Effect of wettable and hydrophobic biochar addition on properties of sandy soil

Sandy soils have high hydraulic conductivity and low retention ability for water and nutrients, resulting in low fertility. As water retention of coarse-textured soil is substantially more sensitive to the amount of organic carbon than fine-textured soils, the amendment of sandy soils with biochar is often used. The objective of this study was to find the effect of water-repellent and wettable biochar addition on the porosity, P, saturated hydraulic conductivity, Ks, soil water retention curves, SWRC, plant available water content, AWC, water drop penetration time, WDPT and contact angle, CA of sandy soil. It was observed that biochar addition led to a significant increase in both P and AWC in all treatments, indicating a positive impact on soil water retention. The water-repellent biochar addition led to the statistically significant decrease in Ks, caused by the water-repellent biochar particles between the sand grains preventing water movement in the soil. The wettable biochar addition led to a statistically insignificant decrease in Ks. The addition of very strongly and extremely water-repellent biochar induced slight severity of water repellency (40° ≤ CA < 90°) and did not induce persistence of water repellency (WDPT < 5 s) in the biochar-soil mixture. After an addition of wettable biochar, the biochar-soil mixtures were wettable. A relation between the Ks and CA in sandy soil amended with wettable and hydrophobic biochars was found, which is a novelty of our study.