Soil Microbial Counts Research Articles

Effect of biofertilizers on soil microbial count, nutrient availability and uptake under november sown onion

Biofertilizers improves the soil microbial content, Soil nutrient status and nutrient uptake by plant. In an experiment, fifteen treatments comprised of various combinations of biofertilizers, organic manures and chemical fertilizers were compared to access the impact of different sources of nutrient on performance of onion. The highest soil organic carbon (0.40%) was observed in the treatments T12 (Farm Yard Manure (FYM) @ 20 t/ha) and T11 (FYM myctes count (29.9 X 104) was recorded in T11 (FYM @ 20 t/ha + Azotobacter + VAM) treatment while highest fungal @ 20 t/ha + Azotobacter + Vesicular-Arbuscular Mycorrhizae (VAM)). Highest bacterial (24.5 X 106) and actino-count (17.5 X 103) was observed in T3 (Azospirillium+ Recommended dose of NPK) treatment. At the time of harvesting, available nitrogen (N), available phosphorus (P) and available potassium (K) were higher in treatment T3 (Azospirillium + Recommended dose of NPK), T9 (Azotobacter+ VAM + Recommended dose of NPK) and T13 (Poultry treatment (162.6 Kg ha-1) as compared to all other treatments except T1 and T9 treatments while P uptake (13.6 Kg ha-Manure @ 5t/ha) treatments respectively than that in other treatments. Azospirillum and Azotobacter application along with recommended dose of N, P and K improved the fertility status of soil. The N uptake was significantly higher in T3 treatments. The present study highlights the need of use of biofertilizers along with organic and inorganic 1) was significantly higher in T9 treatment than that in other treatments except T1, T3, T5 and T7 treatments. The K uptake was significantly higher in T3 treatment (126.9 Kg ha-1) as compare to all other treatments except T1 and T9 manures/fertilizer to enhance the nutrient availability and improve soil health.

Bacterial community shift and hydrocarbon transformation during bioremediation of short-term petroleum-contaminated soil

A laboratory study was conducted to evaluate the impact of bioaugmentation plus biostimulation (BR, added both nutrients and bacterial consortia), and natural attenuation (NA) on hydrocarbon degradation efficiency and microflora characterization during remediation of a freshly contaminated soil. After 112 days of remediation, the initial level of total petroleum hydrocarbon (TPH) (61,000 mg/kg soil) was reduced by 4.5% and 5.0% in the NA and BR treatments, respectively. Bioremediation did not significantly enhance TPH biodegradation compared to natural attenuation. The degradation of the aliphatic fraction was the most active with the degradation rate of 30.3 and 28.7 mg/kg/day by the NA and BR treatments, respectively. Soil microbial activities and counts in soil were generally greater for bioremediation than for natural attenuation. MiSeq sequencing indicated that the diversity and structure of microbial communities were affected greatly by bioremediation. In response to bioremediation treatment, Promicromonospora, Pseudomonas, Microcella, Mycobacterium, Alkanibacter, and Altererythrobacter became dominant genera in the soil. The result indicated that combining bioaugmentation with biostimulation did not improve TPH degradation, but soil microbial activities and structure of microbial communities are sensitive to bioremediation in short-term and heavily oil-contaminated soil.

Metal contamination status of the soil-plant system and effects on the soil microbial community near a rare metal recycling smelter.

Four heavy metals (Cd, Cu, Pb and Zn), two metalloids (As and Sb) and two rare metals (In and Tl) were selected as target elements to ascertain their concentrations and accumulation in the soil-plant system and their effects on the structure of the soil microbial community in a typical area of rare metal smelting in south China. Twenty-seven soil samples 100, 500, 1000, 1500 and 3000m from the smelter and 42 vegetable samples were collected to determine the concentrations of the target elements. Changes in soil micro-organisms were investigated using the Biolog test and 454 pyrosequencing. The concentrations of the eight target elements (especially As and Cd) were especially high in the topsoil 100m from the smelter and decreased markedly with increasing distance from the smelter and with increasing soil depth. Cadmium bio-concentration factors in the vegetables were the highest followed by Tl, Cu, Zn, In, Sb, Pb, and then As. The concentrations of As, Cd and Pb in vegetables were 86.7, 100 and 80.0%, respectively, over the permissible limits and possible contamination by Tl may also be of concern. Changes in soil microbial counts and average well colour development were also significantly different at different sampling distances from the smelter. The degree of tolerance to heavy metals appears to be fungi > bacteria > actinomycetes. The 454 pyrosequencing indicates that long-term metal contamination from the smelting activities has resulted in shifts in the composition of the soil bacterial community.

Soil microbial characteristics and the influencing factors in subtropical forests

Soil microorganisms play an important role in the soil formation, nutrient cycling, and regulating plant productivity. Bacteria, fungi and actinomycetes are main microbial groups being responsible for the soil ecosystems. However, responses of soil microbial communities to litter characteristics and soil properties at the regional scale are poorly understood. Litter characteristics, soil properties and soil microbial communities were measured in coniferous forests and broadleaved forests at three natural forests (Dinghu Mountain National Field Forest Ecosystem Research Station (DHS), Ailao Mountain National Field Forest Ecosystem Research Station (ALS), Daming Mountain Nature Reserve Station (DMS)) and a plantation (Heshan National Field Forest Ecosystem Research Station (HSZ)) ecosystems in order to explore the effects of litter characteristics on soil microbial community structure. In our study, the soil microbial communities were analyzed by dilution-plate method. Furthermore, we analyzed the determined factors of soil microbial community structure in the forest ecosystems. The results showed that season, forest type and sampling site influenced the soil microorganisms and community structure. There were the obvious seasonal dynamics of soil microorganisms in subtropical region, China. The soil microbial counts and the ratio of fungi and bacteria in wet season were higher than those in dry season. The counts of bacteria and total microorganisms in coniferous forests were less than those in broadleaved forests. Moreover, the ratios of fungi and bacteria were greater in coniferous forests than that in broadleaved forests. Similarly, the counts of bacteria and total microorganisms in plantations were less than those in natural forests. Besides, the fungi in the two forests showed the different trends in dry season and wet season. Soil fungi in natural forests were higher than that in plantation in dry season, but it showed the opposite pattern in the wet season. The ratio of fungi and bacteria was significantly higher in plantation than that in natural forests. Linear regression results showed that variations of fungi, actinomycetes and total microorganisms were primarily explained by the litter quality in coniferous forests, but the variations of fungi and actinomycetes were explained by the litter storages in broadleaved forests. Redundancy analysis (RDA) results showed that soil and litter properties explained 79.7% of total variation in microbial community structure. Furthermore, the variations of microbial community structure were explained 19.1%, 16.7%, 16.6% and 11.6% by soil total nitrogen (STN), soil organic carbon (SOC), soil water content (SWC) and the ratio of soil organic carbon and the nitrogen (soil C:N), respectively. Overall, our findings will facilitate a better understanding of soil microbial characteristics in subtropical forests.

Contributions of long-term tillage systems on crop production and soil properties in the semi-arid Loess Plateau of China.

This study determined the long-term effect of tillage systems on soil properties and crop yields in a semi-arid environment. Field pea (Pisum sativum L.) and spring wheat (Triticum aestivum L.) were alternately grown in six tillage systems at Dingxi (35° 28' N, 104° 44' E), north-west China starting in 2001. After the first 6 years of experiments, conventional tillage with stubble incorporating (TS) and no-till with stubble cover (NTS) increased soil organic matter by 9.9% and 13.0%, respectively, compared to the conventional tillage with stubble removed (T); both TS and NTS also increased soil microbial counts, available K and P, and total N. No-till with stubble removed (NT), NTS and NTP (no-till with plastic mulching) had 20.7%, 62.6% and 43.7% greater alkaline phosphatase activity compared to the T treatment. Soil catalase, urease and invertase activities were all greater in the no-till treatments than in the T treatment. Averaged across 6 years, both wheat and pea achieved highest grain yields under NTS treatment. No-till with stubble retention is the most promising system for improving soil physical, biological and chemical properties, and increasing crop yields, and thus, this system can be adopted in areas with conditions similar to the semi-arid north-west China. © 2015 Society of Chemical Industry.

Soil Characteristics, Microbial Compostion of Plot, Leaf Count and Sprout Studies of Cocoyam (<i>Colocasia</i> [Schott] and <i>Xanthosoma</i> [Schott], Araceae) Collected in Edo State, Southern Nigeria

Cocoyam ( Colocasia [Schott] and Xanthosoma [Schott]) belongs to the family Araceae and Alismatales order. The aim of this study is to collect cocoyam from the eighteen Local Government Areas (LGA) in Edo state and describe them based on leaf count and sprout percentage. Using random stratified sampling methods, cocoyam were collected. Field trials were conducted in the Experimental Garden, Department of Plant Biology and Biotechnology. The soil was subjected to analysis at the Soil Science Department, University of Benin to determine its characteristics and suitability for the growth of these arable crops. The soil microbial count was 6.25 X 10 5 and 1.34 X 10 5 cfu/g for bacterial and fungi respectively Phosphorus, potassium, manganese and copper were low, zinc and iron were moderate whereas soluble salts were high in the soil. Results of percentage sprout indicate accessions from Esan south east had highest percentage sprout of 92.0 % while accessions from Owan East had the lowest percentage sprout value of 33.3 %. Visible sprouting was observed beginning from seventh day after planting. Leaf count reveals varied levels of significance at P ≥ 0.5 from March to July. Highest mean count of 1.35± 0.85 was obtained from Egor in March. In April, highest mean count of 5.42± 2.00 was obtained from Esan North East and 8.58 ± 1.69 as highest mean count in May was obtained from Ovia North East. Owan West had the highest mean count in June and July with 14.50±2.84 and 15.50± 1.76 respectively. This study suggests great amount of cocoyam diversity. Their leaves is an important vegetable which may be available all year round. The cocoyam accessions can sprout with minimum requirements. More investigation is required to elucidate their constituents of these uncommon vegetable.

Effect of conventional and organic orchard floor management practices on enzyme activities and microbial counts in a ‘Cripp's Pink’/M7 apple orchard

Organic (ORG) production practices are increasingly being used in South African apple orchards. Whether ORG orchard floor management practices differ in their effects on soil enzyme activities and microbial populations from conventional (CON) practices have not been adequately investigated, particularly with regard to soil chemical characteristics and orchard performance. To seek clarification a randomised field trial was carried out in the winter rainfall region of the Western Cape. In this trial ‘Cripps Pink’/M7 apple trees received straw mulch with compost (ORG) or synthetic fertiliser and herbicide (CON) in the tree rows. Soil microbial enzyme activities and microbial counts were determined by colorimetric assays and dilution plating, respectively. Activities of β-glucosidase, acid phosphatase and urease, and actinobacteria counts tended to be greater in the ORG than the CON treatments. Activities correlated positively with soil zinc and manganese concentrations and with leaf zinc, but negatively with soil copper. β-glucosidase and acid phosphatase activities also correlated negatively with ammonium and nitrate nitrogen in the soil, and with leaf nitrogen concentration. Yields decreased with increasing β-glucosidase and acid phosphatase activities. Therefore, although ORG practices increased soil microbiological activity relative to CON management, they did not improve yield.

Efficiency of Repeated Phytoextraction of Cadmium and Zinc from an Agricultural Soil Contaminated with Sewage Sludge

Long-term application of sewage sludge resulted in soil cadmium (Cd) and zinc (Zn) contamination in a pot experiment conducted to phytoextract Cd/Zn repeatedly using Sedum plumbizincicola and Apium graceolens in monoculture or intercropping mode eight times. Shoot yields and soil physicochemical properties changed markedly with increasing number of remediation crops when the two plant species were intercropped compared with the unplanted control soil and the two monoculture treatments. Changes in soil microbial indices such as average well colour development, soil enzyme activity and soil microbial counts were also significantly affected by the growth of the remediation plants, especially intercropping with S. plumbizincicola and A. graveolens. The higher yields and amounts of Cd taken up indicated that intercropping of the hyperaccumulator and the vegetable species may be suitable for simultaneous agricultural production and soil remediation, with larger crop yields and higher phytoremediation efficiencies than under monoculture conditions.

Effects of Manure Compost Application on Soil Microbial Community Diversity and Soil Microenvironments in a Temperate Cropland in China

The long-term application of excessive chemical fertilizers has resulted in the degeneration of soil quality parameters such as soil microbial biomass, communities, and nutrient content, which in turn affects crop health, productivity, and soil sustainable productivity. The objective of this study was to develop a rapid and efficient solution for rehabilitating degraded cropland soils by precisely quantifying soil quality parameters through the application of manure compost and bacteria fertilizers or its combination during maize growth. We investigated dynamic impacts on soil microbial count, biomass, basal respiration, community structure diversity, and enzyme activity using six different treatments [no fertilizer (CK), N fertilizer (N), N fertilizer + bacterial fertilizer (NB), manure compost (M), manure compost + bacterial fertilizer (MB), and bacterial fertilizer (B)] in the plowed layer (0–20 cm) of potted soil during various maize growth stages in a temperate cropland of eastern China. Denaturing gradient electrophoresis (DGGE) fingerprinting analysis showed that the structure and composition of bacterial and fungi communities in the six fertilizer treatments varied at different levels. The Shannon index of bacterial and fungi communities displayed the highest value in the MB treatments and the lowest in the N treatment at the maize mature stage. Changes in soil microorganism community structure and diversity after different fertilizer treatments resulted in different microbial properties. Adding manure compost significantly increased the amount of cultivable microorganisms and microbial biomass, thus enhancing soil respiration and enzyme activities (p<0.01), whereas N treatment showed the opposite results (p<0.01). However, B and NB treatments minimally increased the amount of cultivable microorganisms and microbial biomass, with no obvious influence on community structure and soil enzymes. Our findings indicate that the application of manure compost plus bacterial fertilizers can immediately improve the microbial community structure and diversity of degraded cropland soils.

Microbial and enzymatic activity of soil contaminated with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium.

The aim of this study was to determine the effect of three active substances, diflufenican, mesosulfuron-methyl and iodosulfuron-methyl-sodium, applied in combination, on soil microbial counts, the structure of soil microbial communities, activity of soil enzymes and their resistance to the tested product, the biochemical indicator of soil fertility, and spring wheat yield. Soil samples with the granulometric composition of sandy loam with pHKCl 7.0 were used in a pot experiment. The herbicide was applied to soil at seven doses: 0.057 (dose recommended by the manufacturer), 1.140, 2.280, 4.560, 9.120, 18.240 and 36.480 mg kg−1 soil DM. Uncontaminated soil served as the control treatment. It was found that a mixture of the tested active substances increased the counts of total oligotrophic bacteria and spore-forming oligotrophic bacteria, organotrophic bacteria and actinomycetes, decreased the counts of Azotobacter and fungi, and modified the structure of soil microbial communities. The highest values of the colony development (CD) index and the ecophysiological (EP) index were observed in fungi and organotrophic bacteria, respectively. The herbicide applied in the recommended dose stimulated the activity of catalase, urease and acid phosphatase, but it had no effect on the activity of dehydrogenases, alkaline phosphatase, arylsulfatase and β-glucosidase. The highest dose of the analyzed substances (36.480 mg kg−1) significantly inhibited the activity of dehydrogenases, acid phosphatase, alkaline phosphatase and arylsulfatase. The values of the biochemical soil fertility indicator (BA21) decreased in response to high doses of the herbicide. Urease was most resistant and dehydrogenases were least resistant to soil contamination with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium. The analyzed herbicide had an adverse influence on spring wheat yield, and doses of 18.240 and 36.480 mg kg−1 led to eventual death of plants.

Ascophyllum extract application can promote plant growth and root yield in carrot associated with increased root-zone soil microbial activity

Alam, M. Z., Braun, G., Norrie, J. and Hodges, D. M. 2014. Ascophyllum extract application can promote plant growth and root yield in carrot associated with increased root-zone soil microbial activity. Can. J. Plant Sci. 94: 337–348. Root growth and soil microbial activity were examined in two cultivars of carrot following treatment with Ascophyllum nodosum marine-plant extract. Field experiments were established in grower-managed fields of Maverick and Pronto carrots during 2010 and 2011. Soluble Ascophyllum extract powder (SAEP) was applied weekly, bi-weekly or tri-weekly at rates of 0 (control), 0.25, 0.50, 0.75 or 1.0 g L−1 over 11 to 13 wk. Results indicate that SAEP treatment increased root yields of Maverick and Pronto by about 20 and 15%, respectively, reduced proportion of smaller roots and improved harvest index (HI). Maximum yield was found at or above 0.50 g L−1 SAEP for Maverick and at 0.75 g L−1 for Pronto. Soil microbial colony counts, respiration and metabolic activity increased following SAEP applications, but varied with SAEP rate and application frequency. Using the Biolog microbial analysis system, maximum average well colour development (AWCD), substrate diversity (H), substrate evenness (E), and substrate richness (S) responses to extract treatment generally showed successive increases at 0.50, 0.75 and 1 g L−1 SAEP at tri-weekly application frequencies. With more frequent applications, rates below 1 g L−1 led to greater microbial growth, respiration and functional activities. Principal component analysis (PCA) showed a strong relationship between carrot growth, soil microbial populations and activity parameters. These results suggest that seaweed extract application can result in an increase in soil microbial activity associated with increased yield in carrots.

Influence of post emergence herbicides on weeds, nodulation and yields of soybean and soil properties

A field experiment was conducted at Pantnagar during kharif 2008 to examine the effect of postemergence herbicides in soybean on productivity, weed infestation and soil health. Treatments consisting of clodinafop-propargyl 8% EC at 80, 100 and 165 g a.i. ha−1, Na-acifluorfen 20% SL of 165 and 206.2 g a.i. ha−1, combination of clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL at 80 + 165, 100 + 206.2 and 160 + 330 g a.i. ha−1, imazethapyr 10% SL at 100 g a.i. ha−1, weed free and weedy check were tested in RBD with 3 replications. The soybean variety used for the study was PS1347. Treatment of weed free check was found best by recording highest nodulation, yield and yield attributes, N uptake and soil parameters. It was at par with imazethapyr 10% SL @ 100 g a.i. ha−1, the treatment that showed highest nodule and plant dry weight, weed control efficiency, grain yield (1975 kg ha−1), straw yield (2445 kg ha−1), N uptake (136.4 kg ha−1 in grain and 40.9 kg ha−1 in straw), soil organic carbon, available N, P, K, microbial counts and dehydrogenase activity among different herbicides treatments. Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL was also found effective in weed control with 100 + 206.2 g a.i. ha−1. It was comparable to imazethapyr 10% SL @ 100 g a.i. ha−1 in weed index, weed control efficiency, nodule dry weight, grain and straw yields, N uptake, soil organic C, available N and K, microbial counts and dehydrogenase activity. The highest net return of Rs. 39563 ha−1 was obtained with weed free check, which was at par with imazethapyr 10% SL @ 100 g a.i. ha−1 and Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5 SL @ 100 + 206.2 g ai ha−1.

川西亚高山针叶林土壤微生物及酶对林下植物去除的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 川西亚高山针叶林土壤微生物及酶对林下植物去除的响应 DOI: 10.5846/stxb201212131798 作者: 作者单位: 四川农业大学生态林业研究所,四川农业大学生态林业研究所,四川农业大学生态林业研究所,四川农业大学旅游学院,四川农业大学生态林业研究所,四川农业大学生态林业研究所,四川农业大学生态林业研究所,四川农业大学生态林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31170423，31270498，31200345）；国家“十二五”科技支撑计划项目（2011BAC09B05）；四川省青年基金项目（2012JQ0008，2012JQ0059）；中国博士后科学基金特别资助（2012T50782） Response of soil microorganism and soil enzyme activity to understory plant removal in the subalpine coniferous plantation of western Sichuan Author: Affiliation: Institute of Ecological Forestry,Sichuan Agricultural University,Institute of Ecological Forestry,Sichuan Agricultural University,Institute of Ecological Forestry,Sichuan Agricultural University,College of Tourism College,Sichuan Agricultural University,Dujiangyan,,Institute of Ecological Forestry,Sichuan Agricultural University,Institute of Ecological Forestry,Sichuan Agricultural University,Institute of Ecological Forestry,Sichuan Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生物多样性与生态系统功能的关系是生态学领域研究的热点与难点。但因受研究手段的限制，有关森林物种组成及其多样性变化对土壤微生物数量和酶活性影响的研究少有报道。采用人工去除灌草层的实验方法，研究了川西亚高山针叶林灌草层丧失对土壤微生物数量和酶活性的影响。结果表明：1）灌草层去除后，土壤细菌和真菌数量以CK（对照） > RH（除草） > RS（除灌），而土壤放线菌数量则以RH > CK > RS；2）灌草层去除后，土壤微生物群落构成发生改变，真菌比例有所下降；3）灌草层去除后，土壤酶活性随之发生变化，各种酶活性均以CK > RH > RS。表明林下灌草层去除，尤其是灌木层去除，导致土壤微生物数量下降、群落构成发生变化以及土壤酶活性下降，从而在一定程度上影响到森林生态系统的物质循环功能。 Abstract:Many challenges have been concentrated on the relationship between forest biodiversity and ecosystem functioning in ecology, since relative slower growth rate of tree and shrub species than herb species makes the tree biodiversity-ecosystem functioning interaction experiments become very difficult. In the past two decades, numerous experiments paid more attentions on the grassland and farmland ecosystem, and investigated the relationships between herbaceous plant species composition and ecosystem process. Theoretically, loss of the tree or shrub species might lead to the drastic changes in soil microbial community and enzyme activities in the fragile ecosystem, due to the sensitivity of soil microorganism to environmental change, which implies that we can understand the relationships between forest plant biodiversity and ecosystem process employing the method of simulated understory plant removal experiment. As yet, far less information has been available on the effects of forest plant loss on soil microbial community and enzyme activities. The subalpine forest located in the eastern Qinghai-Tibet Plateau and the upper reaches of Yangtze River is a typical high-frigid forest ecosystem and fragile ecosystem. Therefore, a three-year shrub and herbaceous plant removal experiment was conducted in the subalpine forest of western Sichuan, in order to understand the linkages of forest plant diversity with microorganism and enzyme activity in the forest soil, from July 2007 to July 2009. The understory removal experiments included the control (CK), herb layer removal (RH) and shrub layer removal (RS). Both shrub and herb plant removals changed soil microbial counts significantly. The ranked order of soil bacteria and fungi counts was CK > RH > RS, and the ranked order of actinomycete count was RH > CK > RS. Understory plant removal changed the composition of soil microbial community, and decreased the ratio of fungi in microbial community. The response of soil microbial community to shrub layer removal was more sensitive than that of herb layer removal. Meanwhile, the removal of shrub and herb layer decreased significantly the activities of invertase, urease, cellulose and dehydrogenase in soils, and the ranked order of incidence was CK > RH > RS. The effect of shrub layer removal on soil enzyme activity was more significant than that of herb layer removal. The results indicated that the removals of both shrub and herb layers altered the composition of soil microbial community and decreased the activities of the measured enzymes in soils of the studied plots, implying that the loss of plant species could change the soil microbial process in the high-frigid forest ecosystem. However, the present study only provides valuable information of short-term herb and shrub layer removal experiment, and long-term experiment needs to carry out in the future. 参考文献 相似文献 引证文献

Effect of poly(γ-glutamic acid) on microbial community and nitrogen pools of soil

Given the numerous environmental problems caused by chemical fertilizer overuse, agricultural practices are shifting toward the development of environmentally friendly nitrogen (N) fertilizers. In this study, a pot experiment was conducted to investigate the effect of poly(γ-glutamic acid) (γ-PGA), an effective fertilizer synergist, on rapeseed (Brassica napus cv. Qinyou No. 9) productivity, soil N pools, and soil enzymes. Seven treatments were implemented: T1, a check without urea; T2, a check with urea only; T3, urea mixed with glutamic acid; T4, urea mixed with 3 mg of γ-PGA per kilogram of soil; T5, urea mixed with 10 mg of γ-PGA per kilogram of soil; T6, urea coated with γ-PGA (0.9%, m/m); and T7, urea coated with γ-PGA (3.1%, m/m). The results demonstrated that the application of γ-PGA increased the above-ground fresh weight of rapeseed by 7.57–9.26% and the grain yield per pot by 6.46–10.98% compared with T2. The rapeseed grain yield significantly increased from 15.94 ± 0.55 g pot−1 in T2 to 17.69 ± 0.78 g pot−1 in T7. With the increase in pod numbers and seed numbers per pod, the seed yield was significantly improved after γ-PGA application. Culturable soil microbial count and microbial diversity were increased by γ-PGA application. In addition, the effects of application method of γ-PGA have a more important role on the soil microflora than its amount. The reduced loss of N can be attributed to the capacity of γ-PGA to increase the “ turnover pool.” More mineral N in the soil was immobilized by clays, soil microbes, and γ-PGA at the early growth stage, and the immobilized N was then released at the later growth stage for plant growth. Moreover, urease activity also increased with γ-PGA application. These findings indicated that the urea coated with γ-PGA could be a better choice for agricultural applications.

Founder effect uncovers a new axis in polyethylene succinate bioremediation during biostimulation

Biostimulation is a method of in situ bioremediation wherein native soil microbes are stimulated by nutrient supplementation. In a previous report, we showed considerable polyethylene succinate (PES) degradation by biostimulation. To gain an insight into this, this study was undertaken to investigate the different facets of the microbial population present in both soil and PES-films during biostimulation-mediated PES degradation. It was observed that addition of PES-films to both nutrient-treated and untreated soil resulted in significant reduction of soil microbial counts compared with the corresponding control. It was observed that a small microbial population containing both PES degraders and non-degraders translocated to PES surface. Over time, the population adhering to PES films changed from having both PES degraders and non-degraders to being mainly PES degraders. This newly developed microbial community on PES-films exhibited low diversity with a distinct cluster of metabolic fingerprinting and higher evenness compared with parent soil microbial population. Thus the establishment of a new community on the PES surface is an exhibition of founder effect, which subsequently resulted in the emergence of a more efficient PES-degrading population and subsequently led to considerable PES degradation.

Phosphate-solubilizing soil yeast Meyerozyma guilliermondii CC1 improves maize (Zea mays L.) productivity and minimizes requisite chemical fertilization

Phosphate-solubilizing yeasts have been under-exploited in eco-friendly maize cultivation. In this regard, soil yeasts Meyerozyma guilliermondii CC1, Rhodotorula mucilaginosa CC2 and M. caribbica CC3 were investigated for their plant growth-promoting (PGP) activities. Soil yeasts were isolated and characterized. Maize (Zea mays L. cv. Tainong No.1) and Chinese cabbage (Brassica rapa L. cv. Pekinensis) were used for seed bioassay. Growth-promoting effects of yeasts under greenhouse conditions were evaluated using maize and lettuce (Lactuca sativa L. cvs. Capitata and Taiwan sword leaf). Ultimately, M. guilliermondii CC1 was tested on field-grown maize; treatments included full-dose chemical fertilizers (CF), yeast (CC1), half-dose chemical fertilizers (½CF), CC1 + ½CF and control. Nutrient uptake, growth, and yield of maize and rhizospheric soil microbes were estimated. Strain M. guilliermondii CC1 exhibited better seed vigor index in maize and Chinese cabbage. CC1 + ½CF significantly improved the dry-weights, and nutrient uptakes of maize and sword leaf lettuce under greenhouse conditions. In field, CC1 + ½CF application exerted a pronounced effect on growth of maize, cob yield, nutrient-uptake and rhizospheric soil microbial counts. Our results validated superior biochemical potency and PGP traits of M. guilliermondii CC1 that reduced requisite chemical fertilizer application without affecting the optimal productivity in maize.

Effect of land rehabilitation on physicochemical and microbial properties of a sodic soil

Sodic soils are widely distributed in arid and semiarid regions of the world and suffer from high values of pH, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR) and low fertility. But little is known about the effect of long term land rehabilitation on soil physicochemical and microbial properties of sodic soils. Therefore, the specific objectives of this study were (i) to evaluate the effect of long term (five decades) rehabilitation of sodic land through cropping system on soil physicochemical and microbial properties, (ii) to assess seasonal variation in soil properties of different lands and (iii) to calculate increase in soil fertility through gain percent. For this purpose, changes in soil properties (physicochemical and microbial properties) of rehabilitated sodic land (RSL) were compared with adjacent degraded sodic land (DSL) and non-sodic soil (NSS). When compared to DSL, soil pH, exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) were significantly lower in RSL and NSS, while, soil organic carbon (SOC), available nutrients, microbial biomass (MB), microbial counts and enzyme activities (dehydrogenase, β-glucosidase, protease, alkaline phosphatase and acidic phosphatase) were significantly higher in RSL and NSS. Seasonal fluctuations in soil properties varied significantly from the annual mean and changes were not always identical for all the lands. Microbial biomass and enzyme activities were negatively correlated with soil sodicity parameters (pH, EC, ESP and SAR) except alkaline phosphatase activity. On the basis of gain %, respective decrease in soil pH, EC, ESP and SAR was 44, 78, 61 and 86% and increase in SOC, total nitrogen (Nt) MBC, fungal population, dehydrogenase and protease activities was 65, 88, 73, 65, 66 and 63%. Rehabilitation of degraded sodic land through cropping showed 79% (mean gain %) improvement in soil quality. Our findings conclude that rehabilitation of degraded sodic lands through cropping showed a considerable increase in soil fertility.

Effect of Aboveground Biomass, Temperature and Moisture on Soil Microorganism of Alkali-Saline Grassland

The information on the soil microorganism of alkali-saline grassland was limited. To demonstrate the effect of aboveground biomass, temperature and moisture on soil microorganism of alkali-saline grassland, the soil microbial counts, biomass carbon, diversity index, aboveground biomass, soil temperature and moisture were measured and analyzed in Songnen grassland. The results showed that aboveground biomass, soil temperature and moisture had significant effect (P0.05). To sum up, the change of the soil microbial counts and biomass carbon were related primarily by plant growth.

Effects of Garlic Bulb Aqueous Extract on Cucumber Seedlings, Soil Microbial Counts, and Enzyme Activities

The effects of the aqueous extract of garlic bulbs on cucumber seed germination, seedling growth, soil microbial counts, and soil enzyme activities were investigated using a bioassay test and a pot experiment. Garlic bulb extracts impacted cucumber seed germination and seedling growth but had no significant effects at low concentration. Polyphenol oxidase, saccharase, urease, and catalase activities were increased significantly at all concentrations of aqueous extract tested in the soil. Bacterial counts were increased by garlic bulb extract and trends of actinomycete counts were the same as for bacterial counts. Fungal counts were significantly depressed with increasing concentration of garlic bulb extract. Polyphenol oxidase activity showed significant positive correlations with catalase, saccharase, and urease activities and counts of actinomycetes and a significant negative correlation with fungal counts. The results indicate that garlic may be effective in reducing some obstacles of continuous cropping through its potential effects in appropriate culture systems.

Effects of highly volatile organochlorine solvents on nitrogen metabolism and microbial counts

The effects of highly volatile organochlorine solvents (1,1,1-trichloroethane, TCET; trichloroethylene, TCE; and tetrachloroethylene, PCE) on soil nitrogen cycle and microbial counts were investigated using volcanic ash soil with different fertilizations. All the solvents significantly inhibited the activity of the cycle under the sealed conditions with 10 to 50 mg/g (dry soil) solvents added. No significant difference between the solvents, and between fertilization plots, was observed. Nitrate ion was not accumulated, and instead, ammonium ion was highly accumulated in the presence of the solvents. Nitrite ion was partially detected, while l-glutaminase activity was inhibited. The growths of ammonification, nitritation, nitratation and denitrification bacteria, and filamentous fungi were significantly inhibited in the presence of 10 mg/g (dry soil) of the solvents.&amp;nbsp;