Die Messung der Katalaseaktivität von Böden

The determination of Catalase Activity in Soils by Dr. Beck 1. The elaboration of a method for the determination of the activity of catalase in soils is described. The method envolves the gasvolumetric determination of oxygen released by decomposition of a H₂O₂-solution by soils, suspended in buffers in the presence and absence of the catalase inhibitor NaN₃. 2. The influences of the following factors on catalase activity were studied: Methods for the determination of developed oxygen, enzyme- and substrate concentration, inhibition of catalase by NaN₃, pH- and temperature-optima of catalase and the presence of plant residues in soils. 3. It was found, that there was only a little decrease in catalase activity when fresh or dried samples of soils were stored over a periode of 4 months under laboratory conditions. The catalase activity of different soils showed very good correspondence to the dehydrogenase activity of the soils and less correspondence to the amount of soil respiration and the amylase activity. No relation could be found to the number of microorganisms in soil.     

Die N-Mineralisierung von Böden im Laborbrutversuch

N mineralization in soils under laboratory incubation conditions The potential rate of release of nitrogen by the organic matter in agriculturally used soils was determined under laboratory conditions by means of incubation. Mineralization of the more resistant soil organic matter proceeded linearly with time during an incubation period of 2–3 weeks, when field-moist and air-dried samples were used and at the beginning of the incubation experiment sufficient water was added to bring them to saturation. Mineralization was taking an exponential course in soils with additions of easily decomposable organic matter or in soils with a higher proportion of organic residues from crops. For the 14 investigated arable and grassland soils great variations in the average daily rate of mineralization were found ranging from 5–60 μg N_min/10 g DM. The data correlated very well with the biomass (r = 0.96) and the cell-free protease activity (r = 0.98) of the soils. Different measures of soil management (preceding crops, application of sewage sludge, addition of heavy metals) had a more or less pronounced influence on the rate of mineralization. The optimum temperature was 50°C for N mineralization and 26°C for nitrification. Contrary to nitrification, the soil reaction had only little influence on mineralization and proved also independent of the N_min content of soils. The results indicate that ammonification of organic N compounds may largely proceed via the microbial biomass.     

Die Erodibilität ausgewählter Böden der bayerischen Schichtstufenlandschaft

Erodibility of Selected Soils in the Bavarian Scarpland A laboratory rainfall simulator was used to determine the erodibility (K-factor of the USLE) of 6 soils. 3 of the soils were developed from mesozoic sediments (an Ochrept and an Udipsamment from sandstones, an Udorthent from shale), an Udalf and an Udorthent of loessial origin, and an Udorthent, that was developed from a silty-loamy cover. The measured K-values of the loessial soils agreed well with the calculated. But the calculated K-factors for the 3 Jurassic soils underestimated their erodibility. The erodibility of the silty-loamy soil was overestimated. It could be shown that the measured erodibilities agreed better with field data than the calculated.     

Zur Bestimmung der Kationenaustauschkapazität von Böden mittels Barium

Regarding the Determination of Cation Exchange Capacity of Soils with Barium Very often the cation exchange capacity (CEC) of soils is determined using Ba⁺⁺ as exchange cation. In soils with high contents of organic matter, Ba⁺⁺ cannot be desorbed completely by Mg⁺⁺ or H⁺ but by Ca⁺⁺. Soils containing vermiculite adsorb Ba⁺⁺ in non exchangeable form. The fixed Barium can only be determined by total digestion. Therefore in soils containing vermiculite the exchange with Ba⁺⁺ leads to an underestimation of the CEC.     

Differenzierte Erfassung der Bioaktivität von Pilzen und Bakterien zweier Böden unter Fichte

Differential determination of fungal- and bacterial bioactivity in two spruce forest ecosystems To determine the general bioactivity and the contribution of actinomycetes and fungi in organic and mineral horizons of two spruce forests (Luvic Cambisol and Dystric Podzoluvisol) different physiological methods were utilized and compared. According to microbial measurements (ATP-quantity, heat output) the activity in Ebersberger Forst surpassed that of Höglwald in each horizon. The measurements of ergosterol and chitin delivered contradictory results. A similarity between the amount of glucosamine and that of fluorescein diacetate hydrolysis was observed. In the activity of lignin degrading fungi and ethylene production both soils differed entirely.     

Die Adsorption von HCB und DDD in Böden

The Adsorption of HCB and DDD by soils A method for studying the adsorption of substances with low water solubility by soils has been set up. The method has been verified by two chemicals (HCB, DDD) and a number of different soils. The results have shown a significant correlation between the distribution ratio and the content of organic carbon.     

Bodenatmung,Stickstoffmineralisation und Humusabbau ostafrikanischer Böden nach Trocknung und Wiederbefeuchtung

Soil respiration, nitrogen mineralization and humus decomposition of East African soils after drying and remoistening Soil respiration and nitrogen mineralization of 51 East African cultivated, savanna and forest soils were compared after 3 and 21 weeks of air drying. The average soil respiration after 21 weeks of drying was 1.221 ± 0.106 times higher than that after 3 weeks of drying whereas the average nitrogen mineralization was not increased significantly (factor 1.132 ± 0.256). The increase in soil respiration was correlated positively with the water soluble organic matter. During air dryings of 3 days and moist incubations of 4 days at 30°C, which were repeated 20 times in 10 soils, 3–10% of the organic carbon and 8–19% of the organic nitrogen (low humus vertisol 69%) were mineralized. Changes in the amount and the extinction of humic and fulvic acids were considered to be indicative for an increased humification during the drying and remoistening of soils.     

Dosis- Wirkungs-Beziehungen zur Erfassung von Chemikalienwirkungen auf die mikrobielle Aktivität von Böden: I. Kurvenverläufe und Auswertungsmöglichkeiten

Dose response curves: their use in soil microbiological research and possibilities of evaluation The relation between different concentrations of a toxicant in soils and the resulting effects on biological parameters can be described with dose response curves. Dose response curves make it possible to determine the concentrations of a chemical that create definite effects (?Effective Doses”?, e.g. ED₁₀ and ED₅₀ for 10- and 50% inhibitory effects) or to evaluate the rate of increase of inhibition with increasing concentrations. Some of the mostly used ways to extract these parameters from dose response curves are presented and examined with regard to their suitability in soil microbiological research. Besides graphical procedures for the evaluation of dose response curves a mathematical model for fitting quantitative dose response curves is introduced. With this model the confidence intervals of effective doses can be computed. By showing eight frequently appearing shapes of dose response curves the advantages and limitations of different ways to calculate effective doses are discussed.     

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.     

Ermittlung des Redoxpotentials (Eh-Wert) von Böden und Grundwässern aus dem zeitlichen Verlauf der Elektrodendepolarisation

Calculation of redox potential in soil and groundwater from the curve of the electrode depolarization An inherent problem with redox potential measurements in soil and groundwater is the initial drift of potential readings. This is caused by electrode depolarization. The depolarization kinetics corresponds to a first-order process, mathematically described by an e-function. Based on the depolarization kinetics a method was developed to calculate redox potentials (E_h-values) from only short time (= 10 min) measured depolarization curves. Besides the E_h-value this procedure gives the depolarization constant λ. The method was tested and verified by a number of depolarization measurements in soils and groundwater.     

Zur Definition von Humusformen ackerbaulich genutzter Böden. II. Quantität und Qualität der organischen Bodensubstanz

The definition of humusforms from soils under cultivation. II. Quantity and quality of soil organic matter In the new edition of the German textbook “Practical Studies in Soil Science” the authors presented a proposal of mapping humusforms in arable soils in order to characterize soil and site ecology (Schlichting et al., 1995). This proposal was developed from the definitions “Ochric”, “Mollic” and “Umbric” of the Soil Taxonomy and the FAO classification. The characterization of humusforms in 45 arable surface soils was carried out according to this proposal while soil organic matter (SOM) composition was investigated by means of wet chemistry and CPMAS ¹³C-NMR spectroscopy. “Mollic” in contrast to “Umbric” humusforms could be characterized by a higher carbonyl/carboxyl carbon content probably deriving from proteins, polysaccharides and humic substances. In addition the mollic epipedon contains 10% more litter compounds, whereas in the umbric epipedon humic acids are of major importance. The humin fraction in the mollic epipedon is thought to be raised by the formation of Ca-humates. Our data suggest, that with regard to microbial decomposition a surplus of available organic matter is present in the mollic horizons. The ochric-like epipedon has a much lower humus content compared to “Mollic” and “Umbric” horizons and exhibits the highest amounts of soluble organic matter as well as aromatic and carboxylic C-compounds in the humic fraction. Our data suggest, that SOM quantity and quality of the mollic, umbric and ochric epipedons differ substantially. These findings suggest that the proposal of Schlichting et al. (1995), which was extended by Blume & Beyer (1996), should be regarded as a useful basis to discuss the development of humusforms in soils under cultivation and facilitate soil survey in order to improve site characterization.     

Erodibilität repräsentativer Böden der Hallertau

Erodibility of representative soils of the Hallertau (South Bavaria) Differences between the USA and the Federal Republic of Germany in geology, soil types, and climate necessitate to verify the erodibility of the soils estimated according to Wischmeier and Smith (1978), when using the Universal Soil Loss Equation under local conditions. The erodibility of 5 representative soils of the region Hallertau within the so-called “Unterbayerisches Hügelland” was checked by measuring soil losses using a laboratory rainfall simulator. The estimated and measured erodibilities for two Aquic Hapludalfs from loess and one Ruptic-Alfic Eutrochrept from Tertiary sand compared very well as shown by coefficients of regression of 1. The estimated erodibilities for a Typic Eutrochrept and an Aquic Chromudert, both from Tertiary materials, however, underestimated the soil losses by a factor of 1.5. For all regressions the coefficients of correlation were 0.90. Due to the small number of soils checked, it is only possible to suggest causes for the observed deviations, particularly since the aggregate stability could not be the only property, as demonstrated by measurements.     

PH-Verteilung und Pufferung von Böden

PH-distribution and buffering of soils A frequency distribution of the pH values of 927 soils clearly reflects the three soil buffer ranges (carbonate, pH-dependent charge and aluminium release) by higher frequencies within these ranges and lower frequencies between them.     

Kurzzeittests zur Abschätzung langfristiger Wirkungen potentieller anorganischer Schadstoffe auf die mikrobielle Aktivität von Böden

Short-term experiments for the estimation of long-term effects of inorganic pollutants on soil microbial activity The purpose of the present study was to develope a short-term laboratory method to predict long-term effects of inorganic pollutants on soil microbial activity. Experiments were carried out on a sandy cambisol which had been used in a long-term field plot of the Biologische Bundesanstalt in Berlin. The perfusion technique was suitable to prove long-term effects of concentrations of 50 mg Cd/kg and 1000 mg Pb/kg dry soil on dehydrogenase activity of the test soil. 200 mg Cd/kg and 4000 mg Pb/kg caused higher reductions in the perfusion experiment than in the long-term field trial. Due to the desorption of OH-ions and the dissolution of organic material, effects of NaF-additions were partly compensated in the short-term experiment. The lysimeter technique used here seems to be of minor value to simulate long-term effects of cadmium, lead, and fluorine because unadsorbed portions of these elements and their accompanying ions (e.g. Cl, NO₃) are washed out of the system too slowly. The dehydrogenase activity was more valid to indicate long-term effects on soil microbial activity than ATP-contents and nitrification measurements did.     

Die Ermittlung von langfristigem O2-Mangel (Stickigkeit) in Böden aus Nährstoffanalysen

The evaluation of long lasting O₂-deficiency in soils from nutrient analyses The relation between soil reserve (b) related plant contents (p) of nutrients, which are taken up preferentially under good (Y, e.g. N, K) or poor (X, e.g. Mn, Na) aeration (Y_p: Y_b): (X_p : X_b) decreases with increasing oxygen deficiency, therefore it is a suitable measure for the stifling during the growth season. In four very different landscapes N and Mn turned out to be the most useful indicators. Thus, appropriately combined analyses of plant and soil samples from the rooting zone taken once can replace chronosequent measurements of the E_H and ODR or indirect determinations of air volume, no matter, whether single plant species or the same plant communities are investigated. This method could be applied generally, with threshold values, if the same plants and in a given landscape adequate soil extractants were used.     

Die Bedeutung der Umsetzung von Weizenstroh im Hinblick auf den C- und N-Haushalt von Löß-Ackerböden

The significance of wheat straw decomposition with regard to the C- and N-cycle of a cultivated loess soil In 1984/85, a microplot experiment with ¹⁵N-enriched fertilizer was carried out on a field of the Calenberg loess area near Hannover (surface area of the plots: 1 ± 2 m; experimental soil: stagnigleyic cambisol from loess). On the one hand, the extent of immobilization as well as remobilization of native soil- and fertilizer-N associated with straw incorporation (± 8 t/ha) was quantified. On the other hand, the turnover as well as the alteration of C- and N-masses in the decomposing straw material was studied. About 70% of the initial dry organic matter of straw was mineralized within one year. An enrichment of fertilizer-N as well as native soil-N in the residues of up to 20 kg/ha was observed as compared to the initial N-mass. On a microplot cropped with winter-wheat, microbial N-immobilization of about 30–40 kg/ha (native soil-N and fertilizer-N) occured in the soil after straw incorporation. The immobilization extended to march 1985. Subsequent, associated with a C/N-ratio in the straw of 43, N-remineralization as well as -extramineralization was observed with 40 kg/ha at maximum in december 1985.     

Ermittlung des Spannungszustandes von Böden aus Werten des Eindringwiderstandes von Sonden

Evaluation of the soil consolidation state by using data from penetration resistance probes Penetration resistance data (EW) from handdriven equipment are easily obtainable because the equipment is simple, cheap, and easily carriable. Measurements are performed quickly without extensive destruction of the site. It is the only method to measure soil strength directly and in situ. Therefore, it is worthwhile to propose an interpretation of the results in order to obtain more conclusive statements on the structural soil state. The procedure applied in our study consists in assigning EW values to the principal stress σ_x and in using an auxiliary construction for the vertical component (σ_z ) as a function of penetration depth. The EW value obtained at the final soil depth is assumed to represent stresses at rest, i.e., K₀ = σ_x/σ_z = 1. Drawing a straight line from this point towards the origin of the coordinates EW and soil depth supplies values of the hydrostatic condition for each depth; e.g., values for σ_z are available for each depth. The coefficient for the equivalent stress at rest (K_0E) per depth can now be calculated simply by comparing the measured EW values with the assumed (hydrostatic) vertical depth function of EW. From a total volume of 29 sets of EW versus depth relations, means and standard deviation of K_0E are presented for arable and forest soils from central Europe. K_0E of forest soils tends to be close to 1 showing approximately normal compaction. In arable sites, K_0E > 2 prevail, indicating precompation. These results confirm the general feasibility of the approach to evaluate the compaction state of soil from EW data. Examples are given to show the K_0E characteristics for special cases of mechanical stress situations.