Effect of Land Slope on Infiltration and Some Physical Properties of Soil

Infiltration rate influenced by several parameters such as land slope. Pore dimensions and pore-size distribution affect depth of infiltration. The aim of this study was determination of the infiltration rate and porosity changes in different land slopes. Field experiments were conducted in a loamy soil with different slopes. Soil surface slopes of 0, 10, 20, 30 and 40 degrees were selected. For each slope, infiltration experiments were carried out using double ring for saturated condition and tension infiltrometer for unsaturated condition at water pressure heads of +10, -6, -9 and -15 cm in three replications. The saturated hydraulic conductivity, at different slopes, was calculated using double ring and tension infiltrometer data. Total porosity of the soil was estimated from soil bulk density and particle density using Flint and Flint procedure for different slopes. Macro and meso porosity values, for different slopes, were calculated using Watson-Luxmoore and Dunn-Philip procedures. Micro porosity values were calculated in different slopes according to the total, macro and meso porosity. Results indicated that double ring method overestimated the saturated hydraulic conductivity rather than tension infiltrometer method. In both double ring and tension infiltrometer methods, the saturated hydraulic conductivity values decreased with increase in slope. The particle density in five slopes was approximately constant. 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 decreasing infiltration rate at high slopes can be interpreted.