Impact of leguminous living mulch on soil microbial biomass and activity in different European climatic zones

The positive effect of Living Mulch on soil microbial biomass and its activity was more evident in the Mediterranean environment starting from the main crop planting (t1) . Conversely, in the Northern site the effect of LM was significant in not tilled soil at the main crop harvesting (t2). These preliminary results establish the bases for the final evaluation at end of the project, on the importance of pedoclimatic conditions to prove the effect of Living Mulch at different tillage levels

Brassica spp cover crop affects soil microbial activity, carbon and nitrogen nutrient dynamics

A general positive effect of Brassica on soil microbial biomass and its activity was observed at all European sites in no tilled soil at both sampling date. Conversely, Brassica under tillage may produce a negative effect on biochemical properties after CC suppression. The effect of Brassica on C and N dynamics differed among the european sites when soil was tilled. These preliminary results establish the bases for the evaluation of the interaction between the pedoclimatic conditions and Brassica spp effect on soil properties

Inorganic component in oak waterlogged archaeological wood and volcanic lake compartments

Waterlogged archaeological wood (WAW) is a rare and precious organic material that can hold outstanding cultural values. In order to protect WAW for the next generations, this material must be accurately characterised to set its proper conservation, storage and exhibition conditions in museum environments. In this study, the mineral content found in WAW retrieved in a volcanic lake was investigated by analysing wood ash through scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM-EDS). This micro-destructive approach was coupled with morphological studies carried out through optical microscopy. SEM-EDS was also performed on the WAW and surrounding sediment to study the possible relationship between the mineral composition and the wood degradation state. The analysis revealed that calcium was the most abundant element in all poles, with weight percentages ranging between 24 % and 42 %. This element was more represented in heartwood (HW) than sapwood (SW). In sapwood the second most abundant element was arsenic. Sulfur, iron and potassium were present in all the analysed samples as well. Arsenic was also detected in the sediments; it was particularly concentrated in the samples taken near archaeological wood. The presence of this element can be linked to the volcanic origin of the lake, and its high concentration points to bioaccumulation processes induced by bacteria (erosion bacteria and sulfate-reducing bacteria) and biogeochemical processes favouring precipitation of insoluble compounds. The present work is the first investigation of the mineral content in archaeological wood establishing a contingent relationship with the surrounding volcanic lake sediments.</p

Copper distribution among physical and chemical fractions in a former vineyard soil

The Copper (Cu) contamination of vineyard soils due to the heavy use of copper-based fungicides is a well known problem (Probst et al., 2008; Fernãndez-Calviño, 2008). Since Cu is scarcely mobile in soils, it tends to accumulate in surface horizons (Pietrzak and McPhail, 2004) even after land use change (FERNÃNDEZ- CALVIÑO, 2008). This Cu accumulation is well beyond the natural background concentrations of metal normally found in soils (22-55 mg kg-1 depending on the nature of the parent material) (Baker and Senft, 1995). Adsorption is a key process responsible for accumulation of heavy metals in soil and regulates their concentration in solution, which is also influenced by inorganic and organic ligands (Bradl, 2004; Violante et al., 2008). Cu in soils may occur in several forms that are partitioned between the solution and the solid phases. Cu bioavailability and phytotoxic- ity is closely related to its distribution in different chemical forms. Exchangeable Cu may be readily mobilized to the soil solution, with negative effects for plants and soil organisms. On the other hand, Cu phytoavailability can be reduced by Cu binding to soil organic mat- ter (Bolan and Duraisamy, 2003). Cu distribution in the different chemical forms depends on several soil properties, such as pH, redox potential, cation exchange capacity (CEC), texture, soil organic matter (SOM), as well as Mn and Fe oxides content (McLaren et al., 1983; Sims, 1986). Cu fractionation studies have shown that this metal exists in soils predominantly as organically bound, in residual, precipitated, or acid-soluble form (Berti and Jacobs, 1996; Alva et al., 2000). The most important interfaces involved in Cu adsorption in soils are Fe and Mn oxides, SOM, sulfides and carbonates (Jenne, 1968)

Assessment of soil microbial functional diversity: land use and soil properties affect CLPP-MicroResp and enzymes responses

The assessment of microbial functional diversity is an important indicator of soil quality. Different methodo- logical approaches are currently used; among them are enzyme activities (EA) and CLPP (community level physiological profile) techniques (e.g. MicroResp™, MR). The aims of the study were: i) to assess the efficacy of both methods in capturing differences among various land use categories when different levels of selected ex- planatory variables such as, total organic carbon (TOC) and pH are considered, and ii) to explore, through a quantile regression approach, the possible relationships between each of the two methods with land use cate- gory, TOC and pH. The Shannon diversity index (H’), calculated from EA and MR data, was chosen as a synthetic index deriving from the same mathematical model. The quantile regression model (QRM), the Kruskal-Wallis and Spearman rank correlation tests were performed. Enzyme activities and MicroResp were reliable ecological indicators to assess soil microbial functional di- versity. No correlation was found between the diversity indexes, H’EA and H’MR; it was therefore supposed that the two methods may target complementary components of microbial functional diversity. Both methods were effective in capturing differences among various land use categories, in particular H’MR in soils with low TOC content (&lt; 1.5%). Moreover, the QRM approach allowed a more detailed analysis along the distribution of the diversity indexes (H’EA and H’MR) indicating that H’EA was more dependent on the selected variables

Contaminazione dei prodotti agricoli da arsenico: assimilazione e strategie di mitigazione

Arsenic (As) is an element widely distribu- ted in air, soil, rocks and water. Its presence is due to both the volcanic character of the soil and the erosion of rocks. The highest concentration of this element is found in groundwater. The presence of As in water is mainly due to either natural release of the minerals from the soil (volcanic rocks and iron minerals) or to geothermal activity. The presence of As is also linked to human activities, such as energy production throu- gh coal-fired power plants and other fuels derived from fossil fuels, smelters, waste incineration and use of pesticides in agriculture. In the environment As undergoes oxidation, reduction, methylation and demethylation. The oxidation states are: -3, 0, +3 (arsenite) and +5 (arsenate). Commonly As binds to iron, oxygen and sulfur, which form organic and inor- ganic compounds in different oxidation states. Arsenic is extremely toxic, but the toxicological effects are clo- sely related to the chemical form: inorganic com- pounds have been identified as the most toxic, fol- lowed by organic and finally by arsine gas. The toxi- city varies fact, in descending order to the various forms of speciation. For humans the main source of environmental exposure to As is drinking water, where it is present in inorganic form: both as trivalent arsenic As(III) and pentavalent arsenic As(V), but also through the air and food. Arsenic enters the food chain throu- gh plant crops, which absorb it through their roots according to its bioavailable levels in soils. Arsenate is transported by roots via phosphate transporters, while arsenite is taken up by a subclass of aquaporins (NIP), some of them also transporting silicon (Si). Methylated forms of As (MetAs) are also taken up by NIP and Si transporters. Inside plants, these types of transporters are also involved in the distribution of As between organs and tissues. However, different forms of As have different mobility efficiencies. Crops exhibit different tendencies to accumulate As in different plant parts in their order: root &gt; stem &gt; leaf . As(V) is enzy- matically reduced into As(III) in plant cells by arsenate reductase (AR), leading to the conversion of glutathio- ne (GSH) to its oxidized form (GSSG). Arsenite can be effluxed to the environment by a root Si transporter or methylated. Another pathway of detoxification occurs by the synthesis of phytochelatins (PCs). PC synthesis and their complexation to As(III) are coordi- nated to the transport of the PC–As(III) complex to the vacuole. For a proper assessment of risk/toxicity of a polluted As soil and to predict its attenuation, after application of remediation techniques, it is crucial to establish the mobility, phytoavailability and biogeoche- mistry of the toxic element. In this review we describe the mechanisms of transport, metabolism and toleran- ce that plants show in response to As. Some strate- gies to reduce As in soil and its transport in plant crops are also summarized