Comparison of Four In-situ Methods for Measuring Saturated Hydraulic Conductivity

Soil saturated hydraulic conductivity (ks) is one of the most important soil physical properties. Information on spatial and temporal variations of the property is necessary for improvement of soil and water management. The double ring infiltrometer (DR)، single ring infiltrometer (SR)، guelphpermeameter (GP) and tension infiltrometer (TI) methods were compared in a silty loam soil of a farm field on the Shahrekord University campus. The water level during the experiments was kept constant at 11 cmin both of the double and single ring methods. The successive constant pressure heads in the Guelph permameter method were 11 and 19 cm. The experiment with tension infiltrometerwas performed at the tensions of -15، -10، -6، -3 and -1 cm. The mean saturated hydraulic conductivity using the DR، SR، GP and TI methods were 0. 300، 0. 246، 0. 011 and 0. 295 cm min-1، respectively. Statistical analysis using the Duncan''s test showed that there was no significant difference between the measured ks values with the previously mentioned methods; however، hydraulic methods; except GP (P<0. 01). Conductivity as measured by the GP method was much low، than those obtained using the other methods. The main reason for the large difference in ks value between the GP and other methods was a hard layer with low infiltrability at a depth of 25- 30 cm.