Effect of Biochar and Compost on Hydro-physical Properties of Sandy Soils Alaa Ibrahim, Abdulrasoul Al-Omran, Abdulaziz Al-Harbi and Mohammad I. Al-Wabel Department of Soil Science, Saudi Biochar Research Group, King Saud University, P.O. Box 2460, Riyadh, 11451,4 Saudi Arabia. Corresponding author. Tel.: +966 1 467 8444; fax: +966 1 467 8440. E-mail: rasoul@ksu.edu.sa. ABSTRACT Most of agricultural soils in Saudi Arabia are light-texture soils with low productivity due to low water holding capacity, high infiltration rate, high evaporation and low level of organic matter content. In addition to water shortage problem in which the agricultural sector consumes more than 85% of the total annual water consumption in Saudi Arabia. The trend in recent years has been towards the application of biochar and compost for improving soil productivity through the enhancement of soil structure, bulk density, water holding capacity, water retention, hydraulic conductivity, infiltration and aggregates stability in light-texture soils. A laboratory column experiments were conducted to investigate the effects of date palm waste (biochar) pyrolyzed at different temperatures (400-450 °C) with different particle sizes and application depths on hydro-physical properties of sandy loam soil including: soil water penetrability, infiltration rate, intermittent evaporation, water retention and saturated hydraulic conductivity. Compost and/or biochar were mixed with the air dried soil for making the layer of mixture at rates of 1, 2 and 4% by weight. The thickness of layer were 10 and 20 cm (T10 and T20) from the surface of soil column. The columns subjected to five wetting/drying cycles (each cycle is one week long) by the application of 25 cm3 week-1 of tap water (EC ? 0.4 dS.m-1). The results indicated that applying date palm biochar or compost decreased the waterfront and saturated hydraulic conductivity of sandy loam soil. The cumulative evaporation was the highest with the non-treated soil. The biochar addition caused significant (P<0.05) increases in the amount of conserved and retained water compared to control soil. The values of saturated hydraulic conductivity for the biochar treatments were significantly (P<0.05) lower than those for the control. These results strongly suggest positive improvement for some hydro-properties of coarse-textured soils following date palm biochar addition, especially finer particles (? 1 mm) of biochar. Key Words: Date palm biochar, Compost, Intermittent evaporation, Water retention, Hydraulic conductivity, Cumulative infiltration.