Calibration of TDR coil probe for the soil moisture measurement

Abstract

Soil moisture change in the surface thin soil layer (0-5cm depth soil layer) affects remarkably exchange of water and energy in soils-atmosphere continuum and water resources management. Knowing soil moisture in the surface thin soil layer is also important for the high quality validation of the satellite soil moisture measurement. A tiny sensor of coil probe (CP) of time domain reflectometry (TDR) developed in laboratory by Nissen et al.(1998) was slightly improved in sensor length for the field soil moisture measurement in the surface thin soil layer, which was made of brass and enamel wires (45mm in diameter and 40mm in length). Calibration experiments were conducted to obtain the fundamental characteristics of soil moisture measurement and working conditions of CP. The results suggest that CP can measure precisely soil moisture as same as two-rod TDR probe and apply to the field soil moisture measurement in the surface thin soil layer.