Effect of land slope on some soil physical and hydraulic properties

Pore dimensions and pore-size distribution affect the amount of infiltration. The aim of this study is determination of the infiltration rate, saturated hydraulic conductivity and porosity changing in different slope gradient. Field experiments were conducted in a loamy soil with different slope gradient. Soil surface slope of, 0, 10, 20, 30 and 40 degrees were selected. For each slope, water infiltration experiments were carried out using a double ring and a tension infiltrometer at water pressure heads of +10, -6, -9 and -15 cm, in three replications. Totally 60 water infiltration experiments were carried out. Results indicated that double ring method overestimate the saturated hydraulic conductivity than tension infiltrometer method. In both double ring and tension infiltrometer methods, the saturated hydraulic conductivity values decreased with increase in slope gradient. The particle density in five slopes was constant approximately. The bulk density values of soil were increased with increase in slope. The total, macro and meso porosity were decreased with increase in slope, thus the decreasing of infiltration rate in high slopes can be interpreted.