Abstract

The aim of this work was to evaluate the effect of the land use change (CUS) of a Ñadi soil (Aquands) from secondary forest to naturalised grassland, on the aggregate stability (tensile strength and shrinkage capacity) and its relationship with the soil water tension (drying effect), the wetting capacity and the soil organic carbon. The site belongs to the Alerce soil series. The research unit consists of four land uses: Renewal Alerce Forest (BN1), a secondary native forest (BN2), naturalised pasture 1 (PN1, without mole drainage), and naturalised pasture 2 (PN2, with mole drainage). Four soil depths were sampled at each site. Total porosity (PT), plant available water (ADP), air capacity (CA), aggregate shrinkage capacity (COLE), mechanical resistance (Crushing Test method), repellency index (Sorptivity) and soil organic carbon (CO) were determined. CUS in Aquands alters the water regime causing a loss of PT (down to 28% in H1) and 30% of ADP in the surface horizons (H1 and H2), which restricts the shrinkage capacity of aggregates. Although all the aggregates in every site shrink due to water loss, PN1 and PN2 show less shrinkage (COLE > 0.15) due to lower PT and higher bulk density (0.53 Mg m-3). The intensification of land use causes changes in the CO content of the soil, which decreases as the depth increases (27% to 5%) in all soil uses evaluated.