Stoffbilanzierung in einer Pseudogley-Parabraunerde aus Löß unter Anwendung der IR-Phasenanalyse

Material balance in an aquic Hapludalf from loess by means of IR-phase analysis Grain size fractions of an aquic Hapludalf from loess near Göttingen were examined mineralogically and chemically. On the base of actual mineral composition (mode) by means of infrared spectroscopy weathering balances were made up. The results reveal a strong illite/mica loss of about 80 kg/m², which is due to decomposition in the A-horizon, and which is not compensated by a slight gain in the B-horizon. The mineral balance of the total profile yields a clay degradation of 44 kg/m². Furthermore, in the A-horizon the chemical balance gives evidence of considerable mobilizations and substantial losses mainly of SiO₂, Al₂O₃, MgO and K₂O combined in silicates. Depending on soil horizons and grain sizes the illites have K-contents varying from 4 to 8% K₂O. Al₂O₃ and MgO also show distinct variations. Both components are correlated negatively and decrease (Al₂O₃) respectively increase (MgO) from the top to the bottom.     

Wirkungen technogener Druckbelastung auf die Spannungsverteilung und das Bodengefüge einer Schwarzerde aus Löß

Effect of wheeling on stress distribution and changes in the macro- and microstructure of a cambic phaeozem derived from loess The determination of stress induced changes in the poresystem due to repeated wheeling of a cambic phaeozem derived from loess as well as in the aggregate size distribution, arrangement, and stage are reported. It could be shown, that repeated wheeling always results in a further stress distribution to deeper depths and that the vertical stresses dominate with repeated wheeling. Furthermore the octahedral shear stresses and mean normal stresses exceed the maximum strength defined by the Mohr Coulomb failure line and define a further soil deformation. The process of aggregate deterioration can be verified by radiographs from which not only the changes in bulk density on a mesoscale can be derived but from which also the crack patterns can be defined for the different stages of structure deterioration. Under the well known assumption that pore water pressure is increased due to wheeling, soil compaction and consecutive soil homogenisation by kneading can be differentiated. The consequences for ecological parameters will be discussed.     

Stickstoffumsatz in einer Lößcatena

Nitrogen turnover in a loess catena N-mineralization and mineral-N-contents were determined from spring 1993 to autumn 1995 on arable soils from loess (Luvisol, Calcaric Regosol, Gleyic-Calcaric Regosol and Cumulic Anthrosol) of a catchment area called “Bonartshäuser” farm near Gondelsheim in western Kraichgau (SW-Germany). The aim was to find out, whether the course of net-N-mineralization and mineral-N-content of the soil could be explained by the parameters soil temperature and soil moisture. Soil samples were incubated in polyethylene bags on site for mineralization and aliquots analyzed in the laboratory for the determination of the mineral-N-content. In 1993, 55 kg N ha^—1 were immobilized and up to 170 kg N ha^—1 mineralized depending on the soil type. In 1994, between 181 and 297, and in 1994, between 59 and 230 kg N ha^—1 were mineralized annually. Mineral-N-contents of the different soils throughout the experimental period (n = 45) were found to correlate much better (r² between 0.55 and 0.86) whereas net-N-mineralization (n = 44) showed coefficients of determination (r²) just between 0.08 and 0.53. Except for the Luvisol (37%) only 0 to 8% of net-N-mineralization could be explained by the combined effect of mean soil temperature and soil moisture at the beginning of the incubation using multiple linear regression analysis. Merely 1 up to 9% of mineral-N-content of the soil could be explained by the same effect. The variability and inconsistency shown by net-N-mineralization renders it inappropriate as a tool for predicting nitrogen delivery of the soil and basis for setting rules governing permissible nitrogen amounts in the soil.     

Abbau-, Sorptions- und Verlagerungsverhalten des Herbizides Diuron in einer obstbaulich genutzten Parabraunerde aus Löß

Fate, sorption, and leaching of the herbicide diuron after annual application in an orchard soil (Orthic Luvisol) A three years field trial was conducted in an apple orchard on a loess site (Orthic Luvisol) with annual applications of the herbicide diuron. An accumulation of biologically effective residues of the herbicide was not observed, although a carry-over of herbicide residues in a range of 46–77 μg/kg dry soil in the 0–5 cm layer occurred between different years. After application in May, the residues were rapidly degraded during the following summer months. Disappearance of diuron residues from the 0–5 cm layer conformed to first-order kinetics during the first six months after application. The DT₅₀-values ranged from 14 to 30 days. As the degradation rate decreased with time, the level of remaining residues on a long-term scale was best represented by two combined exponential functions for the fast and slow degradation rate. The distribution coefficient between adsorbed and dissolved residues increased with time, indicating decreasing mobility of herbicide residues. The distribution coefficients and the extractable residue contents were strongly negatively correlated. A few days after a diuron application in May 1994, about 15% of the applied amounts could be analyzed in subsoil samples from 30–60 cm depth (6%) and 60–90 cm depth (9%), while high concentrations of diuron remained in the 0–5 cm soil layer. This was the result of a heavy rainfall (20 mm) and a rapid movement of seepage water into the subsoil due to preferential transport in soil macropores like earthworm channels and shrinkage cracks, which frequently occurred in this untilled loess soil. Different transport patterns were observed during the winter months in 1992/93 and 1993/94, when only low amounts of the diuron applied in spring were leached down to 30–60 cm depth. In winter time, the remaining low concentrations of extractable residues were strongly adsorbed and therefore remained in the upper soil layers.     

Wasseraufnahme und Wasserverbrauch von Ackerbohne und Hafer auf einer Löß-Parabraunerde

Water uptake and water use of field beans and oats grown on a loess-derived grey-brown podzolic soil (Eutroboralf) The terms of the water-balance equation were determined, when field beans (Vicia faba L.) and oats (Avena sativa L.) were grown on a loess-derived soil during two seasons (1982 and 1983). A specific objective of this investigation was to quantify the water uptake from different layers and the total transpiration of both crops, as field beans are known to be susceptible to water shortage. Beside soil physical measurements climatological data for calculation of potential evapotranspiration were recorded. Plants were analyzed due to leaf area and root length density once a week. Actual evapotranspiration including interception, as determined by the soil physical approach, was split up by calculation procedures into actual evaporation, interception and actual transpiration. Total root length and root length density of field beans were much smaller and the rooting system was shallower as compared with oats. Development of leaf area and of roots was slower with beans than oats and was retarted by 2 to 3 weeks. Accordingly the time of maximum transpiration was found begin of June with oats and at begin of July with field beans. Despite reduced root growth Vicia faba transpired 250 mm in total, that is 86 % of what was found for the cereal crop (290 mm). Water uptake field beans however, was restricted to the upper 80-cm profile with 90 % of total uptake. The water uptake per unit length of root was substantial higher with beans than with oats. Due to the delayed development of the bean crop the losses by evaporation and seepage exceeded those from the soil grown to oats by 40mm (64 %). These investigations support the conclusion that yield stability of field beans may be substantially improved by selection of new varieties with increased rooting depth.     

Oberflächenverschlammung und Abflußbildung auf Böden aus Löß und pleistozänen Sedimenten

Surface sealing and runoff generation on soils derived from loess and pleistocene deposits An attempt is undertaken to bring together existing knowledge on the occurence of surface sealing, on subprocesses and factors controlling surface sealing, and on hydraulic properties of seals, with special reference to the soil conditions prevailing in Germany. A conceptional model is proposed that relates different subprocesses such as aggregate breakdown, aggregate deformation, particle rearrangement and different factors such as soil cover, microrelief, stone cover, and macropores to surface sealing and runoff generation. We conclude that loess soils and soils formed on pleistocene deposits are particularly prone to surface sealing, and seals formed on these soils can induce runoff at rainfall intensities of 5 mm h^?1.     

Die Wirkung von Klärschlamm auf die Kationenumtauschverhältnisse in einer Lößlehm-Parabraunerde unter Fichte

The effect of sludge application on cation exchange capacity of a loess loam Parabraunerde under spruce 5 years after sludge application the following effects on cation exchange capacity were found: Sludge application influenced soil chemistry to a depth of 10 cm. Cation exchange capacity was almost doubled in the layer of 0–5 cm, whereas in 5–10 cm only a slight rise was recorded. The proportion of exchangeable cations held by the soil, especially the relation between Ca: Al, was changed from 10:60 to 50:30 in the layer of 0–5 cm. The change was substantially lower in 5–10 cm. By separate analyses of samples the variation of cation exchange capacity as well as of the proportion of exchangeable cations was estimated.     

Beziehung zwischen Bodenorganismen und Gefügeentwicklung auf Löß-Neuland unter Acker- und Waldnutzung

Relationship between soil organisms and soil structure in new reclaimed soils derived from loess under agricultural and forestral use In the Rhenish Browncoal District est of Cologne he question occurs wether forestry or agriculture is the better form of primary use to force structure development in new reclaimed soils derived from loess. The investigations on 10–25 years old reclaimed soils under forestral and agricultural use indicate that humus content, microbiological activities as well as the number of soil meso- and macrofauna individuals like earthworms are increasing with growing age of the forest soils. These processes and the strucutre development are faster under forestral use. Here after about 20–30 years conditions are similiar to those of undisturbed forest soils in comparable substrates. So from the ecological point of view temporal priority should be given to forestral use.     

Der Einfluß einer Kalkung auf Aggregatstabilität und Eindringwiderstand zweier Lößböden

Aggregate Stability and Penetration Resistance of two Normal and Limed Soils To investigate the meliorative effect of liming, the aggregate stability (determined by wet sieving and sedimentation) and the penetration resistance (by a previously described method (Becher 1973 a) of unlimed and limed samples of two field experiments on a Brown Earth-Pseudogley and a Humic Pseudogley were determined. Penetration resistance decreased with decreasing water suction, but it did not show significant relation to liming. Aggregate stability was increased by liming on the Brown Earth-Pseudogley but was lowered on the Humic Pseudogley, while penetration resistance was only influenced in some cases. The behaviour of the Humic Pseudogley was explained by its exceptional high organic matter content (5–6%).     

Veränderung des Scher- und Kompressionsverhaltens von Ap-Horizont-Material aus Löß-Parabraunerden durch Kalkung

Change of shear resistance and compressibility of Ap-horizon material from loess-derived Parabraunerde Standardized artificial bodies prepared from soil material of a loessderived parabraunerde-Ap-horizon were tested with respect to their shear resistance and compressibility. The noncalcareous material was enriched with lime (2 stepts), soil humidity changed (3 steps) and the normal pressure increased (4 steps). Liming generally caused an increased initial shear resistance and led to a lowering of compressibility. The effect of lime is interpreted as an result of flocculation of the clay particles at the points of contact between silt grains in the soil matrix. The problems of transferring those results to the field are discussed.     

Verlagerung von Chlorid und Nitrat in Lößmonolithen unter einfachen nicht-stationären hydraulischen Bedingungen

Nitrate and chloride transport in loess monolithes under quasistationary conditions The transport of nitrate and chloride has been investigated in an experiment with loess-monolithes under non-steady conditions and by a simple mathematical simulation technique approximating non-stationary flow by quasi-stationary conditions. Six precipitation cycles were followed by analysing soil solution drawn off by means of porous cups from the soil columns at different depths and times. At all times, the simulated “pure” transport profiles compare reasonably well with the experimental profiles. In the columns, however, nitrogen mineralisation took place during and before the experiment.     

Die Bestimmung von selektiv freisetzbarem Kalium in Parabraunerde aus Löß und Pelosol aus Gipskeuper-Tonmergeln

The determination of preferentially releasable potassium in hapludalf from loess and chromudert from gipskeuper clay marl Octadecylammonium-chloride (ODA)-extractable potassium and interlayer potassium (K_ZW), exchanged after thermal dissociation of adsorbed NH₄, were determined on particle size fractions of soils from gipskeuper clay marl (typic chromudert) and loess sediments (shallow hapludalf). The extraction by ODA is a diffusion controlled K-exchange process. This is shown by the increase of K-release at small sample quantity and K-concentration in the extraction solution. The ODA-potassium supplies (= Biotit-K) of the two typic chromudert were significantly higher than that of the shallow hapludalf (34000 and 30000 kg/ha vs. 22000 kg/ha, to a depth of 55 cm). Biotit-K was highest in the 2-6μm-fraction for both soils. The smaller the particle size, the larger were the amounts of K_ZW In the clay fractions of all samples they reached between 70 and 80% of total K (K_t). XRD-data give evidence of different mineral genesis processes between the two types of sediments. This is supported by the K_ZW-values of the particle-size fractions. The selectively releaseable interlayer potassium is associated with wedge shaped layers of illite. It can be differentiated from the bulk interlayer potassium by its preferential extractability in the first 3 to 5 heating treatments. This potassium quantity is, on an average, 22% of total clay interlayer potassium.     

Pflanzenaufnahme und Extrahierbarkeit von lithogen,pedogen und anthropogen angereichertem Cadmium in einem Parabraunerde-Ap-Horizont aus Löß

Plant uptake and solubility of lithogeneous, pedogeneous and anthropogeneous cadmium of an Ap-horizon from Orthic Luvisol In a pot trial we investigated the cadmium uptake by ryegrass (Lolium multiflorum) and spinach (Spinacea oleracea) in soil material of an Ap-horizon from Orthic Luvisol consisting of loess contaminated with Cd lithogeneously (stone powder), pedogeneously (soil from Ah- and Bv-horizon) and anthropogeneously (CdO) respectively. The concentration of Cd in the pots was adjusted to 1.5. 3 and 6 mg/kg soil. The total Cd-charge in the soil being at the same level, the tested plants (ryegrass and spinach) took up at least two times more of Cd of anthropogeneous origin (CdO) than of the Cd of geogeneous (pedogeneous and lithogeneous) origins. A remarkably higher solubility of the anthropogeneous cadmium was noticed compared with Cd of geogeneous origin. The DTPA-solution showed these differences most clearly. The relative soluble part of the anthropogeneous Cd was more than 60% of the total content, whereas it was lower by the factor of 2 to 3 in the geogeneously enriched cadmium. In the 0, 1 M CaCl₂- and the acid (O.I M HCI + 0.125 M H₂SO₄)-extraction these differences were not as obvious. The DTPA soluble cadmium fraction and the Cd taken up by the plants tested showed the closest correlations.     

Zum Einfluß landwirtschaftlicher und forstlicher Nutzung auf die Wasser- und Luftverhältnisse typischer Böden aus Löß Nordwürttembergs

Soil water and air regime under forest and agriculture in loess soils in South-West Germany . Investigations on loess soils of South-West Germany showed distinct differences in the water and air regime under forest and agriculture. The water content was higher and the air content lower under cultivation and grassland as compared to forest. These results are caused by less transpiration of agriculture crops on cultivated plots and also by a higher bulk density of this soil due to tillage.     

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.     

Die Rolle der mikrobiellen Biomasse und des mineralisch fixierten Ammoniums bei den Stickstoff-Transformationen in niedersächsischen Löß-Ackerböden unter Winter-Weizen. I. Poolgrößenveränderungen

Significance of microbial biomass and non-exchangeable ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. I. Change of pool sizes Nitrogen transformations in loess soils have been examined by laboratory and field experiments. After straw application (· 8 t · ha^?1), N in microbial biomass (N_mic) increased by about 20 mg · kg^?1 soil (· 90 kg N · ha^?1 · 30 cm^?1) after 9 days of incubation (20 °C). Another laboratory experiment yielded an increase of about 400 mg of NH₄+-N · kg^?1 fixed by minerals within 1 h after addition of 1 M NH₄+-acetate. Defixation of the recently fixed NH₄+ after addition of 1 M KCl amounted to only 60 mg · kg^?1 within 50 days. In a field experiment with winter wheat 1991, an increase in N_mic of about 80 kg N · ha^?1 · 30 cm^?1 was observed from March to June. After July, growth of the microbes was limited by decreased soluble carbon concentrations in the rhizosphere. Different levels of mineral N-fertilizer (0, 177 and 213 kg N · ha^?1) did not affect significantly the microbial biomass. The same field experiment yielded a decrease of non-exchangeable ammonium on the “zero”-fertilized plot in spring by 200 kg N · ha^?1 · 30 cm^?1. The pool of fixed ammonium increased significantly after harvest. After conventional mineral N-fertilizer application (213 kg N · ha^?1). NH₄+-defixation was only about 120 kg N · ha^?1 · 30 cm^?1 until July.