Variability of apparently homogeneous soilscapes in Sao Paulo State, Brazil. I. Spatial analysis

aluminio aluminium analysis base saturation brasil brazil cations densidad density fosforo gestion du sol glycine max ion exchange capacity land use manejo del suelo muestreo organic carbon ph phosphore phosphorus saccharum officinarum sampling sao paulo soil management statistical methods surface layers triticum aestivum utilisation des terres