Determination Of Microbial Biomass Research Articles

Pesticide removal by the bioaugmentation process in secondary treated wastewater

Abstract The work was focused on the effect of the bioaugmentation process on STWW contaminated by pentachlorophenol (PCP: 100 mg L−1) by Pseudomonas putida AE015451. The monitoring of bioaugmentation treatments was assessed by chloride content determination via high-performance liquid chromatography (HPLC), optical density (OD) for microbial biomass determination, and pyoverdine and biofilm production. The process of bioaugmentation by a PGPR Pseudomonas strain showed a high-efficiency removal rate of PCP (100 mg L−1). The contaminant decreased up to 92% after 168 h. The production of pyoverdine and the formation of bacterial biofilm by the strain Ps. putida AE015451 showed an important role in tolerating the toxicity of PCP by using it as a carbon source. The obtained result proved that the pyoverdine production and biofilm formation help the Pseudomonas bacteria to tolerate to the stressed condition as pesticide. Moreover, the co-existence of the iron and PCP molecule ameliorate its biodegradation.

Comparative Effects of Dominant Forest Tree Species on Soil Characteristics and Microbial Biomass

Tree species differ in litter quality and belowground biomass, thereby exerting species-specific impact on soil properties and microbial biomass. A study was conducted to find out the comparative effects of Podocarpus falcatus and Croton macrostachys on basic soil characteristics and microbial biomass, in the Munessa forest, Ethiopia. Four experimental plots under the canopies the respected tree species (two from each) were established for sample collection. From these plots, soil samples were collected from a depth 0-10 cm and 10-25 cm. The results showed that, from the depth 0-10 cm, concentration of organic carbon (C) and nitrogen (N) was larger under C. macrostachys and from the depth 10-25 cm these values were greater under P. falcatus. There was significant difference (p < 0.05) in cation exchange capacity being larger under C. macrostachys. There were no differences in microbial composition between the plots. However, the total phospholipid fatty acids (PLFA) concentration as an entry for microbial biomass determination tended to be significantly larger in soil under Podocarpus plots (382.7 ± 60.9 nmol PLFA g-1 dry soil) vs. 262.2 ± 32.8 nmol PLFA g-1 dry soil (Croton plots). The varying impacts of tree species on soil characteristics and microbial biomass may be partly explained by differences in functional traits related to life-history strategy of the respected species.

Comparative Effects of Dominant Forest Tree Species on Soil Characteristics and Microbial Biomass

Tree species differ in litter quality and belowground biomass, thereby exerting species-specific impact on soil properties and microbial biomass. A study was conducted to find out the comparative effects of Podocarpus falcatus and Croton macrostachys on basic soil characteristics and microbial biomass, in the Munessa forest, Ethiopia. Four experimental plots under the canopies the respected tree species (two from each) were established for sample collection. From these plots, soil samples were collected from a depth 0-10 cm and 10-25 cm. The results showed that, from the depth 0-10 cm, concentration of organic carbon (C) and nitrogen (N) was larger under C. macrostachys and from the depth 10-25 cm these values were greater under P. falcatus. There was significant difference (p < 0.05) in cation exchange capacity being larger under C. macrostachys. There were no differences in microbial composition between the plots. However, the total phospholipid fatty acids (PLFA) concentration as an entry for microbial biomass determination tended to be significantly larger in soil under Podocarpus plots (382.7 ± 60.9 nmol PLFA g-1 dry soil) vs. 262.2 ± 32.8 nmol PLFA g-1 dry soil (Croton plots). The varying impacts of tree species on soil characteristics and microbial biomass may be partly explained by differences in functional traits related to life-history strategy of the respected species.

The effect of human trampling activity on a soil microbial community at the Oulanka Natural Reserve, Finland

Functional and taxonomic diversities of microbial communities in Arctic soils are governed by the extreme abiotic environment and affected by human activities. We assessed the impact of trampling by humans on biotic and abiotic parameters relevant to soil health at the Kiutaköngäs Trail, Oulanka Nature Park, Finland. Soil was sampled from the 0 to 2 cm, 2 to 5 cm, and 5 to 10 cm layers for four levels of trampling pressure: heavily trampled, medium trampled, low trampled sites, and non-trampled control. Measured and estimated abiotic soil parameters included organic matter, pH, water-holding capacity, and bulk density for each soil sample. Biotic parameters included determination of microbial biomass, CO2 evolution and MicroResp®-based community level physiological profiles, and as well as bacterial taxonomic diversity. Results have shown that total organic matter amount might not change significantly under trampling. Nevertheless, absolute substrate utilization, functional diversity, and respiration varied with depth, significantly declining in the immediate subsurface under the trampled sites. On the other hand, the most extreme stress associated with the greatest trampling intensity was associated with an increase in taxonomic diversity but with a proportional decline in Acidobacteria abundance, in line with the increase in pH.

Novel optimization strategy for tannase production through a modified solid-state fermentation system

BackgroundHigh amounts of insoluble substrates exist in the traditional solid-state fermentation (SSF) system. The presence of these substrates complicates the determination of microbial biomass. Thus, enzyme activity is used as the sole index for the optimization of the traditional SSF system, and the relationship between microbial growth and enzyme synthesis is always ignored. This study was conducted to address this deficiency. All soluble nutrients from tea stalk were extracted using water. The aqueous extract was then mixed with polyurethane sponge to establish a modified SSF system, which was then used to conduct tannase production. With this system, biomass, enzyme activity, and enzyme productivity could be measured rationally and accurately. Thus, the association between biomass and enzyme activity could be easily identified, and the shortcomings of traditional SSF could be addressed.ResultsDifferent carbon and nitrogen sources exerted different effects on microbial growth and enzyme production. Single-factor experiments showed that glucose and yeast extract greatly improved microbial biomass accumulation and that tannin and (NH4)2SO4 efficiently promoted enzyme productivity. Then, these four factors were optimized through response surface methodology. Tannase activity reached 19.22 U/gds when the added amounts of tannin, glucose, (NH4)2SO4, and yeast extract were 7.49, 8.11, 9.26, and 2.25%, respectively. Tannase activity under the optimized process conditions was 6.36 times higher than that under the initial process conditions. The optimized parameters were directly applied to the traditional tea stalk SSF system. Tannase activity reached 245 U/gds, which is 2.9 times higher than our previously reported value.ConclusionsIn this study, a modified SSF system was established to address the shortcomings of the traditional SSF system. Analysis revealed that enzymatic activity and microbial biomass are closely related, and different carbon and nitrogen sources have different effects on microbial growth and enzyme production. The maximal tannase activity was obtained under the optimal combination of nutrient sources that enhances cell growth and tannase accumulation. Moreover, tannase production through the traditional tea stalk SSF was markedly improved when the optimized parameters were applied. This work provides an innovative approach to bioproduction research through SSF.

Composition and activity of soil microbial communities in different types of temperate forests

The composition and diversity of forest soil microbial communities may be affected by the composition of plant communities and characteristics of soils. The objective of our study was to compare microbial properties of soils under various types of temperate forests. The samples were taken from soil A horizons under dry and mesic pine forests, acidophilus and fertile beech forests, hornbeam and oak dominated deciduous forests and ash dominated riparian forest. The samples were analysed for pH and the contents of organic C and total N, P, K, Ca, Mg and Mn. Microbial analyses included determination of microbial biomass, basal respiration, community level physiological profiles (CLPPs) measured by MicroResp™ method and phospholipid fatty acid (PLFA) profiles. The soil microbial communities under the pine forests were lower, less active and exhibited different CLPPs and PLFA profiles than those under deciduous forests. The PLFA profiles and CLPPs were correlated to each other revealing that the observed different metabolic abilities under the pine and deciduous forest types resulted from differences in taxonomic composition of soil microbial communities. The CLPPs and PLFA profiles depended on soil texture and the contents of Corg, Nt, and Pt indicating that in the temperate forests the taxonomic and functional composition of soil microbial communities are shaped by both the soil properties and the vegetation. The functional diversity of soil microbial communities was not related to plant diversity indicating that in temperate forests the number of plant species has little effect on the ability of soil microorganisms to degrade different organic compounds.

Effect of Distillery Effluent, Biomethanated Spent Wash, on Microbial Activity Parameters in Soil Under Rice–Wheat Cropping System

The study reports the effect of biomethanated spent wash on chemical and microbial properties of sandy loam soil. A field experiment was conducted to examine the effect of spent wash on biological soil health under rice–wheat cropping system. The soil was analysed for enzyme activity along with determination of microbial biomass and microbial quotient. The maximum fluorescein diacetate hydrolysis (7.09 μg fluorescein g−1 soil h−1), acid phosphatase (5.43 μg p-nitrophenol g−1 soil h−1), alkaline phosphatase (4.57 μg p-nitrophenol g−1 soil h−1) and dehydrogenase (49.9 μg TPF g−1 soil h−1) activity was recorded in treatment with 156 m3 ha−1 of spent wash in three splits. A positive correlation was observed between phosphatase activity and availability of phosphorus. The positive correlation between urease activity and available mineral nitrogen (r = 0.960) indicates increased availability of nitrogen to crops with spent wash application. Among the treatments, spent wash application at 156 m3 ha−1 resulted in highest microbial biomass carbon Cmic (279.84 μg g−1). Maximum microbial quotient (Cmic/Corg) (5.3 %) and minimum metabolic quotient (7.8 μg C–CO2 h−1 mg C biomass−1) was recorded during one time application of spent wash at 125 m3 ha−1 at time of transplanting/sowing. Soil enzymes, involved in energy flow and nutrient cycling in soil showed significantly higher activities with increasing concentration of spent wash application to the soil. Moreover the increase in microbial biomass and microbial quotient indicates positive effect of spent wash on biological soil health which is as important as physical and chemical status of soil.

Functional diversity of soil microbial communities under Scots pine, Norway spruce, silver birch and mixed boreal forests

Functional structure and diversity of forest soil microbial communities may depend on plant diversity. The objective of our study was to compare community level physiological profiles (CLPPs) of microbial communities from uppermost soil horizons under Scots pine (Pinus sylvestris), Norway spruce (Picea abies), silver birch (Betula pendula) and mixed pine–birch–spruce stands representing boreal forests differing in the identity of the dominant tree species and diversity of overstory and understory plant species in the system. The samples of O and A soil horizons were measured for pH, organic carbon, and total nitrogen. Microbial analyses included determination of microbial biomass (Cmic) and measurement of CLPPs with the MicroResp™ system. The studied forest types differed significantly in plant species diversity with birch and mixed forests being the most and the pine forest the least diverse. Functional microbial diversity only slightly differed between the studied forest types and was not related to plant diversity. Despite similar functional diversity of soil microbial communities there were significant differences in CLPPs in the O horizons under the pine, spruce and birch forests indicating that plant cover affects the rate at which particular organic compounds are degraded. Differences in physiological profiles between the birch, pine and spruce forest soils were mainly due to variable decomposition of readily decomposable organic compounds represented mainly by carboxylic acids.

Changes in Plant Nutrients, and Microbial Biomass in Different Soil Depths After Long-Term Surface Application of Secondary Treated Wastewater

Abstract Long-term effects of surface application of secondary treated wastewater on plant nutrients dynamics, the cycling of C and N within the system through the determination of microbial biomass, and associated health hazards were studied in different soil locations. Sites that have been irrigated with wastewater for the last 1, 4, 10, and 17 years were identified and used as sampling locations for this study. Two other sites that have not been irrigated with wastewater were sampled as a control. Soil samples were taken from several sites within each location, and at the following depths: 0-20, 20-40, and 40-60 cm. Results obtained indicated that microbial biomass C and N were increased significantly with increasing application period of treated wastewater. Barley plant tissues analysis showed that plant nutrients content was significantly higher in sites which received wastewater for a long period than other sites. No significances in accumulation of lead (Pb) in barley plant tissues were observed with sites received wastewater for different periods. The bacteriological analysis showed that the total bacterial count of surface soil (0-20 cm) was higher in sites irrigated with wastewater for the last 10 and 17 years. The total coliforms ranged from 0.92x102 cfu/g soil to 3.3x102 cfu/g soil, while fecal coliform were less and detected only in top soils at sites irrigated with wastewater for the last 10 and 17 years.

Determination of microbial biomass and fungal and bacterial distribution in cattle faeces

Abstract As an important component of organic fertilizers, animal faeces require methods for determining diet effects on their microbial quality to improve nutrient use efficiency in soil and to decrease gaseous greenhouse emissions to the environment. The objectives of the present study were (i) to apply the chloroform fumigation extraction (CFE) method for determining microbial biomass in cattle faeces, (ii) to determine the fungal cell-membrane component ergosterol, and (iii) to measure the cell-wall components fungal glucosamine and bacterial muramic acid as indices for the microbial community structure. Additionally, ergosterol and amino sugar data provide independent control values for the reliability of the microbial biomass range obtained by the CFE method. A variety of extractant solutions were tested for the CFE method to obtain stable extracts and reproducible microbial biomass C and N values, leading to the replacement of the original 0.5 M K2SO4 extractant for 0.05 M CuSO4. The plausibility of the data was assessed in a 28-day incubation study at 25 °C with cattle faeces of one heifer, where microbial biomass C and N were repeatedly measured together with ergosterol. Here, the microbial biomass indices showed dynamic characteristics and possible shifts in the microbial community. In faeces of five different heifers, the mean microbial biomass C/N ratio was 5.6, the mean microbial biomass to organic C ratio was 2.2%, and the mean ergosterol to microbial biomass C ratio was 1.1‰. Ergosterol and amino sugar analysis revealed a significant contribution of fungi, with a percentage of more than 40% to the microbial community. All three methods are expected to be suitable tools for analysing the quality of cattle faeces.

Using GC-MS for the quick analysis of carbon dioxide for soil microbial biomass determination

Microbial biomass carbon is a common soil parameter used to evaluate microbial abundance in soil environments, and microbial biomass can change in response to disturbances and/or changing environmental conditions. Microbial biomass carbon was determined on 192 soil samples using the chloroform fumigation-incubation method, and after 10 days, gas samples were collected. Gas samples were analyzed for carbon dioxide (CO2) concentration. Determination of CO2 concentration is usually conducted by infrared gas analysis or chemical analysis (an alkali trap and subsequent titration, or soda lime absorption), and these methods were either unavailable or too time consuming for the number of samples analyzed. As a result, we have developed an analytical method for the determination of CO2 in gases using the gas chromatograph/mass spectrometer (GC-MS). This method requires a 5 μL injection, 5 minute analysis time, and the resulting figures of merit are comparable to most procedures present in the literature. Additionally, the microbial biomass carbon values obtained were consistent with previously published values in similar ecosystems.

A rapid method for the determination of microbial biomass by dry weight using a moisture analyser with an infrared heating source and an analytical balance

Microbial biomass is an important biotechnological parameter. The traditional method for its determination involves an oven-drying step and equilibration to room temperature before weighing, and it is tedious and time consuming. This work studied the utilisation of a moisture analyser consisting of an efficient infrared-heating module and an analytical balance for the determination of microbial biomass by dry weight. The method duration depended on the sample volume and was between 7 and 40 min for sample volumes of 1-10 ml. The method precision depended on the total dry weight analysed - 10 mg of total dry weight being sufficient to achieve coefficients of variation of 5% or less. Comparison with the conventional oven method provided a correlation coefficient r(2) of 0.99. The recovery of an internal standard ranged between 94.2 and 106.4% with a precision of 1.39-4.53%CV. Validation revealed sufficient method accuracy, precision and robustness and was successfully applied to the study of yeast and bacterial growth kinetics. Techniques are discussed that allow for increased method precision at low biomass concentrations, and equations are provided to estimate required drying time and method precision based on sample volume and total sample dry weight, respectively. This work presents a rapid method for the determination of microbial biomass, allowing for the timely implementation of biomass-based information in biotechnological and laboratory protocols.

Ammonium immobilisation during chloroform fumigation

The assumption in using the chloroform fumigation technique for microbial biomass determination is that microbes are killed or at least inactivated by the treatment. Problems associated with transformations of the N released on or during fumigation have so far only been associated with the fumigation–incubation method. A laboratory and a field study were carried out to investigate the possible N transformations during biomass determination by the fumigation–extraction method. Labelled NH 4NO 3 (either the NO 3 −, NH 4 + or both pools were 15N enriched) was applied to the soil and biomass determinations made at intervals subsequently. The size and enrichment of the ammonium (NH 4 +), and nitrate (NO 3 −) pools were determined before and after chloroform fumigation. The 15N enrichment of the NH 4 + pool after fumigation could only be explained if immobilisation of ammonium occurred at some time during the 24 h fumigation period. The extent of this immobilisation was calculated. In addition, there was evidence that nitrification occurred during the fumigation procedure at the start of the laboratory study and throughout the field study. The laboratory and field study differed mainly in the dynamics related to NO 3 − uptake and release. There was evidence for uptake of NO 3 − by the microbial biomass with and without utilization. We conclude that the 15N enrichment in the microbial biomass cannot be accurately determined when N transformations and release of non-utilized N occurs during fumigation. The possible immobilisation of mineral N during fumigation will affect the magnitude of the factor used to convert measured microbial biomass N to actual microbial biomass N in soil.

Comparison of methods for determination of microbial biomass in wastewater

Microbial biomass in wastewater was determined by methods used in environmental microbiology and by a method used in wastewater engineering based on a conceptual model simulating fundamental microbial processes in wastewater from measured oxygen uptake rates. The methods originating from environmental microbiology are based on staining and counting of cells for the determination of total cell biomass (acridine orange and DAPI), physiological state of cells (LIVE/DEAD ® BacLight™) and activity of cells (reduction of the redox dye CTC and microautoradiography). Depending on the staining method applied, cell biomasses yielded 15–86% of the biomass defined by the model, and good correlations between cell biomass and model biomass were found. Cell biomass, oxygen uptake and acetate uptake were measured in wastewater, where acetate was added. Substrate uptake rates were found not to be proportional to the increases in cell biomass, suggesting that only a small fraction of the cell biomass was responsible for the main part of the substrate uptake. Despite the differences found between cell biomass and model biomass, it was recommended to use the conceptual model as an engineering tool for simulation of microbial processes and wastewater quality changes. However, there should be a clear distinction between the terms ‘model biomass’, ‘cell biomass’ and different activity measurements of cells.

Soil C extracted with water or K2SO4: pH effect on determination of microbial biomass

Routine determination of soil microbial biomass C has shifted during the past decade from chloroform fumigation-incubation to chloroform fumigation-extraction using 0.5 M K2SO4 as extractant. We compared extractable C with water and 0.5 M K2SO4 in eight soils ranging in pH from 5.4 to 8.3. In unfumigated soils with low pH, extractable C was 0.8- to 1.2-fold greater with water than with 0.5 M K2SO4. However, in unfumigated soils with pH > 7.7, extractable C, although not statistically significant, was 11 to 19% less with water than with 0.5 M K2SO4. In fumigated soils, no difference in extractable C between water and 0.5 M K2SO4 was detected among soils with pH < 7.7, but extractable C was 13 to 17% less with water than with 0.5 M K2SO4 with pH > 7.7. Our results suggest that 0.5 M K2SO4 (1) may flocculate soil and cause adsorption of solubilized C onto colloids at pH < 7.7, but (2) may disperse calcareous soils at pH > 7.7, thereby differentially affecting the fate of solubilized C depending upon soil pH. Our results put into question the widespread adaptability of using chloroform fumigation-extraction to estimate microbial biomass C. Key words: Extractable carbon, chloroform fumigation-extraction, microbial biomass

Carbon and nitrogen mineralization of added particulate and macroorganic matter

Particulate organic matter (POM) is more sensitive than total SOM to changes in management practices and, accordingly, may indicate changes in soil quality. A soil incubation study was conducted to determine the effects of added POM (75 to 250 μm size fraction), or macroorganic matter (MOM, 250 to 2000 μm size fraction) on C and N mineralization and microbial C and N content. A 1 kg composite made from 16 predominantly silt loam soils was amended with 10 g of POM, MOM or MOM ground to a reduced size of 75 to 250 μm (GMOM). The MOM amendment equaled 4.55-fold and POM equaled 1.60-fold of total MOM and POM found in the composite soil. Carbon mineralization of MOM and POM after 8 weeks was approximately 9 and 4%, respectively of the total MOM and POM-C added. Reducing the size of MOM to 75 to 250 μm did not affect mineralization. Nitrogen mineralization was slightly greater in the amended soils after 8 weeks and equaled 5 to 6% of the MOM or POM-total N added. Contribution of POM to total mineralized N from soil organic matter (SOM) in the composite soil was proportional to the POM content in SOM or approximately 12%. Amended soils had 25 to 42% more biomass-C than the control soil 2 weeks after amendment application. After 8 weeks, the amended soils contained about 32% more biomass-C. This increase in biomass-C at 8 weeks accounted for approximately 2% of the added C. At 8 weeks, microbial biomass-N in GMOM-, MOM- and POM-amended soils was about 56, 46 and 14% higher, respectively, than in the control soil. These increases were approximately 8% of the MOM-N added and 2% of the POM-N added. Increases in POM resulted in increases in soil respiration and microbial biomass-C and N, which also are suggested indicators of soil quality. Therefore, POM may be a suitable soil quality indicator that provides similar information as soil respiration or microbial biomass determinations.

Effects of cattle slurry and mineral N fertilizer applications on various components of the nitrogen balance of mown grassland

It is essential to establish more accurate N balances for different soil-plant systems in order to improve N use efficiency. In this study the N balance was studied in a poorly drained clayey loam soil under natural grassland supplied with either calcium ammonium nitrate or cattle slurry at two application rates. The aim was to determine the efficiency of the N applied and the factors which affect this efficiency. Mineralization-immobilization of N was calculated by balance between the quantified inputs and outputs of N. As N inputs increased, output via herbage yield was accompanied by an increase in apparent immobilization of N in the soil and by larger losses of N by denitrification. The difference between cattle slurry and N fertilizer was that the slurry behaved as a slow release fertilizer, its supply of mineral N being greater in the periods of time when fertilizer was applied a long time ago. Denitrification losses (up to 17% of the N applied) are suggested to be the main factor to mitigate in order to increase N use efficiency. A decrease in net mineralization (up to 136 kg N ha-1 year-1) was observed which was related to the mineral N application rate. There was evidence to suggest that this decrease was due both to the immobilization of the N applied and to a decrease in the rate of gross mineralization when mineral N was applied. Microbial biomass determinations could not explain the changes in the mineralization-immobilization equilibrium of N because of the great coefficients of variation for this determination (mean value of 18%). Nevertheless, it contributed to verify and explain some of the changes observed in this equilibrium.

Determination of Microbial Biomass and Nitrogen Mineralization following Rewetting of Dried Soil

AbstractRoutine soil testing procedures that are rapid and precise are needed to evaluate agricultural surface soils for their potential to mineralize C and N. Our objectives were to determine the optimum preincubation time after rewetting of dried soil for estimating soil microbial biomass (SMB) and to identify a quick, reliable biochemical predictor of soil N mineralization potential. Biochemical determinations of SMB were screened on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) having five levels of soil organic C (SOC) as a result of long‐term management. Determinations used (i) field‐moist soil and (ii) soil that was air dried, rewetted, and preincubated for 0.2, 1, 3, 6, 10, and 15 d. Biochemical determinations included arginine ammonification, substrate‐induced respiration (SIR), cumulative C and net N mineralization, and SMBC using the chloroform fumigation‐incubation (CFI) method. Preincubation periods of 1 and 15 d prior to fumigation gave estimates of SMBC using CFI most similar to those determined on field‐moist soil. Arginine ammonification and SIR determinations on dried soil were highly variable, making longer preincubation periods necessary. Carbon mineralization during all preincubation periods was highly correlated to (i) SMBC using CFI determined on field‐moist and dried soil with all preincubation periods and (ii) net N mineralization during 21 d for the Weswood soil, as well as for seven additional soil series each having five to eight levels of SOC. The CO2‐C evolved during the first day after rewetting of dried soil is recommended for rapid estimation of SMBC and potential N mineralization because of its simplicity and precision.

A Method Using Peroxydisulphate Digestion for Total N Analyses in Soils and in Soil Microbial Biomass Extracts

Abstract The persulphate oxidation (TPN) and the Kjeldahl methods (TKN) were compared for measurement of total N in soils and soil extracts. The TPN method was adapted for optimum recovery and precision in the determination of total N. Measurement of total N with TPN and TKN procedures showed the methods to be comparable for both mineral soils and soil extracts. For soil samples with a high content of C (> 5%) and N (> 0.5%), the total N content was highest with TKN. The Flow Injection Analysis (FIA) was very suitable for anlaysis of nitrate in persulphate digestions. The TPN method combined with FIA estimation of nitrate is recommended for analysis of total N in soils and in soil extracts for microbial biomass determinations.

Temporal variation in ped shape in an old pasture soil

Ped shape can influence soil physical properties by determining the morphology of interpedal pores. Monthly variation in soil ped shape was investigated in conjunction with soil physical properties for a pasture soil uncultivated for some years with the intension of identifying whether simple relationships existed between ped shape parameters and physical properties. A brief description of the ped shape quantification method used (Holden, 1993) and results obtained are presented, in conjunction with methods and data for hydraulic conductivity, soil water release, ped stability and microbial biomass determinations. Results indicate significant variation in ped surface roughness throughout one calendar year, but no significant changes in gross shape. Correlations between surface roughness and other soil properties are presented, the most important being the relationship identified between ped surface roughness and soil water characteristic data for a tension of 10 kPa. A significant correlation between ped shape and hydraulic conductivity could not be established. It is concluded that seasonally driven change in ped shape occurs, but that this is poorly related to bulk physical properties of the soil by simple relationships.