阿维菌素对蔬菜地土壤微生物及土壤酶的生态毒理效应

研究了阿维菌素对蔬菜地土壤微生物和土壤酶的生态毒理效应.实验结果表明,阿维菌素在低浓度时（1～10 mg kg^-1）对土壤脲酶活性和脱氢酶活性有轻微的激活作用,而对土壤微生物呼吸强度没有明显的影响;在高浓度时（50～100 mg kg^-1）对土壤微生物呼吸强度、脲酶活性以及脱氢酶活性均有明显抑制作用;不同浓度阿维菌素在不同程度上均会造成土壤微生物生物量的减少和过氧化氢酶活性被强烈激活.     

DEHP对土壤脱氢酶活性及微生物功能多样性的影响

选用肥熟旱耕人为土(黄棕壤),设置了在土壤中施加100 mg kg-1 DEHP与不施加DEHP两个水平,盆栽试验研究了DEHP对土壤脱氢酶活性以及土壤微生物群落功能多样性的影响,以及植物在污染土壤中的修复作用。结果表明,施加DEHP显著抑制了土壤脱氢酶活性,30 d时与对照相比降低了约30%, 第60 d时尽管有缓慢的回升,但仍明显低于对照(p<0.05)。从BIOLOG反应的结果可以看出,DEHP也显著影响土壤微生物的功能多样性,土壤微生物群落的Shannon指数、Simpson指数、McIntosh指数和均度均显著低于无污染的对照,说明DEHP的污染导致了土壤微生物群落功能多样性的下降。种植植物对土壤脱氢酶和微生物活性有很明显的促进作用,并且在一定程度上缓解了DEHP的毒害作用,但并未消除DEHP对土壤微生物的影响。     

Microbial populations,enzyme activities and nitrogen-phosphorus-potassium enrichment in earthworm casts and in the surrounding soil of a pineapple plantation

Summary Total populations of bacteria and fungi, dehydrogenase activity (as a measure of total potential microbial activity), and urease and phosphatase activities were determined in earthworm casts and surrounding laterite soils planted to pineapple. The casts contained higher microbial populations and enzyme activities than the soil. Except for fungal populations, statistically significant (P = 0.05) increases were found in all other parameters. Microbial populations and enzyme activities showed similar temporal trends with higher values in spring and summer and lower values in winter. The earthworm casts contained higher amounts of N, P, K and organic C than the soil (P = 0.05). Selective feeding by earthworms on organically rich substrates, which break down during passage through the gut, is likely to be responsible for the higher microbial populations and greater enzyme activity in the casts.     

长期施肥对棕壤氧化还原酶活性和动力学特征的影响

土壤质量与土壤的生物学性质密切相关,施肥制度对土壤生物学特性的影响研究对土壤质量管理具有重要的意义。本文以沈阳农业大学长期肥料定位试验为基地,研究长期不同施肥制度对土壤理化性质,过氧化氢酶、脱氢酶活性和动力学特征的影响。主要研究结果:施用化肥、有机肥配施化肥降低土壤pH值,提高4种土壤全量养分(全C、全P、全S、全N)含量,有机肥配施化肥提高土壤速效N含量;低量化肥配施有机肥显著提高土壤过氧化氢酶活性及Vmax/Km值和Vmax值,低量化肥配施有机肥显著提高脱氢酶活性及Vmax/Km值,降低脱氢酶Km值。本文的研究表明,合理的化肥施用量及配施有机肥是提高土壤生物学活性的有效手段。     

甜椒根系脱氢酶活性与施氮量关系初探

北方城市郊区,近年来甜椒栽培普遍采取定植后即连续大量施肥,以期以肥促秧,提早封垄,减轻病害。但不少地块植株却表现出茎节缩短、叶片黄绿相间且皱缩,茎尖坏死、落叶、落花、落果、产量下降。 本试验针对生产上施氮量过多的问题,探求甜椒根系脱氢酶活性与施肥、产量的关系,以期为生产上合理施肥提供理论依据。     

Effects of long-term 2,4-D application on microbial populations and biochemical processes in cultivated soil

Summary The effects of 15 years of field applications of 2,4-dichlorophenoxy acetate (2,4-D) on soil microbial population and biochemical processes were studied in a field cropped with maize followed by potatoes. Amine or ester formulations at the rate of 0.95 kg 2,4-D per hectare applied in May and October every year. Fungal, bacterial, and actinomycete populations, and microbial biomass C and N were reduced by the 2,4-D treatment, the reduction being more marked where the ester was used. N mineralization, nitrification, and potentially mineralizable N were reduced by the 2,4-D ester only, while urease activity was depressed by both formulations. Dehydrogenase activity and soil microbial respiration tended to be temporarily increased by the amine, but were reduced substantially by the ester, indicating that the ester probably interfered with nutrient cycling.     

Influence of smoke exposure on soil enzyme activities and nitrification

Summary Soil was exposed to red phosphorous/butyl rubber (RP/BR) aerosols at various relative humidities in a recirculating environmental wind tunnel. Soil microbial and enzymatic activities were measured immediately after exposure and periodically thereafter for 56 days. The nitrification potential was significantly reduced in soil amended with ammonium sulfate and exposed to RP/BR smoke, and could be related to a decline in soil pH. The rate of nitrate formation in unamended soil with time was also reduced, but by 57 days postexposure, concentrations were similat to those of unexposed controls in all but the thinnest soil lense. Soil dehydrogenase and phosphatase enzyme activities were sensitive to RP/BR smoke and in some treatments no activity was detected. The measured activities did not recover within the 56-day postexposure period and in some cases declined. Soil lense thickness was the greatest factor controlling the degree of RP/BR effects, indicating that injury to soil microbial and enzymatic activities may be surficial. Deposition of smoke particles increased with increasing relative humidity, which had a significant impact on the activities measured.     

锰对公鸡乳酸脱氢酶活性和精子密度的影响

本文就日粮锰对公鸡乳酸脱氢酶(LDH)活性及生殖功能的影响进行了研究。结果表明日粮中锰缺乏或过多引起血清、肝脏和睾丸 LDH 活性同步下降。精子数/睾丸Ⅰ组(添加 Mn 0ppm)、Ⅳ组(添加 Mn 300ppm)比Ⅲ组(添加 Mn100ppm)分别降低了35.06%和31.55%,表明精子生成过程对锰的需要量有一定的范围。睾丸 LDH 活性和精子数/睾丸之间 r=0.6791(P<0.05),提示锰缺乏或过多造成睾丸生精功能下降的重要原因之一是由于锰影响了睾丸 LDH 活性。     

Effect of organic mulches on soil bacterial communities one year after application

The application of organic mulches as a soil cover is effective in improving the quality of soil. However, very little information is available on the effect of mulches on the soil microbial community. In this study, we investigated the effect of various organic mulches on soil dehydrogenase activity (DHA) and microbial community structures in the top 1 cm and 5 cm below the soil surface 1 year after application of the mulches. DHA was stimulated at both depths in plots mulched with grass clippings (GC), but was not significantly different from the control for the other mulch treatments. Fatty acid methyl ester (FAME) analysis and denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified 16S rDNA fragments were used to assess changes in the soil microbial community structure. Cluster analysis and principle component analysis of FAME profiles showed that only soil mulched with pine chips distinctively clustered from the other treatments. At the soil surface, bacterial DGGE profiles revealed that distinct shifts in several bacterial populations occurred in soils mulched with GC and eucalyptus yardwaste (EY), while DGGE profiles from soil at the 5 cm depth revealed no distinct changes. Changes in bacterial diversity at the soil surface under different mulches were calculated based on the number of bands in the DGGE profile using the Shannon-Weaver index of diversity ( H). Compared to the control ( H =0.9), the GC- and EY-treated soils showed slightly increased bacterial diversity, with an H of 1.1 and 1.0, respectively. These results indicate that the long-term effect of organic mulches on the soil microbial activity and community structure is highly dependent upon the type of mulch and is mostly exerted in the top few centimeters of the soil profile.