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Natural regeneration of endemic tree Prosopis tamarugo in the Pampa del Tamarugal is almost absent. Soil salinity is probably an important barrier for tamarugo seedling establishment. Despite there are numerous techniques to manage soil salinity, substrates prepared using mix of saline soil and sand are poorly known. In the present study, the effect of different experimental substrates was evaluated on root growth and seedling survival of P. tamarugo. The experimental soils were prepared using natural soil and sand in equal proportion (1:1) and using a double proportion of sand (1:2). Saline soil used as control treatment. Bulk density (B.D.), electrical conductivity (E.C.) and sodium and chloride concentration was characterized for the three experimental soils. Seedling root growth was evaluated through length and root biomass, root/shoot ratio (R/S) and specific root length (SRL). Root biomass was also monitored during the study. Aerial growth was determined using leaf formation. Additionally, salt content in tissues and survival of seedlings were evaluated at the day 50 of initiated of experiment. The natural soil presented a E.C. (176 dS/m) and B.D. (0.9 g/cc) higher tan experimental soils 1:1 (132 dS/m and 1.1 g/cc) and 1: 2 (140 dS/m and 1.4 g/cc). Sodium and chloride concentration decreased on average by 37 and 41% in 1:1 and 1:2 soils with sand amendment respectively in comparison with the natural saline soil. Seedlings grown in the two amendment soils showed significant growth in root length, root biomass, R/S and SRL and significantly increased their root biomass by day 30. They also exhibited a lower sodium and chloride concentration in their tissues, more