# Sustainable Agriculture and Soil Conservation
## 2 Overview of This Special Issue
Specifically, they compared three horticultural systems in Metaponto (south Italy): (1) ECO (organic system with full implementation of agroecological strategies, agroecological services crops (ASC), strip cultivation and organic amendment), (2) GM (organic system with the introduction of ASC) and (3) no ASC (organic system without agroecological services crops). The qualitative response of the DEXi-met model suggested that the treatments with ASC returned similar total energy outputs, indicating the positive effect of this agroecological practice. Therefore, the authors pointed out that the ECO system could contribute to building up more complex agroecosystems, increasing both the resilience and biodiversity in organic agriculture. [PERSON] and [PERSON] [21] presented a standardized method, named Biolog\({}^{\text{(\ref{eq:Bic})}}\) EcoPlates\({}^{\text{TM}}\) (Biolog Inc., Hayward, CA, USA), to analyze the functional diversity of bacterial communities by means of measuring their ability to oxidize carbon substrates. Specifically, they reported a detailed methodological procedure which was easy to follow and reproduce (i.e., a detailed and step-by-step description of soil preparation, dispersion and dilution,optimal bacterial density of the inoculum and so on), based on previous data and experiments. To this aim, a case study of the soils of a Mediterranean olive orchard was reported for comparing the methods and justifying the methodological protocol proposed. The authors emphasized that the results of this methodological paper could be important for correctly evaluating and comparing the microbiological fertility of the soils managed with sustainable, conservation-based practices or conventional, non-conservation-based ones. Topic II comprises four papers. [PERSON] et al. [17] evaluated the impact of differentlevels of crude oil on the soil properties, physiological and chemical parameters of maize leaves and the phenanthrene content in the leaf. The results showed that (1) the soil water content significantly increased as the total petroleum hydrocarbons increased, and the soil electrical conductivity significantly increased compared with the control, and (2) the stomatal length and density, leaf K and Na contents and phenanthrene leaf concentration decreased in the contaminated soil compared with the reference group. The authors concluded that the stomata structure of maize could be influenced by crude oil, thus possibly controlling the accumulation of polycyclic aromatic hydrocarbons in aerial tissues. Practical implications for contaminated soil management were also hypothesized. Indeed, because stomata can play a key role in the aerial uptake of pollutants, regulation of stomatal movement can be usefully applied in phytoremediation of contaminated soil. [PERSON] and [PERSON] [18] investigated the influence of the soil characteristics on the tungsten uptake for three different soils--Histosol, Vertisol and Fluvisol--in the Mediterranean area. Tungsten is largely used in high-tech and military industries. Therefore, soils are increasingly enriched in this element, and the possible transfer in the food chain represents a current issue in agroenvironmental studies. The results showed that tungsten concentrations in the roots and shoots increased with the increasing soil pH and decreased with the increasing organic matter. Further investigations were suggested by the authors to fully understand the mechanisms of tungsten transfer from the soil to the plant and the corresponding environmental impact of this element on human health. [PERSON] et al. [19] reviewed the issue of copper (Cu) accumulation in European vineyard soils due to massive application from different sources (among others, metal-contaminated sludges and Cu-based pesticides for crop defense against pathogens). Although Cu is an essential micronutrient for equilibrated crop growth, excessive Cu concentrations in soil may lead to severe symptoms of toxicity, which are beginning to be recognized in crops and, particularly, in acidic soils.