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61.
Release of aluminium in Northwest-German Acid Brown soils on loess-sandstone solifluction deposits In soil and clay from root zones (50 resp. 80cm) of acid brown soils, the Si and Al released during weathering was determined by fractionated extraction with 0.5 N NaOH in order to arrive at a quantitative approximation of the possible clay and silicate destruction. Extracted Al was 4-10 times higher than Si, and showed a steep gradient between Ah- and B-horizon. The Al(clay)/Al(soil) ratio varied between 0.5 to 1 depending on the admixture of sandstone material to the loess. Assuming that the clay-extracted Al was derived from the destruction of clay, we arrived at a minimum value for affected clay of 1-4,5% of the soil mass or 10 to 40% of the present clay substance. Clay destruction is discussed as Al-release leaving behind a non-crystalline Si-O-OH lattice. 相似文献
62.
Albrecht Hase 《Journal of pest science》1954,27(4):59-60
Ohne Zusammenfassung 相似文献
63.
C. Hase M. Hottinger Y. Moënne-Loccoz G. Défago C. Hase M. Hottinger Y. Moënne-Loccoz G. Défago Y. Moënne-Loccoz 《Biology and Fertility of Soils》2000,32(3):217-221
The effect of cucumber roots on survival patterns of the biocontrol soil inoculant Pseudomonas fluorescens CHA0-Rif was assessed for 22 days in two non-sterile soils, using a combination of total immunofluorescence cell counts,
Kogure's direct viable counts and colony counts on plates containing rifampicin. In Eschikon soil (high fertility status for
cucumber), CHA0-Rif persisted as culturable cells in bulk soil and in the rhizosphere, but colony counts were lower than viable
counts and total cell counts inside root tissues. The occurrence of viable but non-culturable (VBNC) cells inside root tissues
(5 log cells g–1 root) was unlikely to have resulted from the hydrogen peroxide treatment used to disinfect the root surface, as hydrogen
peroxide caused the death of CHA0-Rif cells in vitro. In Siglistorf soil (low fertility status for cucumber), the inoculant was found mostly as non-culturable cells. Colony counts
and viable counts of CHA0-Rif were similar, both in bulk soil and inside root tissues, whereas in the rhizosphere viable counts
exceeded colony counts at the last two samplings (giving about 7 log VBNC cells g–1). In conclusion, soil type had a significant influence on the occurrence of VBNC cells of CHA0-Rif, although these cells
were found in root-associated habitats (i.e. rhizosphere and root tissues) and not in bulk soil.
Received: 12 November 1999 相似文献
64.
Hagedorn Frank Schleppi Patrick Bucher Jürg Flühler Hannes 《Water, air, and soil pollution》2001,129(1-4):119-142
The responses of nitrogen transformations and nitrate (NO_3 -) leaching to experimentally increased N deposition were studied in forested sub-catchments (1500 m2) with Gleysols in Central Switzerland. The aim was toinvestigate whether the increase in NO3 - leaching,due to elevated N deposition, was hydrologically driven orresulted from N saturation of the forest ecosystem.Three years of continuous N addition at a rate of 30 kgNH4NO3-N ha-1 yr-1 had no effects on bulksoil N, on microbial biomass N, on K2SO4-extractableN concentrations in the soil, and on net nitrification rates.In contrast, N losses from the ecosystem through denitrification and NO3 - leaching increased significantly. Nitrate leaching was 4 kg N ha-1yr-1at an ambient N deposition of 18 kg N ha-1 yr-1.Leaching of NO3 - at elevated N deposition was 8 kg Nha-1 yr-1. Highest NO3 - leaching occurredduring snowmelt. Ammonium was effectively retained within theuppermost centimetres of the soil as shown by the absence ofNH4 + in the soil solution collected with microsuction cups. Quantifying the N fluxes indicated that 80% ofthe added N were retained in the forest ecosystem.Discharge and NO3 - concentrations of the outflow from the sub-catchments responded to rainfall within 30 min. The water chemistry of the sub-catchment outflow showed thatduring storms, a large part of the runoff from this Gleysol derived from precipitation and from water which had interactedonly with the topsoil. This suggests a dominance of near-surface flow and/or preferential transport through this soil. The contact time of the water with the soil matrix wassufficient to retain NH4 +, but insufficient for a complete retention of NO3 -. At this site with soilsclose to water saturation, the increase in NO3 - leaching by 4 kg N ha-1 yr-1 through elevated N inputsappeared to be due to the bypassing of the soil and the rootsystem rather than to a soil-internal N surplus. 相似文献
65.
ABSTRACT While previous research has generally found that immigration raises unemployment for natives, effects are often more muted than expected. Anticipated out‐migration responses have been similarly difficult to discern. However, these findings may be byproducts of the long‐run nature of most inquiries, which furthermore do not account for changes in natives’ labor force participation. In response, this study evaluates the impact of the arrival of low‐skilled immigrants on low‐skilled natives in urban areas over a five year period. Initial static results from the Census Basic Monthly Survey clearly indicate that immigrants have a significant negative impact on natives’ labor force participation. Building upon these static panel results, characteristics of immigrants’ destination choices are examined along with the ensuing adjustment process through dynamic analyses of local markets. Surges of immigrants significantly reduce the labor force participation of low‐skilled natives, emphasizing this often neglected channel for labor market adjustment. Previous work may thus understate the true impact of immigrants on local labor markets by focusing on the longer term and ignoring adjustments through participation. 相似文献
66.
67.
Thomas Gimmi Hannes Flühler BjØrn Studer Anders Rasmuson 《Water, air, and soil pollution》1993,68(1-2):291-305
Transport of volatile hydrocarbons in soils is largely controlled by interactions of vapours with the liquid and solid phase. Sorption on solids of gaseous or dissolved compounds may be important. Since the contact time between a chemical and a specific sorption site can be rather short, kinetic or mass-transfer resistance effects may be relevant. An existing mathematical model describing advection and diffusion in the gas phase and diffusional transport from the gaseous phase into an intra-aggregate water phase is modified to include linear kinetic sorption on gas-solid and water-solid interfaces. The model accounts for kinetic mass transfer between all three phases in a soil. The solution of the Laplace-transformed equations is inverted numerically. We performed transient column experiments with 1,1,2-Trichloroethane, Trichloroethylene, and Tetrachloroethylene using air-dry solid and water-saturated porous glass beads. The breakthrough curves were calculated based on independently estimated parameters. The model calculations agree well with experimental data. The different transport behaviour of the three compounds in our system primarily depends on Henry's constants. 相似文献
68.
In many studies on solute transport soil column experiments arc used to obtain the transport characteristics for Convection-Dispersion-Models. Early breakthrough of the solute pulse has been attributed to a non-equilibrium in phase exchange. It is a standard procedure to determine several model parameter values from such breakthrough curves (BTC). This investigation is focused on the physical significance of simultaneously fitted parameter values used in the convection and diffusion-controlled mass transfer model (mobile — immobile phase concept). Saturated column experiments were conducted with solid phases consisting of porous and solid glass beads. One set of model parameter values was obtained from the breakthrough curves by simultaneous optimization and a second set was determined by independent measurements of individual parameter values. Both sets of parameter values described the BTCs equally well but deviated substantially from each other. These discrepancies were analysed in terms of local parameter sensitivities. 相似文献
69.
70.
Antje Giebel Ole Wendroth Hannes Isaak Reuter Kurt‐Christian Kersebaum Jürgen Schwarz 《植物养料与土壤学杂志》2006,169(1):52-59
Spatial distribution of soil mineral‐N content (Nmin) is a scale‐variant process. Precision farming assumes knowledge about the spatial distribution of Nmin. Moreover, sampling in management zones is based on the assumption of spatial dependence between sampling points. In the present study, variability structure of Nmin and the sources of variability were investigated. Within an agricultural landscape, Nmin was investigated across a field in a nested design over four consecutive years. Temporally unstable structure of individual nests require a sampling with several nests in the field. In the investigated field, 35%–49% of the total variability derived from small‐scale variability observed at spatial distances of <5 m and from sampling and analytical errors. Differences between 10 and 26 kg N ha–1 for the soil depth increment 0–60 cm can be expected. Uncertainty due to analytical errors were in the order of 5–10 kg N ha–1 for a 0–60 cm layer. 相似文献