Effects of Sewage Sludge and Acacia dealbata Composts on Soil Biochemical and Chemical Properties

We studied the effects of different composts made of different mixtures of sewage sludge and Acacia plants on the soil biochemical and chemical properties. The proportions of mixed acacia plant and sewage sludge were: AL1/1 (50% acacia/50% sewage sludge), AL1/2 (33.3% acacia/66.6% sewage sludge), and AL1/3 (25% acacia/75% sewage sludge). Composts were added to the soil at a rate of 2%. Soil samples were collected during 150 days and analyzed for soil enzyme activities and chemical properties. An unamended soil was used as the control. Compared to the AL1/1 treatment, soil dehydrogenase, urease, phosphatase and β-glucosidase activities decreased respectively by 14.6%, 15.4%, 12.5%, and 19.3% for AL1/2 treatment and by 20.7%, 25.6%, 23.7%, and 28.4% for AL1/3 treatment. Soil water-soluble carbohydrates and polyphenols were the greatest in AL1/1. The lowest contents of heavy metals in the AL1/1 compost may be responsible for the increase of soil biochemical and chemical properties.     

Degradation of Sevin by soil microorganisms

Microorganisms capable of transforming the pesticide 1-naphthyl N-methyl-carbamate (Sevin) were isolated from soil. Three isolates were able to accelerate the hydrolysis of Sevin to 1-naphthol. Several unidentified intermediates were separated by thin-layer chromatography and also by following the decomposition of Sevin-methyl-¹⁴C. Since 1-naphthol is a biological as well as a chemical decomposition product of Sevin, its transformation by the isolated microbes was also studied. A fungus, identified as Fusarium solani, altered 1-naphthol rapidly. Whereas one strain of bacterium degraded the hydrolysis product gradually, another strain accumulated it under certain conditions. Mixed cultures of the investigated microbes were more effective in transforming Sevin than pure cultures, and this phenomenon was also observed with 1-naphthol as substrate with the exception of one bacterial strain.     

Effect of calcium carbonate as determined by lime requirement buffer pH methods on soil characteristics and yield of sorghum plants

Abstract

A primary limit to crop production in extended regions of northern Greece is the infertility of acid soils, especially nutrient element unavailability or toxicity. An experiment was conducted to determine under greenhouse conditions which buffer pH method selected in a previous laboratory experiment is best suited to predict the lime requirement (LR) of acid soils which is most appropriate in relation to plant growth and nutrient element uptake of sorghum plants. The lime needs of three naturally occurring acid soils were estimated by three methods: Adams‐Evans (AE), Shoemaker‐McLean‐Pratt single buffer (SMP‐SB), New Woodruff (NWOOD), and the calcium hydroxide [Ca(OH)₂] equilibration procedure. Two greenhouse experiments were conducted: (i) Experiment I during the 1996 season with ORESTIAS a sandy loam soil, and (ii) Experiment II during 1997 and 1998 season with XANTHI a loam sandy soil and DRAMA a sandy clay loam soil, respectively. The following results were obtained. Differences were noticed between the soils as well as within the LR methods. The ORESTIAS soil needed 63% more calcium carbonate (CaCO₃) than the XANTHI soil and 70% more than DRAMA soil to achieve the target pH. Among the three LR methods, results showed that in two of the three soils the highest LRs were determined by the NWOOD and the lowest by the Ca(OH)₂ methods. After six weeks of incubation, no one method gave exactly the needed amounts of CaCO to achieve the target pH, the estimated amounts being mostly higher than tiiat needed except for the DRAMA soil. Among the methods, in general the SMP‐SB method predicted lime rates that raised the soil pH nearest to the target pH and the NWOOD soil seemed to be the more consistent for the three soils. The smallest LRs were predicted by the Ca(OH) method. Based upon plant production and nitrogen (N) uptake in the 1996 season, the shoot yields were significantly higher using the SMP‐SB method and lower with the NWOOD method. Similar results were obtained for the XANTHI and DRAMA soils during the 1997 season. On the contrary in the 1998 season (2nd experimental year), the highest yields were obtained with the NWOOD buffer method. For the 1996 and 1997 seasons, tissue N concentrations were partly significantly higher using the SMP‐SB method. In the 1998 vegetation period, the N concentrations were low and the control plants had significantly higher N contents.     

Decomposition of atmospheric hydrogen by soil microorganisms and soil enzymes

The decomposition of atmospheric hydrogen in different types of soil was measured. The decomposition of H₂ was apparently a first-order reaction. H₂ decomposition activity was proportional to the amount of soil with maximum activities at soil water contents of approx. 6–11% (w/w). The activity was lower under anaerobic conditions, but was constant between 1–20% O₂. It was destroyed by autoclaving and was partially inactivated by fumigation with NH₃, CHC1₃ or acetone, by u.v. irradiation and by treatment with NaCN or NaN₃, indicating that biological processes in the soil were responsible for the observed H₂ decomposition. Treatment of soil with toluene or CHCl₃ caused only a partial inactivation. Incubation of soil in the presence of streptomycin or actidione reduced H₂ decomposition by less than 50%, whereas CO consumption was abolished. The H₂ decomposition rates showed H₂ saturation curves with apparent Michaelis-Menten kinetics. Cooperative effects were not observed. V_max was reached at approx. 200 μl1^?1. The K_m values for H₂ were in the range of 30μl 1^?1, but increased to higher values, when the soil had been pretreated with high H₂ mixing ratios. Apparently, the observed H₂ decomposition by soil is not only due to the activity of viable microorganisms, but soil enzymes as well.     

Analysis of bacterial communities in soil by PCR-DGGE targeting protease genes

We studied the effects of the application of organic (OM) and inorganic fertilizer (CF) on soil protease activity and proteolytic bacterial communities in rhizosphere and bulk soil on an experimental lettuce field in Hokkaido, Japan. The protease activity always was higher in soils of the OM than with the CF treatment, and also higher in the rhizosphere than in the bulk soil. We analyzed proteolytic bacterial communities by denaturing gradient gel electrophoresis (DGGE) of the alkaline metalloprotease (apr) and neutral metalloprotease (npr) genes. Most apr forms detected were closely related to apr of Pseudomonas fluorescens, and all npr variants closely resembled the gene of Bacillus megaterium. These results were consistent with findings from tests using cultured bacterial communities, indicating a high specificity of our PCR-DGGE for amplifying apr and npr genes. The community compositions of proteolytic bacteria were assessed by principal component analysis of the DGGE profiles. There were significant differences in the effects of CF and OM on the community compositions of apr- and npr-expressing bacteria, and the communities of the two types of bacteria played different roles in rhizosphere and bulk soil. We found significant correlations between the protease activity and the communities of the two types of bacteria. The results indicate that different proteolytic bacteria release different amounts or activities of protease, and that the composition of proteolytic bacterial communities may play a major role in determining overall soil protease activity.     

Effect of soil microorganisms on the growth of roots in rice seedlings

Abstract

Root system of rice seedlings grown on nutrient solution inoculated with soil microorganisms were examined morphologically in comparison with those obtained under sterile condition. In the presence of soil microorganisms, primary roots increased in their number and decreased in the total length. Inoculated plants had more secondary roots equipped with tertiary roots. In addition, longer root hairs developed densely on primary and secondary roots of the inoculated seedlings.

Anatomical examination of the primary roots revealed that the number and width of cortical layers, as well as the length and width of the cortical cells, were increased by the effect of microorganisms. Microbial effect on outer morphology of rice roots, consequently, was estimated to have been induced from the alteration in histological and cytological activities including the activation of the periclinal divisions of the epidermal cells, the inactivation of the transverse divisions of the cortical cells and the activation of the elongation of cortical cells.     

Temporal responses of soil microorganisms to substrate addition as indicated by amino sugar differentiation

Amino sugars are one of the important microbial residue biomarkers which are associated with soil organic matter cycling. However, little is known about their transformation kinetics in response to available substrates because living biomass only contributes a negligible portion to the total mass of amino sugars. By using ¹⁵N tracing technique, the newly synthesized (labeled) amino sugars can be differentiated from the native portions in soil matrix, making it possible to evaluate, in quantitative manner, the transformation pattern of amino sugars and to interpret the past and ongoing changes of microbial communities during the assimilation of extraneous ¹⁵N. In this study, laboratory incubations of soil samples were conducted by using ¹⁵NH₄⁺ as nitrogen source with or without glucose addition. Both the ¹⁵N enrichment (expressed as atom percentage excess, APE) and the contents of amino sugars were determined by an isotope-based gas chromatography-mass spectrometry. The significant ¹⁵N incorporation into amino sugars was only observed in glucose plus ¹⁵NH₄⁺ amendment with the APE arranged as: muramic acid (MurN) > glucosamine (GlcN) > galactosamine (GalN). The dynamics of ¹⁵N enrichment in bacterial-derived MurN and fungal-derived GlcN were fitted to the hyperbolic equations and indicative for the temporal responses of different soil microorganisms. The APE plateau of MurN and fungal-derived GlcN represented the maximal extent of bacterial and fungal populations, respectively, becoming active in response to the available substrates. The different dynamics of the ¹⁵N enrichment between MurN and GlcN indicated that bacteria reacted faster than fungi to assimilate the labile substrates initially, but fungus growth was dominant afterward, leading to integrated microbial community structure over time. Furthermore, the dynamics of labeled and unlabeled portions of amino sugars were compound-specific and substrate-dependent, suggesting their different stability in soil. GlcN tended to accumulate in soil while MurN was more likely degraded as a carbon source when nitrogen supply was excessive.     

Effect of microorganisms on extractability of Cd from soil with NaOH and DTPA

Because Cd is extremely toxic, an understanding of the factors that allow or prevent Cd entrance into the food chain is important. The fate of Cd in soil is strongly influenced by microbial activity. Thus, an attempt was made to develop a method for studying the effect of microorganisms on Cd sorption to soil and availability to plants. It was found that the amount of Cd extracted from soil to soil suspensions with 0.1 m NaOH is related to microbial proliferation. In addition, an increase of Cd in NaOH extracts occurred concurrently with a decrease of Cd in DTPA extracts. Our observations suggest that the binding of Cd to microorganisms or their products can immobilize Cd and consequently affect its bioavailability.     

Virus adsorption and inactivation in soil as influenced by autochthonous microorganisms and water content

Virus adsorption and inactivation in soil matrix are crucial processes controlling the potential of viruses to contaminate water resources. These two processes behave interactively and are controlled by various factors. In this study, batch and incubation experiments were conducted at 4 °C to compare the adsorption of bacteriophage MS2 in different soils, and to examine its inactivation behavior at different soil water content. Soils with presence/absence of autochthonous microorganisms were used. The interactive effects of sterilization and soil water content on virus inactivation were also evaluated. The Ustisandic Primosols showed no virus adsorption and minimal differences in activation regardless of the presence or absence of soil autochthonous microorganisms. For the Ferriudic Cambosols, however, sterilization increased adsorption and enhanced inactivation, and inactivation was accentuated by decreasing soil water content. The results indicate that soil water content and sterilization had additive effects on virus inactivation, and reveal that the enhanced “adsorption” by sterilization was mainly due to greater die-off in the Ferriudic Cambosols. The greater inactivation observed in the Ferriudic Cambosols, which has relative high contents of Fe- and Al-oxides and low pH, resulting from the additive effect of sterilization and decreasing soil water content was mainly due to increased reactions at the solid–water interface. We conclude that the effect of sterilization and soil water content on virus inactivation depends on soil type, and the extent of inactivation is likely controlled by the content of metal oxides.     

Nitrification results in underestimation of soil urease activity as determined by ammonium production rate

The majority of soil urease activity measurements have been based on the rate of ammonium production under optimal conditions. However, such procedures do not exclude ammonium consumption by the nitrification process. The purpose of this study was to determine the percentage of soil urease activity that is underestimated due to soil nitrification. Six soils with diverse properties were incubated using a standard procedure for measuring soil urease activity. The dynamics of nitrite and nitrate were observed during the incubation. Our results showed that the percentage of underestimation ranged from 7.38% to 15.97%, depending on soil types and whether or not a buffer was used. We recommend that nitrification be taken into account when soil urease activity is assayed by the ammonium production rate method.     

Transport of microorganisms through soil

Microorganisms migrating into and through soil from sources on the land surface may cause a serious threat to both ground and surface waters. It has been estimated that microorganisms can migrate significant distances in the field. Results from various studies suggested that preferential flow through macropores, worm holes, cracks, and fractures is the main reason for such observations. However, a quantitative representation of this phenomenon has not been provided. Microorganisms migrate through soil by advection and dispersion, while being subjected to effects of filtration, adsorption, desorption, growth, decay, sedimentation and chemotaxis. Both laboratory and field investigations have contributed important information on bacterial movement in soils. Qualitative comparisons are generally transferable from laboratory to field situations. Quantitative agreement is much more difficult to establish. Available mathematical modelling of microbial transport is limited in practical application because of the simplifying assumptions used in its development.     

Assessment of pesticide effects on non-target soil microorganisms

Agricultural pesticides should be free of side effects that may cause a lasting disruption of microbial processes that are essential for continued soil fertility. A test program is described here for the assessment of the potential effects of newly-developed pesticides on non-target soil micro-organisms. The pesticides to be tested are applied at the equivalent of their recommended field application concentration and, for a margin of safety, also at the tenfold thereof. The measurement of pesticide effects on the microbial cycling of C, N and S constitute the core of the test program. These measurements are, in some cases, complemented by evaluation of pesticide effects on total and viable microbial numbers, on the abundance of specific components of the soil microbial community, and on the growth rates of selected soil microorganisms. The above test program was applied to evaluate the safety of the herbicides N-(1-ethylpropyl)-3,4-dimethyl-2,6-clinitrobenzeneamine(pendimethalin) l,2-dimethyl-3,5-diphenyl-1H pyrazolium (difenzoquat), S-(4-chlorophenyl)-N,N-diethyldithiocarbamate (thiobencarb), and the fungicides N-[(trichloromethyl) thio]-phthalimide (folpet) and cis-N-[(l,l,2,2-tetrachloroethyl) thio]-4-cyclohexene-1,2-dicarboximide (captafol). No detectable adverse effects were caused by any of the tested herbicides. The fungicides inhibited some of the C cycling activities, but the inhibition was temporary and was associated with their effect on soil fungi.     

Short-term changes in the spatial distribution of microorganisms in soil aggregates as affected by glucose addition

We studied the location of microorganisms in soil aggregates by low temperature scanning electron microscopy and by confocal laser microscopy (direct counts of bacteria) on dissected aggregates. We compared a sandy and a clayey soil and studied the effect of adding glucose on the spatial distribution of microorganisms. In the sandy soil, pores with diameters between 6 µm and 30 µm were the most abundant. In the clayey soil, the pores were <0.2 µm in diameter. In the sandy soil, microorganisms were present both on the surface and inside aggregates, whereas they were concentrated on the surface of clayey soil aggregates. Glucose addition increased the amount of bacteria and fungi on the surface of clayey soil aggregates but not inside them. For the sandy soil, microbial numbers were increased dramatically both inside and on the surface of the aggregates after glucose additions. This study thus evidenced contrasting microbial habitats in soil aggregates.     

On the soil colour,determined by spectrophotometer

Results, here published, are from the determination of the colour, by the use of spectrophotometer (Shimazu, QR-50) with the soils from pedogenic horizons of principal soil types In Japan.     

Suppression of other soil microorganisms by mycelium of arbuscular mycorrhizal fungi in root-free soil

The influence of mycelium of two arbuscular mycorrhizal (AM) fungi, Glomus intraradices and Glomus mosseae, on other soil microorganisms, was examined in root-free soil with and without organic substrate amendment in terms of cellulose. The AM fungi were grown in symbiosis with cucumber in a compartmented growth system, which allowed AM fungal external mycelium to grow into root-free compartments. The fungicide Benomyl was applied to the root-free compartments to create an alternative non-mycorrhizal control treatment. Whole cell biomarker fatty acids were employed to quantify different groups of soil microorganisms including the two AM fungi. Abundance of most microbial groups were reduced by external mycelium of both AM fungi, though differential effects on the microbial community composition were observed between the two AM fungi as revealed from principal component analysis. Inhibition of other soil microorganisms was more pronounced in root-free soil with mycelium of G. mosseae than with mycelium of G. intraradices. In general, cellulose increased the amount of biomarker fatty acids of most groups of soil microorganisms, but cellulose did not affect the influence of AM fungi on other soil microorganisms. Benomyl suppressed growth of the external mycelium of the two AM fungi and had limited non-target effects on other microbial groups. In conclusion, our results show differential effects of external mycelium of AM fungi on other soil microbial communities, though both AM fungi included in the study overall inhibited most microbial groups as examined using whole cell biomarker fatty acids.     

Transformations of chemically fixed liquid anhydrous ammonia by soil microorganisms

Summary The application of liquid anhydrous NH₃ to soil leads to chemical fixation of NH₃ by organic matter and of NH _inf4 ^sup+ by clay minerals. A laboratory study was conducted to ascertain the biological transformations of newly fixed liquid anhydrous ¹⁵NH₃ in a Drummer silty clay loam by incubation of the ¹⁵N-labelled soil with glucose for 0, 7, 30, and 90 days and by sequential extraction of organic-matter-fixed ¹⁵NH₃ with 0.15 M Na₄P₂O₇, 0.15 M KOH, 0.1 M NaOH, and acidified dimethyl sulfoxide. About 16% of the ¹⁵NH₃ injected was fixed, of which 52% was accounted for by clay fixation. The various humic fractions (fulvic acid, humic acid, and humin) were obtained, and the distribution patterns of the fixed ¹⁵NH₃-N in these fractions were compared. The potential availability of the fixed ¹⁵NH₃-N was also estimated. The percentage of the ¹⁵NH₃ recovered as organic-matter-fixed ¹⁵NH₃ decreased as the length of incubation increased (to 28% after 90 days); the decrease was attributed in part to an increase in the amount recovered as clay-fixed NH _inf4 ^sup+ (from 52 to 64%). Changes in the distribution of the organic-matter-fixed ¹⁵NH₃-N in the humic fractions included: (1) an increase in the relative amount of the fixed ¹⁵NH₃ as humic acid in both the Na₄P₂O₇ and KOH extracts, (2) an increase in the percentage of organic-matter-fixed ¹⁵NH₃-N in the fulvic acid fractions as high-molecular-weight components (determined by dialysis) or as generic fulvic acid (determined by sorption-desorption from XAD-8 resin), and (3) an increase in the percentage of the organic-matter-fixed ¹⁵NH₃ as humin. The potential availability of the organic-matter-fixed ¹⁵NH₃-N decreased as the length of the incubation increased, from 22 to 4% over the 90-day incubation period, and was correlated significantly (0.05 level) with Na₄P₂O₇-extractable N. These results suggest that organic-matter-fixed liquid anhydrous NH₃ is initially more labile than the native soil N but becomes less labile with time.     

Effect of lead on growth characteristics of microorganisms in soil and rhizosphere of Dactylis glomerata

The effects of lead oxide and lead nitrate on the growth strategies of microbial communities in the soil and in the rhizosphere of orchard grass (Dactylis glomerata L.) were studied. The maximum specific growth rate of the microorganisms (μ_m) changed significantly when the concentration of mobile forms of lead in the soil exceeded 170 mg Pb/kg, which corresponded to the addition of 400–1000 mg Pb/kg of soil in the form of lead nitrate. The addition of lead resulted in the suppression of a part of the r-strategists and in the more active development of the K-strategists in the adapted microbial community. It was demonstrated that the community of rhizosphere microorganisms could be a more sensitive indicator of lead pollution than the nonrhizosphere microbial community. The values of the auxotrophy index (the ratio between the μ_m values upon the growth on glucose and yeast extract) demonstrated a tendency towards a decrease in the metabolic diversity of the soil microbial community under the impact of lead.     

Resistance of soil microorganisms to starvation

Most groups of soil microorganisms died when exposed to prolonged starvation in a carbon-free solution, but the relative abundance of Bacillus and actinomycetes increased with time. Certain non-sporeforming bacteria also persisted. The ability of individual soil isolates to endure starvation in solution was not correlated with their glycogen content or rate of endogenous respiration. However, cells of the resistant populations were rich in poly-β-hydroxybutyrate, whereas the starvation-susceptible bacteria generally contained little of this substance. Poly-β-hydroxybutyrate was used rapidly in cells deprived of exogenous sources of carbon.     

Effects of trifluralin and metabolites on the decomposition of selected substrates by soil microorganisms

Summary The effects of trifluralin and 12 of its soil-formed metabolites on the decomposition of radio-labelled glucose, protein and cellulose were determined, using ¹⁴CO₂ evolution from soil as a measure of decomposition. Trifluralin increased ¹⁴C-glucose mineralization rates, but these increases could be eliminated by adding N. Trifluralin had no inhibitory effect on the mineralization of protein or cellulose, but five of the metabolites inhibited glucose mineralization. None of the trifluralin metabolites affected protein mineralization. Seven trifluralin metabolites increased the rate of cellulose mineralization when applied at rates exceeding those that would be expected in soil. After considering the rate of metabolite application and the magnitude of the responses observed these compounds are expected to have no major effects on the microbial decomposition processes in soil.