Fungi in coastal tableland soils of northeastern Brazil:Preliminary results

Soil compaction causes reduced agricultural production due to limited root development resulting in reduced water and nutrient access. This is particularly true of soils of the Brazilian tablelands (similar to200000 km(2)) that are characterized by a naturally occurring compact subsoil horizon. Most of these soils have a coeso layer with a density that limits agricultural production. Deep plowing has been the main treatment to alleviate this problem. This study was carried out to identify some fungi associated with an Argissolo Amarelo coeso (Ultisol) in the coastal tableland, in northeastern Brazil (16degrees10' to 16degrees30'S and 39degrees05' to 49degrees40'W). The fungi were evaluated on soil samples from cultivated areas under natural forest, rubber tree (Hevea brasiliensis Willd.), pasture, and annual crops at 0 to 15 cm and 35 to 50 cm depths. The predominant groups (Penicillium spp and Dematiaceac), were analyzed by Random Amplified Polymorphic DNA (RAPD) molecular markers. Other identified groups included Monilia, Aspergillus and Eurotiaceae. The soil under annual cropping showed a trend to higher diversity of fungi. The presence of fungi in the coeso horizon illustrates the biological activity that occurs in a compact subsoil horizon and a probable interaction with the organic C. These preliminary results suggest that die presence, quantity, and activity of associated fungi and bacteria and root dynamics be studied to better understand the environmental and agricultural functioning of this subsurface horizon.