An appraisal on the soil wetting water retention characteristic curve determined from mini disk infiltrometer and sensor measurements

Direct determination of wetting water retention characteristics curve (WWRCC) is time-consuming, needs destructive sampling and invasive sensor placement, and, at times, is difficult to measure due to rapid wetting. The objective of this study was to critically analyze the use of a handy mini disk infiltrometer's (MDI's) measurements for indirect determination of WWRCC parameters (alpha, n) and saturated hydraulic conductivity (K-s). The alpha, n, and K-s were estimated by considering cumulative infiltration (CI), volumetric water content (VWC), and soil water potential (SWP) measurements, divided into 17 subcases and 924 inverse simulations. The inverse simulation was improved by considering measured final VWC as an additional input if alpha, n, and K-s were estimated from MDI measurements. The simulated CI, VWC, and SWP compared well with the measured results with low root mean square error (RMSE) (10(-5) m(3) for CI, <= 10(-2) m(3)/m(3) for VWC, and 10(-1) m for SWP). The mean values determined from all the statistically comparable cases for two soil textures, loam and silt loam, were, respectively, alpha (m(-1)) equal to 1.43 and 0.41, and n equal to 1.5 and 1.61. The WWRCC developed using the mean alpha and n values was close to the measured curves and significantly different from the texture-based pedo transfer function (PTF) estimation. Furthermore, the K-s values estimated from the inverse analysis of MDI measurements were comparable with reference falling head permeameter measurements for both the soils. The observations from this study demonstrated that MDI is a reliable, non-invasive, and non-destructive method for quick indirect estimation of alpha, n, and K-s.

Automated summary

This study analyzed the use of a mini disk infiltrometer (MDI) for the indirect determination of wetting water retention characteristics curve (WWRCC) parameters (alpha, n) and saturated hydraulic conductivity (K-s). The results showed that MDI is a reliable, non-invasive, and non-destructive method for quick estimation of WWRCC parameters.