Hydraulic properties of the diagnostic horizon of Latosols of a regional toposequence across the Brazilian Central Plateau

The Brazilian Central Plateau covers about 40% of the Cerrados Biome and represents 24% of the Brazilian territory. The Latosols correspond to about 40% of the Central Plateau. We analyzed the hydraulic properties of a set of Latosols varying according to clay content and mineralogy along a regional toposequence across the Brazilian Central Plateau. We studied the properties of the diagnostic horizon (Bw) of Latosols located on the South American and Velhas Surfaces. We measured the bulk and particle density, the water retention properties at -1, -6, -10, - 33, -300, and - 1500 kPa by using the centrifugation method, and determined the saturated hydraulic conductivity (Q in the field using the Guelph permeameter. Results showed that the total pore volume explained a proportion of the variance of the water retained that decreased with the water potential. On the other hand, the clay content explained a proportion of that variance that increases when the water potential decreased. The great proportion of variance (90.7%) explained for by the clay content alone at - 1500 kPa showed that there is little variability that can be attributed to clay mineralogy variation. The K, value was related to an effective porosity for the Bw of Latosols studied and was defined as the volume proportion of pore with an equivalent diameter of > 300 mu m, since it was occupied by air at - I kPa. Results showed that water retention properties and, varied mainly according to the clay content and development of large pores without any close link with the mineralogy of the clay fraction