Effect of microbial decomposition of mature leaves on soil pH

The hypothesis that the microbial decomposition of organic matter low in organic nitrogen leads to an increase in soil pH was tested and confirmed in a pot experiment with two different soils into which mature cherry leaves were incorporated.     

Selected kinetic parameters of soil microbial respiration in the A horizon of differently managed mountain forests and meadows of Moravian-Silesian Beskids Mts.

The aim of this study was to find out the effect of intensity of thinning (FD-dense stand = 2044 trees/ha; FS-open stand = 1652 trees/ha) performed in young forest stands (99% spruce, 1% fir) in Moravian-Silesian Beskids Mts. (908 m a.s.l.; 49°30′10″ N, 18°32′20″ E) on V _DS (C mineralization rate immediately after drying and re-wetting of soil), V _BR (basal soil respiration at 60% w/w soil water content measured 5th day after rewetting of dry soil), V _MAX (maximum respiration rate after glucose addition measured from 6th day after rewetting of dry soil), V _DS/V _MAX (heterotrophic respiratory potential) and AC_DS/AC_BR (the potential flush of biologically available C) in Ae horizon of Haplic and Entic Podzols. The AC_DS/AC_BR was calculated from three 24-hour respirations of 7-day incubation according to the equation AC_DS/AC_BR=V _DS V _MAX/(2V _BR(V _MAX−V _DS)). The aim of the work was also to find the effect of circa 11-year abandonment of a mountain meadow in the locality (825–860 m a.s.l.; 49°30′17″ N, 18°32′28″ E) on the same parameters in Ah horizon of Gleyic Luvisol. The studied parameters were measured in the course of the vegetation season 2004 (May–September) at 30-day intervals. The higher intensity of thinning caused alternately higher or lower or very similar values of V _DS, V _BR, V _MAX, V _DS/V _MAX and AC_DS/AC_BR in the course of the season. The abandonment of the meadow increased V _DS, V _BR, V _MAX throughout the whole experiment. V _DS/V _MAX increased due to the abandonment except for the last sampling in September. Alternately higher or lower or very similar values of AC_DS/AC_BR in course of the season appeared on abandoned or moderately mown meadows. The lower intensity of thinning or abandonment of the meadow were connected with increasing number of significant (P < 0.05) correlations between the studied properties. Published in Russian in Pochvovedenie, 2009, No. 3, pp. 346–354. The text was submitted by the authors in English.     

Effect of pH on the solubilization of brewers' spent grain by microbial carbohydrases and proteases

The potential for enzymatic solubilization of brewers' spent grain by carbohydrases and proteases was examined over a broad pH range (pH 3.2-11.2). Enzymes from Trichoderma (Depol 686) were most efficient at a lower pH, while enzymes from the Humicola preparation (Depol 740) were the best performer over the whole range. Profiling of key glycoside hydrolase, esterase and protease activities across the pH range demonstrated that solubilization of spent grain by the Trichoderma enzymes corresponded to the range of maximum activities. This was not the case with the Humicola enzymes, where maximum solubilization of the substrate occurred at pH 9.1, at which pH the determined activities were low. Protease activity in Depol 740 was associated with a high solubilization, but inhibition of proteolytic activity resulted in only a 5% decrease in spent grain solubilization. These results suggest that while enzymes can be used to exploit agro-industrials byproduct, the use of high pH increases the extent of hydrolysis and an unidentified factor produced by Humicola improves the enzyme-catalyzed solubilization of lignocellulosic material.     

Estimating the active and total soil microbial biomass by kinetic respiration analysis

 A model describing the respiration curves of glucose-amended soils was applied to the characterization of microbial biomass. Both lag and exponential growth phases were simulated. Fitted parameters were used for the determination of the growing and sustaining fractions of the microbial biomass as well as its specific growth rate (μ _max). These microbial biomass characteristics were measured periodically in a loamy silt and a sandy loam soil incubated under laboratory conditions. Less than 1% of the biomass oxidizing glucose was able to grow immediately due to the chronic starvation of the microbial populations in situ. Glucose applied at a rate of 0.5 mg C g^–1 increased that portion to 4–10%. Both soils showed similar dynamics with a peak in the growing biomass at day 3 after initial glucose amendment, while the total (sustaining plus growing) biomass was maximum at day 7. The microorganisms in the loamy silt soil showed a larger growth potential, with the growing biomass increasing 16-fold after glucose application compared to a sevenfold increase in the sandy loam soil. The results gained by the applied kinetic approach were compared to those obtained by the substrate-induced respiration (SIR) technique for soil microbial biomass estimation, and with results from a simple exponential model used to describe the growth response. SIR proved to be only suitable for soils that contain a sustaining microbial biomass and no growing microbial biomass. The exponential model was unsuitable for situations where a growing microbial biomass was associated with a sustaining biomass. The kinetic model tested in this study (Panikov and Sizova 1996) proved to describe all situations in a meaningful, quantitative and statistically reliable way. Received: 19 July 1999     

Electrochemical investigation of the effect of pH and solvent on amitraz stability

The widespread use of the pesticide amitraz for pest control of crops, livestock and honeybees has warranted several studies aimed at understanding the degradation of this compound during storage and use. In particular the degradation of amitraz and the nature of the toxicologically significant intermediates formed owing to pH and solvent type has been examined. In this study we report on the use of electrochemical methods to monitor amitraz degradation and to identify the major intermediates formed. While this study examines the use of rapid voltammetric methods for such analyses, it also resolves earlier studies showing the rapid degradation of amitraz to 2,4-dimethylaniline without formation of intermediates first, and also suggests that the degradation of amitraz to 2,4-dimethylphenylformamide and to 2,4-dimethylaniline is more rapid than previously observed at pH above 3. These studies also showed that amitraz degrades to dimethylphenylformamide in ethanol and methanol, and is stable in both acetonitrile and dimethylsulphoxide.     

The effect of pH and calcium on fish and fisheries

The combined effect of Ca and pH on fish and fisheries is considered for both laboratory and field studies. It can be seen that at concentrations less than 100 μeq l^?1, Ca can exert a significant influence on survival times of fish, and similarly in the field, the number of fishless lakes and the number of fish species found in lakes are less dependent on H⁺ concentration at low concentrations of Ca than at high Ca levels. The limited historical field data available suggest that alongside any increase there may have been in surface water acidity, Ca concentrations have also increased, and the latter may have offset to some extent the deleterious biological effects of this increased acidity. Nevertheless, details of seasonal and spatial variations in these important water quality factors will need to be considered before a full understanding of the response to acidity of a fishery can be reached.     

Microenvironment and microbial community in the rhizosphere of dioecious Populus cathayana at Chaka Salt Lake

Journal of Soils and Sediments - Sex effects may cause significant changes in rhizosphere microbial community composition and soil properties. Although dioecious plants are widespread, little is...     

The effect of glyphosate on soil microbial activity,microbial community structure,and soil potassium

The herbicide, glyphosate [N-(phosphonomethyl) glycine] is extensively used worldwide. Long-term use of glyphosate can cause micronutrient deficiency but little is known about potassium (K) interactions with glyphosate. The repeated use of glyphosate may create a selection pressure in soil microbial communities that could affect the nutrient dynamics such as K. The objective of this study was to determine the effect of single or repeated glyphosate applications on microbial and K properties of soils. A 54 day incubation study (Exp I) had a 3 × 5 factorial design with 3 soils (silt loam: fine, illitic, mesic Aeric Epiaqualf) of similar physical and chemical characteristics, that varied in long-term glyphosate applications (no, low, and high glyphosate field treatments) and five glyphosate rates (0, 0.5×, 1×, 2×, and 3× recommended field rates applied once at time zero). A second 6 month incubation study (Exp II) had a 3 × 3 factorial design with three soils (as described above) and three rates of glyphosate (0, 1×, and 2× recommended field application rates applied monthly). For each study microbial properties [respiration; community structure measured by ester linked fatty acid methyl ester (EL-FAME) analysis and microbial biomass K] and K fractions (exchangeable and non-exchangeable) were measured periodically. For Exp I, glyphosate significantly increased microbial respiration that was closely related to glyphosate application rate, most notably in soils with a history of receiving glyphosate. For Exp II, there was no significant effect of repeated glyphosate application on soil microbial structure (EL-FAME) or biomass K. We conclude that glyphosate: (1) stimulates microbial respiration particularly on soils with a history of glyphosate application; (2) has no significant effect on functional diversity (EL-FAME) or microbial biomass K; and (3) does not reduce the exchangeable K (putatively available to plants) or affect non-exchangeable K. The respiration response in soils with a long-term glyphosate response would suggest there was a shift in the microbial community that could readily degrade glyphosate but this shift was not detected by EL-FAME.     

Effects of mulching and cover cropping on soil microbial parameters in the organic growing of black currant

Abstract

Cover cropping and mulching to sustain and improve soil fertility and for weed control are common practices in organic growing systems. In this study, microbial parameters under different kinds of mulches and cover crops were analyzed in a field experiment with organically grown black currant (Ribes nigrum). The experiment comprised a combination of two mulches with bare soil as a control and two cover crops which were compared with bare soil, with and without an extra supply of organic fertilizer. Soil carbon (C) and nitrogen (N) as well as pH were unaffected by any of the treatments. The basal respiration rate was increased by mulching with wood chips throughout the four years of the experiment. During the last two years of the experiment, substrate induced respiration was also measured but was not found to be affected by any of the mulches. The potential ammonium (NH₄ ⁺) oxidation increased significantly after an initial supply of 200 kg N ha^‐1 as solid cattle manure. The increase was significantly lower under wood chips than in bare soil, although an extra 200 kg N ha^‐1 had been supplied under the wood chips. Furthermore, the black currant bushes suffered from a N deficiency in the wood chip treatment. The results showed that there was no substantial lasting build‐up of microbial biomass or organic matter content with wood chips because of lack of N, despite a large initial input of N and easily‐available C. Possible reasons for this deficiency are either increased denitrification under the wood chips or fungal translocation of N to the wood chip layer. Results from this experiment suggests that the evaluation of a few complementary biological soil parameters can be an important tool when developing sustainable growing systems and for indicating environmental stress.     

Sensitivity analysis of critical parameters in microbial maintenance-energy models

Summary Overestimates of microbial biomass and high maintenance rates have caused calculations of annual maintenance requirements to exceed annual C inputs to soil ecosystems. An integrated approach is needed to resolve this inconsistency in the literature. In the present study a mechanistic model for soil microbial systems was used to calculate the maintenance-energy requirements of the soil microbial biomass. This model is base on product formation rather than substrate use and describes an active and sustaining population, with cryptic growth and necromass recycling. Several assumptions, such as death rates, the percentage of active population, and the yield, are required to calculate the maintenance energies, and the sensitivity of these estimated parameters on the maintenance-rate calculation was tested. The total biomass and the yield factor had the greatest effect on the calculated maintenance value. The fraction of active organisms, the death rates, and the different maintenance values for each population had little effect on the maintenance value.     

Method for the estimation of nutrient uptake kinetic parameters using nonparametric statistics

The uptake of many plant nutrients has been shown to follow Michaelis‐Menten enzyme kinetics, and as a result several methods of collecting and analyzing uptake data have been developed. The method proposed here consists of a continuously flowing hydroponic system and a method of data analysis that estimates a value of K_mand V_max for each plant. The method is nondestructive; it does not require large amounts of space; and the plants are near steady‐state uptake. In simulated experiments with various assumptions about variability in the data, the nonparametric statistical analysis of the results provided estimates as good as or better than regression analysis estimates of the two parameters of the Michaelis‐Menten equation.     

Effect of heat treatment on denaturation of bovine alpha-lactalbumin: determination of kinetic and thermodynamic parameters

The effect of heat treatment on the denaturation of alpha-lactalbumin was studied, under different conditions, over a temperature range of 78-94 degrees C. The concentration of the residual immunoreactive protein after different treatments was determined by kinetic analysis, obtaining D and Z values. Thermodynamic parameters were also calculated. Denaturation of alpha-lactalbumin, measured by the loss of immunoreactivity, could be described as an order of reaction of n = 1.5. Results obtained indicated that alpha-lactalbumin was more heat-sensitive when treated in milk than in phosphate buffer. The protein was also denatured more rapidly in the apo form than in the calcium-saturated form. Besides, the thermal stability of apo-alpha-lactalbumin decreased with the binding of oleic acid.     

Relationships between soil pH and microbial properties in a UK arable soil

Effects of changing pH along a natural continuous gradient of a UK silty-loam soil were investigated. The site was a 200 m soil transect of the Hoosfield acid strip (Rothamsted Research, UK) which has grown continuous barley for more than 100 years. This experiment provides a remarkably uniform soil pH gradient, ranging from about pH 8.3 to 3.7. Soil total and organic C and the ratio: (soil organic C)/(soil total N) decreased due to decreasing plant C inputs as the soil pH declined. As expected, the CaCO₃ concentration was greatest at very high pH values (pH > 7.5). In contrast, extractable Al concentrations increased linearly (R² = 0.94, p < 0.001) from below about pH 5.4, while extractable Mn concentrations were largest at pH 4.4 and decreased at lower pHs. Biomass C and biomass ninhydrin-N were greatest above pH 7. There were statistically significant relationships between soil pH and biomass C (R² = 0.80, p < 0.001), biomass ninhydrin-N (R² = 0.90, p < 0.001), organic C (R² = 0.83, p < 0.001) and total N (R² = 0.83, p < 0.001), confirming the importance of soil organic matter and pH in stimulating microbial biomass growth. Soil CO₂ evolution increased as pH increased (R² = 0.97, p < 0.001). In contrast, the respiratory quotient (qCO₂) had the greatest values at either end of the pH range. This is almost certainly a response to stress caused by the low p. At the highest pH, both abiotic (from CaCO₃) and biotic Co₂ will be involved so the effects of high pH on biomass activity are confounded. Microbial biomass and microbial activity tended to stabilise at pH values between about 5 and 7 because the differences in organic C, total N and Al concentrations within this pH range were small. This work has established clear relationships between microbial biomass and microbial activity over an extremely wide soil pH range and within a single soil type. In contrast, most other studies have used soils of both different pH and soil type to make similar comparisons. In the latter case, the effects of soil pH on microbial properties are confounded with effects of different soil types, vegetation cover and local climatic conditions.     

Salt marsh rhizosphere affects microbial biotransformation of the widespread halogenated contaminant tetrabromobisphenol-A (TBBPA)

Estuarine sediments are the repository for a wide range of contaminants. Anthropogenic impacts and variations in the belowground biomass of salt marsh plants potentially select for different sediment microbial communities with different functional capabilities, including the ability to biotransform anthropogenic contaminants. There are large differences in both root morphology and the amount of fine root biomass of Spartina alterniflora and Phragmites australis; Spartina is the species commonly used to replace Phragmites in northeastern US salt marsh restoration projects. Our study compared the effect of these two macrophyte species on sediment microbial communities responsible for the biotransformation of the halogenated flame retardant tetrabromobisphenol A (TBBPA). Sediments were obtained from contaminated and uncontaminated salt marsh field sites in New Jersey. Anaerobic methanogenic sediment microcosms were established and incubated for up to 130 days. TBBPA was reductively dehalogenated resulting in the transient formation of two intermediates, identified as tribromobisphenol A and dibromobisphenol A, and the formation and accumulation of bisphenol A (BPA) as the end product. Spartina sediments from both sites were found to dehalogenate TBBPA more rapidly than the Phragmites or unvegetated sediments, resulting in greater production of BPA. Microbial community diversity as measured by in situ sediment phospholipid fatty acid (PLFA) composition prior to TBBPA exposure, was found to be higher in the uncontaminated sediments; differences in microbial PLFA diversity were not seen in contaminated sediments associated with either the different plant species or unvegetated sediment. The results of this study demonstrate that these two plant species affected sediment microbial community function with respect to dehalogenation capabilities, even though the disturbed and undisturbed sediments varied in microbial community composition.     

The effect of pH and metal binding on the transport properties of humic acids

The molecular weight, shape and size of fractionated humic acids and their metal complexes were determined from sedimentation and diffusion measurements made at various pH values. For all the species studied, the molecular weight and size decreased as the pH became more alkaline. However, the shape of the molecule (approximately spherical) was unaffected by pH. The molecular weight and size of the metal humates depended not only on the type of cation but also on the degree of dissociation ofthe humic acid and the hydrolysis ofthe metal ion.     

The effect of tropical forest conversion on soil microbial biomass

We investigated the effects of converting forest to savanna and plough land on the microbial biomass in tropical soils of India. Conversion of the forest led to a significant reduction in soil organic C (40–46%), total N (47–53%), and microbial biomass C (52–58%) in the savanna and the plough land. Among forest, savanna, and plough land, basal soil respiration was maximum in the forest, but the microbial metabolic quotient (qCO₂ was estimated to be at a minimum in the forest and at a maximum in the plough land.     

Ethion degradation and its correlation with microbial and biochemical parameters of tea soils

Ethion, a highly persistent insecticide in soil, is extensively used in tea cultivation in the tropics. The studies on the environmental impact of ethion in tea soil ecosystems are scanty. Silty loam and sandy loam soils from tea fields of Dooars (Typic Uderthents) and Hill (Typic Dystrudepts), respectively, were investigated for the degradation and effect of ethion application on soil microbial and biochemical variables under controlled laboratory conditions. Ethion degraded faster in the Hill soil than in the Dooars soil. Higher temperature (30°C) aided in faster degradation due to the increased microbial activity in the soils. Ethion application at field rate (FR) had lower half-lives (70 days at 20°C and 42.3 days at 30°C for Dooars soil; 65.4 days at 20°C and 39 days at 30°C for Hill soil) than at ten times FR (10FR; 75.2 days at 20°C and 44.2 days at 30°C for Dooars soil; 70 days at 20°C and 41.8 days at 30°C for Hill soil). Soil microbial biomass carbon, ergosterol content, fluorescein diacetate hydrolyzing and β-glucosidase activities declined in all the treatment combinations up to day 60 for both FR and 10FR doses at 20°C, irrespective of the soil types. At 30°C, the decreasing trend was observed up to day 30 for both the soils. The toxicological effect of ethion on microbiological and biochemical parameters persisted till their corresponding half-lives. The microbial metabolic quotient and microbial respiration quotient were altered, but was short-lived, indicating ethion induced disturbances. The recovery of the depressive action at 10FR ethion spiking on the studied variables was of slightly longer duration than noticed at FR application, although the depressive effect was overcoming after the respective half-lives of ethion. The microbial and biochemical soil parameters were negatively correlated with application of ethion up to day 60 of incubation.     

The effect of pH on sulfate availability in sphagnum peat

Abstract

The influence of pH upon the availability of sulfate‐sulfur in sphagnum peat moss was studied. Samples of sphagnum peat moss amended with 0, 1.41, 2.82, 3.81 and 5.64 g/L Ca(OH)₂, had pH values of 2.8, 3.7, 4.7, 5.8 and 7.0, respectively. Sulfate was extracted from peat samples with a 0.15% CaCl₂.H₂O or a 500 mg P/L (as Ca(H₂PO₄)₂.H₂O) extractant and quantified with a Dionex QIC ion Chromatograph. Sulfate availability from the CaCl₂‐extracted solutions was greatest at pH 4.7 and 5.8, but highest at pH 4.7 only for the P‐extracted solutions, in which no measurable extracted sulfur was found at pH levels greater than 4.7.     

The effect of soil water content and microbial activity on restoring the structure of a Vertisol

Soils with high clay content are susceptible to structural damage, if they are intensively cultivated. The structure of soils of the Vertisol group has the tendency to restore as a result of wetting and drying. Samples of a remoulded clayey soil were exposed to seven successive wetting/drying (w/d) cycles, in order to study the change of some structural features of the newly formed aggregates. To assess the effect of soil water content and microbial activity, two different matric water potential ranges were used under sterile and non-sterile conditions.

Aggregate size distribution depended on both the water potential range and microbial activity and approached to a steady state with increasing cycle number. The water stability of the 2–1 mm aggregates was affected by the activity of soil micro-organisms under wet conditions and by forces of mechanical nature when the soil was reaching dryness. All cases resulted in aggregates of reduced water stability with respect to the natural aggregates. The <50 μm aggregated particles initially preserved stability, but after a number of w/d cycles they collapsed at a rate, depending mainly on the water potential range.     

The effect of different tree species on the chemical and microbial properties of reclaimed mine soils

The chemical and microbial properties of afforested mine soils are likely to depend on the species composition of the introduced vegetation. This study compared the chemical and microbial properties of organic horizons and the uppermost mineral layers in mine soils under pure pine (Pinus sylvestris), birch (Betula pendula), larch (Larix decidua), alder (Alnus glutinosa), and mixed pine–alder and birch–alder forest stands. The studied properties included soil pH, content of organic C (C_org) and total N (N_t), microbial biomass (C_mic), basal respiration, nitrogen mineralization rate (Min-N), and the activities of dehydrogenase, acid phosphomonoesterase, and urease. Near-infrared spectroscopy (NIR) was used to detect differences in the chemical composition of soil organic matter under the studied forest stands. There were significant differences in C_org and N_t contents between stands in both O and mineral soil horizons and also in the chemical composition of the accumulated organic matter, as indicated by NIR spectra differences. Alder was associated with the largest C_org and N_t accumulation but also with a significant decrease of pH in the mineral soil. Microbial biomass, respiration, the percentage of C_org present as C_mic, Min-N, and dehydrogenase activity were the highest under the birch stand, indicating a positive effect of birch on soil microflora. Admixture of alder to coniferous stand increased basal respiration, Min-N, and activities of dehydrogenase and acid phosphomonoesterase as compared with the pure pine stand. In the O horizon, soil pH and N_t content had the most important effects on all microbial properties. In this horizon, the activities of urease and acid phosphomonoesterase did not depend on microbial biomass. In the mineral layer, however, the amount of accumulated C and microbial biomass were of primary importance for the enzyme activities.