Mariana Marasas

Changes in soil arthropod functional group in a wheat crop under conventional and no tillage systems in Argentina

Abstract Different functional groups of soil arthropodofauna present in the agro-ecosystem can be severely modified by tillage practices. The abundance of different trophic groups subject to conventional tillage (CT) and no tillage (NT) practices were evaluated compared to a natural field boundary (FB) in a wheat crop. Arthropods were captured using pitfall traps and collected every 20 days during 10 months, and grouped according to their habits in predators, phytophagous and detritivorous. Tillage systems affected the abundance of arthropod fauna and the proportion between different functional groups as regards a FB. Predators constituted the most abundant group of all arthropods captured, and their number was higher under NT than under CT. In CT, an increase in predators was observed only in spring, probably associated with a recolonisation from the adjacent plots of NT. Phytophagous was the least representative group in the three evaluated systems, it was higher under cropped plots (NT and CT) than in the FB, and was not affected by tillage practices. Under NT, the number of predators, remained higher along the crop development. Phytophagous activity in no till plots remains constant. In FB, the number of captured individuals was lower and relatively stable along the whole sampling period than in the cultivated plots. Ploughing action (CT plots) provoked a decrease in the relative importance of predators and an increase in phytophagous as regards those in NT and FB. Total biomass of captured arthropod fauna showed significant differences between treatments, being higher in NT and lower in CT plots. It is concluded that tillage systems affect not only the abundance of arthropod fauna but also the proportion between different functional groups. The consequences of these changes for soil quality are discussed later on.

Semi-Natural Habitats and Field Margins in a Typical Agroecosystem of the Argentinean Pampas as a Reservoir of Carabid Beetles

Changes in edaphic carabidofauna abundance in a wheat crop plot, its field margins, and four semi-natural adjacent habitats were evaluated. A low specific richness of carabids was found in the wheat crop. No species was found exclusively in the wheat plot, but there were species found in the surrounding habitat. The observed responses of different species regarding moisture conditions determined their presence or absence in these semi-natural habitats as well as in dominance structures of each particular ambient. A gradual decrease in the number of captured individuals from the field margin to the center of the wheat plot was observed. Semi-natural habitats and field margins become an important requirement for habitat and shelter of the best represented species of ground beetles, particularly for predatory and omnivorous varieties.

Seed Conservation by Family Farmers in the Rural–Urban Fringe Area of La Plata Region, Argentina: The Dynamics of an Ancient Practice

Two key components of biocultural diversity are agrobiodiversity and knowledge. There is scarce information regarding seed conservation practices for rural–urban fringe areas, where the Green Revolution model is part of farmers’ rationality. The dynamics of such practice can be observed in La Plata’s Green Belt (Argentina). Conserved seeds and conservation criteria are recorded, in an area where 71.5% of cultivated (traditional and commercial) agrobiodiversity is conserved. With the introduction of commercial seeds, a process appears in which local wisdom comes into play to adapt to external requirements, which leads to the generation of new knowledge. The relation of this practice with the sustainability of family agroecosystems is analyzed.

Brief history of agroecology in Argentina: origins, evolution, and future prospects

ABSTRACT Agroecology emerged as a new approach and paradigm of agricultural science to provide strategies for the design, evaluation, and management of sustainable agroecosystems. It arose as a reaction to the consequences of an environmentally unsustainable and socially exclusive production model. Due to its multidisciplinary and pluri-epistemological character, its scientific approach as a movement, and a series of strategies and techniques, the incorporation and consolidation of agroecology in Argentina recognizes different goals, actors, and stages. The role of nongovernmental organizations, governmental institutions, universities, other educational institutions, and farmers’ organizations is analyzed, and the potential and limitations for future expansion are discussed.