Culturable Microbial Populations Research Articles

Yield and nutrient composition of forage crops and their effects on soil characteristics of winter fallow paddy in South China.

In terms of providing additional feeds and improving the soil fertility, planting forage crops during the fallow seasons is an effective strategy to promote resource utilization. The objective of this research was to compare the effects of planting different forage crops on the yields and nutritive compositions of forage and soil properties of winter fallow paddy in southern China. Five forage crops, including alfalfa (Medicago sativa, AF), common vetch (Vicia sativa, CV), milk vetch (Astragalus sinicus, MV), smooth vetch (Vicia villosa, SV) and Italian ryegrass (Lolium multiflorum, IR), were planted by monoculture on the winter fallow paddy in 2017-2018 (season 1) and 2018-2019 (season 2), respectively. The dry matter yield of IR was significantly higher than those of AF, CV, SV and MV (P<0.05). The crude protein yield of IR was significantly higher than those of AF, CV and MV (P<0.05). The neutral detergent fiber and acid detergent fiber contents of CV, SV and IR were significantly lower than those of AF and MV (P<0.05). Forage crops significantly affected the culturable microbial population of soils (P<0.05). The bacteria, actinomyces and fungi numbers on IR were the highest, while azotobacter number was the lowest. The catalase, acid-phosphatase and invertase activities of IR soil were the lowest. The numbers of bacteria, actinomyces and fungi of IR soil were the highest. IR and SV were the best crops to obtain forage and improve the soil. When producers pursue higher forage yield, we recommend planting Italian ryegrass. If the producers want to improve soil characteristics, smooth vetch is the most suitable plant. These results provide useful information to rice growers for cropping management when growing forage crops (based on the yield and nutritional value) or green manure (based on improving the soil fertility) as an alternative to late rice harvest.

Impact of conservation practices on soil quality and ecosystem services under diverse horticulture land use system

The 20-year study investigated the effects of conservation practices (CPs) and farmers' practices (FPs) on various soil quality parameters, yield, and economics of horticultural land use systems. CPs demonstrated significant improvements in soil organic carbon (SOC), available nitrogen (N), phosphorus (P), and potassium (K), compared to FPs. Horticultural systems exhibited higher SOC and available N and P contents than FPs, with substantial variations among different fruit species. CPs also enhanced soil quality index, functional diversity, culturable microbial populations, enzyme activity, and soil microbial biomass carbon (SMBC) compared to FPs. It was observed that the SMBC values were 25.0–36.6% and 4.12–25.7% higher in 0–15 cm and 15–30 cm, respectively, under CPs compared to FPs for all the land use systems. In CPs, dehydrogenase activities (DHAs) in surface soils were 9.30 and 7.50 times higher under mango- and citrus-based horticultural systems compared to FPs. The CPs adopted in aonla, guava, mango, litchi, and citrus-based horticultural systems increased SOC by ~27.6, 32.6, 24.4, 26.8, and 22.0%, respectively, over FPs. Canopy spread, fruit yield, litter yield, and soil moisture were significantly higher in fruit-based horticultural systems under CPs. Economic viability analysis indicated higher net present values (NPVs), benefit-cost ratio (BCR), and shorter payback periods (PBPs) for horticultural land use systems under CPs. Principal component analysis (PCA) revealed that CPs had a more positive influence on soil parameters, particularly DHA, acid and alkali phosphatase activity, available N, P, and K contents, soil microbial load, and organic carbon. The maximum ecosystem services were contributed through mango-based land uses among all land uses. Mango-based horticultural systems exhibited the least impact from both CPs and FPs, while peach-based systems were most affected by CPs. Overall, the findings highlight the benefits of conservation practices in improving soil quality, microbial populations, enzyme activity, and crop productivity in horticultural systems.

Spatio-temporal diversity of biological aerosols over Northeast India: a metagenomic approach.

Northeast India is considered as one of the major biodiversity hotspots in the world, but the region is underexplored for their microbial biodiversity. Extensive characterization of biological aerosol (bioaerosol) samples collected from various locations of Northeast India was carried out for all four seasons in a year. These were characterized in terms of their constituents, such as pollens, fungal spores, animal debris, and non-biological components, and particulate matters, such as inhalable, thoracic, and alveolic, and finally, the bacterial diversity was determined by DNA-based metagenomic approach. The non-biological (non-viable) component of aerosols is found to vary from 30 to 89% in the pre-monsoon season, which coexists with pollens (4-20%), animal debris (1-24%), and fungal spores (1-17%). The highest number of culturable microbial populations in terms of CFU count was observed in the pre-monsoon samples (i.e., 125.24-632.45CFU/m3), and the lowest CFU was observed in monsoon season (i.e., 20.83-319.0CFU/m3). The metagenomic approach with the samples collected during pre-monsoon season showed a total of bacterial 184 OTUs (operational taxonomic units) with 28,028 abundance count comprising 7 major phylum, 6 classes, 10 orders, 15 families, 13 genus, and 8 species of bacteria. The species-level distribution clearly shows the presence of Gammaproteobacteria (52%) most abundantly, followed by Bacilli (21%), Alphaproteobacteria (14%), Betaproteobacteria (5%), Flavobacteria (5%), and Sphingobacteria (3%). It is the first report from the entire Northeast India to uncover spatio-temporal distribution of biological components and bacterial diversity in aerosol samples through a DNA-based metagenomic approach.

Culturable Microbial Population From the Upper Respiratory Tract of 1,010 Clinically Healthy Horses in Southern Brazil

Microbiological diagnosis of equine respiratory infections is essential for disease management. However, reliable diagnosis can be a challenge due to colonization of the upper respiratory tract (URT) by a diverse microbial population, and because there is a lack of studies with samples from healthy animals. Aiming to guide adequate URT culture, this work reports culturable microbial population from the URT of 1,010 apparently healthy horses from 341 farms in Southern Brazil and identifies the putative presence of pathogenic microorganisms. Nasal swabs were cultured in 5% blood agar, and the isolates were phenotypically identified to genus level. A diverse respiratory microbial population was found, mostly composed of Gram-positive bacteria, including Staphylococcus spp., Bacillus spp., Streptococcus spp. and Corynebacterium spp. The microbiological profile from the nasal cavity of 911 horses was described, with the five most common profiles being: (1) Staphylococcus sp. + Gram-negative bacilli (12.67%), (2) Staphylococcus sp. in pure culture (12.47%), (3) Staphylococcus sp. + Bacillus sp. (10.10%), (4) Gram-negative bacilli in pure culture (6.93%), and (5) Staphylococcus sp. + Bacillus sp. + Gram-negative bacilli (6.73%). Streptococcus equi equi and Rhodococcus equi were detected in 34 horses (3.37%), demonstrating the presence of pathogenic bacteria along with commensal microorganisms in apparently healthy animals. The disclosed data may guide and facilitate microbiological diagnosis of URT infection in horses. The significant presence of Gram-negative bacilli was evidenced, as well as the occurrence of relevant pathogens, such as S. equi equi and R. equi, thus helping to improve diagnosis and antimicrobial therapy.

Bioagent consortia assisted suppression in grey blight disease with enhanced leaf nutrients and biochemical properties of tea (Camellia sinensis)

Microbial bioagents and botanicals contrastingly different in modes of action, and despite being used over the years, their comparative efficacy are not yet fully explored with regard to management of grey blight disease caused by Pseudopestalotiopsis curvatispora Petch in tea plantation of Assam, India. Four microbial antagonists-based formulations and seven botanicals at 2.5–10% concentration were tesed against mycelial growth of grey blight pathogen through dual culture assay and poisoned food technique, respectively, under in vitro conditions. Resultantly, two botanicals viz., Pongamia pinnata L. and Xanthium strumarium L. and two microbial bioformulations viz., Biometa as Metarhizium anisopliae and Biogreen as Trichoderma viride -based consortium of microbial antagonists were evaluated, singly and in combination through field studies in a grey blight affected 12-year -old tea plantation (grey blight susceptible clone TV-23) established on acidic Inceptisol with regard to suppression in grey blight disease incidence (PDI), green tea yield, culturable soil microbial population, leaf nutrients composition, and biochemical properties of tea. The consortium of microbial antagonists (Biogreen + Biometa) registered 11.34% higher suppression in grey blight disease at 4% concentration over combination of P. pinnata + X. strumarium at 10% concentration, both sprayed 5 times at 30 days interval in 150- days period, besides single microbial antagonist (Biometa) being inferior to consortium of microbial antagonists (Biogreen). Such a reduction in PDI resulted in 22.9% higher yield of green tea leaves with consortium of bioagents over botanicals due to significant elevation in soil culturable microbial population, and leaf nutrient composition. These responses were eventually associated with an improvement in biochemical properties (Polyphenols, caffeines, and antioxidants acivity) of tea. Our study, hence, provided both, in vitro and field evidence in favor of multipronged benfits of consortium of microbial antagonists for an extended control of grey blight disease of tea, a reliable alternative to conventionally used chemical fungicides towards tea health care with enhanced quality parameters.

Co-composting of cotton residues with olive mill wastewater: process monitoring and evaluation of the diversity of culturable microbial populations

With the aim to recommend an integrated alternative for the combined treatment of olive mill wastewater (OMW) and cotton residues (CR), and the production of high value and environmentally friendly products, two compost piles were set up. The first pile (control, pile 1) consisted of ginned CR, whereas the second (pile 2) was made of CR with the addition of OMW. A series of physicochemical parameters and the culturable microbial diversity in both piles were assessed. Co-composting (pile 2) displayed higher temperatures during the whole process, a prolonged second thermophilic phase and temperature values higher than 40°C even after the thermophilic stage. Comparing the physicochemical parameters of the pile 2 with those of the pile 1, it was deduced that pH in the former was more acidic during the onset of the process; the EC values were higher throughout the process, while the levels of ammonium and nitrate nitrogen, as well as the NH4+/NO3- ratios, were lower at most of the sampling dates. By evaluating the abovementioned results, it was estimated that the co-composting process headed sooner toward stability and maturity, Isolated microorganisms from both piles were identified as members of the genera Brevibacillus, Serratia, Klebsiella, and Aspergillus, whereas active thermotolerant diazotrophs were detected in both piles at the 2nd thermophilic phase emerging a promising prospect upon further evaluation for enhancing the end-product quality. Our findings indicate that co-composting is an interesting approach for the exploitation of large quantities of agro-industrial residues with a final product suitable for improving soil fertility and health.

Culturable microbial diversity in the rhizosphere of different biotypes under variable salinity

The microbial diversity in the rhizosphere of different biotypes is influenced by different factors like plant species, root exudates and soil environment. Culturable microbial diversity in the rhizosphere of six biotypes (Chenopodium murale (CM), Spergula arvensis (SA), Launaea nudicaulis (LN), Brassica juncea (BJ), Phalaris minor (PM) and Triticum aestivum (TA)) growing in variable saline environment (ECe 8.0 dS m−1) was assessed and compared with the diversity of bulk soils (BS) of same environments. The significantly (P < 0.0001) highest bacterial and actinomycetes population were found in the rhizosphere of BJ whereas SA possessed higher fungal population. Phosphorus and zinc solubilizing bacteria was also found highest in BJ and TA rhizosphere, respectively. High saline soils had greater endospore forming bacterial population. The TA (0.88) and LN (0.87) rhizospheres showed significantly greater Shannon–Weiner diversity index compared to bulk soils (0.45–0.61). Pielou’s index of evenness of different samples ranged from 0.13 to 0.43. Discriminant function analysis revealed that rhizospheres of SA, CM and TA were clearly distinct. The rhizospheric soil of PM and BJ were similar to each other but clearly distinct from others. The observed separation of different biotypes was regulated by dimorphic fungi, nitrogen fixing bacteria, Pseudomonas, and fungi. Thus, our study clearly suggests that culturable microbial populations are influenced by different biotypes and salinity levels.

Solar composting greenhouse for organic waste treatment in fed-batch mode: Physicochemical and microbiological dynamics

Composting is a sustainable means of managing organic waste, and solar composters offer a viable solution in rural areas lacking connection to municipal power supplies. This study tracked the physicochemical and microbiological changes that occur in a solar composting greenhouse during the treatment of food and green cellulosic waste in fed-batch mode, which remain poorly understood. Solar composting greenhouse performed well on waste reduction and nutrient retention, resulting in a 45.0–58.8% decrease in feedstock volume over 12-day composting cycles, a 41% removal in dry matter after three batches of composting, and 29.5%, 252.9% and 96.6% increase in the nitrogen, phosphorus and potassium content respectively after 42 days of composting. Batch feeding and composting jointly influenced microbiological succession by altering the physicochemical properties of compost. The contents of nitrogen and phosphorus, pH, and electrical conductivity significantly accounts for variations in culturable microbial populations. The succession of dominant bacterial genera such as Lactobacillus, Pseudoxanthomonas, Bacillus, and Pseudomonas were closely related to pH, cellulose, NH4+–N, carbon content, and temperature. In addition, Pichia kudriavzevii, Thermomyces lanuginosus, and Scopulariopsis brevicaulis successively became the dominant fungal species during composting. Preliminary compost quality assessments showed that solar composting greenhouse has a high potentiality to transform organic waste into organic fertilizer. Additionally, corresponding purposeful suggestions were proposed for future optimization in this system, mainly from a microbiological aspect.

Response of microbial community composition in soils affected by coal mine exploitation

Surface mining activities, despite their benefits, lead to the deterioration of local and regional environmental quality and play a role in global ecosystem pollution. This research aimed to estimate the culturable microbial population structure at five locations near the opencast coal mine "Kakanj" (Bosnia and Herzegovina) via agar plate and phospholipid fatty acids (PLFA) method and to establish its relationship to the physical and chemical properties of soil. Using the ICP-OES method, the heavy metal pollution of all examined locations (overburden, former grass yard, forest, arable soil, and greenhouse) was observed. Substantial variations among the sites regarding the most expressed indicators of heavy metal pollution were noted; Cr, Pb, Ni, and Cu content ranged from 63.17 to 524.47, 20.57 to 349.47, 139.13 to 2785.67, and 25.97 to 458.73mg/kg, respectively. In the overburden sample, considerable low microbial activity was detected; the bacterial count was approximately 6- to 18-fold lower in comparison with the other samples. PLFA analysis showed the reduction of microbial diversity, reflected through the prevalence of normal and branched saturated fatty acids, their ratio (ranged from 0.92 to 7.13), and the absence of fungal marker 18:2ω6 fatty acid. The principal component analysis showed a strong negative impact of heavy metals Na and B on main microbial and PLFA profiles. In contrast, stock of main chemical parameters, including Ca, K, Fe, and pH, was positively correlated with the microbial community structure.

In situ phytoremediation of polycyclic aromatic hydrocarbon-contaminated agricultural greenhouse soil using celery

ABSTRACT Although celery has been established as an effective plant in the remediation of organic pollutant-contaminated soil, few studies have investigated the associated biological processes in rhizosphere and the effect of celery on agricultural field remediation in situ. In this study, a polycyclic aromatic hydrocarbon (PAH)-contaminated agricultural greenhouse was used as the experimental site, and three celery species (Apium graveolens L., Oenanthe javanica (Blume) DC., Libanotis seseloides (Fisch. & C.A. Mey. ex Turcz.) Turcz.) were applied for in situ remediation. After 90 days, the PAH dissipation rate of the L. seseloides treatment was highest (50.21%), and most of the PAHs were limited to its roots (translocation factor 0.516). This suggested that L. seseloides is a potential species for phytoremediation coupled with agro-production. The culturable microbial population and invertase activity results strongly supported that O. javanica is suitable for the establishment of exogenous bacteria–celery co-remediation techniques. Pearson's correlation analysis showed that the polyphenol oxidase (PPO) activity was highly significantly positively correlated with the PAH dissipation rate (r = 0.984, P < 0.01), and we suggest that PPO can be used as a microecological index during PAH remediation.

Effect of long-term application of mineral fertilizers and FYM on microbial dynamics, yield and quality of FCV tobacco (Nicotiana tabacum) grown in vertisols

A long term manurial experiment (Permanent Manurial Trial) with the objective to study the effect of continuous application of organic manure (FYM) and inorganic fertilizers (NPK) on microbial diversity, yield and quality of Flue-cured Virginia (FCV) tobacco (Nicotiana tabacum L. ) as monocrop was carried out at CTRI Farm, Katheru, for 53 years commencing from 1956-57 to 2008-09. The results obtained before the closing of the experiment (2003- 2008) are discussed in this paper. The microbial dynamics expressed in terms of culturable microbial populations, i.e. bacteria, fungi, actinomycetes, Azotobacter and PSB were measured after 53 years of continuous application of mineral fertilizers and organic amendments to vertisols. The population of bacteria, actinomycetes, Azotobacter and PSB were maximum in plots treated with mineral fertilizers and FYM while fungal population was maximum in mineral fertilizers treated plots. The population of bacteria, actinomycetes, Azotobacter and PSB increased in the treatments with the addition of P and K fertilizers alone or in combination. The fungal population decreased with the addition of NPK along with the FYM. Bacillus, Pseudomonas species of bacteria and Trichoderma, Aspergillus and Rhizopus species of fungi, Streptomyces species of actinomycetes were the main dominating culturable microorganisms in all the treatments. The FYM amended plots sustained crop productivity and microbial populations at higher levels than rest of the mineral fertilizer treatments. The average cured leaf yields indicated that only farm yard manure and inorganic nitrogen application has exerted pressure in increasing the cured leaf yields by 24. 52% and 26. 97% respectively in VT-1158 variety of tobacco in vertisols. The nitrogenous fertilizers alone had the most deleterious effect on crop productivity and the biological soil environment. The results of the present study support the concept of balanced fertilization and integrated nutrient management practices for improving the soil quality and sustained crop productivity.

Drip irrigation with film mulch improves soil alkaline phosphatase and phosphorus uptake

Phosphorus (P) is essential for various metabolic activities in plants and plays an extremely important role in crop development, yield and quality. Organic P fertilizers can provide sustainable P and maintain agroecosystem health; however, the uptake of soil organic P by plants is significantly influenced by soil phosphatase activities. The objective of this study was to quantify the effects of different layout measures (film covering, drip irrigation line density, and irrigation lower limits) in drip irrigation with film mulch on the soil phosphatase activity, culturable microorganism populations and crop growth and yield in a greenhouse. The results show that the greatest levels of soil alkaline phosphatase activity were observed with an irrigation lower limit of 80%, a field capacity of 50%, and film mulch covering but were relatively insensitive to the drip irrigation line density. Soil alkaline phosphatase activity was also significantly correlated with the root growth and culturable microbial populations. Specifically, soil alkaline phosphatase activity was positively correlated with the actinomycete population and root activity but negatively correlated with root volume and root area. These results can be used to improve crop production in greenhouse conditions in China.

Toxicity evaluation of textile effluents and role of native soil bacterium in biodegradation of a textile dye.

Water pollution caused by the discharge of hazardous textile effluents is a serious environmental problem worldwide. In order to assess the pollution level of the textile effluents, various physico-chemical parameters were analyzed in the textile wastewater and agricultural soil irrigated with the wastewater (contaminated soil) using atomic absorption spectrophotometerand gas chromatography-mass spectrometry (GC-MS) analysis that demonstrated the presence of several toxic heavy metals (Ni, Cu, Cr, Pb, Cd, and Zn) and a large number of organic compounds. Further, in order to get a comprehensive idea about the toxicity exerted by the textile effluent, mung bean seed germination test was performed that indicated the reduction in percent seed germination and radicle-plumule growth. The culturable microbial populations were also enumerated and found to be significantly lower in the wastewater and contaminated soil than the ground water irrigated soil, thus indicating the biotic homogenization of indigenous microflora. Therefore, the study was aimed to develop a cost effective and ecofriendly method of textile waste treatment using native soil bacterium, identified as Arthrobacter soli BS5 by 16S rDNA sequencing that showed remarkable ability to degrade a textile dye reactive black 5 with maximum degradation of 98% at 37°C and pH in the range of 5-9 after 120h of incubation.

Effect of pruned material, extracts, and polyphenols of tea on enzyme activities and microbial community structure in soil

ABSTRACTPruning is a regular management practice performed in tea fields, but its effects on soil properties and microbial community structures have not been well explored. Effects of tea pruned material, tea extracts, and tea polyphenols application on soil properties and microbial characteristics, including pH, soil enzyme activities, culturable microbial population, and bacterial community, were investigated in a pot-incubation experiment lasting for 10 weeks. Results indicated that returning of tea pruned material or its extracts significantly increased the soil pH as compared to control. The soil invertase and urease activities, as well as the culturable microbial population treated with pruned material were much higher than those in control, while polyphenol oxidase activity was similar among different treatments. Denaturing gradient gel electrophoresis analysis of bacterial community indicated that the Shannon’s diversity index (H) of all nine treatments receiving additives slightly decreased as compared to control. Pruning returning specifically induced several beneficial bacterial species, including Brevibacterium sp. and Burkholderia sp. In conclusion, pruning returning alleviated soil acidification, induced soil enzyme activities, stimulated culturable microbial population, and reshaped the microbial community. This research suggests that this management could be applied as an alternative agricultural practice in tea cultivation.

Evaluation of the Microbial Viability of Soil Samples from Maize Crops in Freeze-Storage under Different Management Conditions in a Semi-Arid Climate

The effect of freeze-storage on culturable soil microorganism viability was determined for soil samples from three agricultural maize crop systems (under conventional management, direct seeding, and direct seeding with a cover crop). Most culturable soil bacteria were unaffected by the freeze-thaw stress or the prolonged freeze-storage, but the viability of mold and Bacillus mycoides populations decreased drastically after eight months of freeze-storage, limiting the process sustainability to this period. However, these changes did not significantly affect either the total microorganism biodiversity index or the biodiversity differences between treatment. Based on the available results, freeze-storage seems to be a sustainable process for up to eight months that can be allowed in analyses of culturable microbial population biodiversity.

Effects of biocide treatments on the biofilm community in Domitilla's catacombs in Rome

Different types of biofilms are widespread on lithic faces of the Catacombs of Domitilla (Rome, Italy) due to the favorable microclimatic conditions (temperature, high RH% and low irradiance). The biofilm, once established, becomes particularly dangerous due to the coverage of valuable surfaces causing spoilage, softening of materials and mineral precipitation. It is common practice to treat these surfaces with biocides in order to eradicate the microorganisms present. The aim of the present research was to compare the changes occurring to the microbial community present in the biofilm in one site of the Catacombs of Domitilla (CD15) before and after a biocide treatment (a mixture of quaternary ammonium compounds and octylisothiazolone, OIT), applied for a one month period. A multistep approach was followed, based on microscopy, cultural methods and molecular techniques (f-ITS and 16S rDNA sequencing), for the phenotypic and genetic analysis of the culturable microbial population. Our results highlighted that the biocide treatments had little effect against cyanobacteria, while the bacterial population increased in numbers but changed drastically in terms of diversity. In fact, some bacteria proliferate at the expense of the organic matter released by dead microorganisms as demonstrated by laboratory tests. Further, our data describe how the microbial interaction can have different responses depending on the favorable conditions for one kind of microorganism in respect to the others.This study exemplifies the real risks of applying biocide treatments on complex microbial communities and pinpoints the necessity of subjecting treatments to monitoring and reassessment. Moreover, the work showed the potential of bacteria isolated after the treatment for use, under controlled conditions, in combatting unwanted microbial growth in that they possess a positive tropism toward stressed microorganisms and high hydrolytic enzymatic activity against cell components (e.g. cellulose, chitin and pectin). A tentative protocol is proposed.

English

The impact of 9 months cultivation of transgenic Bacillus thuringiensis (Bt) cotton on selected culturable bacterial and fungal populations in rhizosphere soil was investigated. The transgenic Bt cotton line (06Z604M), isoline (99M03) and a non-Bt cotton line (HART 89M) were planted in confined field site in Samuru-Thika where non-Bt cotton had been continuously cultivated for the past 2 years. Rhizosphere soil samples were collected at planting, maturity, flower and boll, and boll-opening stages and harvesting stages of cotton. Numbers of culturable soil microbial groups (bacteria, actinomycetes and fungi) involved in decomposition and nutrients recycling were measured at CFU and population levels. The proteins did not show effects on bacterial, actinomycetes and fungal counts and populations possibly as a result of adsorption of the proteins on soil particles, which could have rendered the proteins inaccessible for microbial utilization. Culturable microbial population and colony counts arranged in decreasing order were 06Z604D>99M03>HART89M, similar to the amounts of MBC and clay in the soils. Moreover, bacteria and fungi counts were higher at 110 DAS in 06Z604D than in 99M03 and HART89M plot soils. Our observations suggest that insecticidal proteins (Cry1Ac and Cry2Ab2) produced by Bollgard II Bt cotton could persist in tropical soils as a result of adsorption on soil clays but that there were no observable effect on the studied culturable microbial groups.The data presented here showed no consistent statistically significant differences (p 0.001) with soil respiration and microbial biomass, which exhibited uneven trend with the treatments. Generally Soil from 06Z604D showed the slight higher microbial populations and CFU count, whilst HART 89M showed slight lower microbial count. This depicts the fact that slight variability in the treatments, quality and content of the root exudates might have a temporal or permanent shift in micro biota populations of a variety of crop studied.This study therefore suggests that a single-year cultivation of transgenic Bt cotton may not affect the functional bacterial and fungi populations in rhizosphere soil. Key words: Bacillus thuringiensis, bacteria, population, colony forming units, fungi, Bt cotton.

English

Angelica sinensis (Oliv.) Diels (family Apiaceae) is a perennial herb that has been widely used in Traditional Chinese Medicine. The soil sickness has become one of the major constrains in A. sinensis cultivation. A pot experiment was done to evaluate the role of biological nature in A. sinensis soil sickness. The pot experiment include three treatments (i) contol, which represent as the soil in pot taken from spring wheat stands, (ii) AA, which represent as the soil in pot taken from A. sinensis stands, (iii) S-AA, which represent as the soil in pot was sterilized by steam at 121°C for 4 h taken from A. sinensis stands. Results showed that the plant height, dry weight of aboveground part and roots, root yield and quality, and the activities of SOD and POD in leaves were significantly higher in sterilized replant soil than in non-sterilized replant soil treatment, while the activity of CAT and content of MDA in leaves were declined, which indicated that soil sterilization improved plant haleness and increased the activities of active oxygen scavenging enzymes. The results also demonstrated that soil sterilization can change the number of culturable microbial populations and the species diversity of bacterial functional group. Higher Shannon-Wiener index was found in rhizosphere soils under sterilized soil cropping than that under non-sterilized soil cropping. This suggests that the biological factor played a causal role in the development of A. sinensis soil sickness and sterilization of continuous cropping soil could change the composition and structure of soil microbial community, which further promote plant growth and alleviate A. sinensis soil sickness. © 2016 Friends Science Publishers

Microbial population dynamics under fertigation by distillery effluent in sugarcane-ratoon cropping system

Distillery effluents, a major by-product of distilleries are a major environmental hazard as they are rich in organic matter, micro- and macroelements. Management of this enormous amount of nutrient-rich effluent and its effective utilization is a major challenge. These effluents can be used as a source of nutrient by C4 crops like sugarcane and subsequent ratoon crops under fertigation system. Impact of fertigation in sugarcane-ratoon cropping system on soil microbial biomass is important as the microbial population plays an important role in the nutrient and biogeochemical recycling. Keeping this in mind, a field experiment was carried out in the sandy loam soil of semi-arid to humid sub-tropical climate of Gajraula (28.85°N, 78.23°E) region, India with different doses of diluted and undiluted effluent for fertigation of sugarcane crop in presence and absence of 50 % recommended dose of fertilizers with suitable replicates. Two post-sown irrigations with four times diluted effluent gave the maximum yield in case of sugarcane crop. Taking into consideration the yield and the culturable microbial population sizes, it can be concluded that one to two post-sown irrigations with diluted effluent can be used to enhance soil fertility in terms of microbial population and to enhance sugarcane and ratoon crop productivity. This package is economically viable and can also take care of distillery waste management and reduction in consumption of chemical fertilizers by 50 %, a key for sustainable agricultural development.

Toxic effects of the joint exposure of decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA) on soil microorganism and enzyme activity

Decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA) are the main contaminants at e-waste recycling sites, and their potential toxicological effects have received extensive attention. However, the impact on soil culturable microbial population and enzyme activity of joint exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the eco-toxicological response in the joint presence of BDE209 and TBBPA for the first time. The results have demonstrated some notable toxic effects due to long-term exposure to either or both contaminants. The inhibition ratios of microbial populations increased with incubation time and increasing concentrations of BDE209 or TBBPA following certain dose–response relationships and time-effect trends. The response sensitivity sequence was fungi>bacteria>actinomycete. The influence of the two chemicals on soil enzymes reached peak values on day 7, and highly significant differences (P<0.01) were observed compared to the controls. Urease was more susceptive to the two chemicals than catalase and saccharase activities. Generally, the joint toxicity of both contaminants on soil microbes, catalase or saccharase activities indicated antagonistic effects, while, as for urease activity, addition role was dominant. Such observations have provided the useful information of potential ecological effects of brominated flame retardants contamination in the environment.