 t of SO(2), and in 1999 these were 5.9, 0.8 and 3400 t, respectively. At each site, soil profiles were sampled with a corer, and samples were separated into litter (L), organic soil layer (O) and mineral soil layers (B, E). Mushrooms, lichens (Cladina spp. and Cetraria islandica), lingonberry (Vaccinium vitis-idaea) and crowberry (Empetrum nigrum) plants were collected at each site, except at a distance of 0.5 km, where only mushrooms were available. In the organic soil layer, 137Cs activity decreased from 8000 Bq/m(2) at a distance of 8 km from the smelter to 1500 Bq/m(2) at a distance of 0.5 km; in litter, 137Cs concentration increased from 6300 Bq/m(2) at 8 km to 14000 Bq/m(2) at 0.5 km. 137Cs activity concentration decreased significantly in plants, mushrooms and lichens as the pollution load increased. In lichens, 137Cs activity decreased from 910 Bq/kg at 8 km to 170 Bq/kg at 2 km, while in lingonberry it decreased from 1470 to 20 Bq/kg and in crowberry from 310 to 20 Bq/kg. Aggregated transfer factors for 137Cs decreased in a similar way in lingonberry from 7.6x10(-2) m(2)/kg at 8 km to 7.7x10(-4) m(2)/kg at 2 km and in crowberry from 1.6x10(-2) to 7.9x10(-4) m(2)/kg.

Agaricales↗
PubMed2001

Soil biochemical activity and growth response of rice Oryza sativa in flyash amended soil.

Soil amended with different proportions of flyash, a solid waste generated from coal-fired thermal power plants, was evaluated as a soil conditioner and nutrient supplement during a field study on the growth of rice, Oryza sativa. Generally, pH and organic carbon (OC) content did not increase significantly (P > 0.05) in flyash amended soil, but significant increases (P < 0.05) in soil conductivity (32%), available phosphorus (48%) and organic matter (OM, 29%) were observed during harvest at the 20 t ha-1 flyash application rate. Amylase, invertase, dehydrogenase and protease activities, and CO2 evolution increased in flyash amended soil over the control. The pigment (chl-a, chl-b, and carotenoid) content in rice plants did not vary significantly (P > 0.05) between different flyash amendments. Total plants biomass and aboveground biomass increased (P < 0.05) significantly (17% and 25%, respectively) at the 20 t ha-1 flyash application. However, there was a retarded growth of underground biomass. Grain and straw yield increased by 21% and 18%, respectively, at 17.5 t ha-1 flyash amendment when compared to the control. Although, a significant increase (P < 0.05) in plant biomass and grain yield in flyash amended soil is encouraging from the point of waste disposal and management, elucidation of reasons for retarded growth in underground biomass will require additional research based on long-term studies.

Amylases↗
PubMed2002

Effect of wood ash application on soil solution chemistry of tropical acid soils: incubation study.

The objective of this study was to determine the effect of wood ash application on soil solution composition of three tropical acid soils. Calcium carbonate was used as a reference amendment. Amended soils and control were incubated for 60 days. To assess soluble nutrients, saturation extracts were analysed at 15 days intervals. Wood ash application affects the soil solution chemistry in two ways, as a liming agent and as a supplier of nutrients. As a liming agent, wood ash application induced increases in soil solution pH, Ca, Mg, inorganic C, SO4 and DOC. As a supplier of elements, the increase in the soil solution pH was partly due to ligand exchange between wood ash SO4 and OH- ions. Large increases in concentrations of inorganic C, SO4, Ca and Mg with wood ash relative to lime and especially increases in K reflected the supply of these elements by wood ash. Wood ash application could represent increased availability of nutrients for the plant. However, large concentrations of basic cations, SO4 and NO3 obtained with higher application rates could be a concern because of potential solute transport to surface waters and groundwater. Wood ash must be applied at reasonable rates to avoid any risk for the environment.

Calcium↗
PubMed2006

Fate of prions in soil: adsorption and extraction by electroelution of recombinant ovine prion protein from montmorillonite and natural soils.

Prions, the infectious agents thought to be responsible for transmissible spongiform encephalopathies, may contaminate soils and have been reported to persist there for years. We have studied the adsorption and desorption of a model recombinant prion protein on montmorillonite and natural soil samples in order to elucidate mechanisms of prion retention in soils. Clay minerals, such as montmorillonite, are known to be strong adsorbents for organic molecules, including proteins. Montmorillonite was found to have a large and selective adsorption capacity for both the normal and the aggregated prion protein. Adsorption occurred mainly via the N-terminal domain of the protein. Incubation with standard buffers and detergents did not desorb the full length protein from montmorillonite, emphasizing the largely irreversible trapping of prion protein by this soil constituent. An original electroelution method was developed to extract prion protein from both montmorillonite and natural soil samples, allowing quantification when coupled with rapid prion detection tests. This easy-to-perform method produced concentrated prion protein extracts and allowed detection of protein at levels as low as 0.2 ppb in natural soils.

Adsorption↗
PubMed2006

Influence of pH and soil copper on adsorption of metalaxyl and penconazole by the surface layer of vineyard soils.

The upper horizons of old vineyard soils have substantial copper contents due to the traditional use of copper-based fungicides. Total copper levels in eight vineyard soils in the Rías Baixas area of Galicia (northwestern Spain) ranged from 60 to 560 mg kg(-1) (mean +/- SD = 206 +/- 170 mg kg(-1)). The adsorption of the fungicides metalaxyl (pK(a) = 1.41) and penconazole (pK(a) = 2.83) by these soils was determined using fungicide solutions of pH 2.5 and 5.5, and desorption of fungicide adsorbed at pH 5.5 was also determined. In all cases, Freundlich equations were fitted to the data with R (2) > 0.96. Penconazole was adsorbed and retained more strongly than metalaxyl, with K(F) values more than an order of magnitude greater. In the desorption experiments, both fungicides exhibited hysteresis. Soil copper content hardly affected the adsorption of metalaxyl, but K(F) values for adsorption of penconazole increased at a rate of about 0.1 mL(n) (microg of penconazole)(1-n) (microg of Cu)(-1), which is attributed to the formation of Cu(2+)-penconazole complexes with greater affinity for soil colloids than penconazole itself. Because the dependence of K(F) for penconazole adsorption on copper content was the same at both pH values, complex formation appears not to have been affected by the solubilization of 6-17% of soil copper at pH 2.5. A similar copper dependence, or lack of dependence, was observed when 100-1000 mg kg(-1) of copper was added as Cu(NO(3))(2).2H(2)O to the solutions from which the fungicides were adsorbed.

Adsorption↗
PubMed2003

Soil properties and crop productivity as influenced by flyash incorporation in soil.

Field experiments were carried out during 1996-97 at Gulawathi, Muthiani and Salarpur Villages, IARI Farm, New Delhi and NCPP Campus, Dadri to evaluate changes in soil characteristics and growth of wheat (Triticum aestivum L.), mustard (Brassica juncea L.), lentil (Lence esculenta Moench.), rice (Oryza sativa L.) and maize (Zea mays L.) by varying amounts of flyash addition (up to 50t ha(-1)) in soils at sowing/transplanting time of crops. Flyash addition in areas adjoining NCPP Thermal Power Plant, Dadri, Ghaziabad, U.P. ranged from 5-12 t ha(-1)] yr(-1) in 1995-96. Shoot and root growth and yield of test crops at different locations after flyash incorporation resulted in beneficial effects of flyash addition in most cases. The silt dominant texture of flyash improved loamy sand to sandy loam textures of the surface soils at the farmers' fields. The increased growth in yield of crops with flyash incorporation was possibly due to modifications in soil moisture retention and transmission characteristics, bulk density, physico-chemical characters such as pH and EC and organic carbon content. The response of flyash addition in the soil on soil health and crop productivity needs to be evaluated on long-term sustainable aspects.

Agriculture↗
PubMed2003

Laboratory-polluted soils: a methodological approach to establish equilibrium conditions for different metal chemical forms in soils.

An approach based on the number of extractions performed over time was applied to study the time necessary to attain equilibrium conditions between the different chemical forms present in two natural soils laboratory-loaded with heavy metals (Cu(II), Pb(II), Zn(II)). The influence of some soil parameters, such as pH value, cation exchange capacity and organic matter content, on the equilibrium time was evidenced both by the different nature of the soils and by the treatment of soils with paper mill sludge. Equilibrium conditions were determined by studying the metal partitioning in the soil on a case by case basis. The behaviour of the three metals was not the same, and the conditions of equilibrium among the different chemical forms were the result of the amount of heavy metals added as well as of the nature of the soil.

Copper↗
PubMed2001

Quantification of bacterial subgroups in soil: comparison of DNA extracted directly from soil or from cells previously released by density gradient centrifugation.

All molecular analyses of soil bacterial diversity are based on the extraction of a representative fraction of cellular DNA. Methods of DNA extraction for this purpose are divided into two categories: those in which cells are lysed within the soil (direct extraction) and those in which cells are first removed from soil (cell extraction) and then lysed. The purpose of this study was to compare a method of direct extraction with a method in which cells were first separated from the soil matrix by Nycodenz gradient centrifugation in order to evaluate the effect of these different approaches on the analysis of the spectrum of diversity in a microbial community. We used a method based on polymerase chain reaction (PCR) amplification of a 16S rRNA gene fragment, followed by hybridization of the amplified fragments to a set of specific probes to assess the phylogenetic diversity of our samples. Control parameters, such as the relationship between amount of DNA template and amount of PCR product and the influence of competing DNA on PCR amplification, were first examined. Comparison between extraction methods showed that less DNA was extracted when cells were first separated from the soil matrix (0.4 microg g(-1) dry weight soil versus 38-93 microg g(-1) obtained by in situ lysis methods). However, with the exception of the gamma-subclass of Proteobacteria, there was no significant difference in the spectrum of diversity resulting from the two extraction strategies.

Bacteria↗
PubMed2001

Interactive effects of soil temperature, atmospheric carbon dioxide and soil N on root development, biomass and nutrient uptake of winter wheat during vegetative growth.

Nutrient requirements for plant growth are expected to rise in response to the predicted changes in CO(2) and temperature. In this context, little attention has been paid to the effects of soil temperature, which limits plant growth at early stages in temperate regions. A factorial growth-room experiment was conducted with winter wheat, varying soil temperature (10 degrees C and 15 degrees C), atmospheric CO(2) concentration (360 and 700 ppm), and N supply (low and high). The hypothesis was that soil temperature would modify root development, biomass allocation and nutrient uptake during vegetative growth and that its effects would interact with atmospheric CO(2) and N availability. Soil temperature effects were confirmed for most of the variables measured and 3-factor interactions were observed for root development, plant biomass components, N-use efficiency, and shoot P content. Importantly, the soil temperature effects were manifest in the absence of any change in air temperature. Changes in root development, nutrient uptake and nutrient-use efficiencies were interpreted as counterbalancing mechanisms for meeting nutrient requirements for plant growth in each situation. Most variables responded to an increase in resource availability in the order: N supply >soil temperature >CO(2).

Adaptation, Physiological↗