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Phosphorus (P) is the second key nutrient for plants and it affects several attributes of plant growth. Identification of a potent phosphate solubilizing microorganism capable of transforming the insoluble P into soluble and plant-accessible forms is considered as the best eco-friendly option for providing inexpensive P to plants. Hence, this study was focused to assess the growth enhancement traits of the phosphate solubilizing bacteria (PSB) isolated from chili rhizosphere. Twelve PSB were isolated by enrichment culture technique and its P solubilization efficiency was checked using Vanadomolybdate phosphoric yellow color method. Among them, two potent strains PS2 and PS3, identified as Pseudomonas aeruginosa KR270346 and KR270347 based on biochemical and molecular characterization, were selected for further study. The Pseudomonas aeruginosa isolates interestingly showed the presence of various potential plant growth-promoting properties including indole acetic acid and siderophore production. The growth enhancement effect of Pseudomonas aeruginosa isolates on chilli showed promising results, and the growth parameters were found to be statistically significant when compared to control. The results demonstrated an eloquent impact on various aspects, namely microbial count and PSB population, phosphatase and dehydrogenase activity, available phosphorous in the soil, plant nutrient uptake, and yield parameters. Inoculation of these two isolates together with the addition of rock phosphate increased comparable amount of available P and these treatments were statistically at par throughout the growth period. The results confirmed the growth-promoting potential of the isolates to develop as biofertilizers either alone or as components of integrated nutrient management systems. [ABSTRACT FROM AUTHOR]

Petroleum contamination in the soil has been well emphasized as a toxic and hazardous soil pollution contributing to a significant portion of soil infertility worldwide. In the present study, bacterial consortium CHM1 composed of 5 strains belonging to genera Klebsiella, Pantoea, and Enterobacter was evaluated for hydrocarbon degradation ability in the soil environment, as well as their performance in remediating ecotoxicity and phytotoxicity. Initially, the degradation efficiency (1.98%/day) in the soil environment was evaluated. Scanning Electron Microscopy combined with Energy Dispersive X-ray spectroscopy revealed an increase in nitrogen content by 24.98% and a decrease in carbon content by 22.76% implying an improvement in soil fertility. The Fourier Transform InfraRed spectroscopy and Gas Chromatographic analysis revealed significant depletion of aromatic, cyclic, long aliphatic, and complex acid and ester content of the test soil. Moreover, the quantitative PCR analysis exhibited the non-competitive coexistence of each component of the CHM1 consortium. Different enzymatic assays revealed elevated dehydrogenase and superoxide dismutase activity in the degradation system due to the introduction of CHM1 in the soil microcosm. Vibrio fischeri -assisted ecotoxicity analysis had established the potential of CHM1 to efficiently minimize the ecotoxicity of hydrocarbon contamination. The phytotoxicity analysis was performed using four different plant models viz. Chickpeas (Cicer arientinum), Coriander (Coriandrum sativum), Fenugreek (Trigonella foenum-graecum), and Spinach (Spinacia oleracea) exhibiting CHM1 amendment helped to restore plant germination and growth in hydrocarbon-contaminated soil system efficiently. The promising results from this study indicated the possible application of the bacterial consortium in hydrocarbon-contaminated land management and soil restoration for cultivation or other plantation purposes. • Successful degradation of mixed type hydrocarbon (MTH) degradation in soil by CHM1. • MTH degradation was confirmed by SEM-EDX, FTIR, and GCMS. • Quantitative PCR analysis confirmed the non-competitive growth of different strains of CHM1. • Dehydrogenase and SOD activity were the dominant metabolisms. • Both ecotoxicity and phytotoxicity were significantly reduced by CHM1. [ABSTRACT FROM AUTHOR]

• A modified DHA-TTC test for microbial activity was developed and validated. • DHA-TTC exhibited a higher sensitivity to toxicants than DHA-INT. • The sensitivity of DHA-TTC was explained through theoretical simulations. • DHA-TTC test offered a cost-effective solution for practical wastewater monitoring. Reliable and cost-effective methods for monitoring microbial activity are critical for process control in wastewater treatment plants. The dehydrogenase activity (DHA) test has been recognized as an efficient measure of biological activity due to its simplicity and broad applicability. Nevertheless, the existing DHA test methods suffer from imperfections and are difficult to implement as routine monitoring techniques. In this work, an accurate and cost-effective modified DHA approach was developed and the procedure for the DHA test was critically evaluated with respect to the standard construction, sample pretreatment, incubation and extraction conditions. The feasibility of the modified DHA test was demonstrated by comparison with the oxygen uptake rate and adenosine triphosphate in a sequencing batch reactor. The sensitivities of the two typical tetrazolium salts to toxicant inhibition by heavy metals and antibiotics were compared, revealing that 2,3,5-triphenyltetrazolium chloride (TTC) exhibited a higher sensitivity. Furthermore, the sensitivity mechanism of the two DHA tests was elucidated through electrochemical experiments, theoretical analysis and molecular simulations. Both tetrazolium salts were found to be effective artificial electron acceptors due to their low redox potentials. Molecular docking simulations revealed that TTC could outperform other tetrazolium salts in accepting electrons and hydrogens from dehydrogenase. Overall, the modified DHA approach presents an accurate and cost-effective way to measure microbial activity, making it a practical tool for wastewater treatment plants. [Display omitted] [ABSTRACT FROM AUTHOR]

Frequent periods of low rainfall accompanying climate change are expected to affect many aspects of agricultural production and greenhouse gas emissions. In this work, we conducted field experiments on soil CO 2 efflux and soil microbial activity using two precipitation treatments and two crop management technologies. While the control treatment was exposed to natural precipitation, the reduced water availability was induced during the early stages of crop growth using rain-exclusion shelters within the water deficit treatment. We aimed to test the difference in the response to water deficit between two management technologies: conventional tillage (CT - ploughed without cover crops) and adaptation technology (AT - no-till with species rich cover crops). After a month of simulated water deficit, the soil CO 2 efflux under a regime of adaptation technology was essentially the same as that under the conventional technology, and the decrease in soil CO 2 efflux ranged between 22 % and 55 %. The water deficit had a technology-specific effect on microbes. While no effect on the microbial carbon under CT was observed, the water deficit decreased Cmic under AT. In contrast, the opposite pattern was observed for DHA. When a normal soil water regime was restored, CO 2 efflux recovered rapidly while recovery of microbial biomass and dehydrogenase activity was more variable. Generally, the soil microbial biomass and activity recovered better under AT. The results show that while the reduction in Rs during water deficit and its recovery after the restoration of the ambient precipitation regime were not affected by the technology, the response of microbial biomass and activity to water deficit depended on the technology with better recovery under AT. [Display omitted] • One-month simulated drought resulted in a decrease in soil CO 2 efflux by 22–55 %. • CO 2 efflux recovered after the end of the water deficit period. • Response of microbial carbon and DHA to water deficit depended on the tillage. • Adaptation tillage technology showed better post-drought recovery of soil activity. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the effects of conventional and organic production system on microbial activity in the soil cultivated with bean and maize crops. The trial in Đurđevo was set up according to the conventional farming system, while organic farming system was used in Futog. Two maize hybrids and two bean cultivars were used in the trial. Soil samples were collected in two periods during 2014 (before sowing, at flowering stage of bean crops, and at 9-11 leaf stage of maize) at two depths, at both locations. The following microbiological parameters were tested: the total number of micro­organisms, number of ammonifiers, Azotobacter sp., free nitrogen fixing bacteria, fungi, actinomycetes, and activity of dehydrogenase enzyme. The results showed that the total number of microorganisms, number of free N-fixers and dehydrogenase activity were higher within organic production, while Azotobacter sp. was more abundant in conventional production. Variations in the number of ammonifiers, fungi and actinomycetes in relation to the type of production were not obtained. Significant differences in microbial activity were also obtained between period and depths of sampling.

This study evaluated the effects of the application of microbial inoculants (N-fixing Klebsiella planticola and Enterobacter spp.), two rates of composite mineral fertilizers, and their combination on microbial biomass carbon (MBC), dehydrogenase (DHA), and proteinase activity (PTA) in Lessivated Cambisol and yield-related properties of maize and wheat grains in a two-year trial. Unfertilized soil was used as a control variant. MBC was measured using the chloroform fumigation-extraction method, DHA was determined spectrophotometrically by measuring the intensity of the formed red-colored triphenyl formazan, while PTA was determined using a titration method by measuring the degree of gelatine decomposition. In grain samples, P was determined spectrophotometrically, K—by flame emission photometry, N—on an elemental carbon/nitrogen/sulfur (CNS) analyzer, and crude proteins—by calculation of N content. Measuring both crops’ yield was carried out at the end of the vegetation. The results indicated that mineral fertilizers are not, in general, negative for soil microbiota when used in the context of sustainable agriculture without monoculture. There is a significant increase in the values of soil MBC, DHA, and PTA in the variants with combined application of bacterial inoculants and lower rates of mineral fertilizers. The highest values of these parameters were determined in the period with a better distribution of precipitation during the vegetation period of the year. The mentioned combination also resulted in a higher grain yield of maize and wheat comparing to the application of lower rates of the NPK nutrients solely. The combined application of high rates of mineral fertilizers and bacterial inoculants resulted in significantly increased N, P, K, and protein content in the grains of crops, and the same applied to yield. Concluding, studied bacterial inoculants can be used to specify the replacement of nitrogen fertilizers, stimulating the microbial biomass and enzyme activity in the soil, helping to ensure that the supply of nutrients contributing to an optimized yield of crops is maintained.

Digestates are commonly used as organic inputs in agriculture. This study aimed to answer four questions: (1) What are the immediate and longer-term impacts of digestates on soil microbial activity?; (2) How much of the digestates’ carbon is mineralized within the first months? (3) How do the nitrogen, lignin, cellulose, and hemicellulose contents of digestates influence microbial activity and carbon mineralization? (4) How does the soil type influence mineralization? To investigate this, dehydrogenase activity (DHA) was measured in a field trial and in laboratory experiments with five digestates (DGs), cattle slurry, and cattle manure. DHA measurements were supplemented with soil respiration experiments using two different soils. DHA was significantly increased by all organic inputs, but decreased back to the control level within seven months under field conditions. Twenty percent to 44% of the organic carbon (Corg) in the digestates was converted to CO2 after 178 days. Soil respiration was significantly negatively correlated to lignin content (r = −0.82, p < 0.01) and not correlated to nitrogen, cellulose, or hemicellulose content. On the basis of equal carbon application, slurry promoted soil respiration and DHA more strongly than digestates in the short term.

Biobeds bioremediation systems are effectively used for minimizing pesticide point-source contamination. For keeping the biobed effectiveness, its biomixture needs to be replaced every so often. The exhausted biomixtures can contain pesticide residues and so they require a special treatment before being discharged into the environment. In this study, we explore the potential of vermiremediation for cleaning up biobed biomixtures contaminated with pesticides. Two biomixtures composed of soil:peat:straw (P) and soil:vermicompost of wet olive cake: olive tree pruning (O), contaminated with high loads of four pesticides, were used. Vermicomposting was carried out by Eisenia fetida earthworms for 12 weeks. Results showed that 50% and 70% of the earthworms colonized the contaminated P and O biomixtures, respectively, but the number of alive earthworms decreased with time just as their weight. The colonization of biomixtures did not significantly affect the dissipation of imidacloprid and tebuconazole, but increased 1.4 fold the dissipation of oxyfluorfen in both biomixtures and that of diuron in biomixture P. Although the presence of high loads of pesticides and the composition of the biomixtures limited the vermiremediation, satisfactory results were obtained for diuron and oxyfluorfen. Complementing vermiremediation with other remediation practices could improve the efficiency of this technology.

The aim of the study was a statistical evaluation of the impact of selected soil factors − water potential (pF), total organic carbon content (TOC) and land use − on the total DNA content and dehydrogenase activity (DHA) in Mollic Gleysol. Additionally, we wanted to establish the interrelations between two of the most important biological parameters in soli: activity of intracellular dehydrogenases and total DNA content. Soil originating from the surface layer of the control site displayed higher DHA (c.a. by 57%) and DNA content (c.a. by 25%) as compared to an cultiavted meadow. Our results also indicate a significant (p

Biological soil crust (BSC) constitutes a consortium of cyanobacteria, algae, lichen, mosses, and heterotrophic microorganisms, forming a miniature ecosystem within the uppermost soil layer. The biomass of different organisms forming BSC and their activity changes along with succession. Previous studies focused primarily on BSC in hyper-arid/arid regions, whereas the ecophysiology of BSC in temperate climates is still not well recognized. In order to determine changes in overall microbial activity and photosynthetic biomass in BSC at different stages of the succession of inland sandy grasslands, we analyzed dehydrogenase activity and determined the content of photosynthetic pigments. We also compared these parameters between BSC developed on the dune ridges and aeolian blowouts in the initial stage of succession. Our study revealed a significant increase in both photosynthetic biomass and overall microbial activity in BSC as the succession of inland shifting sands progresses. We found that chl a concentration in BSC could be considered a useful quantitative indicator of both the presence of photoautotrophs and the degree of soil crust development in warm-summer humid continental climates. The photosynthetic biomass was closely related to increased microbial activity in BSC, which suggests that photoautotrophs constitute a major BSC component. Dune blowouts constitute environmental niches facilitating the development of BSC, compared to dune ridges. High biomass of microorganisms in the dune blowouts may be associated with a high amount of organic material and more favorable moisture conditions. We conclude that deflation fields are key places for keeping a mosaic of habitats in the area of shifting sands and can be a reservoir of microorganisms supporting further settlement of dune slopes by BSC., (© 2023. The Author(s).)

The steadily increasing production of pharmaceutical substances, their widespread use in health care for people and animals and inadequate disposal methods have attracted much interest in risks involved in the presence of these substances and their metabolites in the environment. Drugs present in wastewater are often resistant to biodegradation and can disturb biological processes of removing contaminants from wastewater. It should be emphasized that conventional wastewater treatment plants are not adapted to disposal of such contaminants as pharmaceutical substances. The aim of this study was to evaluate the effect of erythromycin on changes in dehydrogenase activity in activated sludge and oxygen uptake rate of the whole population of microorganisms of active sludge, heterotrophic bacteria and nitrifying bacteria of the first and second phase. A decline in activity of dehydrogenases of activated sludge in the presence of erythromycin was observed. With the concentration of this antibiotic of 150 mg/L, the lowest value of dehydrogenase activity was 35.5 μmol TF/gSS, whereas the degree of inhibition for this concentration reached 33.7%. It was also found that oxygen uptake rate declined for the entire population of microorganisms of active sludge in the presence of the antibiotic. The highest value of the inhibition degree for this oxygen uptake rate was 28.8%. Furthermore, an insignificant decline in the degree of inhibition of oxygen uptake rate was observed for heterotrophic bacteria (13.7%). The most sensitive to erythromycin were nitrifying bacteria. Degree of inhibition of oxygen uptake rate in the presence of this antibiotic for nitrifying bacteria of the first phase reached 40–64.5%, whereas for the bacteria of second phase, this value was 28.2–62%. [ABSTRACT FROM AUTHOR]

As a step toward bioaugmentation of coking wastewater treatment 45 bacteria strains were isolated from the activated sludge of a coking wastewater treatment plant (WWTP). Three strains identified as Bacillus cereus, Pseudomonas synxantha, and Pseudomonas pseudoaligenes exhibited high dehydrogenase activity which indicates a strong ability to degrade organic matter. Subsequently all three strains showed high naphthalene degradation abilities. Naphthalene is a refractory compound often found in coking wastewater. For B. cereus and P. synxantha the maximum naphthalene removal rates were 60.4% and 79.8%, respectively, at an initial naphthalene concentration of 80 mg/L, temperature of 30 °C, pH of 7, a bacteria concentration of 15% (V/V), and shaking speed of 160 r/min. For P. pseudoaligenes, the maximum naphthalene removal rate was 77.4% under similar conditions but at 35 °C. [ABSTRACT FROM AUTHOR]

Certain agricultural practices, such as the repeated application of herbicides or organic amendments to soil, can influence herbicide dissipation. This research has studied the effects of two repeated applications of mesotrione, pethoxamid, and triasulfuron on their dissipation rates in unamended soil (S) and soil amended with green compost (S+GC) or sewage sludge (S+SS). The dissipation experiment has also included an evaluation of the adsorption of the three herbicides by soils and of changes in soil dehydrogenase activity (DHA). The adsorption of the three herbicides by amended soils (Kf range 0.83–2.98) was higher than by unamended soil (Kf range 0.20–0.64). The adsorption coefficients (Kd) of mesotrione and triasulfuron were higher for S+SS, while that of pethoxamid was higher for S+GC, but no relationship between values for the time to 50% degradation (DT 50 ) and adsorption coefficients could be determined. The repeated application of mesotrione decreased its dissipation rate in unamended soil (DT 50 increased from 4.75 to 8.15 days) and amended soils (DT 50 increased from 11.7 to 28.2 days in S+GC and from 17.7 to 37.9 in S+SS), whereas the repeated application of pethoxamid increased its dissipation rate in all the treatments, and the rate for triasulfuron increased only in amended soils. The highest DT 50 values for pethoxamid (12.3 days) and triasulfuron (57.1 days) were in S+GC, and the lowest in S+SS (8.35 and 24.7 days). Soil DHA was stimulated by the presence of GC in the soil and by the first application of mesotrione. The second application of mesotrione and pethoxamid positively affected soil DHA, but this did not occur for triasulfuron. The repeated applications of herbicides and soil organic amendments have different effects on herbicide dissipation, adsorption, and soil DHA, and they should be taken into account when assessing soil quality and other potential environmental implications of pesticide use. [ABSTRACT FROM AUTHOR]

Despite conservation agriculture (CA) is being promoted as a climate resilient technology, limited information is available on its impacts on N storage within soil aggregates vis a vis global warming potential (GWP) under tropical agro-ecosystems. Hence, this study assessed the effects of a medium-term (5-years) CA on total soil N (TSN) changes in bulk soils and aggregates, N 2 O and CO 2 emission, GWP and total C fixed in soils under maize ( Zea mays L.)- wheat ( Triticum aestivum L.) system on the Indo-Gangetic Plains (IGP). The treatments were: conventional tillage (CT), zero tillage (ZT) with planting on permanent narrow beds (PNB), PNB with residue (PNB + R), ZT with planting on permanent broad beds (PBB), PBB with residue (PBB + R), ZT on flat land/plains without crop residue (ZT) and with crop residue retention (ZR + R). Soil samples were collected after five years of a maize–wheat system and TSN in bulk soils and their aggregates of the 0–5 and 5–15 cm soil layers were measured along with N 2 O and CO 2 emissions during the fifth year (2014–15).The soils under PBB + Rhad 37 and 9% more macro-aggregate-and micro-aggregate-associated N concentrations in topsoil (0–5 cm layer) than CT (248 and 299 kg N ha −1 ). However, topsoil soil aggregation and aggregate-associated N contents of PNB + R and ZT + R were similar to CT plots. The dehydrogenase and fluorescein diacetate activities and TSN, microbial biomass N, NO 3 -N and NH 4 -N concentrations were also highest in PBB + R plots in topsoil. The topsoil dehydrogenase activity was significantly correlated (r = 0.426, n = 21, p < 0.05) with CO 2 emission and with N 2 O emission (r = 0.770, n = 21, P < 0.01) during wheat (2014–15). However, topsoil FDA activities and MBN concentrations were only significantly correlated with N 2 O emission in wheat. In the maize–wheat system, highest N 2 O emission was observed in PNB + R plots and least in CT plots. But, PBB + R and PNB + R plots had similar CO 2 emissions to CT plots in both crops. Despite GWP of ZT + R and PBB + R plots in the maize-wheat system were ∼5% higher than CT, greenhouse gas (GHG) intensities in the CT, PBB + R and ZT + R plots were similar. Thus, PBB + R practice is a better management alternative for soil N improvement (and a reduced fertilizer N dose could be adopted in future) than CT since this practice also had 36% and 8.2% higher biomass productivities of maize and wheat, respectively in the maize-wheat cropping system and similar GHG intensity to CT plots. [ABSTRACT FROM AUTHOR]

A field study was carried out to assess the impact of revegetation on Technosol quality in the post-mining sites (Central Coalfield Limited, India). The study evaluated community structure, biodiversity, Technosol quality, and carbon (C) dynamics in the post-mining ecosystem (PME). The multivariate statistical tool was used to identify the key soil properties, and soil quality was evaluated by using Technosol quality index (TQI). One unreclaimed site (0 years) and four chronosequences revegetated coal mine sites (3, 7, 10, and 15 years) were studied and compared with an undisturbed forest as a reference site. Plant biodiversity indices [Shannon index of diversity (2.42) and Pielou’s evenness (0.97) and Patric richness (12)] were highest in 15-year-old revegetated sites. Soil physicochemical and biological properties were recovered with the revegetation age. Soil organic C (SOC) stock significantly increased from 0.75 Mg C ha−1 in 3 years to 7.60 Mg C ha−1 after 15 years of revegetation in top 15 cm of soils. Ecosystem C pool increased at a rate of 5.38 Mg C ha−1 year−1. Soil CO2 flux was significantly increased from 0.27 μmol CO2 m−2 s−1 in unreclaimed sites to 3.19 μmol CO2 m−2 s−1 in 15-year-old revegetated site. Principal component analysis (PCA) showed that dehydrogenase activity (DHA), available nitrogen (N), and silt content were the key soil parameters that were affected by reclamation. A 15-year-old Technosol had a greater TQI (0.78) compared to the control forest soils (0.64) that indicated the suitability of revegetation to recuperate soil quality in mining-degraded land and to increase C sequestration potential. [ABSTRACT FROM AUTHOR]

Three different methods of bacterial viability monitoring were compared to detect chemically or thermally inactivated Escherichia coli. Direct colony enumeration, live/dead bacterial cell staining with a fluorescent dye, and the dehydrogenase activity assay were compared with respect to their ease of use and time required to perform the three different tests. The green (live cell)/red (dead cell) ratio obtained from the fluorescent bacterial cell staining approach showed a linear relationship with the colony forming units; the result obtained with dehydrogenase was similar to those. The sensitivity of the monitoring methods to detect bacterial deactivation varied with different disinfection conditions. After thermal treatment, the sensitivity of the staining approach was lower, while that of the dehydrogenase activity assay was the highest. After chemical treatment, the sensitivity of detection for both methods was similar. [ABSTRACT FROM AUTHOR]

The current study presents results concerning the effect of a static magnetic field (SMF) on synthetic wastewater biodegradation by activated sludge and on dehydrogenase activity of microorganisms of activated sludge. The highest process efficiency was obtained for a SMF of 0.0075 T among the tested magnetic flux density values of 0.005-0.14 T. Decrease in COD was 25% higher for the bioreactor exposed to SMF compared with control experiments. The positive effect of SMF 0.0075-0.0080 T was confirmed in experiments on the dehydrogenase activity of activated sludge. It was also shown that a SMF of 0.007 T increased p-nitroaniline removal from wastewater and influenced the recombination frequency in a streptomycin-resistant bacteria strain of Eschercihia coli. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to present variability of content and quality of soil organic matter on the landslide surface. Attempts were made to demonstrate the progress of the process of soil cover restoration 7 years after the landslides and biochemical activity of soil associated with the restoration of soil cover.Materials and methods: The landslide area was located in southern Poland, in the Sucha Forest District. The soil properties were studied on a regular grid of points, which covered the entire area of the landslide. In soil samples, particle size, soil aggregates content, pH, total carbon and nitrogen content, microbial biomass carbon and nitrogen and the activity of dehydrogenases were determined. Additionally, the fractions of soil organic matter were used in the study as an indicator of soil quality due to the many important interactions of these components in the soil system.Results and discussion: This study identified the landslide area as characterised by a stronger diversification of physical, chemical, and biological properties. The upper part of the landslide (in the area referred to as the landslide niche) is strongly eroded and characterised by the least advanced soil cover recovery. Additionally, low soil organic matter content was observed in the upper part of the landslide, which restricted biological activity of the studied soils. Soil microbial biomass carbon increased with restoration of landslide soils.Conclusions: The soil organic matter plays a key role for the initial stage of soil formation on a landslide. The amount of soil organic matter on the studied landslide had a positive effect on the microbial biomasses C and N, dehydrogenases activity. Estimating the soil organic matter fraction can be utilised as an indicator of changes in soil. [ABSTRACT FROM AUTHOR]

When applying an aided phytostabilization in trace-element-contaminated agricultural soil, the cultivation of forage crops instead of edible crops can reduce the trace elements transfer to humans while minimizing the income loss of farmers. The objectives of this study were to compare the effect of the type of forage crops at the "family" level (Poaceae and Leguminosae) on aided phytostabilization using physical (water stable aggregation), chemical (Mehlich-3 extraction), and biological assessments (dehydrogenase activity). Pig manure and acid mine drainage sludge were used as soil amendments, and four plant species (Loliummultiflorum Lam. var. italicum and Secalecereale L. [Poaceae representatives], Viciavillosa Roth, and Trifoliumpratense L. [Leguminosae representatives]) were cultivated after amendment treatments. Chemical assessment showed that the reduction in bioavailability of trace elements was partly observed in legume crops. The positive effects of plant cultivation were determined through physical assessment. The effectiveness of pig manure as an organic amendment was determined by biological assessment. In some treatments, the synergistic effect of the incorporation of chemical stabilization with both plant families was observed but it was difficult to identify a clear distinction between the two families. The translocation of trace elements from root to shoot was low in all plants, indicating that the cultivation of the plants used in this study is safe with regards to the spread of trace elements into the environment. The results suggest that forage crop cultivation in contaminated agricultural soil could ameliorate soil quality after chemical stabilization. [ABSTRACT FROM AUTHOR]

It was found that using chelating agents increases the efficiency of heavy metal extraction, however, they may have negative effects on soil ecosystem quality. A pot experiment was conducted in a completely randomized design with three replications in order to evaluate the effect of EDTA and Olive Husk Extract (OHE) on some chemical and biological properties of the Pb-contaminated soil. The experimental treatments included EDTA (2 g Na2EDTA salt per kg soil), OHE (2 g TDS of OHE per kg soil) and control (without the chelating agent). The results revealed that the EDTA and OHE treatments increased the Pb availability by 17.7% and 5.5% in comparison to the control treatment, respectively. Although EDTA was more effective in increasing the Pb availability but decreased the soil biological quality index (SBQI). The EDTA treatment significantly decreased the dehydrogenase (DH) activity and germination index (GI). The OHE application significantly increased the available-P, available-K, total N and organic carbon content by 339.92%, 40.79%, 20.9%, and 29.7% compared with control treatment, respectively. Furthermore, OHE considerably increased SBQI from 18.96 to 53.48. Compared to the control treatment higher values of soil respiration activity, DH activity, and carbon availability index (CAI) were observed in OHE treatment. [ABSTRACT FROM AUTHOR]

Most important, yet least understood, question, how microbial activity in soil under saline water irrigation responds to carbon (C) varying qualitatively (most labile form to extreme recalcitrant form) with or without maintaining C/N ratio was investigated in an incubation experiment. Soil samples from a long-term saline-water (electrical conductivity, EC ≈ 0, 6, and 12 dS m-1)- irrigated field were incorporated with three different C substrates, viz., glucose, rice straw (RS), and biochar with or without nitrogen (N as ammonium sulfate, NH4SO4) and were incubated at 25 °C for 56 days. Cumulative respiration (CR), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and dehydrogenase activity (DEA) concentrations decreased with increasing EC (P < 0.05), but less so in soils amended with glucose followed by RS and biochar. The addition of N to soils amended with different C substrates significantly decreased CR, MBC, DEA, and available phosphorus (P) concentrations at a given EC level. [ABSTRACT FROM AUTHOR]

Mercury is considered a very toxic element and important efforts are currently being made aimed at reduce or even eliminating its usage. Despite this trend, there are still sites where contamination by this metal is very marked, especially in the mining environment of Almadén where it has been exploited for thousands of years. The several forms in which Hg occurs in the soil interact differently with the organisms that live in/on it. The soil is a place where many biotic and abiotic variables act together. Through a detailed study of the edaphic characteristics of a decommissioned metallurgical enclosure, the presence of different chemical forms of Hg, the study of microbial activity (DHA) and, finally, parameters of the vegetation cover, such as specific distribution and biomass, we have tried to elucidate the effect of the presence of Hg in this precinct with a very high Hg pollution. The obtained results showed the affection patterns by which the different measured parameters vary, with special incidence to the microbial activity of the topsoil and to the specific distribution of the plants found in the studied area. The statistical multivariate analysis showed that significant correlations have been found between soil Hg fractions and between Hg fractions in plants; furthermore, soil conditions seem to be not related with Hg transfer from soils to plants. Biomass and DHA data indicate that the studied area is not affected by the presence of Hg species and lacks the expected toxic effects on the living organisms. [ABSTRACT FROM AUTHOR]

The contact assay measuring the inhibition of Arthrobacter globiformis dehydrogenase activity as an endpoint to evaluate the toxicity of solid samples was tested in an international ring-test to validate its performance for ISO standardization (ISO/CD 18187). This work reports the results of the ring-test involving 9 laboratories from six countries. At least 8 valid data sets were obtained for each sample and more than three quarters of the participants attained the validity criteria defined in the standard. The coefficient of variation within (CV r ) and between (CV R ) laboratories was generally on average <15% and <30% for negative and positive controls, respectively. Regarding solid samples, the laboratories provided a similar ranking of the samples based on their toxicity, despite some variation in the LOEC values. The logarithmic within-lab standard deviation <0.50 for soils and <0.25 for wastes evidenced a good repeatability. The between-lab variability assessed by a CV R <30%, minimum-maximum factor <4 and a reproducibility standard deviation (SD R ) <0.13 for a great part of the solid samples, confirmed the test reproducibility. Overall, this assay proved to be robust, sensitive and feasible for routine use towards the quality assessment of soils and wastes. [ABSTRACT FROM AUTHOR]

In order to study the influence of different concentrations of zinc and sulfachloropyridazine sodium (SCPS) on anaerobic digestion (AD) during biogas production, we determined the levels of urease, dehydrogenase activity, and volatile fatty acids (VFAs) in batch tests. The experiments were conducted in small AD devices at a temperature of 37 °C using swine manure and wheat straw as raw materials. Four digestion trials were performed using different zinc and SCPS contents: control digestion with no additives (CK), SCPS at 630 mg kg-1 dry weight (S), SCPS at 630 mg kg-1 with zinc at 500 mg kg-1 dry weight (SL), and SCPS at 630 mg kg-1 with zinc at 5,000 mg kg-1 dry weight (SH). The biogas accumulation under S was 1.7 times that with CK, while SL and SH produced 78% and 35% of that under S, respectively. Correlation analysis showed that the accumulated biogas was significantly negatively correlated (p< 0.05) with VFAs, and the urease activity was significantly negatively correlated (p< 0.01) with zinc and significantly positively correlated with VFAs (p <0.05). The dehydrogenase activity was strongly correlated (p<0.01) with the biogas accumulated during the AD of swine manure. [ABSTRACT FROM AUTHOR]

A denitrification baffled reactor (DnBR) was developed to treat p -Cresol-laden wastewater. The effects of different operational parameters including p -Cresol initial concentration, hydraulic retention time (HRT), COD/NO 3 − , salinity and nitrate-free influent were studied on biodegradation and COD removal of p -Cresol. The results show that complete degradation of 1000 mg/L p -Cresol could be reached at HRT of 24 h. Also, in this condition, corresponding COD and nitrate concentration (2500 mg/L for both) were decreased to about 83 mg/L and 4.5 mg N/L, respectively. There was not a significant failure in the performance of the bioreactor at HRT value of 4 h and nitrate removal rate of 1.65 kg N/m 3  d was reached. The highest dehydrogenase activity of the DnBR was 17.65 μgTF/gVS d for organic loading rate (OLR) of 7.5 kgCOD/m 3  d. DnBR could tolerate salinity concentration of 10 g NaCl/L, however increasing of salinity from 10 to 20 g/L caused moderate failure in the reactor performance. The optimum COD/NO 3 − was 0.9. Microbial community was also investigated and PCR results revealed that Bacillus megaterium , Bacillus aryabhattai , and Bacillus cereus were the predominant bacteria in degradation and mineralization of p -Cresol. Accordingly, DnBR could be considered as a promising technique for biodegradation and COD removal of p -Cresol in wastewater. [ABSTRACT FROM AUTHOR]

Previous studies suggest that biochar has potential to benefit soil when used as an amendment, but only few studies have investigated how the different biochars affect the microbial activity of soil in a calcareous soil. Hence, to study the effect of the biochars obtained from wheat straw and cow manure and produced under different production conditions on two biological soil indicators, dehydrogenase activity and soil respiration, after 0, 60, and 120 days of incubation (DOI), an incubation experiment as a completely randomized design with factorial arrangement in three replicates was conducted in a calcareous soil. The results of the study showed that with increasing the pyrolysis temperature (300 and 500 °C) and pyrolysis residence times (1, 3, and 6 h) of biochars, regardless of feedstock source, the dehydrogenase activity and soil respiration decreased. Both maximum activity of dehydrogenase (20.93 μg TPF g−1 24 h−1) and maximum soil respiration (0.26 mg CO2 g−1 24 h−1) were found in the biochar produced from wheat straw at 300 °C, and the residence time of 1 h at the level of 10 t ha−1 and minimum of these soil biological traits was observed in control treatments (soil). Moreover, the maximum activity of dehydrogenase and soil respiration was observed in 60 DOI. Therefore, when applying biochar as an amendment for increasing microbial activity in calcareous soil, the production conditions of biochar, type of biochar, and long- and short-term effects of different biochars should be taken into consideration. [ABSTRACT FROM AUTHOR]

In this study, an anaerobic baffled reactor (ABR) with four compartments was employed to treat alkalidecrement wastewater of polyester fabrics under different organic loading rates. The stable operation of this reactor was achieved in 70 days at a hydraulic retention time of 36 h and mesophilic temperature of 35°1 °C. It is found that the chemical oxygen demand removal and decolorization of this system can be as high as 79.0% and 87.7%, respectively. The different acidogenesis and methanogenesis in four compartmentswas acclimated by the variation of pH, oxidation reduction potential values and operational conditions in the spatial distribution of the first to fourth compartments of the ABR system. In addition, the dehydrogenase activity (DHA) and coenzyme F420 concentrations along the four compartments ranged from 67.8 to 185.21 μgTF/(gVSS·h) (TF: triphenyl formazan; VSS: volatile suspended solids) and 0.123 to 0.411 μmol/g, respectively. These results indicated that the ABR could separate acidogenesis and methanogenesis in longitudinal distribution and treat well the alkali-decrement wastewater. [ABSTRACT FROM AUTHOR]

In this study, the variation of reactor performance, biofilm property and microbial community in response to the elevated Cu (II) in Anammox system were investigated. The nitrogen removal, extracellular polymeric substance (EPS) and copper content in biofilm, soluble microbial products (SMP), dehydrogenase activity (DHA) and microbial community were evaluated. The self-recovery ability was also investigated after stopping Cu (II) supply. Results showed the long-term feeding of Cu (II) significantly suppressed the nitrogen removal in Anammox system. The nitrogen removal rate (NRR) decreased to 0.210, 0.145 and 0 kg m −3 d −1 , respectively in 1, 5 and 10 mg L −1 Cu (II), from the initial 0.50 kg m −3 d −1 , with the decreasing ratio of 57.3%, 71.0% and 100%. With the elevation of Cu (II), the SMP, EPS and copper content gradually increased while DHA sharply decreased. Cu (II) improved the microbial diversity and lowered the Candidatus Kuenenia abundance to 1.36% from the initial 6.50%. The self-recovery ability of Anammox system was unsatisfactory, the NRR only recovered to 26.7% after one month operation free from Cu (II). Finally, the mechanism of Cu (II) interacting with Anammox biofilm was analyzed. [ABSTRACT FROM AUTHOR]

For the first time, the N,N-(pyromelitoylimidyl)-bis-(4-hydroxy tyrosine dimethyl ester benzyl sulfonamide) (PHTBS) as diphenolic monomer containing tyrosine was formed in three steps. PHTBS employed as a monomer in the design of biodegradable and biological polymers. The polycondensation of the this monomer with various aromatic and aliphatic diisocyanates such as 4,4′-methylenebis-(4-phenylisocyanate) (a), hexamethylene diisocyanate (b), isophorone diisocyanate (c) and toluene-2,4-diisocyanate (d) was carried out under traditional polymerization conditions to give poly(urethane-imide-sulfonamide)s (PUIS)s as pseudo-poly(amino acid)s (PAAs). The novel PHTBS and obtained PUISs were characterized with FTIR, 13C-NMR, 1H-NMR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy and elemental analysis. Differential scanning calorimetry and thermogravimetric analysis were used to determine the thermal properties of the polymers. Morphology probes showed these PUISs were nanoshape polymers. On the basis of thermogravimetric analysis data, such PUISs are thermally stable and can be classified as self-extinguishing polymers. The obtained PUISs possessed more bioactivity, moderate thermal stability and high solubility in common organic solvents. Furthermore, soil enzymatic of the PHTBS and the obtained PUISs assay showed that the synthetic materials are biologically active and then could be classified as bioactive and biodegradable compounds. [ABSTRACT FROM AUTHOR]

In an ongoing field experiment, organic and conventional farming (control) were compared for onion bulb yield, biochemical quality, soil organic carbon (SOC), and microbial activity after the sixth cropping cycle. The treatments used for organic production were farmyard manure (FYM, 20,000 kg ha−1), poultry manure (PM, 10,000 kg ha−1), vermicompost (VC, 10,000 kg ha−1), neem cake (NC, 5000 kg ha−1), and a combination of FYM (5000 kg ha−1), PM (2500 kg ha−1), VC (2500 kg ha−1), and NC (1250 kg ha−1); all treatments were compared with the control. Organic treatments produced 24.6–43.6% lower yield consistently for 6 years than the control treatment. No significant difference was observed between PM, FYM, and VC treatments for the bulb yield. Bulb analysis during the sixth year indicated that plants that received FYM, PM, or VC had higher levels of total phenol, total flavonoid, ascorbic acid, and quercetin-3-glucoside than the control plants. All the five organically treated sets had significantly higher values of SOC, microbial population, fungal-to-bacterial ratio, and dehydrogenase activity than the control and the initial values in each treated set. The results indicate that FYM, PM, or VC application enhances biochemical quality and organic farming is more sustainable than conventional farming. [ABSTRACT FROM AUTHOR]

The use of Jatropha curcas L. (Jatropha) as biofuel is currently increasing in tropical and sub-tropical regions. Jatropha species are well known for synthesizing various toxicants. However, the effects of Jatropha plantation on soil microbiota have barely been investigated. Hence, in current experiment, we had investigated the effects of Jatropha cultivation on soil microbial and biochemical properties in winter, summer and wet seasons after 9 years of plantation with different plant population densities. A nearby uncultivated area was included as the control site. Soil organic carbon was found to increase, while carbon: nitrogen ratio (C:N) decreased under Jatropha plantation as compared to control. Irrespective of seasons, mean microbial biomass C (MBC) and microbial biomass N increased under Jatropha plantation. The microbial quotient calculated as the percentage of MBC to soil organic carbon was lowest in summer and relatively constant in other two seasons. There was a significant increase in urease and dehydrogenase enzyme activities due to Jatropha plantation. The rate of decomposition of soil organic matter was faster under Jatropha cultivation compared to the control. The study revealed that irrespective of population density of Jatropha, there was improvement of soil health in terms of biochemical and microbial characteristics. These findings suggest that Jatropha can be used in the bunds of agricultural lands or in the degraded lands without any harmful effects on the soil microbial community. [ABSTRACT FROM AUTHOR]

Purpose: A simple disposal of metal-contaminated sediment on land can inevitably lead to increased soil concentrations of the elements, which consequently jeopardizes the soil environment for living organisms. In order to make the metal-contaminated sediment recyclable and reusable, one possible option is sediment stabilization using immobilizing amendments, in which the metals can be immobilized and the bioavailable fraction accounting for metal toxicity can be reduced. Materials and methods: In the present study, three immobilizing amendments, including zeolite, calcium carbonate (CaCO), and manganese dioxide (MnO), were compared for their ability in reducing cadmium (Cd) bioavailability in the soil receiving Cd-contaminated sediment. Soil chemical analysis, calcium chloride (CaCl)-extractable Cd fraction, plant uptake, and microbial assay were employed to give a relative comprehensive comparison with regard to the amendment efficacy. Results and discussion: Results showed that although the total concentrations of Cu, Pb, and Zn were increased with the addition of sediment in soil, they were still under the guideline limit set at an elevated pH condition. Compared with zeolite and MnO, CaCO showed the best mitigating effects on Cd toxicity, evidenced by reduced CaCl-extractable Cd concentrations, increased dehydrogenase activities, and reduced Cd uptake by sorghum. Conclusions: Incorporation of CaCO with contaminated sediment was a new option of dredged sediment treatment for land application in Dongting Lake region, where the sediment was deviated from the 'waste' stream without causing much concern on soil health. [ABSTRACT FROM AUTHOR]

Severe problems are caused by site burning of rice straw in Valencia, the third largest Spanish city. Removal, incorporation or composting are being tested as alternatives to burning, and the changes they produce in selected soil biological properties have been studied in two field trials. One compares removal, burning and incorporation the straw, and a second evaluates the application of straw-derived compost for rice production. No statistically-significant effects on the measured indicators of biological activity were found in either experiment, indicating that management-induced changes are small. Unexpectedly, burning did not affect negatively enzyme activities or microbial biomass contents since there were no differences between treatments, or usual levels were recovered in a few months. The changes induced by straw removal or incorporation were also not statistically significant. When straw-derived compost applications were assayed, dehydrogenase activity was slightly variable and apparently unaffected by N and compost rates or compost/mineral N combinations, but phosphomonosterase activity seems to increase parallel to compost to mineral N ratio.

This study assesses the effect of long-term (59 years) application of organic and inorganic fertilizers on soil organic matter and enzyme activity. Total organic C, total organic N, hot water soluble C, microbial biomass C and dehydrogenase activity were evaluated in soil from the long-term field experiment in Prague-Ruzyně (Orthic Luvisol, clay loam). Total organic C and N increased significantly in soils treated with organic fertilizers (farmyard manure, compost) and in soils with a combination of organic and mineral NPK fertilizers (manure + NPK, compost + NPK, cattle manure + straw + NPK) compared to soil treated with inorganic fertilizer, cattle slurry + straw and non-fertilized control. Farmyard manure significantly increased hot water soluble C compared to the control. Dehydrogenase activity was significantly increased by all treatments compared to control. The results indicate that additions of organic matter from various sources differ in the effects on soil organic matter and biological activity. The effect of manure was the most favourable; long-term application of cattle slurry + straw is rather similar to mineral fertilization.

Surface mining, as a means of intensive exploitation of mineral raw materials and especially coal, is highly developed area of economy, therefore land degradation is intensive and leading to loss of the productive layer of soil. Biological reclamation of deposol should reduce the harmful consequences of exploitation. The number of systematic and physiological groups of microorganisms and their activities provide correlative information on the biological activity of the soil. In 2011, at the overburden disposal site in Stanari coal mine, the sowing of grass-clover mixture in previously treated deposol was carried out. The aim of the research is to the deposol biological activity in the process of biological reclamation based on the distribution of certain groups of microorganisms and dehydrogenase activity. General microbial activity in deposol in the process of reclamation is determined by the total number of bacteria, azotobacters, ammonifiers, oligonitrophyls, actinomycetes and fungi and the activity of the enzyme dehydrogenase. The research results indicated a greater abundance and deposol dehydrogenase activity in the process of biological reclamation compared to deposol (control).