Microbial Population and Yield of Wheat in Relation to Soil Salinity

The studies on isolations of microorganisms from four different saline soils (ECe 1.85, 5.8, 9.4 and 13.4 dS/m) and roots of wheat ( Kharchia-65 , a salt tolerant variety) plants grown in above soils reveal an interesting correlation between microbial population and soil salinity Vis-a-vis growth and yield. Though growth and yield of wheat decreased with an increase in the salinity of the soils, the fungal and bacterial populations concomitantly increased and the maximum microbial colonies were recorded from the soil, having highest salinity status. A maximum number of fungal colonies (predominantly of Aspergillus sp., Paecilomyces sp., Penicillium sp. etc.) was isolated from the root surfaces of the plants grown on soil having ECe of 1.85 dS/m, whereas a single colony of Fusarium oxysporum occurred from roots of plants of soils having an ECe of 13. 4dS/m.     

Lipid composition of Collembola and their food resources in deciduous forest stands—Implications for feeding strategies

The lipid composition of Collembola and their potential food resources was assessed in three deciduous forest stands, in order to gain insight into food web linkages under field conditions. Fatty acids (FAs) previously assigned as trophic markers in laboratory experiments were used to investigate feeding strategies in situ. As potential food sources soil microbiota and plant debris were characterised by their phospholipid fatty acid (PLFA) composition. Both the amount and the pattern of PLFAs differed between sites and soil depth, in particular the bacterial and plant marker FAs in the upper soil layer. Thus, the availability of resources for micro-detritivores varied due to forest and soil layer. The lipid composition of vital and senescent beech leaves was predominantly influenced by metabolic status and represented a quite homogenous FA resource across forest stands. Comparing Folsomia quadrioculata, Lepidocyrtus lignorum, Neanura muscorum and Pogonognathellus longicornis between the different forests revealed FA profiles to be predominantly affected by site, suggesting a diet shift depending on resources at hand. However, species-specific differences in individual FAs occurred, likely related to feeding strategy and physiological activity. Lipids of Collembola comprised low amounts of bacterial marker FAs, and bacterial consumption may occur to some extent, particularly on Gram-positives. The marker FA for predatory feeding, 20:1ω9, was found in several species, although in low amounts. This contradicts known feeding habits and caution is advisable in using 20:1ω9 as trophic marker. Overall, as indicated by high proportions of oleic (18:1ω9) or linoleic (18:2ω6,9) acid, most species were either plant litter or fungal feeders, with some transitions. The ratio 18:1ω9/18:2ω6,9 is proposed as a tool to distinguish between these two major feeding strategies in Collembola.     

有效微生物菌在反刍动物生产中的研究与应用

文章介绍了有效微生物菌(EM)的组成及特点、研制及使用方式、作用机理、在反刍动物上的研究与应用及影响其作用效果的因素。     

土壤农药污染的微生物修复研究概况

总结了土壤农药污染的现状和危害、农药污染微生物修复的研究历程、农药污染微生物修复资源、农药污染微生物修复影响因素,展望了农药污染微生物修复前景,并分析了有待进一步研究的领域。     

三七根腐病病株和健株根域土壤微生态研究

对比三七健株和急性青枯型根腐病病株根域土壤微生物数目、土壤酶活性以及土壤养分,研究它们与根腐病间的关系。结果表明,病株根际土和根系的细菌数目显著大于健株,而放线菌和真菌数目小于健株;病株根际土和根系各微生物生理类群数目受外界环境影响发生了不同变化;健株非根际土的蔗糖酶、纤维素酶、过氧化氢酶和酸性磷酸酶活性均显著大于病株,但过氧化物酶和多酚氧化酶活性小于病株;非根际土壤放线菌和纤维素酶活性明显相关;病株非根际土的速效氮、磷、钾含量均高于健株,水溶性镁含量低于健株。病株根际土和根系微生态变化,特别是细菌数目的大量增加是急性青枯型根腐病最明显的特征。     

猪舍空气病原微生物与环境通风的关系研究进展

在介绍生猪生产环境控制因素的基础上,综述了猪舍空气中病原微生物种类、猪舍环境通风控制、评价方法、检测技术等方面的研究现状与进展,并对今后的研究方向进行了展望。     

Effect of different biofloc levels on microbial activity,water quality and performance of Litopenaeus vannamei in a tank system operated with no water exchange

In zero-exchange superintensive culture systems, flocculated particles (bioflocs) accumulate in the water column. Consequently, some control over the concentration of these particles must be performed. The objective of this study is to evaluate the effects of three concentrations of bioflocs on microbial activity, selected water quality indicators and performance of Litopenaeus vannamei in a tank system operated with no water exchange. A 44-day study was conducted with juvenile (6.8 g) shrimp stocked in twelve 850 L tanks at a stocking density of 459 shrimp m⁻³. Biofloc levels were expressed as three presets of total suspended solids (TSS) concentrations, as follows: 200 mg L⁻¹ (T200), 400–600 mg L⁻¹ (T400–600), and 800–1000 mg L⁻¹ (T800–1000). TSS levels were controlled by attaching a 40 L settling tank to each culture tank. Reduction of TSS to concentrations close to 200 mg L⁻¹ decreased the time of bacterial cell residence and significantly reduced the nitrification rates in the water (P < 0.05). The tanks in the T200 treatment had a greater variability of ammonia and nitrite (P < 0.05), which led to the need to increase the C:N ratio of the organic substrate to control ammonia through its assimilation into heterotrophic bacterial biomass. But the higher production of heterotrophic bacteria in T200 (P < 0.05) increased the dissolved oxygen demand. Nitrification rates were higher (P < 0.05) in tanks with TSS concentrations above 400 mg L⁻¹, and ammonia and nitrite were significantly lower than in the T200 tanks. We suggest that ammonia and nitrite in the T400–600 and T800–1000 tanks were controlled primarily by nitrifying bacteria, which provided higher stability of these parameters and of dissolved oxygen. Regarding shrimp performance, the reduction of TSS to levels close to 200 mg L⁻¹ was associated with better nutritional quality of bioflocs. Nevertheless, differences in biofloc levels and nutritional quality were not sufficient to affect the weight gain by shrimp. The rate of shrimp survival and the final shrimp biomass were lower (P < 0.05) when the TSS concentrations were higher than 800 mg L⁻¹. Analysis of the shrimps’ gills showed a higher degree of occlusion in the T800–1000 treatment (P < 0.05), which suggests that the shrimp have an intolerance to environments with a solids concentration above 800 mg L⁻¹. Our results show that intermediate levels of bioflocs (TSS between 400 and 600 mg L⁻¹) appear to be more suitable to superintensive culture of L. vannamei since they create factors propitious for maintaining the system’s productivity and stability     

Seasonal fluctuations in microbial populations and available nutrients in forest soils

Viable microorganisms, soil respiration, and available N, Ca, Mg, Na, K, and P contents were determined in samples of five different forest soils collected in spring, summer, autumn, and winter. Viable microorganisms and soil respiration were positively correlated and showed a clear seasonal trend. The soils exhibited high microbial population values in spring and autumn and low values in summer and winter; total respiration values were largely higher in autumn than in the other seasons. Seasonal variations in available Ca, Na, and K contents were much more marked than those found for available N, Mg, and P. Available N and K and the microbial population showed similar seasonal trends whereas available Ca, Mg, Na, and P did not exhibit a distinguishable and uniform seasonal pattern. The quantities of available nutrients in soils followed the order Ca>K=Na>Mg>P>N. Soils developed over basic rocks showed higher values of both microbial density and microbial activity than those in soils developed over acid rocks. All the variables analysed were clearly related to the type of soil but varied with the date of sampling; a significant seasonal effect on the microbial population, microbial activity and available nutrients was detected in all the soils studied.     

沙颍河周口市段水质的生物学监测及评价

对沙颍河周口段水质进行检测,包括微生物学检测、叶绿素a测定等,结合理化检测对其水质做出初步评价。结果表明大闸上游段水质为β中污带,贫营养型;胜利桥段水质为α-中污带,中营养型;地区医院段水质为多污带,属富营养型。     

发酵残渣接种功能微生物菌剂对黄瓜产量和品质的影响

[目的]明确在大田条件下发酵废渣接种微生物菌剂By对连作黄瓜种植的影响,为大棚连作土壤改良和农业有机废弃物资源化提供参考。[方法]采用田间试验,研究了稻草和猪粪在大棚内生物发酵后产生的发酵残渣接种微生物菌剂对黄瓜产量和品质的影响。[结果]发酵废渣接种微生物菌剂By可提高已经发生连作障碍土壤的p H,增加土壤速效养分含量;土壤中细菌、放线菌、真菌数量比对照都有显著增加,细菌/真菌比值也有一定的增加。发酵残渣接种微生物菌剂By可显著增加土壤酸性磷酸酶、脲酶活性,显著增加黄瓜株高、叶片SPAD值,并明显改善影响黄瓜品质的几个重要指标。经过发酵残渣接种微生物菌剂By之后,收获时黄瓜产量高达57 715kg/hm2,比对照高出39.0%,收益高达80 760元/hm2,比对照高出40.0%。[结论]发酵废渣接种微生物菌剂By可有效改良连作土壤肥力状况,促进连作黄瓜的生长,显著增加黄瓜的产量、品质和经济效益。