Ring Size Dependence of Field Saturated Hydraulic Conductivity Measurements in a Clay Loam Soil

Field saturated hydraulic conductivity (Kfs) is one of the most important soil properties that considerably contribute to soil quality. However, specifically in the structured soils, the measurement of Kfs is difficult and time-consuming. Therefore, verifying the simple and fast methods for Kfs measurement is needed for effective soil monitoring. This study was conducted to investigate the effect of ring size (rings with diameters of 5.5, 10.88, 16, and 31.8 cm) on the Kfs measured with simplified falling head (SFH) single ring method in a structured clay loam soil. Furthermore, the effect of conventional tillage on Kfs was assessed and the Kfs measured with double ring (DR) method and SFH procedure was compared. Results showed that while the ring size affected the measured Kfs, the discrepancy between Kfs results of given ring size compared to the smallest ring size (d = 5.5 cm) was practically negligible (factor of discrepancy ≤ 0.27). The effect of tillage operations on the measured Kfs was substantial (discrepancy between Kfs results of 2.1 to 3.1). The SFH and DR techniques yielded statistically different means of Kfs. However, the discrepancy between the Kfs values obtained with the SFH method using the largest ring size and the Kfs values determined with DR method was practically negligible (factor of discrepancy < 0.37). The coefficient of variation of Kfs values obtained with DR was also higher than the SFH measurements. In conclusion, the mean Kfs values obtained with SFH technique were appropriate to monitor the effect of tillage.