Einfluß verschiedener Bodeneigenschaften auf die mikrobielle Toxizität von Blei und Cadmium

Effects of different soil properties on the microbial toxicity of lead and cadmium Effects of different soil properties on the microbial toxicity of lead and cadmium were investigated in laboratory experiments on ten arable and nine preserve area soils. Microbial activity was measured by means of the dehydrogenase and the arginine-ammonification tests. The latter was not suitable to show the microbial toxicity of both metals. Effects of lead on dehydrogenase activity were mainly influenced by its concentration in soil solution (r = 0,79). Thus, all soil properties which determined the adsorption of lead correlated significantly with the relative dehydrogenase activities of the contaminated soils. The most important abiotic factors influencing the toxicity of lead were the soil pH and the CEC. Cd solubility and Cd toxicity were influenced by soil pH in a contrary way. Low Cd concentrations caused greater inhibitions of dehydrogenase activity at neutral and slightly alkaline soil reaction than under acidic conditions. Therefore, correlations between Cd concentrations of soil solutions or clay content and dehydrogenase activity were only significant if partial correlation analysis (constant pH) was used.     

Einfluß von Bodeneigenschaften,Bodennutzung und Bodentemperatur auf die N-Mobilisierung von Kulturböden

Influence of soil characteristics, agricultural use and soil temperature on the N-mobilization of cultivated soils A new N-mobilization model, which considers also the short term and seasonal N-supplying capacity of soil is presented. At a fixed time the potential mobilizable N (N-MOB) is a sum of difficultly mobilizable N (N-MOB_s) originating from the pool of difficultly mobilizable N (N_s) and the easily mobilizable N (N-MOB₁) originating from the pool of easily mobilizable N (N₁). It is possible to characterize soil according to their M₁, N-MOB_s and v (N-MOB_s per day) values. Usefulness of these parameters in N-nutrition and ground water burden from N has been discussed. Basic parameters of this model have been experimentally determined independently with the help of two different experiments i. e. laboratory incubation and column lysimeter using surface soil samples. The easily mobilizable N pool (N₁) values were found in the range of 142 to 814 kg N ha^?1 which corresponded to 1.2 to 7.4 % of organic N content of these soils. The difficultly mobilizable N per day (i. e. v = N-MOB_s per day) in an incubation experiment (35°C) were found in the range of 1.5 to 24kg N ha^?1. However, in the column lysimeter experiment, in contrast, these values at 10°C ranged between 0.05 to 0.9 kg N ha^?1. These values correspond to N-MOB_s values in the range of 11–182 kg N·ha^?1 for a period of 200 days which approximate to a vegetation period. For practical purposes, the N₁ and v values could be calculated by just measuring 3–4 points after 14 days of incubation at 35°C. The results show that N-MOB_s values strongly correlated compared to N₁ values to total N, organic carbon and clay content and non significantly to pH and silt content. The results of an laboratory incubation experiment carried out to assess the effect of temperature on N-mobilization show that even at 0°C there was N-mobilization. The results revealed that in the temperature range of 0–8°C (a range of soil temp. usually observed in winter months) and in the range of 25–40°C (range of summer months temp. for surface arable soil), a small change in the soil temperature would result in enormous increase in the quantity of mobilized N. The highest mobilized N quantity was found above 60°C.     

Pedogenetische Differenzierung von Bodeneigenschaften auf Aggregatebene

Pedogenetic differentiation of soil properties in aggregates Besides the pedogenetic differentiation of soils in horizons a differentiation within horizons across aggregates seems possible. The objective of this study is to check if there is a differentiation of soil properties across aggregates. From a Braunerde, a Podzol-Braunerde, and 2 Podsols from Bavaria and Slovakia aggregates of 10–30 mm in diameter were selected manually from both topsoil and subsoil horizons and mechanically fractionated into a core and a surface fraction. In the aggregate fractions C_org, Al_o, and Fe_d were determined. C_org is generally depleted in the surface fractions of the A-horizons compared to the core fractions. This may be due to favoured microbial degradation of organic matter compared to the aggregate core and preferential leaching of organic C. In the subsoil horizons of the Braunerde C_org is lower in the aggregate surface fraction, in the Podzol, however, it is higher. In Podzols preferential C-input and sorption to aggregate surfaces seems to dominate. Lower Al_o? and Fe_d?concentrations in the aggregate surface fractions of all A-horizons may be explained by preferential acidification of aggregate surfaces as the aggregate surfaces mainly buffer the proton input into structured mineral soils. In the B-horizons only in Braunerde Al_o and Fe_d are lower in the aggregate surface fractions than in the core fractions. The Podzol B-horizons show preferential illuvial enrichment of sesquioxides at aggregate surfaces. Thus, pedogenesis results in the differentiation of soil properties not only between horizons but also within horizons on the level of aggregates. The resulting different chemical properties of aggregate surface and core fractions may affect the sorption capacity of structured soils.     

Einfluss des Porenwasserdruckes auf die Zugfestigkeit von Bodenproben

Effect of pore water pressure on tensile strength Direct tensile testing with measurements of the pore water suction was used to investigate the relationship between tensile strength and suction. The tests were conducted on a till and a clayey soil, both homogenized. A closer view is focused on the relationship between material strain and the development of suction. Beyond, the factor χ of the effective stress equation for unsaturated soils by Bishop (1959), which was calculated by the data of tensile strength and corresponding matric suction is compared to the volumetric χ of the tested soil specimens. It could be shown, that the pore water pressure changes with strain. Therefore, not the initial suction of a soil is relevant for its failure but the actual one that can be measured in the failure zone at the moment of fracture. In addition the application of the volumetric χ in the effective stress equation compared to the χ derived from tensile testing leads to an 1.6 to 2.8 fold overestimation of the contribution of matric suction to soil tensile strength.     

Einfluss unterschiedlicher n-versorgung des winterweizens auf die populationsdynamik von getreide-thysanopteren

In der vorliegenden Arbeit wurde anhand von Felduntersuchungen im Rahmen des IOSDV sowie ergänzenden Laborversuchen der Einfluss einer Stickstoff-Dügung auf ökologische und physiologische Charakteristika von Winterweizen untersucht. Die Stufen der N-Versorgung korrespondierten mit der Thysanopteren-Abundanz. Als richtungsbestimmende Einflussgrösse für das Populationsgeschehen der Thysanopteren konnten die mikroklimatischen Bedingungen im Bestand nachgewiesen werden. Eine erhöhte N-Düngung modifizierte die Bestandesdichte und führte zu einer höheren Luftfeuchte im Bestand als außerhalb des Bestandes. Aus den Daten der Feldbeobachtungen zum Mikroklima und zur Thysanopteren-Abundanz konnte die große Bedeutung der Luftfeuchtigkeit und Temperatur für die Populationsdichte der Thysanopteren nachgewiesen werden. Die Ursache für dieses Populationsgeschehen wurde in Laborversuchen analysiert. Die Ergebnisse dieser Untersuchungen belegten, daß in einem eng begrenzten Bereich zwischen 70 und 80% Luftfeuchtigkeit die Populationsentwicklung begünstigt wird. Außerhalb dieses Bereiches kam es zu populationsbegrenzenden Effekten. Die mikroklimatischen Bedingungen im Winterweizenbestand zur Zeit des Schossens sind entscheidend für die Thysanopteren-Abundanz des Jahres. In the present work the influence of N-supply on ecological and physiological characteristics of winter wheat was examined in cooperation with IOSDV by field and laboratory experiments. The steps of N-supply were corresponding with the density of Thysanoptera. The investigation has shown, that the influence of microclimatic conditions was the trend determining variable of the population characteristics. An increased N-supply changed the density of plant formation and led to an increase of humidity in the population. It was demonstrated in the field experiments that the humidity had a regulating effect on population density. In laboratory experiments the development of the population was favoured in the small range between 70 and 80% humidity. Outside of this range a decrease of population density was observed. The microclimatic conditions in winter wheat during the time of shooting are determining the density of Thysanoptera for a year.     

Der Einfluß von Fungiziden auf die mikrobielle Aktivität eines Bodens

The influence of fungicides on microbial activity in soil The objective of this work was to investigate the influence of the fungicides copper, sulfur, mancozeb, captan-folpet-folcid, quintozene and benomyl on CO₂-evolution and on the dehydrogenase-, xylanase- and urease-acitivities of an acid soil. The investigations showed that a recommended dosage of fungicide caused an increase in CO₂-evolution. After the second and third fungicide application this ‘stress reaction’ was followed by a decrease in CO₂-release below the value of the untreated control soil. Up to the tenth week after pesticide application again an increase of the activity could be shown. This increase might be explained by an inactivation of fungicides, a selection of resistant species, a decreasing competition of microorganisms and mineralization of dead organisms. Finally, after 10 to 14 weeks the activity returned to the value of the untreated soil, that was probably due to the recovery of the affected microflora and/or a new adapted microflora. The various enzyme activities did not follow this scheme exactly. The course was influenced by the mode of action of the particular compound used. Brassicol (Quintozene) differed because of the severe and continous inhibition of the xylanase activity. It can be concluded that the fungicides applied to the soil influence both the CO₂-release and the activities of the soil enzymes tested. Consequently litter decomposition and metabolic activities may be affected for 3 to 4 months.     

Einfluss der Kaliumdynamik im wurzelnahen Boden auf die Magnesiumaufnahme von Pflanzen

Influence of potassium dynamics at the soil-root interface on magnesium uptake of plants At the soil-root interface potassium concentration of the soil solution can be depleted by potassium uptake of the plant. The influence of this effect on the magnesium uptake of ryegrass, barley, maize and rape was studied in pot experiments with luvisols from loess. The results have shown that the rate of magnesium uptake was doubled when the potassium concentration at the root surface decreased below 20 μmol K/1. Magnesium uptake is therefore inhibited by K concentrations above this limit. Application of potassium fertilizer increases the potassium concentration of the soil solution. However, via exchange of adsorbed Mg ions from the soil matrix, K application also increases magnesium concentration of the soil solution. As a result of K application magnesium uptake increases in this case if K concentration of the soil solution at the root surface is kept below 20 μmol K/1 by K buffering or K uptake. Magnesium uptake decreases however, if K concentration exceeds 20 μmol/1 soil solution because the inhibitory effect of potassium on Mg uptake is stronger than the favourable influence of Mg concentration.     

Einfluss der Zwischenlagerung auf die anfängliche Entwicklung rekultivierter Oberböden

Influence of temporary stockpiling on the initial development of restored topsoils Due to increasing construction and open‐cast mining activities on fertile agricultural land, excavation, stockpiling, and restoration of soils have become important issues in soil protection. In this study, we performed a restoration experiment to investigate how the conditions during stockpiling may influence initial soil development and plant growth on a restored site. Four topsoils, which originated from two depths (with uninhibited and inhibited aeration) of a nontrafficked and a trafficked topsoil deposit, were repacked in strips and sown with three meadow‐seed mixtures in strips perpendicular to the soil strips. During stockpiling as well as during the first 2 years after restoration, we assessed the physical and mechanical properties of the topsoils and (after restoration) also plant growth. None of the investigated properties of the topsoils was influenced by the depth in the deposit. In contrast, the coarse porosity and compression index were lower, whereas the bulk density and precompression stress were higher in the trafficked than in the nontrafficked topsoil deposit. However, these differences largely disappeared already in the course of soil restoration. Contrary to our expectations, the plants grew better on the soil of the trafficked topsoil deposit than on the soil of the nontrafficked topsoil deposit in the year of restoration. This might be attributed to the extremely dry and hot summer of that year. In the course of the 2 years following restoration, also the differences in plant growth tended to disappear. The remaining differences in bulk density and plant growth could not be attributed to differences in stockpiling conditions. The results suggest a re‐examination of current soil restoration guidelines. The maximum permitted stockpiling heights for topsoils might be increased in order to reduce the areas required for temporary stockpiling.     

Lysimeterstudie zum Einfluss von Düngung und Bewirtschaftung auf die Ertragsbildung,den Wasserhaushalt und die Nährstoffauswaschung im Trockengebiet der Uckermark

Lysimeter study about the effect of fertilization and management on yield, water balance, and solute leaching in the dry region of the Uckermark Results are presented of a lysimeter study on the effects of fertilization and management on yield, seepage rate, and solute leaching in the dry region of the Uckermark (Northeast Germany) from 1992 to 1999. The crop rotation included sugar beet, summer barley, pea, and winter wheat with fertilization of 280 and 400 kg N ha^—1 within the crop rotation. Additionally to the mineral fertilization, sugar beet was fertilized with the sugar beet leaf or slurry. The average annual seepage rate was 13.7 mm, the nitrogen leaching was 4.3 kg N ha^—1, and the phosphorus leaching was 0.008 kg P ha^—1. Differences between the treatments were negligible and insignificant. The amount of the precipitation from April to September had a significant influence on yields. Furthermore, results of water use efficiency and the effect of different nitrogen rates on yields are presented.     

Einfluß von Meliorationsmaßnahmen auf die kleinräumliche Variation von Waldbodeneigenschaften

Influence of amelioration procedures on the small scale spatial variation of forest soil properties After clearcutting, a podzol-pseudogley derived from silty loam covering clay and a podzolic brown forest soil of sandy texture were treated as follows: CaPMg-fertilization either alone or combined with tilling (after herbicide spray) or ploughing (after mechanical stump extraction); planting of young pines, fertilization with N in the third growing season. Eight years after initiation of the trials, the coefficients of variation for stoniness and bulk density didn't differ between treatments. On the other hand there was clear evidence, that the clearcutand the subsequent amelioration techniques had increased the variability of the organic floor weight as well as of the pH, the carbon and nitrogen contents of the top mineral soil. These effects presumably are due to an irregular mixing of fertilized raw humus and A-horizon material with subsoil layers by harvesting procedures, tilling or ploughing and bioturbation.     

Sorption und Wirkung von Arsen auf die mikrobielle Aktivität von Waldhumusformen

Arsenate adsorption and effects of arsenate pollution on microbial activity of different types of humus soils Perfusion experiments using Na₂HAsO₄ were carried out in order to investigate adsorption and effects of arsenate on microbial activity of L-, O-, and A-horizons of a mull, a moder, and a mor soil. Arsenic adsorption of mineral A-horizons was positively influenced by their contents of amorphous Al- and Fe-oxides. It is assumed that arsenic was mainly precipitated as Al-, Mn- or Ca-arsenate in the organic layers during the perfusion experiments. The Freundlich equation was valid to describe As-adsorption of all layers under investigation. Microorganisms seemed to be very tolerant to arsenate pollution. Soil respiration and enzyme activities were reduced when liquid concentrations exceeded 8 μg As/ml. Extremely high As-additions (up to 10 mg As/g) did not reduce microbial processes to a greater degree than lower ones of 0,5 mg As/g.     

Der Einfluß von P-Ernährung und pH auf die Phosphataseaktivität von Zuckerrübenwurzeln

The influence of phosphorus nutrition and pH on phosphatase activity of sugar beet roots For the determination of acid phosphatase activity (P_ase) of sugar beet roots (cultivar: Reka), plants were cultivated in nutrient solution with 1 or 100 μM P in a growth chamber for 12, 18, 24, 30, 36 and 42 days. The phosphatase activity of intact roots was measured in buffer solutions with pH 4 to 7.2 and 14 mM p-Nitrophenylphosphate (NPP) after 10 min of incubation at 20°C. The influence of P nutrition on P_ase activity was significant at all intervals. At P deficiency the activity was increased by a factor of 4 to 20. During the experimental period the pH optimum was 6. At pH 5 and 7.2 the P_ase activity reached only 63 and 64% respectively of the optimum value. At P deficiency (1 μmol P L^—1) the absolute rate of NPP-hydrolysis at pH 6 was 144 nmol min¹ m¹ root length (day 12 to 36). The plants which received optimum P supply showed only 10% of this value. Sugar beet roots with P deficiency have a high potential of P_ase activity from the acid to the neutral pH-range. Therefore, under this condition they may effectively use dissolved organic phosphorus compounds.     

Auswirkungen des Anbaus von Miscanthus x giganteus auf chemische und physikalische Bodeneigenschaften

Effects of Miscanthus x giganteus cultivation on chemical and physical soil properties Soils under 4—8 years cultivated Miscanthus on different sites in Germany had greater content of organic carbon (C_org) (x¯ = + 0.20%) and total nitrogen (N_t) (x¯ = + 0.02%). Accordingly, the cation exchange capacities (CEC) and contents of plant available potassium had increased. Among the physical soil properties, decreases in bulk density as well as increases in porosity and water retention were observed. These effects seemed to be increasing during continuous growing of Miscanthus in the field.     

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.     

Anwendbarkeit geophysikalischer Prospektionsmethoden zur Bestimmung von Bodenverdichtungen und Substratheterogenitäten landwirtschaftlich genutzter Flächen

Applicability of geophysical prospecting methods for mapping of soil compaction and variability of soil texture on farm land The increasing degree of mechanization in agriculture has resulted in the use of more powerful and heavier tractors and machines. Consequently, mechanical burden to soils has increased, too, which can lead to persistent subsoil compaction at depths below 30 cm. In soils damaged by compaction soil functions like transportation of water and air decrease. Because of that, conditions for plant growth are getting worse and the soils' natural regulation functions could be impaired. In order to take counteractive measures, it is necessary to get information about the status of soil compaction. Up to now, the status of soil compaction can only be determined at single points in laboratory measurements or with less accuracy in field measurements. Therefore, the demand for an efficient planar‐mapping system arises. The applicability of different geophysical prospecting methods with regard to this problem has been examined. For this purpose, geophysical and soil measurements were performed in a field with conventional agricultural land use in Schleswig‐Holstein (Germany) on a young moraine site. We applied GPR (Ground Penetrating Radar) with main frequencies 500 MHz and 900 MHz, supplemented by inductive electromagnetic technique (EM) using the Ground Conductivity Meter EM38 and high‐resolution refraction seismic using compressional and shear waves. Differences in soil type were found by all these geophysical methods and confirmed by soil measurements, therefore, locations with higher risk for compaction (loamy soils) could be distinguished from locations with lower risk (sandy soils). Under humid conditions, radar data showed strong reflections at a depth of approx. 30 cm. During summer, under dry conditions, these reflections did not occur. This temporal variation of radar reflections can be explained by variable water layers inside the soil, which can be regarded as an indicator for compacted soil. The seismic investigation was performed along short (12 m) profiles with dense (20 cm) sensor spacing. Excellent data quality showed that this sort of measurement, known from engineering geophysics, is also feasible for soil investigations. We performed both compressional‐ (P‐) and shear‐(SH‐) wave refraction studies. Differences in soil type of subsoil affected especially seismic velocities of P‐waves. Whether or not areas of compacted soil can be detected is still unknown, because deeper soil horizons of our test area showed only uniformly strong compaction with little contrasts.     

Der Einfluß von Klärschlamm auf die mikrobielle Tätigkeit im Boden

The influence of sewage sludge on microbial activity in soil The effect of untreated, pasteurized and irradiated sewage sludge on soil biology was studied in model and field experiments. Sewage sludge from the sewage plant Geiselbullach in the west of Munich city was used for these experiments. The investigations were performed with 4 soil types according to the different locations. All the results demonstrate that there is an increase in biomass after application of sewage sludge while there were definite influences from the location. No significant relation could be observed according to sewage sludge treatment. Under favourable lab conditions the mineralization of the organic matter applied to the soil with higher amounts of sewage sludge induces in short time a definite decrease in pH. In accordance with these changes in pH there is a corresponding decrease in microbial biomass. Early results on the influence of microbial N-cycle demonstrated that amounts of sewage sludge applied under practical conditions brought an increase in denitrification capacity of the soil. In the experiment with soils nitrification rate was doubled after sewage sludge application.     

Einfluß von Stickstoffernährung und Wuchsstoffapplikation auf die Knolleninduktion bei Kartoffelpflanzen

Influence of nitrogen nutrition and application of growth regulators on tuber initiation in potato plants In water culture the effect of continuous and discontinuous N-nutrition on tuber initiation was investigated. Additional applications of growth regulators on growing stolon tips were carried out. Continuous supply of nitrate or ammonium inhibited completely the tuber initiation in S. tuberosum varieties ?Ostara”? and ?Clivia”?, The inhibition was compensated by application of CCC and ABA on the stolon tip. In contrast to this stolon application of kinetin and root application of CCC were ineffective. Temporarily damaging of the root system led to tuber initiation even when nitrogen was supplied continuously. In S. andigena grown under short day continuous N supply only delayed the tuber initiation but could not prevent it. Discontinuous N supply promotes tuber initiation in S. tuberosum. A sudden increase in N supply caused ?re-growth”? of the tuber, i.e. a stolon was formed on the tuber apex. GA₃ application on the growing tuber had the same effect. The effect of N nutrition on tuber initiation can be explained via changing the balance of endogenous growth regulators in general and the physiological aging of the leaves in particular. Discontinuous N supply seems to reduce cytokinin production in roots and therefore accelerates the aging of the leaves. This in turn favours the formation of inhibitors and/or presumably reduces the GA production in the shoot, which will change the balance of the growth regulators in the stolon tip in favour to tuber initiation.