Variações morfológicas, mineralógicas e hidricas em terra roxa estruturada ao longo de uma vertente em Rio das Pedras (SP)

The lateral variations of soil features such as morphology, mineralogy and water storage were studied in a toposequence of Kandiudox. It is characterized by a very well developed subangular blocky structure whose grades increases both from the botton to the upper part of B horizon as well as dowslope, which is shown also through a gradual incraese of bulk density. In the upper part of the slope, with nearly flat relief, a very fine granular structure occurs in the base of the pedon, which disappears in the lowest part of the slope due the soil structure transformation. The soil profiles are mainly developed from igneous basic rocks. The parent material of the lower part of the toposequence has also a minor contribution of shale according field observations and mineralogical data. Kaolinite is the dominant clay mineral. Minor components are gibbsite, mica and hydroxy interleyered vermiculite. During the period november, 1981 to december, 1982, with respect to the hydrodynamics, there is a gradual increase in the average values of water content dowslope from pedon 1306 to 1308 with a slight decrease in pedon 1309, probably associated to the reduction of total porosity due the increase in bulk density. There is a sharp increase dowslope of the water content of all subsurface horizons with blocky structure as well as the very fine granular one. It was also found that the surface horizons are subject to intense seasonal variations of moisture in the slope which could favor the lateral soil evolution of the subsurface horizon