Comparing Methods to Determine Hydraulic Conductivities on Stony Soils

Determination of the field-saturated hydraulic conductivity (K-fs) can result in very high variability due to soil heterogeneity, the measurement method, the number of replications, and the K-fs calculation method used. Especially for dryland soils, stoniness can influence infiltration rates significantly. To identify this variability as well as its source, six widely used measurement methods were compared: single-ring (SR) and double-ring (DR) infiltrometers, the constant-head well infiltrometer (CH), the inverse auger hole method (IA), the tension infiltrometer (TI), and the rainfall simulator (RFS). The six methods were applied at three locations in a semiarid part of Chile that showed moderate (15%) to high (55%) stoniness. Additionally, K-fs variations due to different calculation techniques for the same measurement method were thoroughly investigated. Results showed that different calculation techniques sometimes gave significantly different estimates of K-fs when using the same data set, and those relative differences were conserved among measurement locations. The borehole methods (IA and CH) showed high discard rates due to stoniness, making these methods less appropriate. The SR and DR methods gave considerably higher K-fs estimates, while the RFS and TI proved good candidates as reference methods for stony soils, with low failure rates and coefficients of variation.