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排序方式: 共有396条查询结果,搜索用时 15 毫秒
111.
Manuela S. Kaufmann Christian von Hebel Lutz Weihermüller Michael Baumecker Thomas Döring Kathlin Schweitzer Eleanor Hobley Sara L. Bauke Wulf Amelung Harry Vereecken Jan van der Kruk 《Soil Use and Management》2020,36(1):104-116
Electromagnetic induction (EMI) data are often used to investigate spatial and temporal patterns of soil texture, soil water content and soil salinity. We hypothesized that the EMI methodology might thus also offer potential to detect agricultural legacy effects originating from fertilizer application and irrigation of different fields. Therefore, we performed EMI measurements on two long-term field experiments (LTFE) at Thyrow near Berlin (Germany) that differed in agricultural management with regard to long-term irrigation in combination with mineral (NPK and lime) and organic amendments (straw and farmyard manure). Two different rigid-boom multi-coil EMI instruments were used to measure simultaneously the apparent electrical conductivity (ECa) over nine different depth ranges to study the entire soil profile from topsoil to deep subsoil. Additionally, soil samples were taken from the different treatments to ground-truth the measurements and disentangle the nutrient application or irrigation effects from natural soil heterogeneity. The soil samples indicated a rather homogenous soil and the correlation between soil parameters or states were not significant. However, the treatments showed significant differences in measured ECa values. In general, ECa values were largest on regularly irrigated as well as on mineral and organic fertilized plots, with regular irrigation exhibiting the largest impact on EMI records even though the last application was months before the EMI measurement. Overall, this study reveals that EMI data can support the classical in situ assessment of agricultural management effects within LTFE, while offering new potentials in detecting and understanding legacy effects of agricultural management on spatial soil properties at farm level. 相似文献
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Dreher UM Hofmann-Lehmann R Meli ML Regula G Cagienard AY Stärk KD Doherr MG Filli F Hässig M Braun U Kocan KM Lutz H 《Veterinary microbiology》2005,107(1-2):71-79
Anaplasma marginale infection in Europe has been limited to the Mediterranean and eastern countries, to Austria and to very sporadic cases in Switzerland. There are no reports of its occurrence in the countries north of Switzerland. A severe outbreak of anaplasmosis in August 2002 in a cattle farm in the canton Grisons, Switzerland, north of the Alps, with more than 300 cattle that had to be culled, came unexpected and gave reason to hypothesize presence of an increased yet undetected prevalence of A. marginale in Switzerland. Randomly selected bovine serum samples collected in 1998 and 2003 were tested using a competitive inhibitory ELISA (cELISA) to test the hypothesis. Our validation of the diagnostic sensitivity and specificity of this test, done in the outbreak herd, yielded 99.2 and 83.3%, respectively, probably underestimating the true specificity. The true seroprevalence of anaplasmosis in Swiss cattle determined by cELISA was likely to be zero with upper 95% confidence limits of 2.49% in the canton Grisons and 1.17% in the rest of Switzerland, respectively, in 1998. For 2003, these estimates were even lower. There was no significant difference in apparent prevalences between 1998 and 2003. In search of a possible reservoir, three chamoises out of 46 free ranging wild ruminants from the Swiss National Park, Grisons, tested positive in the cELISA. This reaction is in accordance with A. marginale or a cross reacting agent such as Anaplasma ovis. From our results we conclude that the hypothesis of an increased prevalence of anaplasmosis in cattle in Switzerland must be rejected. 相似文献
115.
Reference values for the following parameters were established in the cerebrospinal fluid of 27 calves between four and eight weeks of age: specific weight, protein concentration, erythrocyte count, total leucocyte count with cell differentiation, creatin kinase activity, glucose and sodium. If possible, the findings were compared with those of other authors in calves and adult bovines. With 24.3 cells per microliter the 90% quantile of the total leucocyte count was seated significantly above comparable values for adult bovines. Hence, in individual cases markedly higher leucocyte counts can be expected in the cerebrospinal fluid of calves. In agreement with other authors, the protein concentration in calves was lower than in adult bovines. The reference range for creatin kinase activity was increased whereas the one for sodium was only slightly increased compared to earlier investigations in calves and in adult bovines. 相似文献
116.
Hofmann-Lehmann R Cattori V Tandon R Boretti FS Meli ML Riond B Lutz H 《Veterinary immunology and immunopathology》2008,123(1-2):119-123
FeLV was discovered 40 years ago and vaccines have been commercially available for almost two decades. So far, most FeLV pathogenesis and vaccine studies were conducted assaying parameters, such as virus isolation and antigen detection. Accordingly, regressive infection was characterized by transient or undetectable viremia, while persistent viremia is typically observed in cats with progressive infection. Using real-time polymerase chain reaction assays, the spectrum of host response categories to FeLV infection was recently refined by investigating proviral and plasma viral RNA loads. Cats believed to be immune to FeLV infection were found to turn provirus-positive after virus exposure. Moreover, efficacious FeLV vaccines were found unable to prevent provirus-integration and minimal viral replication. Remarkably, no difference was found in initial proviral and plasma viral RNA loads between cats with different infection outcomes. Only subsequently, the infection outcome is associated with FeLV loads. FeLV provirus was found to persist for years; reoccurrence of viremia and disease development was observed in some cats. Thus, aviremic provirus-positive cats are FeLV carriers and, following reactivation, may act as an infection source. However, integrated viral DNA may also be essential for solid protection and long-lasting maintenance of protective immunity. In conclusion, real-time TaqMan PCR and RT-PCR assays are highly sensitive and specific. They yield a more sensitive measure for FeLV exposure than antigen detection, virus isolation or immunofluoresence assays. We recommend the use of real-time PCR assays to identify FeLV exposed cats, particularly in catteries, and investigate obscure clinical cases that may be FeLV-associated. The use of sensitive molecular methods will contribute to a more in-depth understanding of the FeLV pathogenesis. 相似文献
117.
Hermann Stumpe Joachim Garz Wilfried Schliephake Lutz Wittenmayer Wolfgang Merbach 《植物养料与土壤学杂志》2000,163(6):657-662
Investigations carried out at Field F3 of the Halle long‐term fertilization trials using data from 1974 to 1983 showed that with adequate supply of mineral N‐fertilizer soil organic matter (SOM) had no significant effects of yield. Similarly enhanced SOM did not justify a reduction of mineral N (Stumpe et al., 2000). The studies presented here examine the effects of the SOM differences existing after the termination of those trials in 1986 up until 1997 (then mainly differences of hardly decomposable SOM) in comparison to farmyard manuring with enhanced mineral N application (3‐factor‐experiment). As with total SOM, hardly decomposable SOM did not directly affect yields. The effects of FYM treatment observed at lower mineral‐N levels were compensated for by enhanced mineral‐N supply. The direct effect of FYM (40 t ha—1) corresponded to a mineral‐N supply of about 60 kg ha—1 and the residual effect to about 20 kg ha—1. The differences of the C‐content in the soil at the beginning of the present studies continued throughout the experimental period of 12 years. In addition, significant differentiation has been caused by FYM and N fertilization in comparison to unfertilized treatments. The major finding is that differences in SOM content do not lead to yield differences on physically good soils (chernozem‐like soils) if appropriate compensation by mineral‐N fertilization takes place. 相似文献
118.
Determination of kinetic parameters of acid phosphatases in intact sugar beet roots of variable phosphorus nutrition Organically bound phosphorus has to be hydrolysed before its P can be taken up by plants. Both microbes and plant roots possess phosphatases, which could be of importance especially in soils with low concentrations of inorganic phosphorus in the soil solution. This could be the reason why nutrient uptake models underestimate the P-uptake by plants when P-mobilization by the phosphatases of roots is not taken into consideration. Therefore the activity of acid phosphatases (Pase) was determined to answer the following questions: 1) To which extent does the root bound acid phosphatase (Pase) follow Michaelis-Menten kinetics? 2) By which of the four linear transformations of the Michaelis-Menten equation (Lineweaver/Burk, Hanes, Eadie/Hofstee, Eisenthal/Cornish-Bowden) can plausible values of Vmax and Km be determined? 3) Which effect has the P nutrition of the plant on these kinetic parameters? Sugar beet plants were grown in full nutrient solution containing 1 and 100 μM P respectively. The Pase activity of the intact roots was measured at pH 5 using p-nitrophenylphosphate (25—15000 μM p-NPP). Vmax values were calculated per m root length. Acid phosphatase activity principally followed Michaelis-Menten kinetics. Transformations and calculations of Vmax and Km after Eadie/Hofstee and Eisenthal/Cornish-Bowden suggested the existence of at least two enzyme systems (Pase 1, Pase 2). The following kinetic parameters were found: Pase 1: P deficient plants: Vmax: 43—45 nmol m—1 min—1, Km: 31—37 μM NPP; P sufficient plants: Vmax: 7 nmol m—1 min—1, Km: 47—53 μM NPP. Pase 2: P deficient plants: Vmax: 230—293 nmol m—1 min—1, Km: 1579—3845 μM NPP; P sufficient plants: Vmax: 123—171 nmol m—1 min—1, Km: 3027—7000 μM NPP. Thus plants with sufficient P nutrition have a lower affinity to Porg and a lower hydrolysis of Porg. For P nutrition of crops Pase 1 might be the most important enzyme. 相似文献
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