Prevalence of influenza viruses A-H1N1 and A-H3N2 in swine in The Netherlands     

N Masurel  G.F de Boer  W.J.J Anker  A.D.N.H.J Huffels 《Comparative immunology, microbiology and infectious diseases》1983,6(2):141-149

In the period December 1979-May 1980 a respiratory disease spread rapidly through pig herds in The Netherlands. Surveillance of 12 pig farms resulted in isolation of 22 influenza A-Swine-H1N1 (Hsw1N1) strains from 9 pig herds. The morbidity rate was high but the mortality rate was nil. Retardation in growth was observed. Sera collected from affected pig herds showed a fourfold increase in haemagglutination inhibition (HI) titre against A-Swine-H1N1 virus. Sera collected on five farms showed a geometric mean HI titre against the A-H3N2 virus above 100. A significant HI titre increase against this virus was found in sera collected on three farms. These findings indicated a recent infection by this virus. A-H3N2 virus was not isolated. The Dutch Swine-1980 isolates showed in the cross-HI test a distant antigenic relationship with the classical A/Swine/Iowa/30 (H1N1) virus and one-sided close antigenic relationship with A/New Jersey/76 (H1N1) virus.HI antibody to A/Swine/Nederland/80 (H1N1) virus was found in 4, 0, and 44%, to A/New Jersey/76 (H1N1) virus in 0.5, 0.4, and 42%, and to A/Swine/Iowa/30 (H1N1) virus in 0.5, 1, and 30% of pig sera collected in 1976, 1977, and 1980, respectively. HI antibody to A/Hong Kong/68 (H3N2) virus was detected in 36, 56, and 68%, and to A/Victoria/75 (H3N2) virus in 38, 73, and 68% of these sera, respectively.The results of this study indicate that pigs in The Netherlands, like those in North America, Southeast Asia, Japan, and Western Europe harbour A-Swine-H1N1 and A-H3N2 influenza viruses and are thus potential reservoirs for future human pandemics.  相似文献   

Further proceedings of the C.E.C. beef production research seminars     

H. de Boer 《Livestock Production Science》1980,7(5):516-518

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Alimentation des ruminants. Principes de la nutrition des ruminants; Besoins alimentaires des animaux,valeur nutritive des aliments: INRA Publications,Versailles, 1978, 598 pp., 156 tables, 12 photographs in colour, 62 figures of which 4 in colour,FF 140.00, ISBN 340-193-6     

H. de Boer 《Livestock Production Science》1979,6(2):209-210

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Autotrophic nitrification in a fertilized acid heath soil   总被引：1，自引：0，他引：1  

W. de Boer  H. Duyts  H.J. Laanbroek 《Soil biology & biochemistry》1988,20(6):845-850

The nature of nitrification in fertilized, acid heath soils was studied. Autotrophic ammoniumand nitrite-oxidizing bacteria were enumerated in non-fertilized and fertilized heath soils. Ammoniumoxidizing bacteria were not detected in the non-fertilized soils, whereas nitrite-oxidizing bacteria were only found in the organic layer. Enrichment of acid heath soils with NPK fertilizer increased the number of autotrophic ammonium- and nitrite-oxidizing bacteria in the organic (F + H) layer as well as in the upper part of the mineral (Ah) layer, although the pH of the soil hardly changed with fertilization. In soil suspensions of the upper mineral layer of fertilized heath soils, nitrification was shown to be autotrophic as nitrification was completely inhibited by the addition of nitrapyrin under both neutral and acid conditions. Stimulation of nitrification by addition of peptone appeared to be due to the increase in pH caused by ammonification of peptone. Under acid conditions, nitrification seemed to be coupled with net nitrogen mineralization. The possible influence of vegetation on nitrification is discussed.  相似文献   

Fungal biomass development in a chronosequence of land abandonment     

Annemieke van der Wal  Johannes A. van Veen  Henricus T.S. Boschker  Paul Kardol  Wietse de Boer 《Soil biology & biochemistry》2006,38(1):51-60

Based on biomass size, the contribution of fungi to nutrient cycling and soil properties is in general more important in natural ecosystems than in agro-ecosystems. Therefore, we expect an increase of fungal biomass after cessation of cultivation to values of a natural ecosystem. However, so far, information on fungal dynamics in ex-arable land is limited. We quantified fungal biomass in a chronosequence of 26 ex-arable fields in the Netherlands ranging from 1-34 years of abandonment. Agricultural lands and semi-natural heathlands were included as reference sites for initial and final stages of succession, respectively. Fungal biomass values were low at the start of land abandonment and increased during the first 2 years after abandonment. After this initial increase of fungal biomass no further increase was apparent, neither did we find any relations with time since abandonment and changes in soil acidity, organic matter content or organic matter quality (quantity of recalcitrant C and C:N ratio). Therefore, we conclude that the initial increase of fungal biomass is caused by stopping agricultural management activities. A phase of stabilization occurs for at least three decades in which the size of the fungal biomass did not change significantly. We observed much higher values for fungal biomass, total and recalcitrant carbon in the heathland sites. We propose that a change in abiotic soil properties is a prerequisite for further increase of fungal biomass towards levels of representative heathlands.  相似文献   

不同改良剂降低稻米镉含量的效果   总被引：19，自引：0，他引：19  

邓波儿  刘同仇 《华中农业大学学报》1993,12(2):117-121

用盆栽方法,研究了大冶县镉污染土壤应用石灰、钙镁磷肥、草炭、粉煤灰、绿肥等改良剂抑制水稻吸收镉的效果,以及六个水稻品种吸收镉的差异。结果表明,水稻品种间对镉的富集能力存在显著差异;几种供试改良剂均不同程度地降低米镉含量,以施钙镁磷肥大于150 kg/100m~2最为有效,使米镉含量降低77×10~(-2)以上,低于粮食卫生标准,其后效维持一年以上。  相似文献   

包膜控释肥料养分释放速率测定方法的研究   总被引：29，自引：3，他引：26  

熊又升  陈明亮 《华中农业大学学报》2000,19(5):442-445

用直径２ｃｍ、长１０ｃｍ的陶土滤管置于内径３．５ｃｍ、高２０ｃｍ的有机玻璃管中,制成一个封闭式的自动连续过滤装置。将一定量被测肥料置于该装置中,使上端进水,下端收集滤液,装置中溶液体积保持相对平衡,不同时间检测滤液中养分的浓度变化,即可得到时间与养分释放速率的相关曲线。这种方法可望在短时间内完成定量检测包膜化肥质量。  相似文献   

Effect of vegetation manipulation of abandoned arable land on soil microbial properties   总被引：1，自引：0，他引：1  

S. Malý  G. W. Korthals  C. Van Dijk  W. H. Van der Putten  W. De Boer 《Biology and Fertility of Soils》2000,31(2):121-127

 The effect of vegetation composition on various soil microbial properties in abandoned arable land was investigated 2 years after agricultural practice had terminated. Microbial numbers and processes were determined in five replicate plots of each of the following treatments: continued agricultural practice (monoculture of buckwheat in 1997), natural colonization by the pioneer community (arable weeds), and manipulated colonization from low (four species, three functional groups: grasses, forbs and legumes) or high diversity (15 species, three functional groups) seed mixtures from plant species that are characteristic of abandoned fields in later successional stages. The results indicated that differences in above-ground plant biomass, plant species composition and plant species diversity had no significant effect on soil microbial processes (net N mineralization, short-term nitrification, respiration and Arg ammonification), microbial biomass C and N (fumigation-incubation) or colony-forming units of the major microbial groups. Hence, there were no indications that soil microbial processes responded differently within 2 years of colonization of abandoned arable land by later successional plants as compared to that by plants from the natural pioneer weed community. Therefore, it seems that during the first few years after arable field abandonment, plants are more dependent on the prevailing soil microbiological conditions than vice versa. Received: 8 April 1999  相似文献   

Vulnerability of marine resources to small‐scale fishing in a tropical area: The example of Sunda Strait in Indonesia     

Yonvitner Yonvitner  Josep LIoret  Mennofatria Boer  Rahmat Kurnia  Surya Gentha Akmal  Ernik Yuliana  Diarsi Eka Yani  Sílvia Gmez  Ludivica Endang Setijorini 《Fisheries Management and Ecology》2020,27(5):472-480

Although small‐scale fisheries (SSF) play an important socio‐economic role in developing nations, overfishing seems to be increasing the risk of stock vulnerability. This study aims to quantify the pressure of SSF on fish stocks in Sunda Strait (Indonesia) using several biological indicators that are important in quantifying fishing pressure. Data on these indicators were collected monthly for three years (2012–2014) in one of the main fishing ports of the area. The results provide evidence that, although SSF would appear to be the most environmentally sustainable of all the fishing techniques being used today in the coastal waters of Indonesia, the impact of SSF fishing on juvenile fishes in certain areas such as the Sunda Strait must not be underestimated. The results also show the need to protect immature fish of species that are not only commercialised but are also important in subsistence fisheries. Although further studies are needed to assess the impact of SSF on fish stocks in the area, it is suggested management recommendations that include the implementation of marine‐protected areas in nursery grounds and establishing minimum landing sizes well above the size‐at‐maturity for each species, are needed.  相似文献