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In order to investigate the long-term fate of the herbicide chloridazon and its polar metabolites desphenyl-chloridazon and methyl-desphenyl-chloridazon, a lysimeter experiment was conducted. The plant protection product Pyramin WG, which contains chloridazon, was applied to a weighable, monolithic lysimeter and a backfilled, gravitation lysimeter. Leachate, soil and maize samples were analyzed, and the data from the monolithic lysimeter was used to simulate the transport through the soil profile with the pesticide leaching model Pesticide Emission Assessment at Regional and Local scales (PEARL). Chloridazon rapidly degraded to desphenyl-chloridazon and methyl-desphenyl-chloridazon. In leachate, chloridazon was therefore detected at concentrations up to 3.5 μg L−1, whereas the metabolites desphenyl-chloridazon and methyl-desphenyl-chloridazon were present for more than 2 years at higher concentrations up to 24 and 6.1 μg L−1. The concentrations of chloridazon in soil decreased significantly with depth and time, whereas both metabolites increased up to 370 and 16 μg kg−1. The high concentrations, even 916 days after the application, clearly indicate a continuous downward migration and degradation in soil. In maize, chloridazon and purely the metabolite desphenyl-chloridazon were detected in leaves and stems. Desphenyl-chloridazon was additionally found in grains. It was noted that the design and setup of the two lysimeters lead to significant variations in terms of transformation rate, soil retention time and accumulation by plants. A comparison of the simulated results and the leaching rates measured from the monolithic lysimeter yielded adequate results for the metabolites, but rather poor correlation for chloridazon. The results obtained suggest persistence and high dispersion of chloridazon, and especially its metabolites, in leachate and soil. In maize, the migration in leaves and stems and the accumulation by grains might be relevant in terms of food security.

A 13 C natural abundance experiment including GC-c-IRMS analysis of phospholipid fatty acids (PLFAs) was conducted to assess the temporal dynamics of the soil microbial community and carbon incorporation during the mineralization of plant residues under the impact of heavy metals and acid rain. Maize straw was incorporated into (i) control soil, (ii) soil irrigated with acid rain, (iii) soil amended with heavy metal-polluted filter dust and (iv) soil with both, heavy metal and acid rain treatment, over a period of 74 weeks. The mineralization of maize straw carbon was significantly reduced by heavy metal impact. Reduced mineralization rate of the added carbon likely resulted from a reduction of the microbial biomass due to heavy metal stress, while the efficiency of 13 C incorporation into microbial PLFAs was hardly affected. Since acid rain did not significantly change soil pH, little impact on soil microorganisms and mineralization rate was found. Temporal dynamics of labelling of microbial PLFAs were different between bacterial and fungal PLFA biomarkers. Utilization of maize straw by bacterial PLFAs peaked immediately after the application (2 weeks), while labelling of the fungal biomarker 18:2 ω 6,9 was most pronounced 5 weeks after the application. In general, 13 C labelling of microbial PLFAs was closely linked to the amounts of maize carbon present in the soil. The distinct higher labelling of microbial PLFAs in the heavy metal-polluted soils 74 weeks after application indicated a large fraction of available maize straw carbon still present in the soil.

Summary The present study investigated the impact of long-term soil management on the metal retention capacity of soil. We examined the sorption behaviour of Cu, Cd and Zn in soils and in the various particle-size fractions of these soils, which had been amended with farmyard manure, mineral fertilizers or were fallow for 38 years in a long-term field experiment. The soils investigated contained different amounts and origins of organic matter and differed in soil pH, but the mineral phase showed less response to the different soil managements. Batch adsorption and desorption experiments as well as a sequential fractionation schema, which defines seven geochemical fractions, were used to investigate the retention properties of soil. Sequential extraction was conducted with original as well as with metal-spiked soils. Results showed that amounts of Cu, Cd and Zn retained differed by a factor of more than 3 among the treatments in the longterm field experiment, when a massive concentration of metal was added to soil. An increased sorption on

Summary The present work investigates the impact of site management on the retention of organic compounds in soil in a long-term field experiment and focuses on the role of particle size fractions. Specifically, we studied the influence of long-term farming practices on the soil’s ability to adsorb five hydrophobic organic compounds (HOCs), specifically naphthalene derivatives (naphthalene, 1-naphthol, 1-naphthylamine, 1-hydroxy-2-naphthoic acid, 1,4-naphthoquinone). We examined the sorption on soil and its particle-size fractions with varying amounts and origins of organic matter in soil amended with farmyard manure and mineral fertilizers over more than 40 years. The soil organic matter had no significant impact on the sorption behaviour of the HOCs. Adsorption on the clay and silt fraction provided a deeper insight into the mechanisms and indicates a strong affinity with adsorption sites of the mineral phase. Naphthalene derivatives with hydrogen atoms in their functional groups adsorbed more strongly than other compounds on to soils containing smaller amounts of organic carbon. Desorption experiments with five organic extractants showed partitioning models for HOCs between extractant and soil surface. Only in experiments with the most polar extractant, formamide, did we observe an influence of the compound’s functional groups on the desorption mechanisms. Column experiments with a HPLC-system and on-line UV-detection proved to be a satisfactory alternative to batch experiments. This approach should enable investigations of adsorption with larger numbers of compounds and soils at the same time.

Sorption of heavy metals to organic matter and mineral soil constituents can hardly be separated experimentally. Here we studied the retention capacity of organic matter and minerals from soils in a long-term field experiment in which the organic carbon content had been altered, but the mineral phase had remained constant over time. The sorption of Cu, Cd and Zn showed a non-additive contribution of soil organic matter and minerals to the sorption capacity of soil. Sorption on organic matter exceeded mineral sorption from 6 to 13 times. This is the first time that sorption to soil organic matter is quantified in bulk soils.

This study investigated the effect of different farming practices over long time periods on the sorption-desorption behavior of Cu, Cd, and Zn in soils. Various amendments in a long-term field experiment over 44 y altered the chemical and physical properties of the soil. Adsorption isotherms obtained from batch sorption experiments with Cu, Cd, and Zn were well described by Freundlich equations for adsorption and desorption. The data showed that Cu was adsorbed in high amounts, followed by Zn and Cd. In most treatments, Cd ions were more weakly sorbed than Cu or Zn. Generally, adsorption coefficients K F increased among the investigated farming practices in the following order: sewage sludge ≤ fallow < inorganic fertilizer without N ≈ green manure < peat < Ca(NO 3 ) 2 < animal manure < grassland/extensive pasture. The impact of different soil management on the sorption properties of agricultural soils for trace metals was quantified. Results demonstrated that the soil pH was the main factor controlling the behavior of heavy metals in soil altered through management. Furthermore, the constants K F and n of isotherms obtained from the experiments significantly correlated with the amount of solid and water-soluble organic carbon (WSOC) in the soils. Higher soil pH and higher contents of soil organic carbon led to higher adsorption. Carboxyl and carbonyl groups as well as WSOC significantly influenced the sorption behavior of heavy metals in soils with similar mineral soil constituents.

The present study evaluated the effect of fertilizer amendments (organic manure and mineral fertilizers), management practices (fallow and untilled vs. cropped and tilled) on changes of N in bulk soil and N associated with different particle-size fractions. The long-term field experiment was conducted since 1962 in Gumpenstein, Austria, on a Dystric Cambisol. The N content of the topsoils changed distinctively during 28 and 38 yr of treatments under both fallow and cropped management practices. Highest increase in total N content was found in animal-manure (liquid)-treated plots. The remaining ranking was: animal manure (solid) > cattle slurry > half cattle slurry + straw = PK = NPK. Quite short N-half-life values of around 2 yr were found for the cattle-slurry application, while animal manure exhibited longer N-half-lives of around 8 yr. Crop removal of N and mineralization losses in cropped plots obviously were higher than N losses from the bare soil plots lacking a plant cover to keep N in the system. This was confirmed by a consistent shift in the natural 15N abundances. Comparing the mean N contribution of particle-size fractions to the total N amounts revealed the following ranking after 28 and 38 yr of different treatments: silt > clay > fine sand > coarse sand, with small exceptions. Particle-size separates showed more significant responses to changes in the N dynamics of the system due to the various treatments than the bulk soil and can be regarded as the better indicators in this respect.

Nitrogen dynamics in semi-natural environments is crucial for the development and ecological stability of these systems. The present paper shows the results of the reinvestigation of a 15N-tracer experiment, which was established in the Grossglockner massif in Austria at 2300 m a.s.l. in 1974/1975. We show that large quantities of nitrogen introduced by a single pulse labelling (amounting to approximately 1.7% of the nitrogen in the system) into an alpine grassland remain in the soil–plant system, with only 55% being lost during 27–28 years. In the first 10 cm of the four investigated soil profiles 40% of 15N was recovered, being mainly bound in organic forms. A simple site specific model was established on the basis of the results considering a biological, residual and labile N-pool, the latter being the source for N-losses. By the model a long mean residence time close to 100 years was derived for the remaining 15N.

We studied the effect of humified organic matter (OM) on the mineralization of a representative labile organic compound in soil. In an incubation experiment, a 13 C-labeled 2-decanol was added to soil either alone (2-dec p ) or in mixture with two humic acids from compost (HAC p ) and lignite (HAL p ) which had different hydrophobic properties. Isotopic dilution (d 13 C) showed that after 3 months of incubation about 58, 40 and 28% of the added 13 C was retained in the whole soil treated with HAL p , HAC p and 2-dec p , respectively. The higher the hydrophobicity of the employed humic material, the larger was the sequestration of organic carbon in soil. Fractionation of incubated samples revealed that the labeled carbon progressively accumulated in the finest particle-size fractions. However, the high hydrophobicity of the lignite HA favored accumulation of 13 C also in the sand-sized fraction. The NMR spectra of humic extracts showed that the 13 C-methyl group in the original 2-decanol had been oxidized to a 13 C-carboxyl group during incubation for all treatments. This indicated that despite its hydrophilicity, the resulting carboxyl carbon was sequestered into the hydrophobic domains of the humic pool in soil. In fact, the residual 13 C was larger in humic than in fulvic extracts for the control sample (2-dec p ) and even more so in extracts from soil treated with both exogenous humic acids. Our results suggest that labile organic compounds may be effectively protected in soil by humified OM and their microbial mineralization substantially reduced. Innovative soil management practices employing hydrophobic humic substances may increase the biological stability of soil OM and thus contribute to significantly mitigate CO2 emissions from agricultural soils. q 2002 Elsevier Science Ltd. All rights reserved.

Summary Changes in farming practices over long times can affect the sorption behaviour of MCPA ((4-chloro-2-methylphenoxy)acetic acid). We studied the adsorption–desorption mechanisms of MCPA on soil with varied amounts and origins of soil organic matter obtained from a long-term field experiment with various organic amendments. The origin of the soil organic matter seems to be crucial for the sorption behaviour of MCPA. Samples of soil amended with sewage sludge sorbed MCPA more strongly than the soil under any other treatment. Peat-amended soil was second followed by soil receiving animal manure, green manure, mineral fertilizer without N and the fallowed soil. Both the carbon content and the origin of the organic matter are important for the sorption. A decrease of carbon content of a soil does not necessarily imply a reduction of sorption capacity for polar organic acids such as MCPA. Nevertheless, our adsorption–desorption experiments suggest that with decreasing carbon content the role of mineral sorption mechanisms could become more pronounced. Our results showed that interactions of soil organic matter and soil minerals distinctly influence adsorption properties for MCPA.

Diffuse Reflectance Infrared Fourier Transform DRIFT technique was used to investigate decomposition of maize straw residues in particle-size fractions of three European soils in a 1-year incubation experiment that simulated both incorporation and mulching practices. The aliphatic bands in the 2920-2860 cm y1 regions were used to derive decomposition curves and mineraliza- tion rates of maize residues. Evaluation of soil organic matter changes by DRIFT in particle-size fractions depended on soil texture and soil aggregate stability. Decomposition could be followed over the full incubation period only in three size-fractions of the silty German soil because of its intermediate aggregate stability. DRIFT spectra were not useful in the least stable sandy Danish soil and in the most stable clayey Italian soil. Decomposition rates derived from DRIFT results were similar to those obtained by isotopic techniques. DRIFT spectroscopy may represent a rapid and accurate method to follow fresh organic matter degradation directly in soil matrix or particle-size fractions in some soils provided that adequate soil dispersion is obtained. q 2001 Elsevier Science B.V. All rights reserved.

The dynamics of incorporation of fresh organic residues into the various fractions of soil organic matter have yet to be clarified in terms of chemical structures and mechanisms involved. We studied by 13 C-dilution analysis and CPMAS- 13 C-NMR spectroscopy the distribution of organic carbon from mixed or mulched maize residues into specific defined fractions such as carbohydrates and humic fractions isolated by selective extractants in a year-long incubation of three European soils. The contents of carbohydrates in soil particle size fractions and relative δ 13 C values showed no retention of carbohydrates from maize but rather decomposition of those from native organic matter in the soil. By contrast, CPMAS- 13 C-NMR spectra of humic (HA) and fulvic acids (FA) extracted by alkaline solution generally indicated the transfer of maize C (mostly carbohydrates and peptides) into humic materials, whereas spectra of organic matter extracted with an acetone solution (HE) indicated solubilization of an aliphatic-rich, hydrophobic fraction that seemed not to contain any C from maize. The abundance of 13 C showed that all humic fractions behaved as a sink for C from maize residues but the FA fraction was related to the turnover of fresh organic matter more than the HA. Removal of hydrophobic components from incubated soils by acetone solution allowed a subsequent extraction of HA and, especially, FA still containing much C from maize. The combination of isotopic measurements and NMR spectra indicated that while hydrophilic compounds from maize were retained in HA and FA, hydrophobic components in the HE fraction had chemical features similar to those of humin. Our results show that the organic compounds released in soils by mineralization of fresh plant residues are stored mainly in the hydrophilic fraction of humic substances which are, in turn, stabilized against microbial degradation by the most hydrophobic humic matter. Our findings suggest that native soil humic substances contribute to the accumulation of new organic matter in soils.

The sorption and desorption behaviors of four phenoxyalkanoic acid herbicides and their metabolites on four agricultural soils and soil particle size fractions were examined. Generally, there was a trend of increasing adsorption and decreasing desorption in the order mecoprop < MCPA < dichlorprop < 2,4-D. The significant increase in adsorption of the phenolic metabolites can be explained by their lower polarity and enhanced partition in the organic soil matrix. Estimation of sorption distribution coefficients from particle size fraction adsorption data was possible for a sandy soil and a silty Cambisol soil only. It is suggested that increasing steric demand, for example, molecular volume, and slight changes in the polarity of the compounds affect their adsorption properties. Comparison of adsorption and desorption data of structurally similar compounds obtained from a variety of soils allows investigation of structure-induced differences in sorption strength.

The analysis of O-isotopic composition of nitrate has many potential applications in studies of environmental processes. O-isotope nitrate analysis requires samples free of other oxygen-containing compounds. More than 100% of non-NO3- oxygen relative to NO3- oxygen can still be found in forest soil water samples after cleanup if improper cleanup strategies, e.g., adsorption onto activated carbon, are used. Such non-NO3- oxygen compounds will bias O-isotopic data. Therefore, an efficient cleanup method was developed to isolate nitrate from natural water samples. In a multistep cleanup procedure using adsorption onto water-insoluble poly(vinylpyrrolidone), removal of almost all other oxygen-containing compounds, such as fulvic acids, and isolation of nitrate was achieved. The method supplied samples free of non-NO3- oxygen which can be directly combusted to CO2 for subsequent O-isotope analysis.

A method is described to characterise organic soil layers using Fourier transformed infrared spectroscopy. The applicability of FT-IR, either dispersive or transmission, to investigate decomposition processes of spruce litter in soil originating from three different forest sites in two climatic regions was studied. Spectral information of transmission and diffuse reflection FT-IR spectra was analysed and compared. For data evaluation Kubelka Munk (KM) transformation was applied to the DRIFT spectra. Sample preparation for DRIFT is simpler and less time consuming in comparison to transmission FT-IR, which uses KBr pellets. A variety of bands characteristic of molecular structures and functional groups has been identified for these complex samples. Analysis of both transmission FT-IR and DRIFT, showed that the intensity of distinct bands is a measure of the decomposition of forest litter. Interferences due to water adsorption spectra were reduced by DRIFT measurement in comparison to transmission FT-IR spectroscopy. However, data analysis revealed that intensity changes of several bands of DRIFT and transmission FT-IR were significantly correlated with soil horizons. The application of regression models enables identification and differentiation of organic forest soil horizons and allows to determine the decomposition status of soil organic matter in distinct layers. On the basis of the data presented in this study, it may be concluded that FT-IR spectroscopy is a powerful tool for the investigation of decomposition dynamics in forest soils.

Transmission Fourier transformed infrared spectroscopy was used to compare organic soil layers originating from three different sites in two climatic regions. A variety of bands characteristic of molecular structures and functional groups have been identified for these samples from a humic podsol, a dystric cambisol and a spodo dystric cambisol. Similar results were obtained for all three soils. From L to H soil horizons, an increase of the band at 1630 cm−1 and decrease of bands in the region from 1510 cm−1 to 1230 cm−1 were observed. The band at 1630 cm−1 can be assigned to carboxylic and aromatic groups. The decline of the peak intensity at 1510 cm−1 is significantly correlated to the total carbon content and CN ratio. The mineral material of the Ah horizons leads to an increase of the band at 1050 cm−1 due to IR-absorbance of the SiO bond and to an appearance of bands in the region from 900 to 400 cm−1, which are characteristic for clay and quartz minerals. Analysis of the FTIR absorbance showed that intensities of distinct peaks (e.g., at 1510 cm−1) can be a measure of decomposition of forest litter. Therefore, the proposed simple FTIR method has potential for identification and differentiation of organic soil horizons originating from known tree litter. The similarity of the characteristics of the spectra of the three soil profiles investigated suggests a broad applicability of this method to distinguish organic forest soil horizons. On the basis of the data presented in this study, it may be concluded that FTIR spectroscopy offers a simple, powerful, non-destructive tool for the investigation of decomposition of L to H horizons in forest soils.

Stable isotope analysis of 15N/14N and 18O/16O-nitrate was used to investigate the nitrate dynamics and potential groundwater pollution in an Alpine forest stand in Tyrol/Austria. The dynamics of delta15-N(nitrate) values were followed in a forest ecosystem. The stable isotopic values of the throughfall are comparable with other studies. The completely decoupled dynamics of the delta15-N(nitrate) of the precipitation and the surface water was observed. High variations in delta15N-nitrate values in rainfall indicate that nitrate of different sources is deposited at that site. A significant correlation between the delta15N(nitrate) values of the surface water and soil water was obtained, while no significant correlation between the delta15N(nitrate) values of any precipitation sample with the surface water could be found. This suggests that the main source of nitrate in soil water originates from microbiological activity such as nitrification reactions and less from nitrate input by deposition. The results of delta18O(nitrate) measurements strongly supported the microbiological origin of nitrate in the surface and soil water In an additional lysimeter experiment, 15N-labelled nitrate was applied to study nitrate transport in soil. After 130 days and the collection of 300 L leachate, a total of 52% of the applied nitrate was detected in seepage water.

The present study combined a physical fractionation procedure with the determination of the natural abundance of 15N to investigate the impact of organic manure and mineral fertilizer application, and fallow on changes of N associated with different soil particle size fractions. The long-term field experiment was conducted since 1956 in Ultuna, Sweden, on an Eutric Cambisol. Nitrogen in bulk soil and in particle size fractions changed significantly since 1956. The Nt concentrations in bulk soil decreased in all treatments not receiving organic materials. Comparing the N contribution of particle-size fractions to the total N amount revealed the following ranking: silt > clay > fine clay > fine sand > coarse sand. The relative contribution of N in silt sized particles significantly increased from low to high bulk soil N contents, whereas N in clay and fine clay fractions decreased. The C : N ratios of particle size fractions differed considerably more between treatments than C : N ratios in bulk soils. Generally, the C : N ratios decreased from coarse to fine fractions emphasizing the tendency of smaller fractions being more significant as N sink than as Corg sink. 15N abundances varied more between particle size fractions of single treatments than between bulk soil from differently treated plots. Within treatments we observed differences of up to 7.1 ‰ between particle size fractions. In most cases δ 15N values increased with decreasing particle sizes. This pattern on average was similar to changes in δ 13 C. Our results suggest that silt sized particles acted as medium-term sink of introduced N and that 15N abundances in particle size fractions sensitively reflect changes in N status in response to soil management. N-Verteilung und naturliche 15N-Haufigkeiten in Korngrosenfraktionen in einem landwirtschaftlichen Langzeitfeldversuch Die gegenwartige Studie basiert auf einer physikalischen Fraktionierung in Kombination mit der Bestimmung der naturlichen Haufigkeiten von 15N in Korngrosenfraktionen von Boden eines Kleinparzellenversuches in Ultuna, Schweden, der 1956 auf einer eutrophen Braunerde angelegt wurde. Ziel dabei war es, den Einfluss unterschiedlicher organischer Materialien und eines mineralischen Dungers und der Dauerschwarzbrache auf den N-Status der Boden zu untersuchen. Die Nt-Gehalte sanken im Oberboden in all jenen Behandlungen ab, die keine organischen Materialien erhielten. Die hochsten N-Mengen fanden sich in der Schlufffraktion gefolgt von Ton, Feinton, Feinsand und Grobsand. Der relative Beitrag von N in der Schlufffraktion stieg mit zunehmenden Nt-Gehalten des Gesamtbodens an, gleichzeitig nahmen die Beitrage der Tonfraktionen ab. Die C : N-Verhaltnisse variierten wesentlich starker zwischen Korngrosenfraktionen als zwischen den Boden verschiedener Behandlungen. Generell stieg das C : N-Verhaltnis mit abnehmender Teilchengrose an, was die tendenziell grosere Bedeutung der Feinfraktionen als N-Senke denn als Corg-Senke unterstreicht. Die δ 15N-Werte wurden starker von der Partikelgrose als von den Behandlungen beeinflusst. Innerhalb der Behandlungen fanden wir Unterschiede von bis zu 7,1 ‰ zwischen Korngrosenfraktionen. In den meisten Fallen nahmen die δ 15N-Werte mit abnehmender Teilchengrose zu. Unsere Ergebnisse zeigten, dass Schluffpartikel als mittelfristige N-Senke bedeutsam sind und 15N-Haufigkeiten in Korngrosenfraktionen sehr sensitiv auf langerfristige Bewirtschaftungsanderungen reagieren.

In the North Tyrolean Limestone Alps a site was investigated over a four-year period (1998-2001) in order to assess the nitrogen saturation status, the nitrogen budget (quantification of the net uptake of nitrogen by the canopy and of the nitrogen mineralization, nitrogen uptake from roots and N2O emission rates, proof of the origin of nitrate in the soil water with stable isotope analyses), and the effects of the actual nitrogen input on ground water quality. The main goals were to quantify the nitrogen input rate, the nitrogen pools in above-ground and below-ground compartments, nitrogen turnover processes in the soil as well as the output into the groundwater and into the atmosphere. The findings are based on continuous and discontinuous field measurements as well as on model results. While nitrogen input exceeded the Critical Loads of the WHO (1995), nitrogen deficiency and nutrient imbalances were verified by needle analyses. The atmospheric input of inorganic nitrogen was higher than the nitrogen output in 50 cm soil depth. A tracer experiment with 15N helped to prove that not more than half of the applied nitrate could be discharged. This allows the conclusion that nitrogen is stored in the system and that the site cannot yet be said to be saturated with nitrogen. The same result was also obtained by modelling. In addition, it was proved that the nitrogen discharge did not stem from deposition but from processes within the system.