Particle size curves were obtained using a tested and calibrated settling tube (Brambati et al., 1973) for the sandy fraction and an X-ray Micromeritics Sedigraph 5100 for the finer fraction (Johnston and Swanson, 1982; Asadov et al., 2001; Artigas et al., 2005). Organic matter content was measured by L.O.I. method (Tiessen and Moir,1993).