Mikrobielle Aktivitäten in landwirtschaftlich genutzten Böden Niedersachsens. II. Bodencharakterisierung anhand mikrobieller Stoffwechselaktivitäten

Microbial activity of arable soils in Lower Saxony, Germany. II. Soil characterization by microbial activities Field trials were carried out on six soil types in Lower Saxony and were supported by glasshouse and laboratory trials. Soils were sampled frequently to monitor biomass-related and overall microbial activities as well as the activity of soil enzymes. Similar soils showed comparable activity patterns. Crop plants and, especially, the herbicide ‘Flüssig Herbogil’ (dinoterb) affected some microbial functions. Activity patterns can be used in long-term trials to characterize soil types and agricultural practices. In addition, they may be useful in short-time trials to identify ecological and ecotoxicological effects.     

Stickstoffernährung und Al-Toxizität bei Buchenjungpflanzen. I: Entwicklung von Buchenjungpflanzen in Abhängigkeit von der Form der Stickstoffernährung und dem Aluminiumgehalt der Nährlösung

Nitrogen nutrition and Al toxicity with young beech plants. I: Development of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO₃- or NH₄-form. pH-changes of the solutions were either corrected to the initial pH of 4 after two days, or not corrected over a period of two weeks. Root growth of the beech seedlings was inhibited by Al. Reduction of root length and dry matter production was more severe if the plants were fed with ammonium nitrogen compared to nitrate nitrogen. Detrimental effect of Al on root growth was also influenced by the pH of the solution. NH₄-N-nutrition led to pH decrease and therefore to increased solubility and toxicity of aluminium. On the contrary, NO₃-N-nutrition weakened Al toxicity because of pH increase at the root surface and in the AFS. This led to an inactivation of Al in the form of insoluble hydroxy aluminium polymers. Compared to NO₃-N-nutrition NH₄-N promoted shoot growth. During 14 weeks no detrimental effect of Al on shoot growth was observed.     

Stickstoffernährung und Al-Toxizität bei Buchenjungpflanzen. II: Mineralstoffgehalte junger Buchen in Abhängigkeit von der Form der Stickstoffernährung und dem Al-Gehalt der Nährlösung

Nitrogen nutrition and Al toxicity with young beech plants. II: Mineral contents of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO₃ or NH₄-form. pH-changes of the solutions were either corrected to the initial pH of 4,0 after two days, or not corrected over a period of two weeks. The cation contents of the roots and shoots were greater if the nitrogen was supplied in NO₃-form. Increasing Al concentrations in the nutrient solutions led to an increase in Al contents and a decrease in Ca- and Mg-contents in roots and shoots.     

Einfluß langjähriger Gülledüngung auf den Nährstoffhaushalt des Bodens. 1. Mitteilung: N-Akkumulation und N-Nachlieferungsvermögen

Influence of long-term slurry application on soil nutrients. 1. N accumulation and N mineralization potential The influence of longterm slurry applications on the total N content, N fractions and N mobilization potential of the soil was investigated. The following results were obtained:

• – Application of high amounts of slurry over a long period of time resulted in higher total N contents not only in the upper soil layers but also in the layer 60–90 cm.
• – In two sites the higher total N contents are mainly resulting from higher contents of hydrolyzable organic N compounds and in one site of higher contents of non hydrolyzable organic N compounds.
• – The influence of the slurry application on the content of non exchangeable NH₄⁺ is depending on the K saturation of the clay minerals.
• – In incubation experiments N mobilization of the soils supplied with slurry was higher as compared to soils supplied with mineral fertilizer.
• – A highly significant correlation is existing between N mobilization and the content of hydrolyzable organic N compounds and the N_org fraction, determined by means of EUF, respectively.
• – The N_min content of the soils supplied with slurry was higher during the whole growing season.

     

Extraktion eines kupferbelasteten Bodens unter Verwendung eines aminosäurehaltigen Reststoffhydrolysats. 2. Elutionsdynamik und Bilanzierung der Aminosäuren nach kontinuierlichem Eintrag in Bodensäulen

Extraction of a copper contaminated soil material by the percolation of an amino acid containing residue hydrolysate. 2. Time course of amino acid elution and input/output balance of amino acids During 16 days an amino acid containing blood meal hydrolysate (amino acid concentration: 188 mMol·L^?1) was percolated through a column packed soil material (soil content per column: 4.1 kg dry weight, four parallels). The copper contaminated material (soil type: Typic Udifluvent, soil texture: sandy loam, loamy sand) was sampled from an area formerly used for cultivation of hop (Humulus lupus). Besides the investigation of the copper liberation the experiments aimed to determine the elution dynamic and input/output balance of amino acids (time span for amino acids balance 14 days). In total 11.7 L of hydrolysate, containing 2.2 Mol of amino acids, were introduced into each column. The mean amino acid output with the column effluent was 1.13 Mol. This corresponds to an elution degree of 51.2%, related to the sum of applicated amino acids, and to a mean substance specific elution degree of 48.4% reflecting the elution of 15 compounds. The substance specific elution ranged from 9.6% (serine) to 75.5% (valine). The highest concentrations of serine and threonine were determined in the effluents after two days, whereas the histidine concentration was highest at the last sampling. The differences in the percolation properties of the amino acids are discussed in terms of important retention and elimination processes (biodegradation, ad-/desorption, intercalation).     

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

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

Einfluß langjähriger Gülledüngung auf den Nährstoffhaushalt des Bodens. 2. Mitteilung: Bindung und Löslichkeitskriterien der Bodenphosphate

Influence of long-term slurry application on soil nutrients. 2. Fractions and solubility criteria of soil phosphorus Fractions and solubility criteria of soil phosphorus accumulated by long-term slurry application were investigated. The following results were obtained:

• – Slurry application mainly resulted in higher concents of inorganic phosphorus, especially Fe-Al-P, even in deeper soil layers.
• – The accumulation of inorganic phosphorus resulted in an increase of phosphorus availability in all conventional extraction methods used, as well as in higher phosphorus concentration of the soil solution.
• – In the upper soil layers of luvisols and in the deeper soil layers of diluvial sandy soils organic phosphorus was enriched, but did not significantly influence phosphorus intensity and delivery.
• – Compared to soils supplied with mineral fertilizers there are no particularities in phosphorus dynamics, from which differences in the interpretation of “available” phosphorus values with respect to phosphorus recommendation scales could be concluded.

     

Phosphordüngewirkung eisenhaltiger Klärschlämme

<?show $38#Bo;>Phosphorus fertilization effect of sewage sludges treated with iron compounds The result of waste water treatment with iron salts are sewage sludges with higher P but also Fe contents. The effect of such sludges on P availability in soils is not clear and was, therefore, compared with CaHPO₄ as a P mineral fertilizer. In experiments (Mitscherlich pots, 6 kg soil) two sandy soils (pH 4.3 and 4.9), two luvisols ( pH 6.3 and 7.2), a loess (13 % CaCO₃), and quartz sand all differing in their P status were treated with two sewage sludges which differed in their molar Fe:P ratios (sludge Gö: 1:0.3, sludge Sh: 1:1.2). For sludge Gö the P elimination had been carried out with FeSO₄ and the sludge was stabilized with FeCl₃ + Ca(OH)₂ (filter press). For sludge Sh P was eliminated by FeCl₃ in the aerobic basin. The first crop was maize (total shoot dry matter), the second red clover. In case of sludge Sh both crops took up in comparison to CaHPO₄ the same amount of P from all substrates with the exception of quartz sand. The effect of sludge Gö was quite different: from the neutral luvisol soils maize was able to take up only 64—82 % P and red clover 77—82 % P only as compared to CaHPO₄. On the sandy soils maize and red clover grew after sludge Gö as good or better than after CaHPO₄ application and P uptake was quite similar (83—106 %). This result was concomitant to an increase of pH values (from 4.3 to 4.9, 4.9 to 5.6, respectively). The negative efficiency of P uptake in heavy soils after application of sludge Gö resulted from an increase of P sorption and decrease of orthophosphate concentration in soil solution. This sludge contains a high proportion of iron hydroxides/oxides with free sorption sites for P. In future P elimination from waste water should be done without iron salts. At least during the process of conditioning no Fe salts should be used.<?show $6#>     

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.     

Schätzung der Denitrifikation in landwirtschaftlich genutzten Böden. I. Grundlagen

Estimating denitrification in agricultural soils: I. Basic assumptions Despite a common interest of soil scientists, groundwater hydrologists, agronomists, and climatologists in quantifying soil nitrogen losses through denitrification, these are often neglected when the nitrogen turnover of agricultural soils is modelled. This is the first of two papers describing a semi-quantitative denitrification model that has been derived from data collected from soils of a catchment area near Viersen in the Lower Rhine Valley in West Germany. A field study was conducted to study the soil environment of denitrifying microorganisms. The results of this study were used to evaluate the effect of soil water, soil air and soil temperature, of the amount and quality of the organic matter, and of the pH-value on denitrification. To this end an existing model to quantify denitrification was extended. Provided the seasonal nitrogen excess of a field is known, the model in its new form enables an estimation of the extent of field-specific denitrification rates. This paper describes the effects of the parameters under consideration on denitrification, the model components used to describe these parameters, and the development of the denitrification model.     

Maßstabsabhängige räumliche Variabilität mikrobieller Bodenkenngrößen in einem Buchenwald

Scale-dependent spatial variability of microbiological characteristics in soil of a beech forest The spatial variability of the microbial biomass content (C_mic), the microbial respiration rate (basal respiration) and the metabolic quotient (qCO₂) was analyzed in sandy Cambisols and Luvisols in a beech forest in Northern Germany. Highest variability of microbiological features and, thus, the distance of independent samples was around 10 m that is discussed with reference to spatial hierarchy. Structural changes between the 10 m and 50 m grid were suggested for the Ah horizon due to the break of correlations of C_mic content and the contents of C_org and plant-available Ca, Mg, K and N_t. The C_mic content correlated with the C_org content close to tree trunks and ecotones like borders of the forest and clearings. The qCO₂ did not generally increase with declining pH value. High H⁺ concentrations and C_org content in the litter layer near to the tree trunk indicated retarded microbial mineralization rates. High proportion of microorganisms that are resistant to low pH value and adjusted ro readily-degradable substrates seems to dominate in the soil close to the tree.