Hydraulic properties under different water repellency levels

Water repellency increases soil infiltration opportunity time. Also soil hydraulic properties affects by soil water repellency. The main objective of this study was to compare the hydraulic properties of soils under different water repellency levels. Therefore, Three levels of water repellency (zero, weak and strong) were artificially created in a silty clay loam soil by adding urban sewage sludge (S0=0:100; S50=50:50 and S80=80:20 sludge weight: soil ratio). Soil water retention curve and water repellency were determined using sand box and pressure plate apparatus and water drop penetration time (WDPT) method, respectively. Van Genuchtens parameters (n, α, m, θs, θr) were determined using RETC software. The results showed that an addition of urban sewage sludge to soils led to an increased WDPT (61 and 25 times) in the water repellency Soils (S80 and S50) .water content corresponds to matric potentials has changed with increasing soil water repellency, also soil water retention curve has changed to biomodal curve in the repellent soils. It shows that the Van Genuchtens parameters affected by water repellency. Also, adding of urban sewage sludge on the soil hydraulic conductivity was significant (P ≤0.0001) and resulted in a decreased 33.80-46.20% in in soil hydrophobicity.