The hydraulic properties of a sandy soil treated with gel-forming soil conditioner

The irrigated sandy soils in the arid regions have limited water retention capacity. A laboratory study was conducted on a sandy soil to investigate the effect of a gel-forming soil conditioner (Jalma) on the soil water retention relationship (psi-theta), soil water diffusivity (D(theta)), and saturated hydraulic conductivity (K-s). Zero, 0.2, 0.4, and 0.8% of Jalma (J) were uniformly mixed with a sandy soil (Typic Torripsamments). The soil water distribution, horizontal wetting front advance (X), and infiltration (I) were measured. The results indicate: (1) the available water content increased exponentially with increasing J, but K-s decreased exponentially with increasing J; (2) the X and I decreased with increasing J, and their relationships with time can be described by power functions; (3) the D(theta) increased with increasing theta and decreased with increasing J. Two approaches were taken to calculate K(theta) by using: (1) the D(theta) functions and the complete theta-psi relationship, and (2) the measured K-s and a limited range of the theta-psi relationship. The two approaches were found to be comparable, but the second approach is recommended since it required simpler and available data. The calculated K(theta) increased with increasing theta and decreased with increasing J. Generally, this study revealed that the addition of gel-conditioner improved the hydraulic properties of sandy soil and that the best rate of Jalma is 0.4%. This addition rate limited deep percolation losses while maintaining adequate infiltration and water retention characteristics.