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 von Bodeneigenschaften auf die Segetalflora von Ackerflächen

Impact of soil properties on weed distribution within agricultural fields Occurrence and distribution of weeds on agricultural fields are often heterogenous. The influence of various soil properties on the spatial structure and density of weed populations was investigated on two agricultural fields with special regard to three weed species (Polygonum amphibium, Cirsium arvense, Veronica hederifolia). Based on field specific sampling grids, weed counting and soil sampling were done. For all grid points, soil analysis was carried out (texture, organic C, total N, pH, soil nutrients P, K, Mg). Soil texture, soil organic C, and soil nutrients are the factors with the highest influence on the occurrence of the species studied.     

Wirkung von Gummimehl auf Phaseolus vulgaris

Effects of ground rubber on Phaseolus vulgaris Phaseolus vulgaris was grown in sand culture containing ground rubber. The rubber caused red-brown and black spots and stripes to appear on the veins. The leaves developed widespread chlorosis. The vascular bundle tissues and the mesophyll differentiated incorrectly. Brown deposits were found in all tissues, some being manganese enriched. Plants were analysed for Boron, Cadmium, Manganese and Zinc after a vegetation period of 49 days. Zinc toxicity was considered ground rubber's primary effect. It also caused Boron starvation and excess of Manganese.     

Einfluß chemischer Bodeneigenschaften auf Ausmaß und Zusammensetzung der Denitrifikationsverluste drei verschiedener Bakterien

Effect of soil properties on the quantity and quality of denitrification with different bacteria The influence of 4 different soils on the intensity and quality of gaseous denitrification losses from 3 bacteria (Aeromonas “denitrificans” S224, Azospirillum lipoferum DSM 1843 and Bacillus licheniformis ATCC 14580) was examined in model experiments at complete anaerobic conditions at the expense of a relatively high nitrate concentration (300 μg NO₃^? N/g dry soil) at standard conditions (30°C, 80% WHC). The soils (Ah-material) were obtained from gleyo-eutric Fluvisol (A), orthic Luvisol (L), calcaric Fluvisol (AR) and eutric Cambisol (KB) and represented different chemical properties. Gas production (CO₂, NO, N₂O, N₂ and CH₄) was analyzed by gaschromatography in regular intervals, whereas changes in N_t, C_t, water extractable organic carbon (C), nitrate, nitrite, ammonium, pH (H₂O) were determined at the end of each experiment. The intensity and composition of denitrification (NO, N₂O, N₂) differed considerably from organism to organism and from soil to soil. With A. “denitrificans” NO was released from the calcaric Fluvisol and orthic Luvisol, whereas B. licheniformis produced this gas only from the Cambisol. A. lipoferum did not produce NO in any of the soils tested. N₂O was liberated by A. “denitrificans” in all soils, but A. lipoferum produced it only in the Fluvisol and B. licheniformis exclusively in the Cambisol. Apparently, the production of NO and N₂O as products of incomplete denitrification at relatively high nitrate concentration is determined primarily by the organism in question and in the second place by the chemical properties of the soil. The main properties that govern the quality of denitrification in soils are discussed.     

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.     

Einfluß der Bodeneigenschaften auf die Freisetzung der gelösten organischen Substanz (DOM) aus dem Oberboden

Influence of Soil Properties on the Release of Dissolved Organic Matter (DOM) from the Topsoil A percolation experiment over a period of three month with small monoliths from forest and grassland soils varying in their anthropogenic changes was carried out to identify, to weigh and to quantify important soil properties for DOM release from the topsoil. Quality of soil organic matter determines the amount of DOM released from the topsoil if the soils have a low ability to adsorb and to precipitate DOM. Favorable conditions for high DOC concentrations in the soil solution are wide C/N ratios in the soil and in the hot water soluble fraction, a high soil content of hot water soluble organic carbon and a high portion of hot water soluble organic carbon in the total organic carbon content. Anthropogenic changes of the soils are effective to DOM release via changing quality of soil organic matter. Long dry periods and large water fluxes can further increase DOM release. The effects of soil organic matter can be disguised in soils with a high DOM retention capacity (high CEC, high content of exchangeable bases, Fe_ox and Fe_d). Then adsorption and precipitation determine DOM release from the topsoil and contribute to a decrease of DOM release.     

Bereitstellung von van-Genuchten-Parametern zur Charakterisierung der hydraulischen Bodeneigenschaften

Providing the Parameters of Unsaturated Soil Hydraulic Functions on the Basis of Soil Texture, Bulk Density and Type of Horizon The hydraulic conductivity function can be described by the van Genuchten equation, whereby its parameters are estimated from typical water retention data of soil types and textural classes. The value of saturated hydraulic conductivity can be derived from tables (e.g. Kartieranleitung, 1982) in case measured data are lacking. Especially in well structured or sandy soils saturated conductivity may differ by 1…2 orders of magnitude. This will lead to a shift of the conductivity function. But nevertheless for the first approximation of fluxes in soils such parameters can be used. Thus, soil dependent values of groundwater recharge and pollution can be roughly quantified.     

Einfluß 85jähriger differenzierter organischer und mineralischer Düngung auf Bodeneigenschaften im Statischen Versuch Bad Lauchstädt

Influence from a 85-year differentiated organic manuring and mineral fertilization on soil fertility in the static experiment at Bad Lauchstädt The results of the static experiment started on chernozem from loess at Bad Lauchstädt in 1902 are used to demonstrate the influence of differentiated organic manuring (no manuring, 20 t and 30 t ha^?1 of farmyard manure) and mineral fertilization (NPK, NP, NK, N, PK, no fertilization) on the organic matter and nutrient contents in soil. After 85 years the content of organic C (C) in the topsoil was higher by 0, 5% after organic and mineral fertilization than after mineral fertilization. Exclusive mineral fertilization (NPK) increased the C-contents in soil by 0, 2% than without fertilization. Farmyard manure considerably reduced nutrient deficiency, which is due to plots without mineral fertilization. This holds especially true for potassium and phosphorus deficiencies. With rising pH value the Mn content in the soil diminished.