Rolf-Alexander Düring

Reducing tillage intensity — a review of results from a long-term study in Germany

Abstract This paper reviews research performed at the Justus-Liebig-University of Giessen, Germany into the impact of different tillage systems on soil properties and quality. The impact of intensive soil tillage treatments on several soil properties was described by means of selected data obtained through long-term interdisciplinary research. The experiments were based on comparative application (long-term, up to 18 years investigations) of the respective tillage options on different soils (e.g. Eutric Cambisol, Eutric Fluvisol) ranging in texture from sand to a silt loam. These soils are located at five field sites with different crop rotations in the central German state of Hesse. Tillage intensity of the systems was considered to decrease in the following sequence: Conventional plough tillage (CT), reduced tillage (RT), and no-tillage (NT). For elucidating the impact of tillage intensity, the tillage extremes CT and NT were compared. Physical conditions of soil as influenced by the application of RT were considered to be intermediate between CT and NT. In general, bulk density in the upper layer of NT soils was increased, resulting in a decrease in the amount of coarse pores, and a lower saturated hydraulic conductivity when compared with the CT and RT soils. Surface cover by crop residues and higher aggregate stability under NT protected soil fertility by avoiding surface sealing and erosion. Lateral losses of herbicides were also reduced under NT conditions, whereas the susceptibility for preferential vertical transport of herbicides needs further evaluation. Accumulation of organic matter and nutrients near the soil surface under NT and RT were favorable consequences of not inverting the soil and by maintaining a mulch layer on the surface. Those improvements were associated with enhanced biological activities in NT and RT topsoils. Increased earthworm activity in NT treatments was associated with a system of continuous macropores which improved water infiltration rates. Earthworms support decomposition and incorporation of straw. Soils which have not been tilled for many years were more resistant to vehicle passage; consequently, the compaction by traffic was lower. Penetration resistance curves indicate that a uniformly stable structure had developed over the years in NT soils. Overall, the results show that RT and NT were beneficial to the investigated soil properties. If crop rotation, machinery, and plant protection are well adapted for the introduction of conservation tillage, these systems may replace conventional ploughing systems in many cases in German agriculture.

Sorption and bioavailability of heavy metals in long-term differently tilled soils amended with organic wastes

In this study, bioavailability and enrichment studies were focused on Cd, Zn and Cu in two different soils (sandy loam and silt loam), which were treated with compost and sewage sludge, respectively, both under conventional tillage (CT) and no tillage (NT). Long-term NT resulted in a significant increase in Cd and Zn extracted by aqua regia in a soil profile (0-25 cm), especially in the 0-3 cm layer. In the sandy loam, a slight increase in cadmium due to sewage sludge application was observed. Results from EDTA-extractable heavy metal analyses were not consistent but NH(4)NO(3)-extractable concentrations were significantly lower in the NT soil. Bioavailability of heavy metals was reduced in the long-term NT, resulting in lower uptake of Cd and Zn by plants and accumulation in the soil. The effect of tillage on enrichment of heavy metals in soils was more significant than the impact of the fertilisation by means of legally allowable application rates of organic wastes. This work suggests that non-tilled soils enriched in heavy metals should not be amended with organic waste in the long term.

Secondary Metabolites Released by The Burying Beetle Nicrophorus vespilloides : Chemical Analyses and Possible Ecological Functions

Burying beetles of the genus Nicrophorus localize small vertebrate carcasses by emitted volatiles. The carcass that serves as reproduction and breeding site is buried in the soil by the beetles. Biparental care for offspring includes both preservation of the carrion and its preparation as diet and nursery. Buried carcasses show no signs of microbial decay, and those experimentally treated with Nicrophorus secretions are known to grow fewer bacteria and fungi. In order to investigate the chemical composition of these secretions, we used GC-MS for analysis of methanolic extracts of anal and oral secretions released by adult N. vespilloides. Furthermore, we analyzed the headspace of adult N. vespilloides by SPME-GC-MS and searched for compounds with known antimicrobial activity. We identified 34 compounds in the headspace, and anal and oral secretions, 26 of which occurred consistently. We discuss the ecological relevance of these compounds with respect to both their antimicrobial activity and ecological relevance.

Comparison of decision support systems for an optimised application of compost and sewage sludge on agricultural land based on heavy metal accumulation in soil.

Two different decision support systems (DSS) for the application of organic wastes on agricultural land were developed. Both DSS calculate the maximum application period of organic waste considering exhaustion of the uptake potential of soils for heavy metals. The definition of the uptake potential differs between the DSS alternatives. In the first DSS (DSS-AR), the uptake potential is derived from the difference of actual total heavy metal concentration in soil (according to aqua regia digestion) and the respective statutory limit value. The other DSS (DSS-SI) calculates the remaining sorption capacity of the soil for a heavy metal, i.e. the difference between the predefined maximum and the actual heavy metal concentration at the sorbent. The concentration of sorbed heavy metal is derived from pedotransfer functions (general purpose Freundlich isotherms) using predefined limit concentrations in soil solution (WHO drinking water quality standards) or the actual concentration of soluble heavy metal (according to neutral salt extraction), respectively. For evaluation of their individual characteristics, both DSS were tested in model scenarios using soil data (basic physicochemical properties; Cd, Pb, and Zn concentrations) from various agricultural regions and German guidelines for organic waste application. The DSS-SI showed a better performance than the DSS-AR in this context. The capacity of the soil for heavy metal uptake was used with higher efficiency, i.e. the potential was maximised while environmental limit values were still complied with. Furthermore, the DSS-SI offered a better approximation of the natural variability of soil conditions using an extended set of soil properties in comparison to the DSS-AR. Despite these indications of good DSS-SI performance, the approach requires improvement with regard to the pedotransfer functions implemented in order to consolidate and extend the range of predictions. Furthermore, it should be noted that assessment of the DSS-SI is influenced by the availability of data and is only valid under the current environmental and statutory framework at the regional scale observed. For this reason, transfer of the results of this study into regions with other administrative structures and/or environmental conditions is critical. Individual testing of the DSS-SI and the DSS-AR is required prior to the intended transfer, i.e. implementation of the approaches in the decision support process.

Analysis of wastewater samples by direct combination of thin-film microextraction and desorption electrospray ionization mass spectrometry.

An analysis method for aqueous samples by the direct combination of C18/SCX mixed mode thin-film microextraction (TFME) and desorption electrospray ionization mass spectrometry (DESI-MS) was developed. Both techniques make analytical workflow simpler and faster, hence the combination of the two techniques enables considerably shorter analysis time compared to the traditional liquid chromatography mass spectrometry (LC-MS) approach. The method was characterized using carbamazepine and triclosan as typical examples for pharmaceuticals and personal care product (PPCP) components which draw increasing attention as wastewater-derived environmental contaminants. Both model compounds were successfully detected in real wastewater samples and their concentrations determined using external calibration with isotope labeled standards. Effects of temperature, agitation, sample volume, and exposure time were investigated in the case of spiked aqueous samples. Results were compared to those of parallel HPLC-MS determinations and good agreement was found through a three orders of magnitude wide concentration range. Serious matrix effects were observed in treated wastewater, but lower limits of detection were still found to be in the low ng L(-1) range. Using an Orbitrap mass spectrometer, the technique was found to be ideal for screening purposes and led to the detection of various different PPCP components in wastewater treatment plant effluents, including beta-blockers, nonsteroidal anti-inflammatory drugs, and UV filters.

Multifunctional weaponry: the chemical defenses of earwigs.

Earwigs protect themselves against predators using pincer-like cerci and/or malodorous exudates secreted from abdominal glands. Little is known about the chemistry of these secretions and their potential functions. However, because earwigs live in aggregations and overwinter in soil, they are exposed to high microbial loads throughout their lifecycle, and we therefore hypothesized that the secretions are used not only to deter predators but also to combat pathogens and parasites in their environment. We analyzed the defensive secretions of the European earwig Forficula auricularia, the short-winged earwig Apterygida media and the woodland earwig Chelidurella guentheri by gas chromatography-mass spectrometry. The secretions of all three species contained 2-methyl-1,4-benzoquinone and 2-ethyl-1,4-benzoquinone, whereas A. media also produced 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. The latter has not been identified in the exudates of insects before. The composition and/or quantity of these components were species-specific and partially sex-specific. All secretions showed antimicrobial activity against Gram-positive and Gram-negative bacteria as well as two entomopathogenic fungi. Furthermore, the secretion of F. auricularia displayed nematicidal activity against Caenorhabditis elegans. Our data support the hypothesis that earwig secretions are multifunctional, serving both to deter predators and sanitize the microenvironment.

Microwave assisted EDTA extraction—determination of pseudo total contents of distinct trace elements in solid environmental matrices

Quantitative determination of metals in environmental matrices became important in the past few decades because of increasing pollutant concentrations in aquatic and terrestrial ecosystems. The extraction phase in the process of determining metals is crucial but very time-consuming. Consequently, new extraction techniques for extractable metals have been developed which probably will substitute conventional procedures in the future. The aim of this study was to improve a closed vessel microwave assisted extraction (MAE) by using EDTA as an exclusive extraction agent (MAE-EDTA) for the determination of pseudo total metal contents in solid environmental samples. For this purpose, a large set of soil and compost samples were analyzed. MAE-EDTA was compared with both closed vessel microwave assisted aqua regia extraction (MAE-AR) and a conventional aqua regia extraction (AR) method for the determination of pseudo total Cd, Cu, Mn, and Pb contents of soil and compost samples. Certified reference materials were used for comparison of recovery rates from different extraction protocols. Metal concentrations in soil and compost extracts were determined by ICP-OES. MAE-AR which was considered as a reference MAE method for further steps of the study, showed the same extraction yields in the determination of pseudo total metal contents of the investigated elements (As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, Zn) in soil and compost samples as the conventional AR. MAE-EDTA gave similar values as the reference methods in the determination of Cd, Cu, and Pb amounts in soil samples and Cd, Mn, and Pb amounts in compost samples. The recovery rates ranged between 89.0-117.1% for soil samples and 93.5-104.0% for compost samples. MAE-EDTA provides fast processing of the samples that is less than one hour, including time for cooling of the samples. Apart from significantly less processing time, minimal consumption of sample and reagent chemicals is a strategic characteristic of MAE-EDTA procedure which has advantages including accuracy and reduction of contamination. The drawback of MAE-EDTA was that the optimized conditions for the metals Cd, Cu, Mn and Pb may not be generally applicable for the other metals. Therefore, the analytical parameters available in MAE-EDTA should be further investigated for the metals of interest.

Validation of a standard field test method in four countries to assess the toxicity of residues in dung of cattle treated with veterinary medical products

Registration of veterinary medical products includes the provision that field tests may be required to assess potential nontarget effects associated with the excretion of product residues in dung of treated livestock (phase II, tier B testing). However, regulatory agencies provide no guidance on the format of these tests. In the present study, the authors report on the development of a standardized field test method designed to serve as a tier B test. Dung was collected from cattle before and up to 2 mo after treatment with a topical application of a test compound (ivermectin). Pats formed of dung from the different treatments were placed concurrently in the field to be colonized by insects. The abundance, richness, and diversity of insects developing from egg to adult in these pats were compared across treatments using analysis of variance tests. Regression analyses were used to regress abundance, richness, and diversity against residue concentrations in each treatment. Results of the regression were used to estimate mean lethal concentration (LC50) values. The robustness of the method and the repeatability of its findings were assessed concurrently in 4 countries (Canada, France, Switzerland, and The Netherlands) in climatically diverse ecoregions. Results were generally consistent across countries, and support the methods formal adoption by the European Union to assess the effects of veterinary medical product residues on the composition and diversity of insects in dung of treated livestock. Environ Toxicol Chem 2016;35:1934-1946.

Analysis and dissipation of the antiparasitic agent ivermectin in cattle dung under different field conditions

Cattle treated with the veterinary parasiticide ivermectin fecally excrete residues. The authors report the exposition and dissipation characteristics of these residues in dung of ivermectin-treated cattle and in soil beneath this dung on pastures in Canada, France, Switzerland, and The Netherlands. Residues were quantified for dung collected from cattle after 3 d, 7 d, 14 d, and 28 d posttreatment and subsequently exposed in the field for up to 13 mo. The authors optimized a high-performance liquid chromatography-fluorescence detection method to detect ivermectin residues in dung and soil matrices. They showed that a solid phase extraction and purification step generally can be eliminated to reduce the time and cost of these analyses. They also found that the addition of water to relatively dry samples improves the extraction efficiency of residues. They then analyzed the field samples to document differences in ivermectin dissipation in cattle dung among sites, with 50% dissipation times of up to 32 d and 90% dissipation times >396 d. They further showed that the dissipation characteristics of residues are comparable between dung of ivermectin-treated cattle and dung to which ivermectin has been added directly. Lastly, they report the first use of a desorption electrospray ionization-high-resolution-mass spectrometric method to detect residues of metabolites in a dung matrix. Environ Toxicol Chem 2016;35:1924-1933.

Nontarget effects of ivermectin residues on earthworms and springtails dwelling beneath dung of treated cattle in four countries

The authorization of veterinary medicinal products requires that they be assessed for nontarget effects in the environment. Numerous field studies have assessed these effects on dung organisms. However, few studies have examined effects on soil-dwelling organisms, which might be exposed to veterinary medicinal product residues released during dung degradation. The authors compared the abundance of earthworms and springtails in soil beneath dung from untreated cattle and from cattle treated 0 d, 3 d, 7 d, 14 d, and 28 d previously with ivermectin. Study sites were located in different ecoregions in Switzerland (Continental), The Netherlands (Atlantic), France (Mediterranean), and Canada (Northern Mixed Grassland). Samples were collected using standard methods from 1 mo to 12 mo after pat deposition. Ivermectin concentrations in soil beneath dung pats ranged from 0.02 mg/kg dry weight (3 mo) to typically <0.006 mg/kg dry weight (5-7 mo). Earthworms were abundant and species-rich at the Swiss and Dutch sites, less common with fewer species at the French site, and essentially absent at the Canadian site. Diverse but highly variable communities of springtails were present at all sites. Overall, results showed little effect of residues on either earthworms or springtails. The authors recommend that inclusion of soil organisms in field studies to assess the nontarget effects of veterinary medicinal products be required only if earthworms or springtails exhibit sensitivity to the product in laboratory tests. Environ Toxicol Chem 2016;35:1959-1969.