Alterações na dinâmica evolutiva de latossolo bruno pela calagem

Soils as open systems, mantained in steady state by natural fluxes, are suscetible to perturbations by anthropic activities that may induce a new dynamic state. This hypothesis was tested on samples from experimental plots limed 23 years ago with up to 40 t ha -1 , to identify possible mineralogical changes. Liming increased pH, Ca, Mg, Na, and CEC, and decreased organic C, exchangeable Al, K, and Mn. The effect of the lime originally applied on the surface layer (0-20 cm) was evident down to 60-80 cm depth. In the soil solution, liming increased pH, Ca, Mg, and decreased the activity of Al, whereas H 4 SiO 4 was unaffected. The increase of dissolved organic carbon, and of SO 4 2- indicates that the microbiological system was also affected. The mineral stability diagram (pH - 1/3pAl versus pH 4 SiO 4 ) indicates an equilibrium condition for kaolinite at the soil original steady state, in accordance with the dominance of kaolinite over hydroxi-interlayered smectite (HIS). In the 40t ha -1 plot, even though mineralogical changes were not detected by XRD, the decrease of the Al activity indicates a decrease of the HIS interlayering process.