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.     

Schätzrahmen für die effektive Durchwurzelungstiefe mehrschichtiger Böden

Estimating the effective rooting depth of layered soils The values of the effective rooting depth given by the Soil Mapping Instruction are valid only for homogenous soils. In addition to these values a calculation is presented estimating the effective rooting depth of layered soils. This method is proposed as a reference method in databases of soil information systems.     

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.     

Kurzfristige pH-Pufferung von Böden

Short-time pH buffering of soils Changes in pH of 60 soils after HCl addition were related to reaction time and soil characteristis. Between 80 and 100% of the added protons were taken up by the soils within a few seconds, resulting in the release of exchangeable Ca, Mg and Al in strongly acid soils. The decrease of proton activity between 0.25 and 30-70 h can be formally described as a diffusion process. pH buffering depended on soil pH and organic C content but not on clay content. Buffering decreased from pH 3.5 to about 6 and increased again up to pH 7. Increase of C_org increased buffering mainly from pH 6-7.     

Adsorptionsisothermen als Regelgrößen beim Transport von Schwermetallen in Böden

Adsorption isotherms as regulators controlling heavy metal transport in soils The adsorption and desorption of Pb²⁺ and Cd²⁺ from equilibrium solutions with heavy metal contents up to 5000 μg/1 were determined in bulk experiments for soil samples from an acid Braunerde developed in loess loam, taken from the humic surface layer of the mineral soil (0–10 cm) and from the subsoil fairly free from organic matter (30–40 cm). Pb and Cd in solutions were determined by flameless atomic absorption spectroscopy. Pb was more strongly retained in the solid phase than Cd, and higher amounts of heavy metals were retained in the humic surface soil than in the subsoil free of organic matter. In the case of Pb adsorption/desorption showed slight hysteresis in the subsoil. The quantity/intensity (Q/I) relationships found in the experiments could be described by the Freundlich equation. The Q/I-relationships were substituted in the general transport equation. With a simulation model the transport of Pb and Cd through the soil with vertical water flow was calculated by the use of the Continuous Simulation Programming Language (CSMP). Two different cases were considered: a small, continuous increase in the heavy metal input of the soil surface, and a high, instantaneous peak input. Simulation of the transport and distribution mechanisms induced by the inputs over a period of 10 years showed strong retention of lead in the surface layer and consequently a strong damping of the concentration peak in the soil solution. In contrast, cadmium is distributed more quickly over the whole profile, yet the concentration peak in the solution phase is, too, damped considerably in the surface layer by temporary retention in the solid phase. The results of the simulation runs are in accordance with the situation in real soils where often strong accumulation of Pb is found in the top soil, while Cd is accumulated only slightly.     

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.     

Schwefelformen saurer Böden unter Nadelwald in Nordostbayern

Fractions of sulfur of four soils under coniferous forests in northeast Bavaria The sulfur status of four forest soils (Podsol-Regosol, Braunerde-Pseudogley, two Braunerde – soils) located in northeast Bavaria are investigated. Total sulfur, water-, chloride- and phosphate-extractable, Ester-SO₄-S and C-bonded S were determined in the organic and mineral layers. Total S, highest in the Oh-horizons, fluctuates between 68–1851 ppm. There are quite narrow correlation coefficients between total S and total organic carbon (r = 0,85) and between C-bonded S and total organic carbon (r = 0,82). However, phosphate-extractable S is correlated to the amounts of amorphous sesquioxids (r = 0,88). Therefore, the water-, chloride- and phosphate-soluble S added, accounts for only 8–23% of total S in the Podsol-Regosol, for 12–56% in the Braunerde-Pseudogley, but for 17–84% in the Braunerde-soils, rich on sesquioxides. In contrast, organic carbon bonded S is highest in the organic layers and in the Ah-horizons. Except of the Podsol-Regosol, this fraction decreases with increasing soil depth, whereas Ester-SO₄-S shows an increasing tendency. The carbon bonded S is correlated to both total organic C (r = 0,82) and total N (r = 0,87). Ester-SO₄-S has no clear pattern of distribution. Water soluble S is partly bound to organic colloids. The differences in the depth functions of the water soluble and of the Ester-SO₄-fractions in the organic layers may attribute to the influence of atmospheric sulfur input.     

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.     

Methodenvergleich zur pH-Bestimmung von Böden

Comparison of methods for determining of soil-pH Comparative studies are being described of pH-determinations in suspensions with m-KCl, 0.1 m-KCl, 0.01 m-CaCl₂ and water of soils derived from loess and sand. For a standard the pH-values in 0.01 m-CaCl₂-suspensions were chosen, considering, that such CaCl₂-solution reflects best conditions in natural soil solution. Mean differences of pH(H₂O)-, m-KCl- and 0.1 m-KCl-values as compared to pH(CaCl₂)-values were + 0.56, — 0.27 and — 0.02 for the soils derived from loess, and + 0.63, — 0.11 and + 0.18 for those from sand. Taking into account the pH-dependence of the difference pH(CaCl₂)-values were + 0.56 – 0.11, — 0.27 – 0.26 and — 0.02 – 0.21, for the soils derived from loess, and + 0.63 – 0.21, — 0.11 – 0.14 and + 0.18 – 0.10 for those from sand. Taking into account the pH-dependence of the difference of pH(H₂O)-values of sandy soils, and its dependence on the present electrolyte content with all soils, further the unequal differences of the pH(KCl)-values with soils from loess as compared to sand, and their particular large variability with soils from loess, it is being argued that the CaCl₂-method may only insufficiently be substitued by any one of these methods. pH-values obtained at a soil-to-liquid-ratio of 1:2.5 were only slightly different from those with a ratio of 1:1. A suspension effect could not be observed with the application of a glasselectrode.     

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.     

Stickstoffdynamik von Böden mit Abwasserverrieselung

Nitrogen dynamic of soils with wastewater irrigation The nitrogen status of a Sandy Cambisol and a Loamy Luvisol of Berlin, which were flooded with wastewater over a period of 100 years were studied. The two-year examination of the water, redox and nitrogen dynamics showed great differences in nitrogen leaching and the intensity of nitrification and denitrification processes.     

Kolorimetrische Bestimmung von Dicyandiamid in Böden

A colorimetric method for the determination of dicyandiamide in soils A colorimetric method derived from the diacetyl reaction for the determination of creatine has been developed for the determination of dicyandiamide in soil extracts. Dicyandiamide reacts with 1-naphtol and diacetyl forming a red colour complex with maximum absorption between 535 and 540 nm. The detection limit ranges between 0.1 and 0.3 mg dicyanidiamide-N/100 g soil. In soil extracts neither naturally occurring substances nor metabolites of dicyandiamide influenced this colour reaction. After addition of 1, 5, 10, 20 mg dicyandiamide-N to 100 g soil and immediate extraction by water an average recovery rate of 95% was found. The relative standard deviation amounted to ± 1.60%.     

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.     

Abbau von Monolinuron in verschiedenen Böden

Degradation of monolinuron in different soil types The degradation of ¹⁴C-methyl, -ureido- and -phenyl-labelled monolinuron was studied in laboratory experiments with different soil types. Mineralization of the ureido-group was followed by two methods. It was found, that the mineralization rate depends on the soil. For the herbicide monolinuron there was a definite degradation characteristic. The release of ¹⁴CO₂ from the methyl- and ureido-group was faster than from the phenylring. In soil extracts monolinuron was found together with one or two radioactive substances not yet identified. Soil respiration was unchanged after the application of monolinuron. In a sterile soil no degradation occurred.     

Zur Bestimmung von Gips in Böden

On the determination of gypsum in soils The (020) X-ray reflection of gypsum at 7,56 Å is nearly specific and may be used for detection and quantitative measurement of the mineral in soil samples. By X-ray powder diffractometry gypsum can be detected as far down as 0,5% by weight. This limit may be extended down to 0,005% by concentration in the density fraction 2,1–2,5 g/cm³. For quantitative measurements references may be prepared from sample parts by dehydration of the original gypsum and adding known quantities of this mineral. So it is possible to compare samples of nearly identical grain size distribution, and mineral contents. This is important in the powder-diffractometrical quantitative measurement of a mineral with low hardness and good cleavage where mechanical stress during homogenisation lowers the intensities of X-ray reflections. Under comparable conditions for sample and reference, gypsum contents can be determined in the range of 0,5 to 20% by weight with an accuracy of ± 3% (relative).     

Myxobakterien-Artenspektren von Böden in Abhängigkeit von bodenbildenden Faktoren unter besonderer Berücksichtigung der Bodenreaktion

Spectra of myxobacter-species of soils, dependent on soil-forming factors with special regard of the soil-reaction. 1) The spectra of myxobacter-species for 9 groups of soil samples were described. In total 444 soils were examined. Each series or subseries (table 3) comprised more than 20 samples. 2) An interclimatic comparison showed that soils from tropical rain forests were extremely rich in species, while crude soils from subarctic tundra are inhabited only by few species. In the latter myxobacteria were distributed even more sparsely than in substrates from arid and extremely arid deserts (table 1). 3) Couples of samples from beaches and primary dunes showed that the sea water exerted a negative effect upon myxobacteria. In primary dunes the conditions for myxobacterial development were much better than in beach samples without higher vegetation (table 2). On the other hand, flooding by fresh water can cause favourable ecological conditions for myxobacteria. Neutral soils from river-meadow forests had a diversity of species. Deciduous beech forests, which are the predominating climax plant communities in Middle Europe, normally yielded less species, even if the soil-acidity was low. - Here an intraclimatic comparison can be realized (table 3). 4) Alpine soils are suited to study the influence of soil-pH upon the distribution of myxobacteria. At pH = 5,O and higher they were more frequent than in acid substrates (table 4). 5) The resistance of myxobacteria against heat and drought is discussed. Only members of the genus Myxococcus really are true ubiquitous organisms.     

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.