Three-and-a-half Decades of Progress in Monitoring Soils and Soil Hydraulic Properties

This article will focus on the evolution of soil water monitoring and determination of soil hydraulic properties with emphasis on large-scale soil-plant-atmosphere (SPA) experiments, beginning with the lead author's participation in this work in 1976 at University of California, Davis and evolving to current experiments involving the co-authors. Experiments to be highlighted include the HAPEX-MOBILHY (France, 1986), HAPEX-Sahel (Niger, 1992), NASA BOREAS (Canada, 1994-96), to the current NASA AirMOSS project (2011-15). This article will demonstrate sample data from a wide range of technology from neutron probe, to capacitance probes and other dielectric sensors, to the principle for the P-band radar in the current NASA AirMOSS project.