bluuebunny/crossref_metadata_2025 huggingface dataset:
The maize root system in situ: Evaluation of structure and capability of utilization of phytate and inorganic soil phosphates
Authors: Beck Erwin , Fußeder Anton , Kraus Michael
Published: February 2007

The dependence of the morphology of the maize (Zea mays L.) seminal root system on physical, chemical and biotic parameters was investigated with pot cultures in quartz sand and in a natural loamy sand soil. Low O2‐supply to the soil resulted in a substantially smaller root biomass despite a relative increase in total root length. Reduced N‐supply also stimulated root length growth, but also enhanced the formation of laterals. The presence of soil microorganisms, in comparison to sterile cultures, resulted in a reduced length of the main roots, and the production of slender laterals with a decreased root hair density. Generally, the structural variability of laterals in response to different growth conditions was much more pronounced than that of the main roots.

A major part of the work reported here was dedicated to a detailed study of phosphate (P) acquisition by the maize root system under field conditions. Radioactive labelling of the roots and radioautography of soil cores revealed the in situ distribution pattern of the maize root system. Controlled labelling of the soil with radioactive phosphate allowed the documentation of the development and replenishment of the phosphate depletion zone around roots. Finally, the longevity and phosphate uptake activity of the different parts and tissues of the primary root system of maize was examined by electron microscopy and tracer studies including pulse chase experiments. From these studies the phosphate‐acquiring strategy of the maize root system appears as follows: The capability of P uptake decreases in the order: root hairs, 1st order laterals, 2nd order laterals, main root. The life‐spans of the components of the maize root system increase by the sequence: root hairs, laterals, main root. Inorganic P uptake, therefore, mainly occurs during the first weeks of root development. Dying back of the root occurs in an ordered manner resulting in a relocation of stored P predominantly into the main root cortex. Furthermore, it could be shown that competition for P between roots of the same or of adjacent maize and/or lupin plants virtually does not occur in situ.

The utilization of phytate‐P was studied with 14C/32P‐labelled Camyo‐inositol‐hexaphosphate supplied to maize plants grown in sterile quartz sand or in hydroponic cultures. The ratio of P‐ and C‐uptake as well as the incidence of phytate hydrolysis products in the rooting medium indicated the capability of maize roots to acquire P from phytate by enzymatic hydrolysis. This was confirmed by enzyme studies of the root tissues. A specific hydrolyzing enzyme (phytase; molecular weight 51 kD) could be detected in the cell wall of the root, especially in the root tip, which initiates phytate dephosphorylation. Further breakdown is presumably accomplished by monophosphoric phosphohydrolases.
Phosphorus Efficiency of Buckwheat (Fagopyrum esculentum)
Authors: Amann Christine , Amberger Anton
Published: February 2007

The ability of buckwheat (Fagopyrum esculentum) roots to acquire phosphorus (P) was characterized by investigating P uptake, morphological features, and chemical changes in the rhizosphere.

Over a range of nutrient solution P concentrations (5–500 μmol · L−1), maximum shoot growth was achieved with a P supply between 5 and 100 μmol · L−1. Root weight and root length, as well as length and frequency of root hairs, were higher at low P levels. Root surface and the root surface/shoot dry weight ratio reached high values.

Though P uptake rates were only moderate (0.15 pmol · cm−1 root · sec−1), shoot P concentrations were high (1.8% of dry weight with 100 μM P) predominantly being inorganic (80%). Phosphorus efficiency was characterized by a high specific absorption rate (810 mmol P · kg−1 root dry wt · d−1) rather than by an efficient utilization for dry weight production.

Root exudates of low‐P plants had lower pH values than exudates of high‐P plants and increased the solubility of FePO4 and MnO2 to a greater extent. Amounts of exuded organic acids and phenolics were low and could not account for the observed solubilization of FePO4 and MnO2.

Enhanced hydrolysis of glucose‐6‐phosphate by exudates from low‐P plants was due to an increased “soluble” acid phosphatase activity, and root surface phosphatase activity was also slightly enhanced with P deficiency. In the rhizosphere soil of buckwheat, some depletion of organic P forms was observed, and in pot trials with quartz sand, buckwheat utilized glucose‐ 6‐phosphate as a P source at the same rate as inorganic P.
Role of root‐induced changes in the rhizosphere for iron acquisition in higher plants
Authors: Marschner Horst , Treeby Michael , Römheld Volker
Published: February 2007

Plants can mobilize iron (Fe) in the rhizosphere by non‐specific and specific (adaptive) mechanisms. Non‐specific mechanisms are, for example, rhizosphere acidification related to high cation‐anion uptake ratios, or citric acid excretion. The specific mechanisms are root responses to Fe deficiency and can be classified into two different strategies. The Strategy I is typical for dicots and monocots except for grasses (graminaceous species) and is characterized by increased plasma membrane‐bound reductase activity, enhanced net excretion of protons and enhanced release of reducing compounds, mainly phenolics. The reductase activity is stimulated by low pH, and with supply of FeIII chelates, ferric reduction at the plasma membrane takes place prior to uptake. In contrast, in graminaceous species (Strategy II) these root responses are absent, but enhancement of release of FeIII chelating compounds ‐ phytosiderophores ‐ takes place. These phytosiderophores are very efficient in mobilizing FeIII from artificially prepared sparingly soluble inorganic compounds (e.g. FeIII hydroxide) and from calcareous soils. The ferrated phytosiderophores are taken up by grasses at rates 102 to 103 times higher than Fe supplied either as synthetic chelate or microbial siderophores (e.g. ferrioxamine B), indicating a specific membrane transport system for ferrated phytosiderophores in roots of grasses. In calcareous soils phytosiderophores not only mobilize Fe, but also Zn, Mn, and Cu by chelation. However, only the FeIII phytosiderophores are taken up preferentially by Fe deficient grasses. The ecological advantages and disadvantages of Strategy I and Strategy II for Fe acquisition from calcareous soils are discussed.
Effect of zinc deficiency in wheat on the release of zinc and iron mobilizing root exudates
Authors: Zhang Fusuo , Römheld Volker , Marschner Horst
Published: February 2007

The effect of Zn deficiency in wheat (Triticum aestivum L. cv. Ares) on the release of Zn mobilizing root exudates was studied in nutrient solution. Compared to Zn sufficient plants, Zn deficient plants had higher root and lower shoot dry weights. After visual Zn deficiency symptoms in leaves appeared (15–17 day old plants) there was a severalfold increase in the release of root exudates efficient at mobilizing Zn from either a selective cation exchanger (Zn‐chelite) or a calcareous soil. The release of these root exudates by Zn deficient plants followed a distinct diurnal rhythm with a maximum between 2 and 8 h after the onset of light. Re‐supply of Zn to deficient plants depressed the release of Zn mobilizing root exudates within 12 h to about 50%‐, and after 72 h to the level of the control plants (Zn sufficient plants).

The root exudates of Zn deficient wheat plants were equally effective at mobilizing Fe from freshly precipitated FeIII hydroxide as Zn from Zn‐chelite. Furthermore, root exudates from Fe deficient wheat plants mobilized Zn from Zn‐chelite, as well as Fe from FeIII hydroxide. Purification of the root exudates and identification by HPLC indicated that under Zn as well as under Fe deficiency, wheat roots of the cv. Ares released the phytosiderophore 2′‐deoxymugineic acid. Additional experiments with barley (Hordeum vulgare L. cv. Europa) showed that in this species another phytosiderophore (epi‐3‐hydroxymugineic acid) was released under both Zn and Fe deficiencies.

These results demonstrate that the enhanced release of phytosiderophores by roots of grasses is not a response mechanism specific for Fe deficiency, but also occurs under Zn deficiency. The ecological relevance of enhanced release of phytosiderophore also under Zn deficiency is discussed.
Carbon Turnover in the Rhizosphere
Authors: Helal Helal M. , Sauerbeck Dieter
Published: February 2007

Considerable progress has been made during the last decade towards understanding and quantifying the input and turnover of plant carbon in the rhizosphere. This was made possible by the development (partially by the authors) and combination of appropriate new methods, such as:

–homogeneous labelling of whole plants with 14C

–distinction between root and microbial respiration

–separation of soil zones of known distances from the roots

–determination of microbial soil biomass.

These methods were applied to study the following aspects:

–release of organic plant carbon into the soil by growing roots

–utilization of this plant carbon by the microbial biomass in the rhizosphere

–related influence on the turnover of soil organic matter, and

–spatial range of such root influence in the soil.

About 19% of the total photosynthetic production of the investigated plants was released into the rhizosphere as organic material. Most of this (15%) was transformed by the rhizosphere microorganisms into CO2, while only a small fraction (4%) remained in the soil, mainly as microbial cells (2.5%). As a result, microbial rhizosphere biomass increased considerably. Relative to the organic C‐input, however, the incorporation of root derived carbon by the microbial biomass was remarkably low (13%).

Along with the increase in microbial rhizosphere biomass, the presence of plant roots also enhanced the decomposition of soil organic matter and affected soil aggregate stability. Root carbon and root influences were even detected up to 20 mm away from the roots. This may be partially attributed to the contribution of root derived volatiles. Accordingly, both the actual volume of the rhizosphere and its metabolic significance is greater than what has so far been assumed. Possible interactions involving root, soil and microbial carbon are discussed.
Interaction of maize roots and rhizosphere microorganisms
Authors: Schönwitz Roswitha , Ziegler Hubert
Published: February 2007

The interaction between the roots of Zea mays L. and its rhizosphere microflora was studied in nutrient solution with respect to two exemplary aspects ‐ water soluble vitamins and the four most frequent carbohydrates.

The exudation of vitamins and sugars into the medium is increased in a solid substrate (glass‐ballotini simulating soil structure) in comparison with nutrient solution only. The amounts of vitamins released (1 to 421 ng per plant) are high enough for a pronounced influence on the rhizosphere microflora to be expected. However, the microbial population feeding on the exudates has very simple nutritional demands. In spite of appreciable amounts of vitamins found in the inoculated nutrient solution, the growth of vitamin requiring species is not stimulated compared to the soil population.

The roots are mostly inhabited by shorter rods and occasionally by actinomycete‐like filaments. The percentage of the root area covered by its microflora, assuming a monolayer, is 4% in the root region where root hairs are just emerging, 7% in the root hair zone and 20% in the oldest part of the roots, 10 mm below the grain.

In the presence of rhizosphere microorganisms, root dry weight is lower than that of axenically grown plants because the diameter of the primary root is diminished. In addition, the vitamin and sugar content of the root is affected by rhizosphere microorganisms. The results can be interpreted as an indication that phytohormones may participate in interactions between roots and bacteria.
Plant, Microbial and Soil Factors, Determining Nitrogen Fixation in the Rhizosphere
Authors: Werner Dietrich , Berggold Regine , Jaeger Dieter , Krotzky Arno , Papen Hans , Schenk Sigrid , Thierfelder Heidemarie
Published: February 2007

A genotype effect on associative (rhizosphere) N2‐fixation was observed with two cultivars of Sorghum bicolor (nutans) with a maximum rate of 8 μmol C2H4 · h−1 · plant−1 in one genotype compared to 0.9 μmol in the other. Characteristics of the high fixing genotype were a reduced transpiration rate, a lower number of stomata and increased root exudate production per gram root dry weight with higher concentration of dicarboxylic acids. The bacterial rhizosphere composition revealed a three times higher number of N2‐fixing bacteria, a tenfold reduction of actinomycetes and a threefold reduction of Arthrobacter associated with the high fixing cultivar compared to the low fixing genotype. From these and other plant rhizospheres two new nitrogen fixing bacteria, Pseudomonas stutzeri and Erwinia herbicola, were characterized. With the N2‐fixing bacteria Azospirillum brasilense and Klebsiella pneumoniae an enhancement of specific nitrogenase activity by aromatic compounds, for example phenolics, the herbicide alachlor and the insecticide carbofuran was demonstrated. An oscillating nitrogenase activity in Azospirillum brasilense under microaerobic conditions was found, resulting from an encystation and deencystation under those conditions. Experiments with wheat roots demonstrated that reduced oxygen tensions, essential for a maximum rhizosphere N2‐fixation, reduced root growth significantly and altered the N‐metabolism of the roots.
Gas‐chromatographic Separation of Organic Acids and Electrophoretic Determination of Phosphatases from VA Mycorrhizal Roots
Authors: Fabig BjöRn , Vielhauer Konrad , Moawad Atef M. , Achtnich Wolfram
Published: February 2007

A report is given on methods for separation and identification of organic acids, including phenolic acids, and on the determination of phosphatases from VA mycorrhizal (VAM) roots.

For gas‐chromatographic preparation of the samples containing the organic acids silylation and methylation were tested, as well as various solvents and silylating reagents. Columns of different polarity were examined for their separation properties. Gas‐ chromatographic separation of the acids was incomplete on the packed column OV 7. With the capillary column PVMS 54 separation was much better, but improvements are still needed.

Mycorrhiza‐specific phosphatases (MSP) appearing as three bands were found by electrophoresis with porosity‐gradient gels in mycorrhizal roots of Allium, Sorghum and Eupatorium plants. In these three species each MSP was located at the same position. Inoculated onion roots enzymatically digested with cellulase and pectinase showed no root‐specific phosphatases, but still revealed MSP. Further improvements in electrophoresis techniques are being investigated.
Distribution pattern of total lipids and lipid fractions in forest humus
Authors: Ziegler Frank , Zech Wolfgang
Published: February 2007

Mull, moder, and mor humus profiles were investigated for their total lipid contents and the behaviour of lipid‐phosphorus and of five neutral lipid classes identified by HPTLC. The quantitative distribution of total and neutral lipids among the humus types is, besides by natural differences between the various parent litter materials, mainly controlled by soil physicochemical properties. In particular strongly acidic conditions, i.e. conditions corresponding to a reduced biological activity, inhibit significantly the decomposition of lipid compounds in (moder and) mor humus. A feature of the lipid depth functions is the input of microbial and root litter‐derived lipid material in the fermentation layers and a considerable lipid accumulation in the A horizons, probably at least partly due to mechanical transport processes. Phospholipids show no distinct variation dependent on the humus type, as far as the organic layers are concerned. But obviously, lipid‐P in the mineral, soil is closely correlated with, and therefore is a valuable measure for, the overall biological activity increasing from mor to moder and mull humus.
Bodenanalytische Diagnose von K‐ und Mg‐Mangel in Fichtenbeständen (Picea abies Karst.)
Authors: Liu Jin‐Chen , Trüby Peter
Published: February 2007

Für 44 Fichtenbestände Südwestdeutschlands wurden signifikante Beziehungen zwischen den Gehalten an austauschbarem K, Mg, Ca und Al im Boden und den entsprechenden Gehalten der Nadeln nachgewiesen. Enge Zusammenhänge ergaben sich außerdem zwischen dem austauschbaren Mg im Boden und dem Vergilbungsgrad älterer Nadeln. Anhand der in der Nadelanalyse gebräuchlichen Grenzwerte wurden kritische Gehalte an austauschbaren Nährelementen im Boden abgeleitet. Für Mg liegt der Bereich akuten Mangels bei Gehalten < 2 μeq/g Boden. Die Bodenanalyse kann hierfür alternativ zur Nadelanalyse eingesetzt werden. Für K ist eine ähnlich scharfe Abgrenzung des Mangelbereichs nicht möglich. Bei Gehalten < 2 μeq/g Boden ist jedoch ein Auftreten akuten K‐Mangels wahrscheinlich. Es kann aber auch bei höheren K‐Gehalten (2–5 μeq/g Boden) K‐Mangel auftreten. Für eine Diagnose von K‐Mangel stellt die Bodenanalyse daher lediglich eine Orientierungshilfe dar.
Effect of temperature on the fragmentation of humic acids in alkaline solutions
Authors: Khairy Ahmed H. , Ziechmann Wolfgang
Published: February 2007

The fragmentation of one synthetic and four soil humic acids was studied in solutions of sodium hydroxide (pH 13) at different temperature between 0 and 90°C. The dissolved parts of the initial amounts of humic acids decreased to a minimum with the increase in temperature from 0 to 10°C. The fragmentation in this region was a function of both; temperature and concentration. At 15–20°C all of the initial amounts of humic acids were dissolved. The rate of fragmentation increased rapidly between 15 and 20°C and later slowed down between 20 and 40°C. This was due to the reaggregation of the particles of the produced hymatomelanic acids into particles of similar solubilities as those of the residual nonfragmented parts of the humic acids. This reaggregation took place probably through the formation of hydrophobic bonds. The fragmentation increased at temperatures above 40°C, and reached a maximum between 50 and 70°C depending on the type of the humic acid. The decline in fragmentation at temperatures higher than those corresponding to the maxima is most probably due to chemical reactions, in which the fragmentation products especially fulvic acids recombine together at about 60°C. Importance of these results in analytical methods of extraction and characterisation of humic acids is discussed.
Direct determination of potassium‐calcium activity ratio in soils with two ion‐selective electrodes. II. Interactions of potassium and calcium ions with soils
Authors: Yu T. R. , Beyme B. , Richter J.
Published: February 2007

The interactions of potassium and calcium ions with two variable charge soils and one constant charge soil were examined by measuring the pK‐0.5pCa value with two ion‐selective electrodes, together with measurements of single ion activities. The constant charge soil showed a much higher preference for calcium relative to potassium than the variable charge soils. The relative affinities of potassium, calcium, sodium and aluminum ions with exchange sites were not constant, but were a function of surface properties of the soil. pH affected the pK‐0.5pCa value in both the variable charge soil and the constant charge soil. The strong competition of aluminum ions for exchange sites was the major cause of the higher preference of soils for calcium ions relative to potassium ions at low pH. The pK‐0.5pCa value was always smaller in sulfate systems than in chloride systems, with the difference more distinct in variable charge soils. In addition to an initial fast reaction, some potassium ions were immobilized at later times, even for the highly weathered variable charge soil.
Influence of various fertilization on the mineralogical composition of clay fractions in long‐term field experiments
Authors: Leinweber Peter , Reuter Gerhard
Published: February 2007

Soil samples from several long‐term experiments in the German Democratic Republic (GDR) were taken from plots with and without K‐supply. The fine, medium and coarse clay fractions were isolated using ultrasonic dispersion and sedimentation techniques and then investigated by x‐ray. Comparisons between the mineralogical compositions found and the results of x‐ray analyses of clay fractions from untreated Ah‐horizons of the same sites point to accelerated mineral transformations in unfertilized plots. Reductions in the illite contents are proved using the x‐ray diffraction diagrams. In connection with the question of the transformational products of this accelerated illite weathering, a new possibility for evaluation by curve‐fitting Lp‐corrected x‐ray diffraction diagrams was tested on one example. The degradation of the illites is partly accompanied with drastic reductions in the amounts of Ca‐lactate soluble and adsorbed K. Organic fertilization with 10 to 15 tons of farmyard manure per hectare per year prevented these negative mineralogical changes.
Further evidence concerning the importance of soil air‐filled porosity, soil organic matter and plants for denitrification
Authors: Prade Klaus , Trolldenier Günter
Published: February 2007

Previous experiments with artificially compacted mixtures of soils derived from two horizons of a mollic luvisol have shown the significance of air‐filled porosity, organic C content and presence of roots for denitrification. To test the validity of these results for natural conditions undisturbed soil cores were taken during tillering from fields cropped to wheat. Denitrification was measured at different constant soil moisture levels. The denitrification rates were in agreement with those found in the earlier experiments. In the light of the new data the previously established regression function parameters were only slightly modified. This confirmed our former findings that the effect of low air‐filled porosity and high soil organic C on denitrification was greater in cropped than in uncropped soil.
Organism specific denitrification in samples of an Udifluvent with different nitrate concentrations
Authors: Munch Jean Charles
Published: February 2007

Model experiments were carried out to elucidate the interrelations between the ratio of N2O to N2 gases released by the denitrification of different amounts of nitrate on the one hand and of the activity of bacterial populations on the other hand. Soil samples amended with 2 different amounts of nitrate were sterilized, inoculated with either their natural bacterial population or by strains of denitrifying soil bacteria and incubated anaerobically in gas‐tight flasks. Results of these experiments are:

The composition of denitrification gases (N2O, NO, N2) was exclusively caused by the species of the active microorganism in the soil: the nitrate concentration only influenced the denitrification rate, but not the N2O/N2 ratio of each organism.

The amounts of nitrite formed transitorily were also specific for the type of organism. These amounts of nitrite influenced neither the emission of N2O (and NO) nor the ratio of N2O to N2 or of N2O to consumption of nitrate.

The N2O formation depended primarily on the microbial soil population and secondly on the nitrate concentration in correlation with the type of the denitrifying population.
Zur Verwendung von Gesteinsmehlen in der Landwirtschaft. II. Wirkung von Gesteinsmehlen als Bodenverbesserungsmittel
Authors: Blum W. E. H. , Herbinger B. , Mentler A. , Ottner F. , Pollak M. , Unger E. , Wenzel W. W.
Published: February 2007

Fünf Gesteinsmehle unterschiedlicher chemisch ‐ mineralogischer Zusammensetzung wurden bezüglich ihrer Eignung als Bodenverbesserungsmittel in der Landwirtschaft untersucht.

Die höchste Kationenaustauschkapazität (KAK) weist das Mehl aus smectitreicher vulkanischer Asche auf. Die höchste Säureneutralisationskapazität (SNK) wurde für carbonathaltige Mehle ermittelt. Mehle aus silikatischen Gesteinen (Granit, Basalt) wiesen für beide Parameter die geringsten Werte auf.

Durch jahrzehntelange Aufbringung von 1000 kg carbonatischem bzw. tonmineralischem Gesteinsmehl je ha und Jahr könnte bestenfalls unter extremen Bodenbedingungen (humusarme Sandböden) eine nennenswerte Erhöhung der SNK bzw. der KAK erzielt werden. Siliciumreiche Mehle, z.B. aus Granit (“Urgesteinsmehl”), wären selbst in diesem Fall wirkungslos.
Phosphat‐Düngerbedarf von Getreide und Zuckerrüben im südniedersächsischen Lößgebiet
Authors: Baumgärtel Gerhard
Published: February 2007

In den Jahren 1984 bis 1986 wurden 105 P‐Düngungsversuche zu Winterweizen, Wintergerste und Zuckerrüben auf tiefgründigen Lößböden in Südniedersachsen durchgeführt. Die mineralische P‐Düngung mit Triple‐phosphat variierte zwischen 0 und 250 kg P2O5/ha. Die P‐Gehalte (H2O) der Versuchsböden lagen zwischen 6 und 38 und betrugen im Mittel 18 ± 8 mg P/kg. Neben der P‐Wasser‐Methode wurden folgende Methoden angewandt: CAL, DL, NaHCO3 und EUF.

In keinem Versuch wurden die Erträge von Getreide und Zuckerrüben durch P‐Düngung erhöht, obwohl die Flächen 1986 bereits im dritten Jahr keine P‐Düngung erhalten hatten. Die P‐Gehalte der Pflanzen (0.3–0.6% P i. TS) wiesen ebenfalls auf eine ausreichende P‐Ernährung hin. Auch nach einer Erhöhung der P‐Gehalte um durchschnittlich 20 mg P‐H2O/kg Boden durch eine Düngergabe von 1500 kg P2O5/ha kam es in den folgenden Jahren zu keiner Ertragssteigerung. Für diese Standorte wird deshalb bei einer Fruchtfolge aus Zuckerrüben und 2x Getreide ab 5 mg P‐H2O/kg bzw. 5 mg P2O5‐CAL/100 g Boden eine P‐Düngung in Höhe der P‐Abfuhr vom Feld empfohlen. Dies entspricht für die 3‐jährige Fruchtfolge ca. 180 kg P2O5/ha, wenn die Ernterückstände auf dem Feld verbleiben. Bei P‐Gehalten von über ca. 12–14 mg P‐H2O/kg Boden kann die P‐Düngung unterhalb des Entzuges liegen oder ausgesetzt werden.
Eine Infiltrationsmethode zur Messung der hydraulischen Leitfähigkeit im Felde
Authors: Gäth St. , Frede H.‐G. , Meyer B.
Published: February 2007

Zur Messung gesättigter hydraulischer Leitfähigkeiten im Felde wird eine Infiltrationsmethode, die von Reynolds und Elrick (1985) entwickelt wurde, vorgestellt und mit der Labor‐Stechzylinder‐Methode verglichen.
Eine Methode zur Ermittelung der wasserspannungsabhängigen Änderung des Sauerstoffpartialdruckes und der Sauerstoffdiffusion in einzelnen Bodenaggregaten
Authors: Zausig J. , Hell U. , Horn R.
Published: February 2007

In ausreichend belüfteten, ungesättigten schluffigen und tonigen Böden können anaerobe Zonen auftreten, die dem Aggregatbereich zugeordnet werden. Betrachtet man den Sauerstoffhaushalt des Bodens, so sind deshalb auch Untersuchungen auf der Ebene des Einzelaggregates im wassergesättigten und ungesättigten Zustand notwendig. Deshalb wurde der Sauerstoffpartialdruck in einzelnen Bodenaggregaten unterschiedlicher Textur als Funktion des Entwässerungsgrades kontinuierlich gemessen. Hierzu wurde eine O2‐sensitive Mikroelektrode entwickelt, die bei einem Spitzendurchmesser von 0.5 mm hinreichend stabil für die Messung in sandigen Böden ist.

Einzelne wassergesättigte Aggregate wurden mit je einer pO2‐Elektrode und einem Mikrotensiometer (Spitzendurchmesser < 0.5 mm) bestückt und das Matrixpotential sowie der Sauerstoffpartialdruck im Aggregat während der Entwässerung kontinuierlich aufgezeichnet. Es zeigt sich, daß anfangs anaerobe Aggregate in Abhängigkeit von Textur und Struktur bei unterschiedlichen Wasserspannungen belüftet werden. In tonreiche Polyeder eines Pelosol‐Gleyes erfolgt der Lufteintritt erst bei wesentlich höheren Entwässerungsgraden als in die lehmigen Prismen eines Braunen Auenbodens, die bereits bei Überschreitung eines Entwässerungsgrades von 150 hPa eine deutliche Erhöhung des Sauerstoffpartialdruckes aufweisen. Entsprechend niedrig sind die relativen scheinbaren Diffusionskoeffizienten Ds/Do. So werden für die feinkörnig texturierten Aggregate des Pelosol‐Gleyes selbst bei Matrixpotentialen < −200 hPa noch Werte für Ds/Do von 1 · 10−3 gemessen.
Eigenschaften und Entstehung der Humuskörper typischer Wald‐ und Ackerböden Schleswig‐Holsteins
Authors: Beyer Lothar , Blume Hans‐Peter
Published: February 2007

Die Humuskörper von Oberhang‐Parabraunerden und Unterhang‐Podsolen (Wald, konventionelle und biologische Ackernutzung) wurden naßchemisch mittels Streu‐ und Humus‐Stoffgruppenanalyse, sowie makro‐ und mikromorphologisch untersucht. Ein geringes Nährstoffangebot und mangelnde Bioturbation hemmen in den Waldböden den Abbau der Streu. Humusakkumulation und Huminstoffverlagerung sind im Podsol stärker als in der Parabraunerde. Unter Ackernutzung hat die Humusmenge bei konventioneller Nutzung stärker abgenommen. Organische Düngung fördert die Bioturbation und begünstigt den Abbau der Streustoffe.
Feldversuche zur Nmin‐Dynamik eines stauwasserbeeinflußten Plaggeneschs unter Winterzwischenfrüchten nach Anbau von Körnerleguminosen (Vicia faba L.)
Authors: Raderschall Rainer , Gebhardt Harald
Published: February 2007

In den Jahren 1987/88 wurde ein Feldversuch mit dem Ziel durchgeführt, drei verschiedene Zwischenfrüchte (Wintergerste, Winterrübsen und Welsches Weidelgras) auf ihre Eignung hin zu untersuchen, die residualen Nmin‐Mengen nach dem Anbau von Körnerleguminosen (Vicia faba L.) in ihrem oberirdischen Aufwuchs zu speichern und damit vor einer Auswaschung über Winter zu bewahren. Im Verlauf der Untersuchung wurde weiter die zeitliche Nmin‐Dynamik unter den Zwischenfrüchten im Vergleich zur Brache beobachtet. Als Versuchsboden diente ein grauer Podsol‐Plaggenesch mit Staunässeneigung.

Die Zwischenfrüchte konnten von Herbst 1987 bis Frühjahr 1988 23–52 kg N/ha in ihrer oberirdischen Pflanzenmasse akkumulieren. Infolge der Staunässeneigung des Bodens konnte im Verlauf der Untersuchung eine außergewöhnlich hohe NH4+‐N‐Dominanz von 92–100% nachgewiesen werden. Außerdem ergaben sich Hinweise auf eine NH4+‐N‐Verlagerung von 0–30 in 30–60 cm Bodentiefe sowie auf Denitrifikationsphänomene.
A Method for Determining Phosphate Diffusion Coefficients by Bulk Diffusion in Soil
Authors: Kaselowsky Joachim , Bhadoria Pratapbhanu B. S. , Claassen Norbert , Jungk Albrecht
Published: February 2007

A method is described for the determination of phosphate diffusion coefficients by bulk diffusion in soil using the concentration distance method. Two soil blocks only differing in phosphate concentration are brought into contact. After a diffusion period of two weeks the soil blocks are separated, frozen in liquid nitrogen and sliced into layers about 0.02 cm thick by means of a refrigerated microtome. The soil samples are extracted with 4 N HCl, a procedure which fully recovers the added amount of fertilizer P and thus includes the total amount of P that diffuses from one soil block to the other. A concentration distance profile for P and a calculation of the P diffusion coefficient is presented.
Die Interpretation von K/Ca‐Austauschkurven mit Hilfe einer einfachen GAPON‐Gleichung
Authors: Fischer Walter R.
Published: February 2007

K/Ca‐Austauschkurven unterschiedlicher Böden lassen sich durch eine GAPON‐Gleichung beschreiben, deren Koeffizienten iterativ an die Meßwerte angepaßt werden. Die sich ergebenden Werte für das „labile Kalium”︁ stimmen sehr gut mit den Gehalten an austauschbarem K überein, während nur etwa 5–25% der Kationenaustauschkapazität erfaßt werden.
Organischer Kohlenstoff im Niederschlag nordrhein‐westfälischer Fichten‐ und Buchenbestände
Authors: Bartels Ulrich
Published: February 2007

In der Zeit von November 1984 und Oktober 1988 wurde in Nordrhein‐Westfalen an vier Waldstandorten der organisch gebundene Kohlenstoff im Niederschlagswasser durch Messung der UV‐Absorption (254 nm) abgeschätzt. Im Freilandregen werden etwa 10kg/ha deponiert, in den Waldniederschlägen von Buche und Fichte die 4– bzw. 7–fache Menge. Der Jahresgang zeigt Maxima während der Vegetationszeit, besonders zwischen Mai und Juli.
Untersuchung zur Anwendbarkeit von Sorptionskoeffizienten für die Simulation der Verlagerung von 2, 4, 5‐T und LAS in Böden
Authors: Schernewski Gerald , Matthies Michael , Litz Norbert
Published: February 2007

Die Anwendbarkeit von Sorptionskoeffizienten zur Prognose der Verlagerung von 2, 4, 5‐Trichlorphenoxyessigsäure (2, 4, 5‐T) und von n‐Dodecylbenzolsulfonat (LAS) im Feld (Winter) wurde für vier Bodentypen mittels des mathematischen Simulationsmodells EXSOL untersucht. Für 2, 4, 5‐T sind in Schüttelversuchen bestimmte, lineare Gleichgewichts‐Sorptionskoeffizienten KD nicht geeignet, wohingegen KD‐Werte aus Perkolationsstudien an Bodensäulen gut auf das Freiland übertragbare Ergebnisse liefern. Für LAS ergibt ein Boden‐Lösungsverhältnis von 1:2 und eine Schüttelzeit von 4 Stunden Sorptionskoeffizienten, die in etwa die tatsächliche Verlagerungssituation im Feld widerspiegeln.
Nitrogen losses from agricultural soils through denitrification ‐ a critical evaluation
Authors: Rheinbaben Wolfgang Von
Published: February 2007

The direct measurement of gaseous N losses through denitrification requires a complicated methodology. Mostly alternative approaches are used to estimate these losses for a particular arable or grassland site. Evaluation of the literature shows that N losses as a result of denitrification ‐ determined by the 15N balance, by direct mass spectrometry of N2 + N2O and by the acetylene inhibition method, respectively ‐ may reach about 10 % of the fertilizer input on agriculturally used sites without irrigation or organic manure addition. The estimation of denitrification losses can be improved by considering site‐specific parameters affecting denitrification like total carbon content, pH, time of fertilizer application as well as soil temperature and soil moisture conditions.
Modelling Multi‐Ion Transport in Saturated Soil and Parameter Estimation. I: Theory
Authors: Wenlin Chen , Yunzhu Li , Van Ploeg Rienk R. Der
Published: February 2007

A coupled convective‐dispersive model was developed to describe the solute movement of four ionic species (Ca2+, Na+, SC42 and CI) through soil. The model considers precipitation and dissolution of calcium sulfate as well as cation exchange or adsorption during steady‐state water flow in saturated soil columns. With the model hypothetical miscible displacement experiments were carried out. The governing partial differential equations were solved numerically with an implicit Crank‐Nicolson scheme. With the use of obtained results the effect of various model parameters on the shape of the calculated breakthrough curves was investigated. It was found that the processes of dissolution and precipitation, cation exchange or adsorption do have a definite influence on the shape of the breakthrough curves.
Blei‐und Cadmiumgehalt von Buchenwurzeln (Fagus silvatica L.) in Stammfuß‐ und Zwischenstammbereichen
Authors: Turcsányi GáBor , Fangmeier Andreas
Published: February 2007

In einem ca. 150‐jährigen Buchenbestand wurde eine signifikante Bodenversauerung im Bereich der Stammfüße festgestellt. Buchenwurzeln aus diesem Bereich weisen erhöhte Bleigehalte im Vergleich zum Zwischenstammbereich auf; die Cadmiumgehalte werden jedoch nicht beeinflußt. Die Bodengehalte beider Bereiche unterscheiden sich weder für Blei noch für Cadmium.
Simultaneous Determination of Low Molecular Weight Organic Acids in Soil Solution by Ion Chromatography
Authors: Elkhatib E. A.
Published: February 2007

A simple and precise ion chromatographic (IC) method for determination of citric, malonic, succinic, formic, acetic and propionic acids in soil solution was developed. It requires a prior cleanup to the soil solution samples by anion exchange resin (AG1‐X8) and determination of organic acids using a Dionex Model 2010i IC. Separation of organic acids by IC permitted their quantitation by conductivity measurements, following suppression of background conductivity by a fiber suppressor. A high degree of precision was achieved in the quantitation of organic acids studied. With the IC method, citric, malonic, succinic, formic, acetic and propionic acids can be determined simultaneously in 16 min. A single operator can analyze about 30 samples in a single working day.
Amidase and urease activity in soil as affected by sludge, salinity and wetting and drying cycles
Authors: Gomah Abdel Hakeem M. , Al Nahidh Saad I. , Amer Hussien A.
Published: February 2007

Three incubation experiments were carried out to assess the effect of different levels of sludge, salinity and of different wetting and drying cycles on amidase and urease activity in a calcareous silt loam soil. Both amidase and urease activities were largely increased with the increase in the amount of sludge applied. The addition of NH4+ ‐ N with sludge slightly reduced both activities. Addition of increasing amounts of a 1:1 NaCl: CaCl2 salt mixture increasingly reduced the soil activities of amidase and urease. This effect was less severe in sludge amended soil. The data also showed that drying of either unamended or sludge amended soil cause a marked drop in amidase and urease activity. Rewetting increased both enzyme activities.
Interactions of some nematicides with Azospirillum lipoferum and the growth of Zea maize
Authors: Fayez M.
Published: February 2007

The possible interaction of four nematicides (Terbufos, Carbofuran, Fenamiphos, and Aldicarb) with Azospirillum lipoferum and growth of two Zea maize cultivars was studied in a greenhouse experiment. Application of nematicides, Fenamiphos in particular, resulted in higher plant length, dry matter production and N yield over the nematicide‐untreated plants. Azospirillum spp. inoculation stimulated the growth of nematicide‐treated Z. maize. Among the nematicides used, Carbofuran and Aldicarb inhibited the nitrogenase activity on plant roots more seriously than Fenamiphos and Terbufos. Generally, the inhibition percentages in acetylene reducing activity in soil of inoculated treatments were lower (14.4 ‐ 61.8%) than those reported for the uninoculated ones (21.4 ‐ 73.9%). Soil, irrespective of treatment, regained a part of its normal N2‐ase activity with time. Field concentrations of all nematicides showed different inhibitory effects on N2‐ase activity of Azospirillum spp. in culture medium, such effects increased with increased doses (10‐ and 100‐ fold) and incubation periods (10 days). The contribution of Azospirillum spp. to the N economy of soil treated with nematicides is discussed.
The effect of water movement on the transport of dicyandiamide, ammonium and urea in unsaturated soils
Authors: Abdel‐Sabour Mamdouh F. , Massoud Massoud A. , Baveye Philippe
Published: February 2007

A laboratory experiment was conducted to investigate the relative mobility of dicyandiamide (DCD) and jointly applied ammoniacal salts or urea in three different soils of lower Egypt, and to determine the extent to which DCD separates from N‐fertilizer in unsaturated soil undergoing leaching.

The experimental results suggest that, under conditions of water flow, DCD is readily separated from NH4+ but parts from urea to a far lesser extent. The large difference in mobility between DCD and NH4+ should severely limit the effectiveness of DCD as a nitrification inhibitor in the three soils considered when applied in conjunction with ammoniacal salts. In two out of three cases, the situation is similarly unfavorable in the case of joint DCD and urea application. However, the observation that DCD, in a low CEC sandy loam, moves within the soil solution at a slightly lower rate than urea suggests that joint application with urea would keep at least part of the DCD in contact with the NH4+ ions and, therefore, would preserve some of the effectiveness of DCD under leaching conditions in this soil.
Ureaform as a Slow Release Fertilizer: A Review
Authors: Alexander Alvin , Helm Hans‐Ulrich
Published: February 2007

Ureaform (UF) is a condensation product between urea and formaldehyde consisting of short chains from methylene‐diurea to tetramethylenepentaurea. The rate of nitrogen release is mainly related to chain solubility. The mineralization of UF is governed by microbial activity. A wide spectrum of organisms is known to be involved. The degradation is mainly influenced by the biological fertility of the soil, temperature and to a limited degree by moisture, whereas pH and particle size have no pronounced effect. The importance of the activity index (A.I.) as a unit to evaluate the quality of an UF product and the versatility of the UF system in general are discussed. More recent trial results with UF products show the beneficial effects of the particular kind of slow release nitrogen fertilizer in meeting needs for improved fertility management and reduced pollution of drainage waters.
High rates of domestic sewage sludge on a calcareous soil and their effect on wheat growth using a pot experiment
Authors: Rawajfih Zahir , Gharaibeh Sameh
Published: February 2007

A pot experiment was carried out to explore the use of high loading rates of domestic sewage sludge from Jeresh (Jordan) on a calcareous soil. Sludge was mixed with soil in volume ratios of 1:8, 1:6, 1:4, 1:2, 1:1, 2:1, and 4:1 with the unamended soil as a control. Wheat (Triticum durumL.) was grown in the pots for 60 days. The addition of sludge at a ratio of 1:8 increased wheat growth significantly; 1:6 ratio resulted in better growth than the control, although the increase was not significant at the 5% probability level. Other ratios suppressed wheat growth. The analysis of sludge‐soil mixtures indicated that the addition of sludge increased the extractable P, K, Fe, Zn, Mn, and Cu in the mixtures. The addition of sludge to soil increased N and P in wheat tissue to optimum levels, but decreased K content. Iron and Zinc increased in wheat tissue due to the addition of sludge to soil, however Mn and Cu were not much affected.
A method for determining Michaelis‐Menten kinetic parameters of nutrient uptake for plants growing in soil
Authors: Seeling Björn , Claassen Norbert
Published: February 2007

The relationship between nutrient influx (In) and solution concentration at the root surface (Clo) has not yet been determined for roots growing in soil because of difficulties in measuring Clo. Corn was grown on two soils with 12 and 21% clay. Each soil had five K levels ranging from low to very high. Potassium influx (In) was determined from K uptake between two harvests and root length. Clo was then calculated from the average soil solution concentration and In by assuming that diffusion is the main transport mechanism for K to the root. Potassium influx plotted against Clo showed a saturation curve, typical of a Michaelis‐Menten kinetic relationship. The Michaelis‐Menten uptake parameters, maximum influx (Imax) and Michaelis constant (Km), were obtained by the “Hanes” plot. There was close agreement, without lack of fit, between calculated and observed data. The proposed procedure therefore appears to be suitable for estimating the uptake kinetics of roots growing in soil. Requirements for applications of the method are discussed.
Einfluß von Bikarbonat auf die subzelluläre Verteilung von blatt‐ und wurzelappliziertem Eisen bei Sonnenblumen (Helianthus annuus L.)
Authors: Dockendorf Hans , Höfner Werner
Published: February 2007

18 Tage alte Sonnenblumenpflanzen wurden unter Klimakammerbedingungen 9 Tage (bis zum Auftreten von Chlorose) in Nährlösung kultiviert. Anschließend wurden die Fe‐Gehalte in Wurzel und Sproß und die subzelluläre Fe‐Verteilung im Cytoplasma der jungen Blätter bestimmt.

In den Bikarbonatvarianten mit Fe in der Nährlösung hatten die jungen Blätter deutlich verminderte Gehalte an Chlorophyll und Fe. Die subzelluläre Fe‐Verteilung in diesen Blättern blieb aber unverändert, allerdings mit absolut niedrigen Fe‐ und Proteingehalten der Chloroplastenfraktion im Vergleich zur Kontrolle ohne Bikarbonat.

Junge Blätter der Pflanzen in der Bikarbonatvariante ohne Fe in der Nährlösung hatten nach Fe‐Blattapplikation unveränderte Chlorophyllund höhere Fe‐Gehalte, und in den im Saccharose‐Gradienten getrennten subzellulären Fraktionen höhere Gehalte an Fe und Protein im Vergleich zur Kontrolle.

Eine Inaktivierung des Fe im Blatt durch Bikarbonat im Nährmedium ließ sich somit nicht nachweisen. Da die Konzentrationen an gelöstem Fe in der Nährlösung durch Bikarbonat kaum vermindert wurden, kann der Fe‐Mangel der Pflanzen dieser Variante nicht durch ein unzureichendes Fe‐Angebot, sondern nur durch eine Störung des Fe‐Aufnahmevorgangs verursacht sein.

Blattappliziertes Fe wurde durch Bikarbonat in der Nährlösung weder in seiner Aufnahme, noch in seiner physiologischen Wirksamkeit beeinflußt, was ebenfalls fär einen primären Bikarbonateffekt im Wurzelbereich spricht. Obwohl das Cytoplasma‐pH in Blättern der Blattapplikationsvariante nicht signifikant verändert wurde, ist ein lokaler Einfluß der applizierten Fe‐EDTA‐Lösung (pH 5,1) auf den pH‐Wert des Apoplasten und damit auf die Fe‐Mobilität nicht völlig auszuschließen.
Effect of plant growth regulators on paddy rice
Authors: Nian Lu Shen , Cong Luo Ru , Hong Nong Fong , Sheng Ye Shuany , Höfner W.
Published: February 2007

The effect of 4 plant growth regulators (FOR), BAS 111, DCiB, EL 500, Terpal C, on growth and yield of paddy rice was studied in field experiments in Southern China. PGR‐application was practiced by seed soaking, root dipping at transplanting and leaf spraying at elongation stage respectively, using a 2, 5 × 10−5 M concentration of the particular PGR.

There was only a minor stem reducing effect of the PGRs at the early stage of tillering, most pronounced after seed soaking. But at harvest time all trials reached the same plant height. In spite of this, seed soaking with EL 500, BAS 111 and Terpal C increased grain yield between 10 and 13 % in the first crop. The results are discussed in connection with a direct PGR‐effect on the generative phase of rice.
Einfluß von NPK auf die Biomasseproduktion und Stickstoffbindung der stengelknöllchenbildenden Gründüngungsleguminosen Sesbania rostrata und Aeschynomene afraspera im Naßreisanbau
Authors: Becker Mathias , Ladha Jagdish K. , Ottow Johannes C. G.
Published: February 2007

Die Anwendung der stengelknöllchenbildenden Leguminosen Sesbania rostrata und Aeschynomene afraspera als Gründüngung (GD) für Naßreis verspricht in der low‐input Landwirtschaft der Tropen gute Einsatzmöglichkeiten. Der Erfolg dieser Leguminosen als GD wird vor allem von der Biomassebildung und der Stickstoffbindung auf Böden mit geringer N, P und K‐Verfügbarkeit abhängen, weil ihrem Einsatz dort primär Bedeutung zukommt. Infolgedessen wurde der Einfluß von N‐, P‐ und K‐Düngern auf Wachstum und Stickstoffbindung (Azetylen‐Reduktions‐Test) der betreffenden Leguminosen und auf den Ertrag von Naßreis (IR64) in Modell‐ und Feldversuchen auf den Philippinen untersucht.

P‐ und K‐Dünger stimulierten sowohl das Wachstum als auch die N2‐Bindung von S. rostrata und A. afraspera significant. Der N‐Ertrag einer PK‐gedüngten S. rostrata lag 40% über dem der ungedüngten GD.

Im Gegensatz zu Wurzelknöllchen wurde die potentielle N2‐Bindung (ARA) der Stengelknöllchen beider Leguminosen durch mineralischen N (Harnstoff) nicht reprimiert, sondern sogar gefördert, was zu einer Erhöhung des N‐Ertrages führte. In allen Fällen erhöhte eine Gründüngung signifikant den Ertrag von Naßreis.

Durch Einbeziehung einer relativ geringen mineralischen NPK‐Düngung in ein auf GD basierendes Naßreisbausystem lassen sich die Biomassebildung und Stickstoffbindung von S. rostrata und A. afraspera und der Reisertrag (IR64) nach GD erhöhen.