Zur Bedeutung des Aggregierungsgrades für die Spannungsverteilung in strukturierten Böden

The effect of soil aggregation on stress distribution in structured soils The mechanical compressibility of arable soils can be described by preconsolidation load value and by the shear resistance parameters of the bulk soil and single aggregates. In order to quantify the effective stress equation must be also known the hydraulic properties of the soil in dependence of the intensity, kind, and number of loading events. The soil reacts as a rigid body at very fast wheeling speed inclusive a very pronounced stress attenuation in the top soil while stresses will be distributed in the soil threedimensionally to deeper depths at slower speed. These variations can be explained by the mechanical as well as by the hydraulic parameters of the bulk soil and single aggregates. Thus, the pore water pressure value of the bulk soil as a parameter of the effective stress equation further depends on the hydraulic properties of the inter- and intraaggregate pore system and continuity. As can be derived from the results the pore water pressure values are identical irrespective of the predessication for clayey polyhedres at high load while in coarse textured prisms the pore water pressure value depends on load and predryness. The consequences for soil strength under dynamic loading are shortly discussed.     

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.     

Die Bedeutung amorpher AI-Verbindungen für Al-Freisetzungsraten in carbonatfreien,sandigen Böden

The importance of amorphous Al-compounds regarding Al-release rates in carbonate-free, sandy soils In a preceding investigation the kinetics of proton consumption and the release of elements in carbonate-free, sandy forest soil horizons was analyzed by pH-stat-titrations. The soil matrix should reveal losses of Al and DOC equivalent to the amounts mobilized, and several extraction procedures (wet combustion: C_org; Pyrophosphateextraction: Al_p, C_org-p; Oxalate-extraction: Al_o) were applied in order to distinguish between different pools. In eight of the ten horizons investigated the dissolution of Al resulted in equivalent decreases of organically bound Al (Al_p), four of them also exhibited reductions of C_org-p?levels equal to the release of DOC. For the other two horizons, Al mobilization could be attributed to the dissolution of organic and inorganic amorphous Al-compounds, each fraction contributing about half of the total. Like the release of Al and DOC, the losses of Al_p, Al_o and inorganically bound Al (Al_o?Al_p) could be well described as 1st order reactions, the constants of dissolution [h^?1] of Al_p (0.027), Al_o (0.023) and C_org-p (0.026) being in accordance with those of Al-(0.027) and DOC- (0.024) release, respectively. For the dissolution of inorganic Al-compounds the reaction constants (0.066 and 0.052) were calculated to be nearly double.     

Regenwürmer als Bioindikatoren für Schwermetallbelastungen von Böden unter Freilandbedingungen

The use of earthworms in monitoring soil pollution by heavy metals Total heavy metal contents (HNO₃-soluble) and exchangeable fractions (Ca(NO₃)₂-soluble) of Pb, Zn and Cd were measured in soils, litter layers and earthworms (dry masses) from forest, arable and pasture sites in a transect of the main wind direction and varying distances (1.5, 5.4, 11.4, 15.6 km) to a lead smelter near Bad Ems, Germany. Additionally, cast materials of Lumbricus terrestris-individuals were collected from the surface of the pasture sites. In the observed area total soil contents of Pb and Cd exceeded the C-level and total contents of Zn the B-level of the “Netherland-list”. Heavy metal contents in soils and earthworms decreased with increasing distance to the smelter. Pb showed the best correlation. Correlation between total contents of Pb and Cd in soils and earthworms were significant (rs = 0.66; p < 0.05 and rs = 0.67; p < 0.01, respectively). The uptake of heavy metals by Lumbricus rubellus, L. terrestris and Aporrectodea caliginosa was metal specific rather than species specific with factors of accumulation being <1 (Pb), 2.7–7.6 (Zn) and 19.5–85.5 (Cd). The heavy metal contents of the observed cast materials signified the different transfer of elements from soil material via earthworm individuals to the faeces. In the cast materials the amounts of Pb were high and the amounts of Zn and Cd were low. This indicates a high accumulation rate for Zn and especially for Cd in the tissues of the observed earthworm individuals. The present data support the necessity of ecotoxicological threshold levels.     

Die Bedeutung der Aggregierung für die Nährstoffsorption in Böden

The role of structure for nutrient sorptivity of soils The influence of the aggregation in 2 differently textured and structured soils (Haplumbrept and Chromudert) on the cation exchange capacity CEC was investigated. The results clearly demonstrated, that from the total soil (< 2 mm), natural and disturbed aggregates (Ø 5–8 mm) and the separated outer and inner part of those aggregates, the undisturbed aggregates had the lowest CEC. Furthermore, the aggregate skin was more chargeable than the inner part, due to a higher amount of silt and clay in that part. Because of higher bulk densities of the aggregates and theoretically increased tortuosity, the solution of elements in percolating water, especially in clay soils, is limited to the interaggregate pores. Thus, measured differences between the element distribution in different compartments can be explained.     

Untersuchungen zum Bodenlufthaushalt in einem Bodenbearbeitungsversuch. 2. Gasdiffusionskoeffizienten als Strukturmaße für Böden

Investigation of the soil gas regime in a tillage experiment: 2. Apparent diffusion coefficients as a measure of soil structure In a soil tillage experiment with nursery stock on three different soils the apparent diffusion coefficients for CO₂ were measured using soil cores of different depths at different times. Not-tilled, herbicide treated plots were compared with rototilled plots. The relationship between the relative apparent diffusion coefficient and the air content may be described by an exponential regression function D_s/D_a = 0.0085 · e^6.8E_L, if all measurements are taken into the calculation. By dividing into different soil textures different regressions are obtained for the three studied soils: a sand, a silt and a clay loam. In many cases it is possible to show by the changing D_s(E_L) regression changes of the soil structure with depth or as a result of tillage. In all these cases the soil of the not tilled plots turns out to be better structurized than that of the tilled ones, demonstrated by higher D_s-values at equal E_L. The interpretation of the differences is being tried with the aid of soil pore tortuousity and continuity. Finally the measured D_s(E_L) relationships are applied to characterize the soil gas regime for two seasons, using CO₂ concentration profiles of the soil air on a day in summer and fall, respectively. It is shown, that CO₂ production reaches farther down in summer than in fall.     

Rekonstruktion des Ausgangszustandes und Bilanzierung von Böden einer Moränenlandschaft

Reconstruction of the original composition and balancing of soils developed on glacial till In this paper a method for the reconstruction of the original composition of soils formed on heterogeneous glacial till is described. As an exampel the original contents of carbonates, iron and clay were calculated in two soils. The soils investigated are “Rostbraunerde” under forest and ?Braunerde”? under meadow. The “Braunerde” has been regularly irrigated with waste water for the last 70 years. The heterogenity of the fine earth of the parent material is caused by the successive deposition of materials with varying particle size distribution as well as in situ cryoclastic weathering of the different rock fragments. The reconstruction was calculated from the relation between the above mentioned weatherable components and less weatherable components in the pleistocenic sediments of Berlin. The sorting grade (So, Muller, 1962), median (Md) of the particle size distribution in the 2–600 γ fraction and the contents of coarse sand, Zr and Ti in the fraction 2-2000 pm were considered as unweatherable. The calculations were performed using multi regression analysis. The influence of the pedogenetic processes of decarbonatisation, acidification, clay formation and clay migration as well as the pedological changes resulting from the waste water irrigation were quantified through the comparison between the calculated original and the measured actual contents of the weatherable components.     

Plutonium in Gemüse,Obst und Böden

Plutonium in vegetables, fruits, and soils The plutonium content of fruits and vegetables from the Karlsruhe area in the years of 1971 - 1975 was determined. In vegetables the Pu-239 and Pu-240 activities were highly different, fluctuating between 64 fCi/kg fresh weight and values below the detection limit of about 6 fCi/kg. The activity of most of the vegetables and of all fruits was not higher than 10 fCi/kg. The nuclide Pu-238 could be identified in a qualitative way only, i. e. all measuring values remained below the detection limit of about 17 fCi/kg. The total-alpha-activities which were simultaneously determined in the vegetable and fruit ashes were in the range of 0.5 -19 pCi/kg fresh weight. Soil samples taken from the same region had a mean Pu-239 and Pu-240 activity of 5.9 ± 1.4 fCi/g and a total-alpha-activity of (10 ± 1.5) · 10³ fCi/g. Samples taken from the immediate vicinity of the Karlsruhe Nuclear Research Centre did not show increased activity levels.     

Ein Bestimmungsschlüssel für natürliche und technogene Substrate in Böden städtisch-industrieller Verdichtungsräume

A key to recognize natural and technological materials in soils of urban and industrial environment In the most cases soils of urban and industrial environment are influenced by man. They often consist of mixtures of changed natural or technological materials. The identification of these materials means a problem to the soil scientist missing exact characteristics, especially of the technological materials. Improving the field examinations a key was developed to recognize the materials of the urban environment.     

Zur Pedogenese und Klassifikation von Marschböden des Unterweserraumes. I. Gesamtnährstoffe,Carbonatgehalt, Kationenbelag und Diatomeenflora als Indikatoren für Sedimentations-Bedingungen und Bodenentwicklung

Development and Classification of Marsh Soils from the Unterweser Region, West Germany. I. Total Nutrients, Carbonate Content, Exchangeable Cations and Diatom Flora as Indicators of the Role of Sedimentation Conditions in Soil Development This study was carried out to see how much sedimentation conditions determine the properties– in particular the Ca/Mg ratio – of marsh soils (fluvaquents of coastel areas). The following results show, that the marsh soils properties are not determined by different sedimentation conditions: – The vertic fluvaquents don't have a higher clay content than the mollic and aeric fluvaquents – The total (t) contents of P, Ca, Mg, K and Na varied because of different soil development – The Ca_t/Mg_t ratio in soils with CaCO₃ was higher than in soils without CaCO₃, and – related to the Ca_a/Mg_a ratio – it can also be used as a classification characteristic (a = exchangeable) – The Ca_a/Mg_a ratio varied greatly because of differences in exchangeable Ca content. Vertic fluvaquents sometimes, but not often, have a higher content of exchangeable Mg than the mollic and aeric fluvaquents. Comparing maps of the Weser area as it appeared at various times in the Holocene with the soil map, shows that the sedimentation pattern is invariably brackish-marine. This is further confirmed by the diotom flora of the soils tested. Thus the properties of marsh soils, long believed to be dependent on sedimentation conditions, are the product of different continuance and intensity of soil development.     

Zur Interpretation erhöhter Schluffgehalte in Böden des Bayerischen und des Oberpfälzer Waldes

On the interpretation of raised silt contents in soils of the Bavarian and Upper Palatinate Forest For the Bavarian and Upper Palatinate Forest (Bavaria), 41 representative pedons were examined for aeolian components using grain‐size analysis. Soils derived from loess (three pedons) are only available in the foreland of the Bavarian Forest near to the river Danube. Soils with aeolian fractions (one pedon) also exist in the adjacent part of the Bavarian Forest. No indication for loess components (37 pedons) were found in all other parts of this mountain range: these soils are missing a coarse‐silt maximum in their upper layer as should be expected for loess‐influenced soils. However, 17 of these pedons have a medium‐silt maximum in their upper layer interpreted as a result of intense physical weathering. Therefore, the widely occurrence of soils with aeolian components cannot be confirmed for this low‐mountain range of E Bavaria.     

Stickstoffverbindungen in Böden und ihre Beziehung zur Humusdynamik. 2. Mitteilung: Zur Bestimmung und Zuordnung des Amidstickstoffs

Nitrogen compounds in soils and their relation to humus dynamics. 2. Communication: On the determination and attachment of amide-nitrogen The amide-nitrogen fraction in soils – so far very insufficiently defined – has been determined in the hydrolysates of 12 different soil samples. The proposed procedure allows to split this amide-nitrogen fraction into two better befined N-fractions, namely: real amide-N (EAN) and pseudo-amide-N (PAN). This splitting is based on. 1.) a detailed N-fractionation, especially a quantitation of aspartic acid + glutamic acid (AG) and ammonia in the hydrolysate, 2.) on the fact, that pure proteins and ?soil proteins”? do not significantly differ in terms of their amino acid composition (average basis per mol protein) and deductive hereupon 3.) on the assumption, that the calculated NH₄/AG- ratio of 0,5 from pure proteins can be transferred to ?soil proteins”?. Methodically the real amide-N (EAN) and the pseudo-amide-N (PAN) are determined as follows: After quantitation of aspartic acid + glutamic acid (AG) in the soil hydrolysate EAN can be calculated by the equation: EAN = (AG) X 0,5. PAN amounts to the difference between Ammonia of the hydrolysate and EAN. For the 12 soil samples the PAN/EAN-ratios are in the range 1,5–11,7.     

Eigenschaften,Entwicklung und Wert rekultivierter Böden aus Löß im Gebiet des Rheinischen Braunkohlen-Tagebaues

Conditions, genesis and value of recultivated loess soils Physical, chemical, microbiological and micromorphological investigations have been executed on recultivated loess soils deposited between 1963 and 1968 and under agriculture since than. The main results are: 1. Dry deposited materials are often strongly compressed at 50-120 cm depth. Wet and dry deposited materials may be compressed at 30-50 cm by tillage. 2. The new soils show already a notable carbonate metabolism, loss of sodium and magnesium and a certain enrichment of humus and potassium. 3. Well recultivated soils are forming fertile Pararendzina soils, whereas the other ones are developing into difficult Pseudogley soils. 4. Land evaluation gives values of 60 to 80. However, fertility is not as high, and 10-15 should be subtracted from the values. 5. In compressed soils, melioration by deep loosening and drainage is the only method to evoid further degradation. It is, however not free from difficulties.