Effect of Organic Farming and Agricultural Abandonment on Beneficial Arthropod Communities Associated with Olive Groves in Western Spain: Implications for Bactrocera oleae Management

Agricultural abandonment and intensification are among the main land-use changes in Europe. Along with these processes, different proposals have been developed to counteract the negative effects derived from agricultural intensification, including organic management. In this context, we aimed to determine how organic management and farmland abandonment affect Bactrocera oleae and its main groups of natural enemies: hymenopteran parasitoids, spiders, ants, carabids, and staphylinids. Between May and October 2018, four samplings were carried out in nine olive groves (three under organic management, three under traditional management, and three abandoned) in a rural area on the border between Spain and Portugal (Salamanca, Western Spain). Our results suggested differences between the natural enemy community composition of abandoned and organic groves, with slightly higher levels of richness and abundance in abandoned groves. We found no differences between organic and traditional groves. The managed olive groves sustained a different natural enemy community but were similarly rich and diverse compared with the more complex abandoned groves, with the latter not acting as a reservoir of B. oleae in our study area. Both systems may provide complementary habitats; however, further abandonment could cause a reduction in heterogeneity at the landscape scale and, consequently, a biodiversity loss.

Organic farming practices change the soil bacteria community, improving soil quality and maize crop yields

Background The importance of organic farming has increased through the years to promote food security allied with minimal harm to the ecosystem. Besides the environmental benefits, a recurring problem associated with organic management is the unsatisfactory yield. A possible solution may rely on the soil microbiome, which presents a crucial role in the soil system. Here, we aimed to evaluate the soil bacterial community structure and composition under organic and conventional farming, considering the tropical climate and tropical soil. Methodology Our organic management treatments were composed by composted poultry manure and green manure with Bokashi. Both organic treatments were based on low nitrogen inputs. We evaluated the soil bacterial community composition by high-throughput sequencing of 16S rRNA genes, soil fertility, and soil enzyme activity in two organic farming systems, one conventional and the last transitional from conventional to organic. Results We observed that both organic systems evaluated in this study, have higher yield than the conventional treatment, even in a year with drought conditions. These yield results are highly correlated with changes in soil chemical properties and enzymatic activity. The attributes pH, Ca, P, alkaline phosphatase, and β- glucosidase activity are positively correlated with organic systems, while K and Al are correlated with conventional treatment. Also, our results show in the organic systems the changes in the soil bacteria community, being phyla Acidobacteria, Firmicutes, Nitrospirae, and Rokubacteria the most abundant. These phyla were correlated with soil biochemical changes in the organic systems, helping to increase crop yields. Conclusion Different organic management systems, (the so-called natural and organic management systems, which use distinct organic sources), shift the soil bacterial community composition, implying changes in their functionalities. Also, our results contributed to the identification of target bacterial groups and changes in soil chemical properties and enzymatic activity in a trophic organic farming system, which may contribute to higher crop yields.

Impacts of Erosion on the Sustainability of Organic Olive Groves: A Case Study (Estepa Region, Southwestern Spain)

Spain has more than 2.5 M ha of olive groves, with 60% of this area (i.e., 1.5 M ha) concentrated in the region of Andalusia (Southern Spain). Assuming the socio-ecological characteristics of these crops, of which their contribution to ecosystemic services (ES) is fundamental for society, it is highly relevant to direct their management towards practices that guarantee their durability. Organic management of olive groves constitutes a multifunctional model that contributes to ensuring its sustainability and represents 2.4–3.5% of the olive grove area in Spain. Taking the Protected Designation of Origin (PDO) Estepa (Southwestern Spain) as a study model, where organic olive groves are novel, a study of the impacts of erosion on the economic, social, and environmental factors associated with this management was carried out in addition to estimating its impacts. The results showed how organic management promotes edaphic fertility, keeping the levels of diffuse pollution under the legislative limits. Although the increase in erosion has negative effects on the sustainability/durability of agricultural holdings, organic management consolidates a sustainable model that satisfies farmers’ demands. Therefore, organic farming is a model that focuses on the correct use of natural resources associated with the geographical region of study, and contributes to increasing the sustainability of olive groves.