Impact of Polymers and Biochar on Hydro-Physical Properties of Sandy Soil.

Water scarcity in arid and semi-arid regions is a major concern for agricultural authorities around the world. Saudi Arabia (SA) located in arid environment is suffer from limited water resources with a dominion of sandy soil which characterized by low water-holding capacity and high infiltration rate. One of the challenges in SA is to develop water management techniques can conserve water and increase water use efficiency. The recent trend in the world is the application of soil amendments such as biochar, compost, and polymers for improving water productivity through enhancement soil hydro-physical properties. A laboratory column experiments were conducted to investigate the effects of date palm waste biochar (pyrolyzed at temperatures 400-450 °C) and synthetic polymers on hydro-physical properties of sandy soil. The experiment consist of five rates of biochar (0, 2, 4, 6 and 8%), five rates of the polymers (0, 0.2, 0.4, 0.6 and 0.8%), and mixture of them. The treatments were set on top 10 cm of surface soil column. The columns were subjected to five wetting/drying cycles (each cycle period is one week) using tap water (EC ? 0.4 dS.m-1) with water application rate of 25 cm3 week-1. Furthermore, a field experiment of tomato was also conducted using same soil amendments. The polymer and/or biochar were mixed with a surface air dry soil making a 10 cm mixture layer with a rates of 0.0, 2, and 4% for biochar, 0.2, and 0.4 % for polymer, and mixture of them. The column experiments results indicated that although both biochar and polymer decreased the waterfront, saturated hydraulic conductivity, and cumulative evaporation of sandy loam soil; however, the biochar was more efficient in improving the soil hydro-physical properties. Moreover, the biochar application led to significant (P<0.05) increases in amount of conserved and retained water compared to the polymer and control soil. The field experiment revealed that the biochar significantly increase the tomato yield productivity compared to the polymer and biochar. Finally, the results strongly suggest positive improvement for hydro-physical properties of coarse-textured soils using date palm biochar. The biochar can be considered more suitable and lower cost than polymer in arid environment. Key Words: Date palm biochar, Polymer, Intermittent evaporation, Water retention, Hydraulic conductivity, Cumulative infiltration.