Schwermetalle im Boden eines Klärschlamm-Versuchsfeldes

Heavy metals in soil of a sewage sludge experimental field The total amounts of Zn, Cd, Pb, Cu, Cr and Ni were determined in different depths of soils which have obtained sewage sludges in amounts between 180 and 1620 dt dry matter/ha. The elements Zn, Cd. Pb and Cu have been most enriched in the first twenty cm of the soils. The contents of Zn, Cd and Pb in the depth of 40–60 cm also showed a significant increase. The treshold values for Zn and Cd in soils were almost attained respectivly slightly exceeded in the first twenty cm of the soil which has obtained 1440 dt dry matter sewage sludge per ha.     

Validierung eines 2-Regionen-Modells zur Simulation des Stofftransportes im Boden anhand von Laborsäulen- und Feldversuchen

Validation of a 2-domain-model for the simulation of solute transfer in soils by laboratory and field experiments The simulation of water and solute transfer in the unsaturated zone on the basis of the classical convective dispersive model gives dissatisfactory results in many cases. Especially in the zone of evapotranspiration the observed penetration depths of surface-applied chemicals often exceed calculated values. This has been attributed to preferential flow in domains with accelerated flow. The aim of the investigations presented here was to extend the conventional theory of solute transfer in order to enable improved model predictions without introducing too much complexity to the model which might reduce its applicability. The mobile-immobile-concept of Coats and Smith (1964) was chosen to extend the model FLOTRA (Wagner et al., 1992), which is based on the convective dispersive approach. The model parameters additionally needed by the model are the immobile water content θ_im and the solute transfer coefficient α. The applicability of the model was tested on the basis of several laboratory and field experiments. It is shown, that with the mobile-immobile-approach modeling results of water and solute transfer in the top soil layers, which are most important in view of soil and groundwater protection, were improved compared to the calculations with the classical convective dispersive model.     

Korrelationen von Enzymaktivitäten im Boden

Correlations of Enzyme-Activities in Soil Enzyme-activities often have been used as indicators of the biological state of soil. In this connection some questions may be posed: Which enzyme is the best indicator of biological activities in soil, what is the relationship of enzyme-activities to other ecological parameters and what is the interdependency between different enzymes? To answer these questions we measured activities of amylase, catalase, invertase, pectinase, urease, xylanase and cellulase at nine alpine and subalpine sites. Furthermore the CO₂-evolution, contens of nitrogen, carbon, organic matter, the soil density, total bacterial number and water capacity were determined. With these data correlation coefficients were calculated. The best relationships were found between cellulase-xylanase and amylase-invertase activities (Table 1). While catalase and pectinase are in the middle range, urease shows relatively low values. There are highly significant correlations between enzyme-activities and the content of nitrogen, carbon, organic matter, soil density or the CO₂-evolution (number of samples used for calculations was 68). Almost no correlations were found with total bacterial count (Table 2). For these calculations 34 samples of each parameter were used. To prove that the lower number of samples is not the reason for low correlation coefficients we computed data of 17 samples (Table 3). The water capacity is depending on soil density and content of organic matter and the correlations are in the same range (Comparison Table 1 and 3). This means that 17 samples of each parameter are enough for these calculations. Enzyme-activities proof therefore to be good indicators of the biological state of soil. It is inappropriate to characterise biological activities of soil by total bacterial counts only.     

Umsatz im Boden und Ertragswirkung rohphosphathaltiger Düngemittel

Turnover in soil and yield response of phosphate rock containing fertilizers Solubility of phosphate rocks is the better the higher the carbonate substitution in the given phosphate rock type. From the soil factors, pH is of importance. At soil pH < 5 phosphate rocks are fairly soluble and their yield effect equals that of fully processed fertilizers. In a soil pH range from 5 to 7, pH does not play such a decisive role as has been assumed. Other soil factors such as H⁺ buffer power of soil, Ca²⁺ and particularly the phosphate concentration in the soil solution are equally relevant for phosphate rock dissolution. The evaluation of numerous field experiments provided evidence that in the above cited pH range fully processed fertilizer phosphates are superior to phosphate rock containing fertilizers with regard to phosphate uptake, yield formation, and phosphate recovery. Also the residual effect of rock phosphate is poorer than that of fully processed phosphate fertilizers. There is some evidence that phosphate rocks show a relatively good response on deep rooting soils which allow a vigorous root growth and on soils with a sufficiently high level of soil moisture. In a soil pH range > 5 rock phosphate containing fertilizer are not suitable for maintenance fertilization, since under such conditions the phosphate concentration in the soil solution is relatively high thus suppressing the dissolution of phosphate rock.     

N-Umsatz von verschiedenem Pflanzenmaterial im Boden in Gefäß- und Feldversuchen

Turnover of nitrogen of different plant material in the soil in pot and field trials In pot and field trials, effects of various plant materials like green rape, sugar beet leaves, potato foliage, straw of wheat, maize, or field beans, on the turnover of N in the soil (mineralization, N_min-concentrations, NO₃-leaching) and on yield and N uptake by some crops was tested in relation to mineral N fertilizer application. In both experiments, widely corresponding results were obtained: Irrespective of the N contents of the plant material, biological immobilization of N always was combined with beginning mineralization (pot trial: decrease of NO₃ leaching in late fall). Green rape (C/N = 12/1) showed already after 4 weeks in the field trial a marked net mineralization (N_min) of 20–30% of the added nitrogen which was quantitatively reflected in higher removals of N. Beet leaves (C/N = 20/1) were decomposed at a much slower rate in combination with an increase in N removals of subsequent crops by 6-20 % depending on the rate of mineral fertilizer application. All types of straw (CM = 57-8611) and potato foliage (CM = 73/1) caused a marked biological immobilization of N which resulted in reduced N removals depending on turnover rate (potato foliage: fast, wheat straw: slow) and N contents of the organic material. Different plant residues (straw, leaves) were applicated on a harvested field with cereal to test comparatively one part of the total value of different preceding crops; at onset of vegetation the N_min-contents in soil, depending on the climatic conditions during the non-growing season for mineralization, were analyzed.     

Einfluß variierter Temperatur und Feuchte auf mikrobielle Aktivitäten im Boden unter Laborbedingungen

Influence of varied soil temperature and moisture on microbial activities under laboratory conditions Under laboratory conditions the influence of temperature (10°C, 20°C, fluctuation from 5° to 30°C within 12 h with additional freezing for 3 days) and soil moisture (30%, 60% w.h.c., remoistening to 60% for 1 week) on several microbial activities was investigated. The biomass-related, glucose-induced short-term respiration and the dehydrogenase activity (TTC reduction) were higher at 10°C in most cases as compared to 20°C. Independent of freezing fluctuating temperature caused the lowest activities. The nitrogen mineralization (including nitrification), however, was affected in the opposite way. No marked influences were observed with β-glucosidase, arylsulfatase, and alkaline phosphatase. In the sandy loam nearly no effects of the soil moisture occurred and in the loamy sand especially the dehydrogenase activity was higher at 30% w.h.c., whereas the nitrogen mineralization was lower. From the results it can be concluded, that ecological conditions favouring mineralization without substrate addition may even reduce microbial biomass by decomposition.     

Abbau und biozide Wirkung von Pflanzenschutz-und Schädlingsbekämpfungsmitteln im Boden am Beispiel von Kelevan

Degradation and biocide effect of chemical plant protecting agents and pesticides in soils by the example of the insecticide Kelevan By the example of the insecticide Kelevan it is proved that by means of a combined test plan degradation and biocide effect of chemical plant protecting agents and pesticides in soils can be tested simultaneously. For this test two different test soils as described in leaflet No. 36 of the Biologische Bundesanstalt (BBA), Braunschweig, are each divided in test samples of about 200 g dry matter. To answer the question whether besides the biotic an abiotic degradation of Kelevan and its primary subsequent products takes place in top soil, too, one part of the soil samples was sterilized by overheated steam. Afterwards these and the non-sterilized soil samples were treated with known amounts of Kelevan[cage-U-¹⁴C] and in accordance to leaflet No. 36 of the BBA stored in the dark at 22°U65% r. h. or under field conditions for different periods. To investigate the effect of Kelevan and its metabolites on microorganisms in top soil, further soil samples were treated with increasing amounts of Kelevan and also stored for different periods. At the end of storage periods on an average W,2 % of applicated radioactivities were recovered in the soil samples with Kelevan[cage-U-¹⁴C]. Whereas readioactivities of sterilized soil samples were nearly quantitatively extractable, increasing radioactivity amounts were held back under the same extraction conditions by the native soil samples, which were present as organic residue components of Kelevan(cagc-U-¹⁴C) and not as ¹⁴C-containing carbonate. During degradation, in both test soils as well under laboratory conditions as under field conditions, about one third of Kelevan[cage-U-¹⁴C] was transferred within 30 months via Kelevan acid[cage-U-¹⁴C] to Chlordecon[cage-U-¹⁴C] and about two thirds were transferred into various unknown ¹⁴C-labelled degradation products. The results of microbiological investigation prove that microorganisms were evidently neither selected nor decimated in both test soils by Kelevan and its degradation products.     

Atmung eines Bodens im Gemüsebau zu Beginn der Vegetationsperiode

Respiration of a soil used for vegetable crops at the beginning of the vegetation period Soil respiration was measured with a new portable soil respiration system (PP Systems, Hitchin, England) in vegetable plots in the greenhouse and field near Bonn from January to May 1996 with the following results:

• 1 The equipment proved suitable for the purpose over a wide range of temperatures.
• 2 Soil respiration ranged from less than 26 mg CO₂ in winter, 30–180 mg CO₂ in spring to 700 mg CO₂ m^?2 h^?1 in summer with large variations.
• 3 The largest soil respiration was recorded from peat-based commercial potting compost with small variations between measurements.
• 4 The Q₁₀ was 2,5 (±0,6) in the field for temperatures between 5–25°C.
• 5 The rate of soil respiration was affected by soil cultivation with the effect declining with temperature: Ploughing, which unveiled cold and produced a coarse soil surface, reduced soil respiration, whereas soil respiration was increased by fine soil cultivation.
• 6 In vegetable plots, soil respired 6–12 kg in cold (4°C), 40–50 kg CO₂ in cool (14°C) conditions in April and 170–210 kg CO₂/ha and 24 hours in warm (27°C) weather.

     

Auswirkungen der Gamma-Bestrahlung und Pasteurisierung von Klärschlamm auf seine mikrobiellen Eigenschaften und die Mineralisierung im Boden

Effect of γ-irradiation and pasteurization of sewage sludge to the microbiological properties and the mineralization in soil Hygienic aspects of sewage sludge application in agricultural practice are of increasing importance. Because parasites are extremely sensitive to γ-irradiation a dose of 300 krad is equivalent to pasteurization. The total bacteria count of the sewage sludge is reduced by this dosage by 90 to 99%. Enzymic activity is reduced after radiation at a rate of about 39%. Especially amylase, catalase, and alkaline phosphatase are extremely sensitive to irradiation. Mineralization studies of sewage sludge with different pretreatments in different soil types indicated no significant differences.     

Dicyandiamidabbau im Boden in Abhängigkeit von der Temperatur

Effect of temperature on the breakdown of dicyandiamide in the soil The breakdown of dicyandiamide in a soil (sandy silty loam, pH 6.2, 0.13 % N) was investigated in relation to temperature. 1. The rate of conversion of dicyandiamide (DCD) (20 mg DCD-N/100 g soil) to guanylurea increased with rising temperature (10°–90°C). After 20 days, 14–100 % of the added DCD was metabolized. Small amounts of DCD (0.67 resp. 1.34 mg DCD-N/100 g soil) were broken down completely within 20–80 days at 8°–20°C. 2. Guanylurea was transformed to guanidine and then to ammonium. Increasing temperature in the region of 10° and 30°C accelerated the transformation. At higher temperatures (up to 70°C) an accumulation of guanidine occurred.     

Der Einfluß agrochemischer Substanzen auf den Stroh- und Zelluloseabbau im Boden

The influence of agrochemical compounds on the decomposition of straw and cellulose in soil Supplementary to earlier investigations the decay of large amounts of straw-material with normal quantities of pesticides and normal amounts of straw-material with large quantities of pesticides was proved in a gasanalytical instrument and in pot-experiments. At the same time the straw-decay was tested in pot-experiments. The soil used in these pots has been untreated or treated for several years with different kinds of plant-Protecting-solutions. Finally there was made a test about the decay cellulose (KOZOVA 1963) with the same and different investigation materials. The results are as follows: 1. The use of plant-protection in wheat does not diminish the decay of straw even if the double quantity of straw treated with a medium-quantity of pesticides is added and normal quantities of straw treated with high quantities of pesticides are added to the soil. 2. Agricultural soils, which are cultivated for many years by using pesticides, do not show less straw-decay. 3. The decay of pure cellulose in the laboratory tested by the method of Kozova (1963) was diminished in soils, which had been treated for many years with herbicides and herbicides added with other plant-protection-means. This restriction seems to depend on unfavorable food-conditions for microorganisms eating cellulose in a soil without weed, since the direct dipping of cellulose in herbicid-liquid is not causing any decay-restriction. 4. On the other hand the direct sprinkling of the cellulose-filter-discs with fungicid-solutions of normal concentration diminished the decay strongly. However the decay was not restricted under field-conditions. This seems to be due to the fact that in the growing plants the fungicides have been transformed to a large extend and only small amounts could reach the soil.     

Umsatz von 15N markiertem Nitratstickstoff im Boden in Abhängigkeit von Strohdüngung und Bodenfeuchte

Turnover of ¹⁵N labelled nitrate nitrogen in soil as related to straw application and soil moisture In incubation experiments the effect of straw application on the turnover of ¹⁵N labelled nitrate has been studied at two soil moisture levels (brown podzolic soil). High ¹⁵N losses were found at the high soil moisture level. These losses are supposed to originate from denitrification. At both soil moisture levels straw application reduced significantly the ¹⁵N losses. Straw application resulted in a remarkable decrease of the ¹⁵NO₃ content in the soil and promoted the incorporation of ¹⁵N into the organic soil fraction. The incorporation of ¹⁵N into α-amino N and particularly into the rest hydrolyzable-N fraction was favoured by straw, while the incorporation into the amide-N fraction was hampered. Exhaustive cropping (Lolium multiflorum and Sinapis alba) on the soil incubated before with ¹⁵N, showed that the ¹⁵N incorporated into the organic fraction was poorly available. Thus straw application resulted in significant yield depression. It is assumed that the fraction of the rest hydrolyzable N is hardly available to plants.     

Einfluß unterschiedlicher Düngung auf pH,N, C und die Gehalte an CAL-extrahierbarem K und P im Boden

Influence of different fertilization on pH, N, C and CAL-extractable K and P in the soil The influence of different fertilization (mineral fertilizer, different kinds and quantities of farmyard manure and biocompost, horn meal) on soil properties was studied during 8 years of cultivation. The plots were planted and harvested as practised under local farming conditions. The pH of the non-fertilized plots decreased from 5.84 to 5.69, while it was increased by fertilization with farmyard manure or biocompost. N_t in the soil was not influenced by different fertilization. C_t was increased by high biocompost application, stayed constant on the other fertilized plots but decreased on the nonfertilized plots from 1.08 to 0.99%. Without fertilization, plant available nutrients were diminished from 7.3 to 4.3 mg P(CAL) 100 g^?1 and from 22.5 to 13.9 mg K(CAL) 100 g^?1. However, if the plots were fertilized with mineral or organic fertilizer, the nutrient content remained on the initial level. Storing farmyard manure under roof or covering with straw or polyethylene sheet did not affect the criteria of soil studied.     

Einfluß der N-Düngung von Apfelkulturen auf Nitratgehalte im Boden,stickstoffhaltige Reservestoffe im Baum und Ertrag

Effect of N-fertilization in apple orchards on soil nitrate contents, nitrogenous reserves in the tree, and crop yield It should be investigated how nitrate supply affects crop yields and incorporation and mobilization of nitrogenous reserves with Golden Delicious' apple trees on M 7 and M 9, and whether N fertilizer needs are influenced by N reserves in the trees. Two trials were carried out in 1981–1983. In the first one on al loess soil increasing N levels (0, 40, 80, 120 kg N/ha) were applied. In the second one, on a podsolic sandy soil, N was applied either in spring and/or in August (0/0, 80/0, 40/40, 0/80 kg N/ha). N fertilizers were applied to the herbicide strips only. Both orchards were in their best cropping age. Soil nitrate contents were mainly influenced by N-fertilization. Precipitation and drip irrigation caused translocation of nitrate and leaching from the soil layer investigated (0–90 cm). Thus, on the sandy soil almost no nitrate was left in spring, whereas on the loess soil various amounts of nitrate were still available in the subsoil depending on N fertilization in the preciding year. In plots where N fertilization was at optimum, the soil nitrate contents varied between 65 and 130 kg N per hectare herbicide strip over the main growing season (May–August). In the bark N reserves were mainly proteins, but almost equal amounts of protein and soluble N were found in the wood. N reserves were incorporated into the bark mainly between October and December, but even earlier than September in the wood. They were mobilized from April through July. Arginine was stored in the wood in considerably higher amounts than in the bark. Asparagine contents showed a sharp increase immediately after blossom time, particularly in the bark. There was almost no significant influence of the different fertilizer patterns on incorporation and mobilization of nitrogenous compounds. The N-reserves had no effect on crop weight. Highest crop yields were obtained whenever at least 40 kg N/ha were applied in spring. Additional N supply in August did neither increase incorporation of N-reserves nor crop yields. The nitrogenous reserves in the trees can be ignored in estimating N-fertilizer needs. On the other hand, the soil nitrate contents at bud break in April should be taken into account.