A broad spectrum screening of Schmallenberg virus antibodies in wildlife animals in Germany

To identify native wildlife species possibly susceptible to infection with Schmallenberg virus (SBV), a midge-transmitted orthobunyavirus that predominantly infects domestic ruminants, samples from various free-living ruminants, but also carnivores, small mammals and wild boar were analyzed serologically. Before 2011, no SBV-specific antibodies were detectable in any of the tested species, thereafter, a large proportion of the ruminant population became seropositive, while every sample taken from carnivores or small mammals tested negative. Surprisingly, SBV-specific-antibodies were also present in a large number of blood samples from wild boar during the 2011/2012 and 2012/2013 hunting seasons. Hence, free-ranging artiodactyls may play a role as wildlife host.     

Compost and P amendments for stimulating microorganisms and maize growth in a saline soil from Pakistan in comparison with a nonsaline soil from Germany

A 92 d greenhouse pot experiment with maize (Zea mays L.) was carried out with a strongly saline soil from Pakistan (P‐s) in comparison with a nonsaline soil from Germany (G‐s) similar in pH and texture. The aim was to evaluate salinity effects on the decomposition of compost and effects of compost and P amendments on (1) plant growth and (2) microbial‐biomass formation. The yield of maize shoot‐C and root‐C increased in both soils in the order nonamended control < +triple superphosphate (TSP) (A1) < +compost (A2) < +(compost + TSP) (A3) < +TSP‐enriched compost (A4). In comparison with the control, the highest yield in treatment A4 was nearly doubled on the G‐s, but was increased more than 8‐fold on the saline P‐s. Averaging the three compost treatments, 32% of the compost added was decomposed in the German soil and 36% in the Pakistani soil on the basis of the compost recovered as particulate organic matter. These data were roughly in agreement with the CO₂‐evolution data. This indicates that the decomposition of compost was not affected by salinity. Compost‐derived CO₂ was mainly evolved until day 32, the root‐derived CO₂ from day 74 until the end of the experiment. The addition of compost resulted in higher contents of microbial biomass C and biomass P, but also in that of NaHCO₃‐extractable P. These three properties were significantly interrelated (r = 0.64–0.85), but on a lower level of significance than the relationships between shoot‐C, root‐C, and NaHCO₃‐extractable P (r = 0.90–0.93). Applying compost enriched with TSP (incubation of compost and TSP for 24 h) provided considerably more P to plants and microorganisms than the separate addition of these two components. The results suggest that the role of the microbial biomass as a sink and source for available P deserves further attention.     

An approach to rheometry in soil mechanics—Structural changes in bentonite, clayey and silty soils

Rheology is regarded as the science of flow behaviour, where, based on isothermic equations, the deformation of fluids and plastic bodies subjected to external stresses may be described. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr-Coulomb's equation, and finally, Bingham's yielding are well known relationships and parameters in the field of rheology.

Rheometry is a well established measurement technique to determine the specific rheological properties of fluid and plastic bodies. However, the application of this technique in soil mechanical investigations is yet relatively uncommon. In order to explain point contact processes and strength an extrapolation of such findings to data of triaxial, direct shear or oedometer tests is still missing. Thus, this paper aims to introduce rheometry as a suitable method to determine the mechanical behaviour of soils and mineral suspensions when subjected to external stresses. To do this a Na-bentonite, Ibeco Seal-80 (IS-80) has been used as a testing material, and the suspensions were equilibrated with NaCl solutions in different concentrations in order to determine the ionic strength effects on interparticle strength and changes in mechanical properties. Furthermore a vertisol, a clayey oxisol, both from Brazil, and loess material from Israel, saturated with NaCl in several concentrations were analysed.

A parallel-plate-rheometer MCR 300 (Modular Compact Rheometer, Paar Physica, Ostfildern, Germany) has been used to conduct oscillatory tests. From the stress–strain relationship parameters and specific characteristics as thixotropy, storage modulus G′ and loss modulus G″, viscosity η, yield stress τ_y and the linear viscoelastic deformation (LVE) range including a limiting value γ_L were determined and calculated, respectively. With aspect to salt effects, amplitude sweep tests on CaCO₃ rich Avdat loess show an increasing stability due to higher NaCl concentrations. In a comparative test of Avdat loess and Ibeco Seal-80, turbulent versus sliding shear behaviour could be illustrated. To demonstrate clay mineralogy effects or textural effects clay rich substrates from Brazil, a smectitic vertisol and a kaolinitic oxisol were compared, showing a higher level of stored elasticity (stability) in case of smectites and a lower value in regard to kaolinites. These preliminary results of amplitude sweep tests show that rheometry is a potential method of investigating microstructural characteristics of mineral suspensions and of clayey or silty soils.     

Adenylates as an estimate of microbial biomass C in different soil groups

Adenylate (i.e. adenosine tri- (ATP), di- (ADP) and monophosphates (AMP)) and microbial biomass C data were collected over a wide range of sites including forest floor layers and forest, grassland and arable soils. Microbial biomass C was measured by fumigation extraction and adenylates after alkaline Na₃PO₄/DMSO/EDTA extraction and HPLC detection. Our aims were (1) to test whether the sum of adenylates is a better estimate for microbial biomass than the determination of ATP, (2) to compare our conversion values with those proposed by others, and (3) to analyse whether soil properties or land use form affect the relationships between ATP, adenylates and microbial biomass C. A close relationship was found between microbial biomass C and ATP (r=0.96), but also with the sum of adenylates (r=0.96) within all appropriately conditioned soil samples (n=112). In the mineral soil (n=98), the geometric means of the ATP-to-microbial biomass C ratio and the adenylates-to-microbial biomass C ratio were 7.4 and 11.4 μmol g⁻¹, respectively. The mean ratios did not differ significantly between the different texture classes and land use forms. In the forest floor, the ATP-to-microbial biomass C ratio and the adenylates-to-microbial biomass C ratio were both roughly two-thirds of those of the mineral soil. The average adenylate energy charge (AEC) of all soil samples was 0.79 and showed a strong negative relationship with the soil pH (r=−0.69). However, the AEC is presumably only indirectly affected by the soil pH.     

Über die räumliche und zeitliche Variabilität scheinbar fixer Wasserhaushaltsgrößen am Beispiel von Bodenaggregaten

Temporal and spatial variability of hydrological parameters of single soil aggregates The hydrological parameters determined for a single soil profile are usually not assumed to be variable and are often taken to represent a larger area and longer period of time, without consideration of spatial and temporal changes in the environment like cultivation or weather. Naturally structured and homogenized, subsequently restructuring aggregates from a “Stagno-haplic Luvisol” (FAO, 1991) with different possibilities of swelling were analysed with regard to the characteristics of the water retention curve and hydraulic conductivity. The experiments verified that the pattern of the water retention curve with respect to single aggregates was not constant but depended on the aggregate's initial intensity and frequency of desiccation. Additionally, effects on the hydraulic conductivity were determined. The measured values varied with the amount of swelling and shrinking, to which the aggregates were exposed. Thus, the calculation of hydraulic conductivity according to the model of Van Genuchten (1987) is doubtful. Therefore, the quantification of ecological characteristics from such parameters has to be questioned. The main cause for the described effects can be seen in the induced and only partly reversible structuring process, i.g. aggregate compaction due to shrinkage and rearrangement of particles inside the aggregate during repeated swelling and shrinkage. Additionally, physico-chemical hydrophobicity was supposed to have a major influence under certain circumstances.     

Untersuchungen über den Einfluß des Bodengefüges für den Eindringwiderstand in Böden

The influence of soil structure on penetration resistance Penetration resistance depends strongly on the soil structure. However, because roots may either penetrate aggregates or grow around them, the value determined for the bulk soil can only be used as a first approximation. If e.g. unconfined aggregates are penetrated, the penetration resistance increases with increasing size. If however, the aggregates are confined by being embedded in gypsum then the penetration resistance is higher but is independent of aggregate size. Thus, the outer skin is stronger than the inner part of the aggregates. When single prisms are penetrated horizontally, then the penetration resistance is smaller than the resistance to vertical penetration. On the other hand, for polyhedral structure the penetration resistance is of the same order of magnitude in both directions.     

Soil microbial community composition as affected by restoration practices in California grassland

Agricultural practices have strong impacts on soil microbes including both the indices related to biomass and activity as well as those related to community composition. In a grassland restoration project in California, where native perennial bunchgrasses were introduced into non-native annual grassland after a period of intensive tillage, weeding, and herbicide use to reduce the annual seed bank, microbial community composition was investigated. Three treatments were compared: annual grassland, bare soil fallow, and restored perennial grassland. Soil profiles down to 80 cm in depth were investigated in four separate layers (0-15, 15-30, 30-60, and 60-80 cm) using both phospholipid ester-linked fatty acid (PLFAs) and ergosterol as biomarkers in addition to microbial biomass C by fumigation extraction. PLFA fingerprinting showed much stronger differences between the tilled bare fallow treatment vs. grasslands, compared to fewer differences between restored perennial grassland and annual grassland. The presence or absence of plants over several years clearly distinguished microbial communities. Microbial communities in lower soil layers were little affected by management practices. Regardless of treatment, soil depth caused a strong gradient of changing habitat conditions, which was reflected in Canonical Correspondence Analysis of PLFAs. Fungal organisms were associated with the presence of plants and/or litter since the total amount and the relative proportion of fungal markers were reduced in the tilled bare fallow and in lower layers of the grassland treatments. Total PLFA and soil microbial biomass were highly correlated, and fungal PLFA biomarkers showed strong correlations to ergosterol content. In conclusion, microbial communities are resilient to the grassland restoration process, but do not reflect the change in plant species composition that occurred after planting native bunchgrasses.     

Microbial reaction in activity, biomass, and community structure after long-term continuous mixing of a grassland soil

Long-term continuous mixing at 40% water holding capacity (WHC) or as slurry at 400% WHC should result in increased soil organic matter decomposition rates in comparison to a control treatment at 40% WHC, but may have strong impacts on soil microbial indices for activity, biomass, and community structure. The amount of extractable inorganic N (NO₃-N+NH₄-N) accumulated in the soil solution after 40 weeks of incubation at 25 °C was 3% of total N in the control treatment and 4% in the two continuous mixing treatments. However, in the treatment mixing at 40% WHC, this 33% increase compared to the control treatment might be explained solely by the decrease in microbial biomass N. In the control treatment, microbial indices decreased in the order microbial biomass C (−10%), microbial biomass N (−40%), ergosterol (−45%) and ATP (−60%). In the treatment mixing at 40% WHC, all four microbial biomass indices were significantly lower than the respective index in the control treatment. This was especially true for microbial biomass N. In the treatment mixing as slurry, only the contents of microbial biomass C and ATP were significantly lower in comparison to the control treatment. The correspondence analysis ordination biplot of the phospholipid fatty acid (PLFA) profiles showed distinct clusters for the three treatments at the end of the incubation. The strongest relative decline of 64% was observed for the fungi-specific PLFA 18:3ω6 in the treatment mixing as slurry in comparison to the control treatment. The content of total bacterial PLFA decreased only by 23%. The differences between the control treatment and the treatment mixing at 40% WHC were less apparent. Fungi represent on average 21% of total microbial biomass C at the end of the incubation if the ergosterol content is recalculated into fungal biomass C. In accordance with this percentage, 22% of the group-specific PLFA could be attributed to fungi.     

Die Bestimmung der Aggregatstabilität - ein Methodenvergleich

The determination of aggregate stability - a comparison of methods The mechanical load bearing capacity and strength of aggregates against external forces can be described and quantified by indirect test (wet sieving method) and direct tests (e.g. crushing test, direct shear test). With the mean of the crushing test and the direct shear test in the shear box it is possible to achieve definite stresses, with which the influence of pore water pressure on soil stability can be explained by the occurence of water menisci forces. It is also possible to proof the pore water pressure dependent increase of strain by the particle reorientation during the process of aggregation. By the method of wet sieving, however, the summarized effect of hydraulic and mechanical processes can be described qualitatively only. A definite relation to single processes is therefore not possible.     

Transport of zinc,copper, and lead in a sewage sludge amended calcareous soil

The application of sewage sludge on farmland is practised in many countries since sludge is rich in macro- and micro- nutrients. However, increasing use of sewage sludge on farmland has raised concerns about the potential transport of heavy metals into food chains and groundwater. This study determined for a calcareous soil the effects of sludge application on soil physical properties and transport of zinc (Zn), copper (Cu), and lead (Pb). Secondary anaerobic digested sewage sludge was applied at rates of 0, 25, 50, and 100 t/ha (on a dried weight basis) for four consecutive years and mixed in the top 20-cm of soil. Corn (Zea mays L.) was planted as a spring crop, followed by wheat (Triticum aestivum) as a winter crop. Sludge application increased the dissolved organic matter content and modified the soil structure, increased the soil infiltration rate, saturated hydraulic conductivity, and aggregate stability, and decreased the bulk density. Sludge application greatly increased DTPA (diethylenetriamine pentaacetic acid)-extractable soil metal concentrations to 50 cm depth and significantly to 1 m. In the plots that received four application of 100 t/ha sewage sludge, the mean concentrations of Zn, Cu, and Pb in subsoil increased by 1600, 7, and 4.5 times, respectively, compared with the control. The results indicate that a combination of enhanced soil physical properties, heavy and inefficient irrigation and high organic matter content with heavy metals cause significant metal mobility. High sludge applications pose risks of groundwater and food chain contamination and rates are best restricted to those reflecting the nutrient demand of crops (20 t/ha every 4 to 5 yr or an average of 4 to 5 t/ha/yr).