CONDIÇÃO ESTRUTURAL DE UM ARGISSOLO NO RIO GRANDE DO SUL, EM FLORESTA NATIVA, EM PASTAGEM CULTIVADA E EM POVOAMENTO COM EUCALIPTO

This study aimed to define the critical limits of physico-hidric attributes to areas under forest and pasture and to evaluate the intensity of compression of these uses in a Hapludalf in South Brazil. The use of soils were: Native Forest - formed for arboreal species; Pasture - five years old, constituted of Brachiaria brizantha associated with Paspalum lourai and Trifolium sp.; Eucalipto 20 - Eucalyptus saligna with 20 years old, installed under conventional tillage; Eucalipto 4,5 - Eucalyptus saligna under 2nd rotation, 4.5 years old. It was evaluated the hydraulic conductivity, macro, micro and total porosity and bulk density. The eucalypt is a potential crop to be used in recovering degraded areas with no commercial objective. Soil compression increase bulk density and decrease macroporosity and total porosity until the layer of 0.40 m in eucalyptfor commercial use and until 0.10 m in pasture. Values based on restriction and yield of annualcrops or in the least limiting water range have potential to be used as restrictive values for perennial and pasture crops.