Surface soil moisture monitoring with near-ground sensors: Performance assessment of a matric potential-based method

This study develops an indirect method for the estimation of surface soil moisture (SM) by means of monitoring in situ soil water potential. Field work was carried out in ten sampling units selected according to coverage, soil, and topographic factors. Relative humidity and soil temperature were hourly measured to assess the soil-water potential through Kelvin's Law for each sampling unit. Water potential was used as input in the soil moisture retention curve for field conditions to assess SM by fitting the Fredlund-Xing model. To verify the performance of our approach, we measured the surface volumetric SM by the gravimetric method for 2,211 soil samples collected in the same survey period. Results show a non-linear relationship between gravimetric SM and the indirect estimation displaying a determination coefficient of 68.4%. The proposed approach is a suitable exploratory alternative to support continuous SM monitoring studies. (C) 2020 Elsevier Ltd. All rights reserved.