How does calcium and sodium in saline water affect the potential of different rates and size of sugarcane biochar to soil water repellency remediation?

Abstract

Soil water repellency (SWR) is a growing problem in arid and semiarid regions with non-saline water limitations. The objective of this study was to investigate the potential of different rates and sizes of sugarcane biochar on reducing soil water hydrophobicity when using saline and non-saline water. Eleven sugarcane biochar application rates from 0 to 10% with two different sizes including <0.25 and 0.25-1 mm were studied. The experiment was conducted in two strongly and extremely water-repellent soil. In addition, to investigate the effect of electrolyte concentration on biochar potential for SWR reduction, calcium chloride and sodium chloride electrolyte solutions with 5 concentrations including 0, 0.15, 0.3, 0.45 and 0.6 mol L^-1 were considered. The results showed that both sizes of biochar reduced the soil water repellency. While in strongly repellent soil the 4% biochar was enough to change the soil from strongly repellent to hydrophilic, in extremely water-repellent soil, the use of 8% of fine biochar and 6% of coarse biochar changed the extremely water-repellent soil to slightly hydrophobic and strongly hydrophobic respectively. Increasing the electrolyte concentration caused the expansion of soil hydrophobicity and reduced the positive effect of biochar to water repellency management. Increasing the electrolyte concentration in sodium chloride solution has a greater effect on increasing hydrophobicity than in calcium chloride solution. In conclusion, biochar could suggest as a soil-wetting agent in these two hydrophobic soils. However, the salinity of water and the its dominant ion could increase the amount of biochar for soil repellency reduction.

Keywords: Electrolyte concentration; Soil hydrophobicity; Soil water contact angle; Sugarcane biochar.