Soil Physical Properties at U.S. Climate Reference Network Sites.

The role of in situ soil moisture is getting increased attention in predicting drought, flood, and many other soil moisture related issues in the U.S.  Soil moisture networks are adopting advanced in situ soil moisture measurement sensors, but many of them lack site-specific soil physical property data to evaluate the soil moisture.  The U.S. Climate Reference Network (USCRN) between 2009 and 2011 added in situ soil moisture measurements to 114 above-ground climate monitoring sites across the continental U.S.  At each site, soil moisture Hydra Probes were installed at five soil depths (5, 10, 20, 50, and 100 cm) in three separate soil pits.  During the field install, soil samples were collected from the depths in the pits where the Probes were buried.  Soil bulk density, texture and water potentials at 33 and 1500 kPa indicated strong variations within and between soil pits.  While distinct relationships were detected between the soil texture and water potential with large scatter, no distinct or consistent relationship was detected when comparing the bulk density to texture and the water potential.  Results of these soil properties across the USCRN sites underscore the need to understand how soil properties vary in the field and recognize their impact on soil moisture and the sensor factors that can affect the evaluation of in situ soil moisture.