In two sites in Balcarce and Necochea counties, on eight trees, mechanical impedance of soil (RM) and fine roots (under 2 mm in diameter) density were determined in the first 50 cm under the soil surface and near the stem. A very high density of fine roots was found at 20 cm depth in both sites, while a low density of f ine roots was observed in soil zones with high RM values. These high values corresponded with a clayey horizon in Balcarce site and a till induced pan in Necochea site. Over 0.5 Mpa RM values the fine roots diminished. RM should be considered as an important tool to detect radical growth limitant conditions and the basis to select tillage during pre-plantation labors.