In Situ Moisture Release Curves to Determine Soil Water Characteristics.

Recent advances in lab instrumentation have established straightforward and accurate methods for creating moisture release curves (MRC), yet creating a spatially dense network of hydraulic properties data from samples is a daunting task.  Thus, there remains a need to characterize soil hydraulic properties in situ. Although field-generated MRCs are not new, reliance on water potential given by tensiometers with limited range, or solid matrix sensors that are often inaccurate, has brought only modest success. Data from these field methods seldom matches the data obtained on the same soils using the more precise laboratory methods. The objective of this study is to determine if calibration improvements of a solid matrix water potential sensor can finally overcome the challenge of matching field and lab MRCs. To do this, volumetric water content and water potential sensors were collocated in different soil types and depths and monitored during wetting and drying events over two years. Field cores were taken and tested using a Wind-Schindler drying technique combined with a chilled mirror hygrometer. Data show an good match between the field and laboratory techniques indicating important opportunity for spatially distributed environmental monitoring stations to include moisture release information as a part of their output, supplying critical data to models.