In Venezuela approximately 200 000 ha are planted with coffee (Coffea arabica L.) mostly on the steep slopes of the Andes. Traditionally, coffee is cultivated with few or no agrochemical inputs in an agroforestry system, cropped under the shade of tree species of the leguminous family and other bushes. In recent years, with adoption of high yielding, early varieties of short stature, coffee is being produced in full sunlight with addition of mineral fertilizers and pesticides. The soil microbiological properties especially those related with the fluxes of energy and nutrient cycling, respond promptly to changes in soil conditions, often much earlier than organic carbon and, in this way, are early indicators of alterations in soil quality. In this study, we compared the microbiological activity (basal respiration), microbial biomass and derived ecophysiological ratios of topsoils (0-5 cm) collected from eight farms in the municipalities of Merida and Trujillo that practice traditional (agroforestry or shaded coffee), conventional (sun coffee or intensive monoculture) and organic (agroforestry or shaded coffee) production. The organic agriculture farms showed the highest contents of total organic carbon, water soluble carbon, basal respiration and microbial biomass compared with traditional and conventional farms. This means a more sustainable coffee system with better conservation of natural resources and environment-friendly production. On conventional farms, added fertilizers and pesticides negatively affect microorganism performance and are more inefficient in terms of carbon and energy use.

The microbiological activity is essential to maintain soil quality, and agroforestry systems emerge as an alternative to the agro-ecological and sustainable land management. This work evaluated the effect of the Caturra and Catuaí coffee varieties, and the weather fl uctuation on some microbiological properties of the soil, as indicators of quality in an agroforestry system. The soil samples were taken from the top layer with a depth of 5cm, during a year in dry and rainy seasons. The highest CO2 emissions were observed in soils with the Catuaí variety, in the dry season. On the other hand, Carbon levels