Calibration of Buriable Soil Moisture Sensors Made Inside the Country for TDR System in Different Soil Textures

Measuring soil moisture by time domain reflectometry (TDR) is an indirect, safe and fast method, which is on the basis of the dielectric constant of the soil. Applying TDR has an adequate result for most soil conditions, but for atypical conditions such as salinity and high organic matter soils associated with the error. The solution is to perform high-precision calibration to be all situations to estimate the soil moisture. The aim of this study was calibrated burial sensor used in order to increase the accuracy of TDR soil moisture of different textures, which is simulated in the IRAN. In this study, three types of soil texture viz. heavy, medium and light soil were tested in the order of forest lands, crops and rangeland at east Azarbaijan, IRAN. The soil moisture variations were measured by TDR and gravitational methods. Several linear and nonlinear models were developed to model of soil moisture as a function of dielectric constant and measured moisture. Then, a few calibrated appropriate linear and polynomial equations were presented for different soil texture that calculate the actual moisture based on the dielectric constant and the measured moisture measured by the TDR method.