Fig. 2. Results of amplitude sweep tests with (distilled water) saturated samples of (a) a Calciudert (and under predrained conditions), Santana do Livramento, (b) a sandy and (c) a clayey Hapludox from Cruz Alta, (d) a clayey Hapludox under natural forest, and (e) a clayey Hapludox under no-tillage conditions, both from Santo Ângelo. G' = storage modulus, G'' = loss modulus, = shear strain, SOM = soil organic matter, Fe_d = dithionite-soluble iron.