Liming influences some electrochemical properties of soils of variable charge that may affect clay dispersion and aggregate stability. This hypothesis was tested after five years of incorporation of increasing rates of limestone (0, 4.5, 9.0, 13.5 and 18 t ha-1) into a Brown Latosol (Haplohumox). Dolimitic limestone was plowed down to 17 cm depth into the soil during the spring of 1992 when field plots began to be cultivated annually with continuous corn. Soil samples used in this work were collected in the spring of 1997. Liming increased the amount of clay dispersed in water (R² = 0.93**), negative surface electric potential (R² = 1.00**), point of zero salt effect PZSE (R² = 0.85*) and slightly decreased soil organic matter (R² = 0.83*), but had no effect on soil aggregate stability. The increase on PZSE was probably caused by the decrease of soil organic matter. Clay dispersion was positively associated with surface electric potential (R² = 0.93**) and its increase was probably due to higher repulsive forces among soil particles as a consequence of either increases on CEC and on thickness of electric double layer.
variable charge soils; liming; soil aggregation; clay dispersion