On the influence of coarse fragments on soil water retention

[1] The classical determination of the soil water retention curve (SWRC) by measuring soil water content θ at different matric potentials ψ using undisturbed soil samples is time consuming and expensive. Furthermore, undisturbed soil sampling can be an intricate task when coarse soil fragments (>2 mm) are present. The objective of this study was to test whether tension infiltrometry could be used to estimate the SWRC of stony soils and to investigate to what extent the coarse fragments affected the SWRC. Tension infiltrometer measurements were conducted at 44 sites with stony soils in arid Chile. Soil water retention curves obtained through inverse modeling were compared with laboratory-determined water retention (θ, ψ) data pairs. Differences were found to be small, confirming the applicability of the inverse modeling method. Rock fragments had a significant indirect influence on water retention for matric potentials higher than −0.30 kPa, which could be attributed to their direct influence on pore size distribution.