Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil

The impact of biochar pyrolyzed at 450 ± 10 °C and made from date palm (D) and olive tree (O) wastes on the hydrophysical characteristics of sandy soil was assessed in this study through a laboratory column experiment. Two different application rates (wt/wt) were tested: 1% and 5%. The prepared biochars were added at 25 °C to the upper 10 cm layers of the soil columns. The outcome showed that, in comparison to O, D biochar possessed slightly less alkalinity and more salinity. The corresponding values for pH and EC in D and O biochars were 8.99 and 4.10 dS/m and 9.42 and 2.17 dS/m. Therefore, these biochars should be used cautiously as soil amendments in saline–sodic soils because of their excessive salinity, especially D biochar. On the other hand, they are safe to employ as amendments in acidic and non-saline soils. Cumulative evaporation (CE) decreased with all treatments, and the highest decrease of 10.2% (compared to control treatments after five cycles) was observed for D biochar and 5% application rate (D450, 5%). Moreover, the available water increased by 182%, 158%, 153%, and 29% for D450, 5%, D biochar and 1% application rate (D450, 1%), O biochar and 5% application rate (O450, 5%), and O biochar and 1% application rate (O450, 1%), respectively. The saturated hydraulic conductivity decreased by 94.8%, 87.0%, 76.6%, and 35.1% for D450, 5%, D450, 1%, O450, 5%, and O450, 1%, respectively. It was also found that the date palm biochar was more efficient than olive waste biochar in decreasing the cumulative infiltration and infiltration rate. Finally, this study showed the superiority of biochar prepared from date palm trees over that prepared from olive tree waste for improving the hydrophysical properties of sandy soil.