Mediterranean soils are particularly threatened by salinization and low levels of organic matter content. In order to assess an edaphic sustainable use, we need to study its characteristics and better understand the temporal and spatial evolution. In this study, a total of 14,852 ha located in a western Mediterranean basin were selected as the study site where 1417 and 1451 topsoil samples were analyzed in 2001/2002 and 2011/2012, respectively, for Soil Organic Matter (SOM) content, pH water (pHw) and electrical conductivity (EC). Classical statistics and geostatistics techniques were used and the individual soil samples were related with the cultural system (CS) practiced–rainfed/irrigation–and the Reference Soil Group (RSG)–Cambisols, Calcisols, Luvisols, and Fluvisols. Predictive maps were created by interpolation using the Ordinary Kriging algorithm. The main results of this study were that, when transitioning from a rainfed to irrigation CS, SOM content is maintained in Cambisols but decreases in the other RSGs, pHw is maintained and EC increases in Fluvisols, Luvisols, and Cambisols. Over time in the rainfed CS all RSGs maintained SOM and pHw but EC increased in Fluvisols, Luvisols, and Calcisols and in the irrigation CS SOM decreased in Luvisols, pHw increased in Fluvisols and Calcisols and EC increased in all RSGs.

Ecosystem services (ES), as an interconnection of the landscape mosaic pieces, along with temporal rivers (IRES) are an object of research for environmental planners and ecological economists, among other specialists. This study presents (i) a review on the importance of IRES and the services they can provide to agricultural landscapes; (ii) a classification tool to assess the impact of IRES to provide ES by agricultural landscapes; (iii) the application of the proposed classification to the Caia River in order to identify the importance of this intermittent river for its surrounding agricultural landscape. The classification of the ES follows the Common International Classification of Ecosystem (CICES) classification that was adapted for the purposes of this study. Firstly, the list of ES provided by agricultural landscape was elaborated. In the next step, we assessed the potential of IRES to provide ES. Next, IRES impacts to ES within the agricultural landscape were evaluated according to observations from the conducted field monitoring in the study area. This study focuses on the relevance of the intermittent Caia River—a transboundary river in Spain and Portugal—and its ephemeral tributaries in the agricultural landscape. Our study estimates that each hydrological phase of IRES increases the ES provided by the agricultural landscape. However, the dry phase can potentially have negative impacts on several services. The intensification of the agricultural sector is the main provision of the water resource within the Caia River basin, but we were able to identify several other ES that were positively impacted. The present study is in line with the conclusions of other authors who state that IRES constitute a valuable resource which should not be underestimated by society.

Abstract:The soil exchange complex consists of colloidal materials on which ion exchange phenomena occur allowing it to attract, retain, and exchange elements that have opposite electric charges. Since their mineral constituents (clay) and organic components (humus) are mainly of a negative nature retained or exchanged ion are predominantly cations. Historically, failing to monitor parameters like the exchange sodium percentage (ESP) has led to the permanent deterioration of soils which have become completely unproductive, largely reducing the sustainability of the agricultural systems. This study assesses how the sodium exchange capacity in irrigated soils differs from the rainfed ones through a sample survey that was carried out in the 15,031 ha of the Caia Irrigation Perimeter and adjacent areas, located in the municipalities of Elvas and Campo Maior, Portalegre District, Portugal where 14,280 georeferenced samples were collected from the top soil layer (0-20 cm), which were mixed 10 at a time so that each composite sample representing 11.1 ha. Then the samples were analyzed regarding the most relevant parameters for characterizing the soil exchange complex including the concentrations of exchanged bases and Cation Exchange Capacity (CEC). The results were arranged in a georeferenced grid with 1451 entries. Using classical statistical analysis and Geographic Information Systems (GIS) software, it was possible to relate the individual soil samples analyzed with the cultural system practiced (irrigated or rainfed) and the present soil group which permitted us to analyze the influence of the cultural system in the soil exchange complex. The distribution chart of the exchange sodium and CEC were created. The obtained results confirm a general decrease of CEC values and an increase of the exchangeable sodium content of irrigated explored soils when compared to the rainfed ones, putting forward noteworthy ideas not only regarding the necessary changes towards the sustainability of these irrigated agricultural landscapes, but also considering the impact of these productive techniques on different agricultural systems.

Soil's microbiological settlement in a Zea mays parcel under long-term agricultural practices aiming to minimize the disruption of the soil's structure, composition and natural biodiversity was analyzed by culture-dependent and culture-independent processes. Of the different processes, morphological-type differentiation of cultured microflora produced the best results and, while Polymerase Chain Reaction (PCR)-agarose electrophoresis has also provided us with reliable ones, soil PCR-DGGE (Denaturing Gradient Gel Electrophoresis) did not, which may occur because of the dependence of the method on the practice. Over a three-year period, this soil seemed very stable as its C/N ratio remained roughly constant and available for microbial growth. Because no soil overturning occurred, we were able to maintain most of the cultured microbial population whose fluctuations depended only on edaphoclimatic conditions. The number of cultured bacteria, molds, total microorganisms, and the biodiversity indices were usually lower in the driest season (fall) than in the rest of the year, except for Acinetobacter and Stenotrophomonas, which showed the opposite behavior. Coincident with the rise in temperature during the summer, the relative abundance of Gram+ bacteria increased, mostly reflecting an increase in the spore-forming bacteria Streptomyces and Bacillus. Despite these variations, the evenness index and the quantity of distinct microbiological life remained practically unaltered, recovering their maximum levels when the proper edaphoclimatic conditions were present, which indicates the long-term stability of the microbial community in this soil. The performed study put forward important insights for assessing the sustainability of maize production under long-term conservation agriculture management systems, highlighting that adequate management might prevent the degradation of soil quality, thus contributing to promote sustainable agriculture.

In the Mediterranean basin, edaphic salinization, sodification and alkalinization related to anthropic pressures and climatic changes may hinder the ecosystem sustainability. It is pertinent to study the mid and long-term variability of these soil characteristics in face off the macro agricultural system in use (i.e., irrigation or rain-fed). Four irrigated soils from the Caia Irrigation Perimeter (Portugal), Fluvisols, Luvisols, Calcisols and Cambisols were analysed in the mid-term, from 2002 to 2012, for its available Ca2+, Mg2+, K+ and Na+ content. Overall, Ca2+, K+ and Na+ significantly increased during the period of this study by 25%, 8% and 7%, respectively. Soil organic matter (SOM) and pH for the irrigated soils in the area were already assessed in previous studies with the overall SOM remaining constant (p ≥ 0.05) and pH increasing (p < 0.01) by 5%. We provide the predictive maps for Na+ and the CROSS predictive & HotSpot evolution map from 2002 to 2012. Rain-fed soils were analysed in the long-term, from 1965 to 2012, for their SOM, pH and non-acid cations (Ca2+, Mg2+, K+ and Na+) content. While SOM, pH and the exchangeable Ca2+, Mg2+ and K+ significantly increased (p < 0.01) by 23%, 8%, 60%, 21% and 193%, respectively, exchangeable Na+ significantly decreased (p < 0.01) by 50%. These results may be related to the local climate changes as, according to the Thornthwaite classification, it went from sub-humid with great water excess (C1B2s2b4) in the climate normal 1951/1980 to sub-humid with moderate water excess (C1B2sb4) in 1981/2010 to semi-arid with little to none water excess (DB2db4) in 1991/2020. The irrigated areas in this Mediterranean region are slowly departing from sustainable goals of soil conservation and better edaphic management and conservation practices, that address the registered climatic changes in the area, could be adopted.

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Abstract:The effect of freeze-storage on culturable soil microorganism viability was determined for soil samples from three agricultural maize crop systems (under conventional management, direct seeding, and direct seeding with a cover crop). Most culturable soil bacteria were unaffected by the freeze-thaw stress or the prolonged freeze-storage, but the viability of mold and Bacillus mycoides populations decreased drastically after eight months of freeze-storage, limiting the process sustainability to this period. However, these changes did not significantly affect either the total microorganism biodiversity index or the biodiversity differences between treatment. Based on the available results, freeze-storage seems to be a sustainable process for up to eight months that can be allowed in analyses of culturable microbial population biodiversity.