Calibration and field verification of TDR based on phase difference for measuring soil water content

The objective of this study is to test the performance of time domain reflectometry(TDR) based on phase difference detecting with independent intellectual property rights measuring soil water content.A laboratory calibration experiment using soil column was conducted to obtain the calibration equations for TDR measuring soil water content,and field test was also conducted to validate these calibration equations.The results showed that,there was no significant effect of bulk density on the calibration relationship between time measured by TDR and soil water content,but the soil texture had a significant effect.It could be calibrated using three calibration formulas in sandy soil,loamy clay soil and clay soil,respectively.All of R2 were greater than 0.98,and the estimated standard errors were less than 0.020 cm3/cm3.The root mean square errors were less than 0.035 cm3/cm3 for TDR measuring soil water content in the field.Therefore,this new TDR instrument was reliable to measure soil water content in the field using calibration equations from the laboratory experiments.