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.     

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.     

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 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.     

Schätzung der Denitrifikation in landwirtschaftlich genutzten Böden. I. Grundlagen

Estimating denitrification in agricultural soils: I. Basic assumptions Despite a common interest of soil scientists, groundwater hydrologists, agronomists, and climatologists in quantifying soil nitrogen losses through denitrification, these are often neglected when the nitrogen turnover of agricultural soils is modelled. This is the first of two papers describing a semi-quantitative denitrification model that has been derived from data collected from soils of a catchment area near Viersen in the Lower Rhine Valley in West Germany. A field study was conducted to study the soil environment of denitrifying microorganisms. The results of this study were used to evaluate the effect of soil water, soil air and soil temperature, of the amount and quality of the organic matter, and of the pH-value on denitrification. To this end an existing model to quantify denitrification was extended. Provided the seasonal nitrogen excess of a field is known, the model in its new form enables an estimation of the extent of field-specific denitrification rates. This paper describes the effects of the parameters under consideration on denitrification, the model components used to describe these parameters, and the development of the denitrification model.     

Bodengefüge gegen Verdichtungen schützen – Lösungsansätze für den Schutz landwirtschaftlich genutzter Böden

Protecting soil structure against compaction—proposed solutions to safeguard agricultural soils To safeguard the ecological soil functions and the functions linked to human activities, measures against harmful changes to the soil are required, in line with the precautionary principle. The German Federal Soil Protection Act sets obligations for precaution in agricultural land use and, if harmful changes to the soil are foreseeable, measures for averting a danger. The results of a research project of the Federal Environmental Agency show that it is possible to describe an impairment of the soil structure, using methods of soil analysis. But this as a sole information would not qualify for the identification of harmful changes to the soil in the context of the Soil Protection Act, which requires an assessment of the severity of disruption of soil functions and the respective subject of protection. This would make additional soil investigations on site mandatory. Approaches in agricultural engineering and soil physics have introduced procedures to preserve the soil structure, in accordance with the precautionary principle. But these procedures have different goals and different ranges of application and hence offer partial solutions to safeguard against soil compaction. The assessment model of “trafficability by measuring the rut depth” provides information about the compaction status of the soil under applied conditions for farming gear, without providing detailed information about affected soil layers. The soil‐physical model of classifying soils into “risk classes for harmful soil compaction” focuses on the relationship between topsoil compaction and crop yields. The soil‐physical models “precompression stress” and “loading ratio” provide information for the assessment of subsoil compaction and a prognosis of a possible impairment of the soil structure at the water content of field capacity. It is necessary to validate the individual models with additional regional data about soil structure before a final assessment of the prognoses is made.     

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.     

Schätzung der Denitrifikation in landwirtschaftlich genutzten Böden. II. Ergebnisse und Bewertung

Estimating denitrification in agriculturally used soils: II. Results and evaluation This is the second of two papers describing a denitrification model. Whereas in the first paper the model approach was described, the second paper deals with results obtained with the model. To evaluate the model's performance, 14 profiles in the catchment area of a water-work were studied in detail. For each site the potential and the actual annual denitrification rates were estimated. It was found that the least favorable conditions for denitrification occurred in the sandy soils of the study area. Consequently, estimated denitrification rates were lowest (< 10 kg N ha^?1 a^?1) in these soils. Estimated denitrification rates were highest (50 kg N ha^?1 a^?1) in peal and river plain soils, with either a high amount of organic matter and/or a high groundwater table. In silty loess soils, denitrification losses were estimated to be 20 to 35 kg N ha^?1 a^?1. With use of the anion concentrations in the surface layer of the groundwater, a plausibility study was conducted to evaluate the estimated denitrification losses. Its results show that the values obtained are realistic. However, a true calibration of the model is still necessary.     

Einfluß polychlorierter Biphenyle auf die mikrobielle Aktivität in Böden

Effects of polychlorinated biphenyls on soil microbial activity In laboratory experiments the microbial toxicity of the PCB congeners 5 (2, 3-Dichlorobiphenyl), 8 (2, 4′-Dichlorobiphenyl), 29 (2. 4, 5-Trichlorobiphenyl) and 77 (3, 3′, 4, 4′-Tetrachlorobiphenyl) which is supposed to be extremely toxic to wildlife was investigated using Parabrownearth-Ap and Podsol-Ahe horizon material. In addition the technical PCB mixtures Arochlor 1242 and 1260 were tested. Microbial toxicity was measured by means of long-term respiration (CO₂-evolution), short-term respiration (CO₂-evolution 12 h, after addition of glucose), and dehydrogenase activity (TTC reduction) tests. 1 mg/kg of the Dichlorobiphenyls 5 and 8 reduced the long-term and short-term respiration of the Podsol-Ahe during the whole experiment (35 and 28 days, respectively). The Trichlorobiphenyl 29 became effective after addition of 10 mg/kg. No effect except a short stimulation of long-term respiration was observed for PCB 77 (Tetrachloro-PCB). Due to its higher sorption capacity, all PCB congeners reduced the microbial activity of the Parabrownearth-Ap to a lower degree. In general the toxicity of PCBs decreased with increasing degree of chlorination in both soil horizons. The technical mixtures reduced the long-term respiration only after high additions of 50 mg/kg (Podsol-Ahe) and 100 mg/kg (Parabrownearth-Ap), respectively. Arochlor 1242 proved to be more toxic than Arochlor 1260.     

Die Bedeutung von hohen Aluminiumgehalten für die Humusanreicherung in sauren Waldböden

The role of aluminium on humus accumulation in acid forest soils The impact of soil-borne aluminum on humus accumulation was investigated in a forest soil of the chestnut zone (Castanea sativa) in southern Switzerland (Ticino). Soil samples of two soils formed on bedrocks which differ mainly in their aluminum content were extracted with HNO₃, NH₄Ac.-EDTA, NH₄Cl, KCl, and NH₄F-HCl and analyzed for the most abundant elements. On gneiss which contains up to about 10% of total aluminum the common soil type in this area is a Cryptopodzol. This soil is similar to the nonallophanic Udands. It is rich in wellhumified organic matter and shows dark-colored A_h-, A(E)- and B_h-horizons. The soil samples of these horizons are extremely rich in nonexchangeable aluminum which is, however, extractable with NH₄Ac.-EDTA. It is assumed that this Al is intimately bound to the organic matter. The soil samples of these horizons contain large amounts of HNO₃-extractable phosphorus. Up to 90% of this P appears in the organic fraction. The content of NH₄F-HCl-extractable P is only 0.7 to 3.4 mg/kg. It is concluded that due to excessive Al in the organic matter the humus mineralization is inhibited compared to the Haplumbrepts of the region.     

Schutzwürdige Böden in Nordrhein-Westfalen — Bodenkundliche Kriterien für eine flächendeckende Karte zum Bodenschutz

Valuable soils in Northrhine-Westphalia — soil scientific criteria for generating a complete map for soil protection At the Geological Survey of Northrhine-Westphalia a map was developed: Soils to be protected in Northrhine-Westphalia at a scale of 1:50.000. It is based on the Soil map of Northrhine-Westphalia at a scale of 1:50.000. This map indicates areas where such land uses should get high priority which need, save and develop the identified main soil functions. There are three groups of land use with main soil functions:

• natural habitat with high potential of biotope evolution
• agricultural production on soils with (regionally) high fertility
• regional specifica, including soils as archives of natural and cultural history.

Land uses disregarding or lowering these soil functions have to be placed otherwhere or have to be compensated by areas with comparable functions. The criteria generating this map are given and discussed. The evaluation of information coming from the digital soil map runs soil protection under the aim of securing the kind and state of soil substrate and characteristics, giving the functionality of soils in favor of other media of the environment.     

Der Einfluß der Fauna auf die Stoffverlagerung sowie die Homogenität und die Durchlässigkeit von Böden

The influence of the fauna on displacement and on homogeneity and permeability of soils The influence of the most important soil animals (mammals, ants, termites, woodlice and earthworms) on displacement and on homogeneity and permeability of soils is discussed in reference to both older and more recent literature. Nearly all soil animals cause displacement of organic and mineral soil particles. The quantity, intensity and direction of this activity depends upon the morphological characters of the species involved. The homogeneity of soils is positively influenced only by the earthworms (and related forms) whereas the activity of the other soil fauna mostly has a contrary effect as far as shorter periods are concerned. The permeability of soils increases in different dimensions due to the activity of all species discussed. Permanent vegetation and non-tilling for the most part favour the activity of the soil fauna. Recent field experiments dealing with minimum or zero tillage have made this fact fairly evident.     

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.     

Protonenpuffersubstanzen in Böden

Proton buffer compounds in soils A classification of solid soil buffer substances according to the type of proton accepting sites, viz. carbonate buffer, variable charge buffer, silicate buffer and hydroxide buffer is proposed. The buffer reactions are discussed in some detail and so are formation and transformation processes of buffer. An association of pH-ranges to various buffer compounds is hampered by an insufficient knowledge of the acid strength of the different functional groups.