Effects of Olive Mill Wastewater on Soil Microarthropods and Soil Chemistry in Two Different Cultivation Scenarios in Israel and Palestinian Territories

Although olive mill wastewater (OMW) is often applied onto soil and is known to be phytotoxic, its impact on soil fauna is still unknown. The objective of this study was to investigate how OMW spreading in olive orchards affects Oribatida and Collembola communities, physicochemical soil properties and their interdependency. For this, we treated plots in two study sites (Gilat, Bait Reema) with OMW. Among others, the sites differed in irrigation practice, soil type and climate. We observed that soil acidity and water repellency developed to a lower extent in Gilat than in Bait Reema. This may be explained by irrigation-induced dilution and leaching of OMW compounds in Gilat. In Bait Reema, OMW application suppressed emergence of Oribatida and induced a community shift, but the abundance of Collembola increased in OMW and water-treated plots. In Gilat, Oribatida abundance increased after OMW application. The effects of OMW application on soil biota result from an interaction between stimulation of biological activity and suppression of sensitive species by toxic compounds. Environmental and management conditions are relevant for the degree and persistence of the effects. Moreover, this study underlines the need for detailed research on the ecotoxicological effects of OMW at different application rates

The Amorphous Nature of Soil Organic Matter - Aging, Swelling and Wetting and their interplay with water

Boden ist unter Feldbedingungen einer Dynamik von Temperatur und Feuchte ausgesetzt. Dadurch werden Quellungs- und Schrumpfungsprozesse sowie Veränderungen in den Oberflächeneigenschaften der organischen Bodensubstanz induziert, die nur in den seltensten Fällen vollständig reversibel sind. Von diesen Veränderun-gen werden direkte Auswirkungen auf das Sorptions- und Transportverhalten organischer Schadstoffe erwartet. Trotz dieser Bedeutung sind die zugrunde liegenden Prozesse bis heute noch weitgehend unverstanden. Ziel dieser Arbeit war es, die organische Bodensubstanz, basierend auf der Modell-vorstellung als amorphe Matrix, von einem neuen Blickwinkel zu beschreiben. Mit Hilfe der in der Bodenchemie noch wenig bekannten Methoden der 1H-NMR-Relaxometrie und Differential Scanning Kalorimetrie wurden ihre Wasserbindung und Matrixeigenschaften charakterisiert. Im Zentrum stand die Charakterisierung des Glasübergangsverhaltens und der physikalischen Alterung sowie deren Beeinflus-sung durch Wasser, Feuchtebedingungen und Temperatur. Die organische Bodensubstanz zeigt sowohl typisches als auch irreversibles Glas-übergangsverhalten, wobei Wasser in antagonistischer Weise als kurzfristig wirken-der Weichmacher und langfristig wirkender Hartmacher fungiert. Die zugrunde liegenden Strukturrelaxationsprozesse äußern sich in einer langsamen physikochemi-schen Alterung der organischen Matrix über einen Zeitraum von mindestens sechs Monaten. Änderungen in den Feuchtebedingungen führen zu einer Beschleunigung und teilweisen Umkehrung der Alterung. Hystereseeffekte als typisches Merkmal amorpher Stoffe wurden bei Matrixeigenschaften und bei Wasseraufnahme und -abgabe beobachtet. Quellungsprozesse führen zu einer Veränderung der Poreneigenschaften, Porengrößen und Wasserbindung. Die Matrixalterung könnte auch für die zeitliche Variabilität der Benetzungseigenschaften von Bodenproben verantwortlich sein, und mikrobiell gebildete extrazelluläre Substanzen stellen einen weiteren wichtigen Einflussfaktor dar. Die Ergebnisse zeigen die Bedeutung der Matrixalterung für Sorption und Stofftrans-port in bodenkundlich relevanten Zeiträumen. Das Verständnis der Matrixalterung kann zu einem tieferen Verständnis der Alterung sorbierter Schadstoffe führen. In der weiteren Forschung sollen deshalb Zusammenhänge zwischen Struktur, Mikrobiologie, Alterung und Schadstoffbindung untersucht werden.Under field conditions, soil is subjected to temperature and moisture dynamics. These induce swelling and shrinking as well as changes in the surface characteristics of soil organic matter, which are not fully reversible. These changes are expected to affect sorption and transport of organic contaminants. Despite this relevance, the underlying processes are still only scarcely understood. The objective of this research were to describe soil organic matter from a new viewpoint considering it as amorphous matrix. Water binding and matrix properties were characterized with 1H-NMR-Relaxometry and Differential Scanning Calorimetry, both of which represent young methods in the field of soil chemistry. We characterized the glass transition behavior and physical and physicochemical aging of soil organic matter and their interplay with water, moisture conditions and temperature. Soil organic matter reveals typical as well as atypical glass transition behavior, where water acts in antagonistic way as short-term plasticizer and long-term antiplasticizer. The processes of structural relaxation express in physicochemical aging of the organic matrix, and lasts for at least six months. Fluctuations and changes of moisture conditions accelerated or reversed the aging process. We observed hysteresis for water absorption as well as matrix properties, and swelling most probably results in a change of pore size, pore characteristics and water binding. Matrix aging may also be responsible for the changes in soil wettability in the course of time, and extracellular polymeric substances (EPS) most probably are additionally involved in the aging process. The results show the relevance of matrix aging for sorption and transport. Understanding of the processes underlying and affecting aging of soil organic matter, will lead to a better understanding of contaminant aging. Future research therefore should concentrate on the interrelations between structure, microbiology and aging of contaminants and soil organic matter

Multiannual soil mulching in agriculture: analysis of biogeochemical soil processes under plastic and straw mulches in a 3-year field study in strawberry cultivation

Purpose: The application of plastic mulching differs globally as well as climate, soils, crops, and agricultural practices, making it difficult to generalize the reported impacts on soil. Because literature is scarce about the influence of plastic mulching on soil under temperate, humid climate, the objective of this study was to understand how multiannual plastic mulching influences central soil parameters and processes under Central European cultivation conditions to evaluate its impact on soil quality in the long term. Materials and methods: Central soil parameters and processes like leaching, aggregation, soil organic matter (SOM), and microbial biomass were investigated in a strawberry cultivation in Southwestern Germany. The field experiment compared a plastic-covered ridge–furrow system with subsurface drip irrigation (PC) to the same system with straw coverage (SC) in three soil layers (0–10, 10–30, and 30–60 cm) at seven dates within a 3-year period. Soil analyses comprised soil temperature and moisture, pH, bulk density, water-stable aggregates, soil organic carbon, dissolved organic carbon, and microbial biomass carbon and nitrogen. Results: Rainfall infiltration impeded by PC reduces soil moisture but neither reduces leaching nor promotes (macro-)aggregate formation or stability; however, it maintains a loose and friable soil structure in surface soil (0–5 cm), compared to SC. PC promotes SOM accumulation and shifted SOM composition to a more hardly degradable SOM, especially below the topsoil (10–60 cm). Furthermore, PC revealed no indications of an increased microbial biomass or activity accompanied with an enhanced SOM decomposition due to the shifted microclimate. The seasonal, time- and depth-dependent effects, observed in some parameters, emphasize the importance to include them in future studies for a more holistic process understanding. Conclusion: Our study showed no indications that multiannual plastic mulching influences soil quality within the 3 years of this study. Further research is advisable to support our findings on a larger scale and longer time periods and across various soil and crop types.Universität Koblenz-Landau (3155

Multiannual soil mulching in agriculture: analysis of biogeochemical soil processes under plastic and straw mulches in a 3-year field study in strawberry cultivation

PURPOSE: The application of plastic mulching differs globally as well as climate, soils, crops, and agricultural practices, making it difficult to generalize the reported impacts on soil. Because literature is scarce about the influence of plastic mulching on soil under temperate, humid climate, the objective of this study was to understand how multiannual plastic mulching influences central soil parameters and processes under Central European cultivation conditions to evaluate its impact on soil quality in the long term. MATERIALS AND METHODS: Central soil parameters and processes like leaching, aggregation, soil organic matter (SOM), and microbial biomass were investigated in a strawberry cultivation in Southwestern Germany. The field experiment compared a plastic-covered ridge–furrow system with subsurface drip irrigation (PC) to the same system with straw coverage (SC) in three soil layers (0–10, 10–30, and 30–60 cm) at seven dates within a 3-year period. Soil analyses comprised soil temperature and moisture, pH, bulk density, water-stable aggregates, soil organic carbon, dissolved organic carbon, and microbial biomass carbon and nitrogen. RESULTS: Rainfall infiltration impeded by PC reduces soil moisture but neither reduces leaching nor promotes (macro-)aggregate formation or stability; however, it maintains a loose and friable soil structure in surface soil (0–5 cm), compared to SC. PC promotes SOM accumulation and shifted SOM composition to a more hardly degradable SOM, especially below the topsoil (10–60 cm). Furthermore, PC revealed no indications of an increased microbial biomass or activity accompanied with an enhanced SOM decomposition due to the shifted microclimate. The seasonal, time- and depth-dependent effects, observed in some parameters, emphasize the importance to include them in future studies for a more holistic process understanding. CONCLUSION: Our study showed no indications that multiannual plastic mulching influences soil quality within the 3 years of this study. Further research is advisable to support our findings on a larger scale and longer time periods and across various soil and crop types

Agricultural mulching and fungicides—impacts on fungal biomass, mycotoxin occurrence, and soil organic matter decomposition

Plastic and straw coverage (PC and SC) are often combined with fungicide application but their influence on fungicide entry into soil and the resulting consequences for soil quality are still unknown. The objective of this study was to investigate the impact of PC and SC, combined with fungicide application, on soil residual concentrations of fungicides (fenhexamid, cyprodinil, and fludioxonil), soil fungal biomass, mycotoxin occurrence, and soil organic matter (SOM) decomposition, depending on soil depth (0–10, 10–30, 30–60 cm) and time (1 month prior to fungicide application and respectively 1 week, 5 weeks, and 4 months afterwards). Soil analyses comprised fungicides, fusarium mycotoxins (deoxynivalenol, 15-acetyldeoxynivalenol, nivalenol, and zearalenone), ergosterol, soil microbial carbon and nitrogen, soil organic carbon, dissolved organic carbon, and pH. Fludioxonil and cyprodinil concentrations were higher under SC than under PC 1 week and 5 weeks after fungicide application (up to three times in the topsoil) but no differences were observed anymore after 4 months. Fenhexamid was not detected, presumably because of its fast dissipation in soil. The higher fludioxonil and cyprodinil concentrations under SC strongly reduced the fungal biomass and shifted microbial community towards larger bacterial fraction in the topsoil and enhanced the abundance and concentration of deoxynivalenol and 15-acetyldeoxynivalenol 5 weeks after fungicide application. Independent from the different fungicide concentrations, the decomposition of SOM was temporarily reduced after fungicide application under both coverage types. However, although PC and SC caused different concentrations of fungicide residues in soil, their impact on the investigated soil parameters was minor and transient (< 4 months) and hence not critical for soil quality

Physico-Chemical Soil Properties Affected by Invasive Plants in Southwest Germany (Rhineland-Palatinate)—A Case Study

The invasive plant species Impatiens glandulifera native to Asia mainly occupies European riparian ecosystems. It is still unclear to which extent this invasive plant can alter physico-chemical soil properties in terms of carbon turnover, microstructural stability and soil hydraulic properties threatening native plant species, here represented by Urtica dioica. Soil samples were collected from three sites in the Palatine forest near the river Queich, including bare soil (Control), or soil within dense stands of either I. glandulifera or U. dioica with similar texture. Basic soil parameters including SOM content and quality were analyzed. SOM is known to impact soil microstructural stability and soil hydraulic properties. We therefore assessed microstructural stability, the pore size distribution and the wettability. Our results implied more recalcitrant SOM for soil colonized by U. dioca including a lower pH. For soil colonized by I. glandulifera less recalcitrant SOM was detected indicating a reduced degradation which is likely given due to lignin as a predominant component in the plant biomass of I. glandulifera Soil microstructural stability was higher for soil colonized by the invader showing a slight increase with soil depth, due to higher SOM content. All in all, this case study indicates that I. glandulifera most likely affects the soil microbiome while basic soil parameters, soil hydraulic properties, wettability and soil microstructural stability showed no significant effect

RecA-independent ectopic transposition in vivo of a bacterial group II intron

Final full-text version of the paper available at: http://nar.oxfordjournals.org/cgi/content/abstract/28/21/4397 .-- Copyright © by Oxford University Press. -- Http://nar.oxfordjournals.org/RmInt1 is a group II intron of Sinorhizobium meliloti which was initially found within the insertion sequence ISRm2011-2. Although the RmInt1 intron-encoded protein lacks a recognizable endonuclease domain, it is able to mediate insertion of RmInt1 at an intron-specific location in intronless ISRm2011-2 recipient DNA, a phenomenon termed homing. Here we have characterized three additional insertion sites of RmInt1 in the genome of S.meliloti. Two of these sites are within IS elements closely related to ISRm2011-2, which appear to form a characteristic group within the IS630-Tc1 family. The third site is in the oxi1 gene, which encodes a putative oxide reductase. The newly identified integration sites contain conserved intron-binding site (IBS1 and IBS2) and δ′ sequences (14 bp). The RNA of the intron-containing oxi1 gene is able to splice and the oxi1 site is a DNA target for RmInt1 transposition in vivo. Ectopic transposition of RmInt1 into the oxi1 gene occurs at 20-fold lower efficiency than into the homing site (ISRm2011-2) and is independent of the major RecA recombination pathway. The possibility that transposition of RmInt1 to the oxi1 site occurs by reverse splicing into DNA is discussed.This work was supported by grant BIO99-0905 from the Comisión Asesora de Investigación Científica y Técnica and by grant BIO4-CT98-0483 from the Biotechnology Programme of the EU.Peer reviewe

Restructuring of a Peat in Interaction with Multivalent Cations: Effect of Cation Type and Aging Time

<div><p>It is assumed to be common knowledge that multivalent cations cross-link soil organic matter (SOM) molecules via cation bridges (CaB). The concept has not been explicitly demonstrated in solid SOM by targeted experiments, yet. Therefore, the requirements for and characteristics of CaB remain unidentified. In this study, a combined experimental and molecular modeling approach was adopted to investigate the interaction of cations on a peat OM from physicochemical perspective. Before treatment with salt solutions of Al³⁺, Ca²⁺ or Na⁺, respectively, the original exchangeable cations were removed using cation exchange resin. Cation treatment was conducted at two different values of pH prior to adjusting pH to 4.1. Cation sorption is slower (>>2 h) than deprotonation of functional groups (<2 h) and was described by a Langmuir model. The maximum uptake increased with pH of cation addition and decreased with increasing cation valency. Sorption coefficients were similar for all cations and at both pH. This contradicts the general expectations for electrostatic interactions, suggesting that not only the interaction chemistry but also spatial distribution of functional groups in OM determines binding of cations in this peat. The reaction of contact angle, matrix rigidity due to water molecule bridges (WaMB) and molecular mobility of water (NMR analysis) suggested that cross-linking via CaB has low relevance in this peat. This unexpected finding is probably due to the low cation exchange capacity, resulting in low abundance of charged functionalities. Molecular modeling demonstrates that large average distances between functionalities (∼3 nm in this peat) cannot be bridged by CaB-WaMB associations. However, aging strongly increased matrix rigidity, suggesting successive increase of WaMB size to connect functionalities and thus increasing degree of cross-linking by CaB-WaMB associations. Results thus demonstrated that the physicochemical structure of OM is decisive for CaB and aging-induced structural reorganisation can enhance cross-link formation.</p></div

Aging effects on WaMB transition temperature (A), Lorentzian line fraction (B) and on the amount of mobilisable water (C), expressed by the difference of the respective parameters after and before aging.

<p>Positive values indicate an increase, and negative values indicate a decrease in the parameter, respectively. Dotted line along zero shown in (C) distinguishes the positive and negative effects.</p