Verteilung der Wurzelsysteme von Zea mays L. und Lupinus luteus L. in Mischkultur im Hinblick auf die Konkurrenz um Phosphat und Kalium

Distribution of the root systems of Zea mays L. and Lupinus luteus L. in mixed cropping with respect to competition for phosphate and potassium The spatial distribution of the root systems of maize (tasselling stage) and lupins (late flowering stage) in mixed cropping was studied with respect to root competition for macronutrients in a sandy soil under field conditions by means of the radioautographic method. The greatest root densities were measured for both species in the upper 40 cm soil layer within a radius of 10 cm around the respective shoot. Whereas the root growth of the lupins was almost entirely restricted to this region of soil, the root system of maize was found to extend further than 10 cm horizontally. In order to evaluate a possible interspecific root competition for macronutrients such as P and K, particular attention was paid to the interpenetration of the root systems of the two plant species. However, only a weak mutual interpenetration of the root systems of adjacently (about 50 cm apart) grown maize and lupin plants could be observed. The in-situ separation patterns determined for the roots of maize and lupins labelled with ³²P and ³⁵S, respectively, did not indicate that any root competition between the two species for the immobile macronutrients P and K had taken place. However, it is to be expected that intraspecific competition, i. e. reduced uptake due to the overlapping of the depletion zones of P and K, took place both within the root systems of maize and lupin.     

Der Einfluß von Bodenart,Durchlüftung des Bodens,N-Ernährung und Rhizosphärenflora auf die Morphologie des seminalen Wurzelsystems von Mais

Influence of soil type, soil aeration, nitrogen supply and rhizosphere flora on the morphology of the seminal root system of maize The influence of the soil type (quartz sand – humous loamy sandy soil), soil aeration, nitrogen supply and rhizosphere flora on the morphology of the seminal root system of maize plants grown in pot culture was investigated. The morphological parameters of number, length, diameter and root hair formation (both length and density) of the main and the lateral roots were determined in addition to the total root length and number and the lateral root density. 1. The biomass production of the shoot and root system was nearly identical in both soils. The total root length growth, however, was enhanced in the sandy soil due to the stimulated formation of first order lateral roots. This increase was correlated with a decrease in the mean diameter and root hair length of the main and lateral roots. 2. A decreased O₂-supply to the soil resulted in a drastic reduction of root biomass, which was correlated, however, with a (relative) increase in total root length (due to the stimulation of the length growth of the first order lateral roots). The root hair length, on the other hand, was reduced under O₂-deficiency. 3. Reduced N-supply resulted in a decrease of the shoot/root-ratio with both substrates which could be ascribed to the enhanced formation and length of the first order lateral roots. 4. The presence of soil microorganisms in quartz sand culture resulted in a reduction of shoot biomass. In comparison with the sterile control culture the total length of the main roots was retarded, the main and lateral roots were more slender and root hair formation was reduced. 5. The experimental results show that the lateral root system demonstrates a significantly greater plasticity than does the main root system.     

Einfluß von Müllkompost und Eisenverbindungen auf die Eisen-, Zink- und Manganaufnahme von Sonnenblumen und Mais im Gefäßversuch

Influence of compost and Fe-compunds on the uptake of Fe, Zn and Mn by sunflower and maize in pot experiments The influence of compost and different iron compounds on the uptake of Fe, Zn and Mn from calcareous soils was investigated in a pot experiment using sunflower and maize. Regardless of the iron compounds applied, the addition of compost resulted in an increase of the Zn content in both plant species. The compost treatment without Fe, resulted in a lower Fe content in sunflower and maize. This effect was partly or completely counteracted by the addition of Fe compounds. Very high Zn contents were observed in the Fe – EDTA treatments. The Zn content was further increased when compost was also added. In treatments in which compost was omitted none of the Fe compounds applied increased the Fe content of the plants.     

Verteilung von grenzabständen auf bodenkarten und ermittlung von risikofunktionen

Distributions of boundary spacings were analysed for different soil maps (1:25000, 1:5000) by a statistical procedure. The distributions of boundary spacings are satisfactorily described by negative exponential functions. Therefore, connections between mean boundary spacings, sampling interval and the risk of missing boundaries can be evaluated, and it is shown, that the connection between sampling interval and risk of missing boundaries is landscape specific.This results can be used for planning soil survey, particularly for special survey activities.     

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 der Mineralstoffversorgung auf die Prädisposition von Phaseolus vulgaris gegen Colletotrichum lindemuthianum (Sacc. et Magn.) Br. et Cav. I. Wirkung verschiedener Nährstoffe und des Blattalters auf die Symptomausprägung

Influence of mineral nutrition on the predisposition of Phaseolus vulgaris against Colletrotrichum lindemuthianum (Sacc.et Magn.) Br.et Cav. I. Effects of different mineral nutrients and leaf-age on the disease severity 1. The N-concentration between 2–12 mMol N/I did hardly influence the disease, higher concentrations up to 52 mMol/I led to a severe disease increase. Potassium at concentrations of 5–10 mMol/I showed little effect on disease, higher concentrations up to 50 mMol also strongly increased the predisposition. 2. Calcium had a remarkable influence on symptom expression. Lower concentrations (1.15–0.25 mMol/I) increased the symptoms, higher concentrations up to 4.25 mMol/I reduced the disease, but only at a high disease level resulting from high N- or K-concentration. 3. The influences of Mg, P and Fe were of minor importance. 4. Usually, bean-leaves show resistance against C. lindermuthianum when the leaves are old. This is prevented by high N- and K-concentrations. 5. The change of predisposition related to the N- and K-concentration in the nutrient solution was confirmed with 3 additional bean varieties (‘Comtessa’ ‘Perry Marrow’, ‘Pizzaro’). No further increase of disease severity could be achieed with variety ‘Wavero’ which was generally very sensitive. 6. The monogenic resistance of incompatible combinations (‘Titan’/δ and ‘Titan’/λ) could not be changed with high N- or K-concentrations.     

Einfluß der VA-Mykorrhiza auf P-Aufnahme und Regenerationsfähigkeit von Mais (Zea Mais L.) unter Wasserstreß

Influence of the VA-Mycorrhiza on P uptake and recovery potential of corn (Zea mays L.) under water stress conditions In a seven week pot experiment the influence of the VA-Mycorrhiza on P uptake and water stress tolerance of corn was investigated. During the eight day water stress period the VAM-plants took up less phosphorus than the control plants. However, during the successive five day recovery period under a normal water regime the VAM-plants showed an increased root growth and an enhanced phosphorus uptake compared with the control plants. The free prolin concentration was lower in leaves of VAM-plants than in those of nonmycorrhizal plants at the end of the water stress period, pointing to a different water stress tolerance.     

Einfluß von Bikarbonat auf die subzelluläre Verteilung von blatt- und wurzelappliziertem Eisen bei Sonnenblumen (Helianthus annuus L.)

Influence of bicarbonate on the subcellular distribution of iron applied to roots or leaves of sunflower (Helianthus annuus L.) 18 days old sunflower seedlings were transferred and cultivated for 9 days ( untill chlorosis appeared) in nutrient solutions. After that Fe concentration of roots and shoots and the subcellular distribution of Fe in the cytoplasm of the young leaves was determined. Bicarbonate in the nutrient solution with Fe reduced the concentration of Fe and chlorophyll in the young leaves of the plants, also the concentration of Fe and protein in the chloroplast fraction of the cytoplasm, but the subcellular distribution for Fe remained unchanged compared with the control. Leaf spray with Fe-EDTA to plants in nutrient solution without Fe + bicarbonate resulted in higher Fe but unchanged chlorophyll concentrations in the young leaves, while the cytoplasm fractions of these leaves had higher concentrations of iron and protein compared with the control. An inactivation of leaf iron by bicarbonate in the nutrient medium could not be demonstrated. There was no significant lowering of the concentration of disolved Fe in the nutrient solution by bicarbonate, indicating a disturbance of Fe-up-take rather than an insufficient Fe-supply as a factor for iron chlorosis. The physiological activity of leaf applied Fe was not diminished by bicarbonate in the nutrient solution. This observation too points to a primary effect of bicarbonate in the root area. The pH of the cytoplasm from young leaves remained unchanged after leaf spraying with Fe-EDTA. In spite of this there might be a local effect of sprayed solution (with pH 5,1) on the pH of solutes in the apoplast, influencing the mobility of leaf applied Fe.     

Einfluss assoziativer rhizosphärenbakterien auf die äHrstoffaufnahme und den Ertrag von Mais

In mehrjährigen Feldversuchen (1990–1995) in Nordostdeutschland wurde der Einfluß selektierter assoziativer Rhizosphärenbakterien auf den Ertrag und die Nährstoffaufnahme bei Mais untersucht.

Der Trockenmasse‐ und Kolbenertrag zur Siloreife bzw. der Samenertrag wurde durch die Bakterienstämme Pseudomonas fluorescens (PsIA12), Agrobacterium rhizogenes (A1A4), Rhizobium trifolii (R39) und z.T. durch Stenotrophomonas maltophilia (PsIB2) in den Jahren 1990 bis 1995 auf lehmigen Sandböden wiederholt signifikant, auf sandigem Lehm zum Teil signifikant erhöht. Maissorten können unterschiedlich auf die Bakterieninokulation reagieren. Die Bakterien stimulierten insbesondere bei Jungpflanzen die Wurzelentwicklung und die Nährstoffaufnahme (N, P, K) aus dem Boden. Sie bildeten Phytohormone (Auxine und z.T. Cytokinine) und überlebten, auch unter Feldbedingungen, im Rhizosphärenraum von Mais während der gesamten Vegetation.     

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.     

Einfluß von Fe-und Mn-Mangel auf den Kationen-und Anionengehalt von Mais und Sonnenblumen

Effect of Fe-and Mn-deficiency on the cation and anion content of maize and sunflower. 1. In sandculture experiments with maize and sunflower the influence of Fe-and Mn-deficiency on the concentration of inorganic ions and organic acids in the plants was studied. 2. Fe-deficiency increased in both maize and sunflower plants the excess of cations (C-A) and the amount of organic acids (SOS). In sunflower this reaction was less intensive than in previous experiments with younger plants. 3. Mn-deficiency did not lead to the same clear reaction in both plant species as in the case of Fe-deficiency, although in the later harvestings (C-A)-and (SØ)-values of the deficient plants increased. 4. In both plant species the cultivars with higher susceptibility to Fe-chlorosis did not differ in their reaction on Fe-or Mn-deficiency from the normal cultivars. 5. A specific reaction of the plants on either Fe-or Mn-deficiency in respect to their ion concentration could not be confirmed.     

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.     

Die horizontale Verteilung von Radiocäsium im Waldboden unter Fichte und Buche

Horizontal distribution of radiocesium in forest soils under spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) The horizontal distribution of radiocesium in the soil under the canopy of several beeches and spruces was examined. At the base of spruces mean ¹³⁷Cs activities are about twice, and under beeches 5 to 15 times as high as under more distant parts of the canopy. Between 80 and 95% of the ¹³⁷Cs activity can be attributed to the Chernobyl fallout, the rest to the global fallout from weapons testing in the 1950s and 1960s. While the ¹³⁷Cs accumulation at the base of spruces can be explained by litter fall and remains of bark, the up to 30 times increased values at the base of beeches are explained by stemflow. Mean activity of radiocesium in the bark of spruce (0,62 Bq/g dry weight) is about twice as high as in the bark of a beech. This can be explained by considering that in contrast to beeches the ¹³⁷Cs activity in the soil under spruces is corresponding to some extend with the main rooting zone. Thus, we expect an increased uptake by the roots of this species and a subsequent transfer to the bark.     

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 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.     

Einfluß von Chelatoren auf die Calcium-Verlagerung im Sproß höherer Pflanzen

Influence of chelating agents on calcium translocation in the shoots of higher plants Using 28-day-old plants and shoots of bush beans as well as isolated haulms of barley taken from the field 24-hour experiments were carried out to investigate how equimolar additions of the chelating agents Na₂H₂ EDTA (EDTA) or citric acid to the ⁴⁵CaCl₂ uptake solution (0.5–1.0 mM/l) influenced Ca-translocation in the shoot. The following results were obtained:

• 1 If Ca²⁺ was taken up by the intact root system, equimolar additions of EDTA to the CaCl₂-uptake solution reduced Ca-uptake, and therefore the translocation of Ca to and within the shoot was also lowered.
• 2 Chelating agents favoured Ca-translocation in the shoots only when Ca-uptake as a chelate by the plasmalemma of the root cells was prevented using DNP or when the roots were by-passed by injecting chelates or by removing the roots themselves.
• 3 Additions of MgCl₂ (0.5 mM/l) or DNP (10^?5-10^?4 M/l) to the ⁴⁵CaCl₂ uptake solution (0.5 mM/l) of isolated shoots reduced the favourable effect of equimolar EDTA-levels on Ca-translocation because Mg²⁺ and DNP themselves increased Ca-translocation.
• 4 From the effects of Mg²⁺ and DNP it was concluded that the favourable influence of chelating agents on Ca-translocation within the shoot can be explained on the one hand by the reduction in adsorption of Ca²⁺ on negatively charged cell walls of the xylem and on the other hand by the diminished accumulation and precipitation of Ca in the xylem-surrounding tissue.
• 5 On the basis of the results obtained here, stem injections of chelating agents or treatments which influence the content of native chelating agents in the plants appear to be possible starting points for the improvement of Ca-translocation within the shoot.