An Improved Calibration Determining Soil Bulk Density with Time Domain Reflectometry

Abstract

Soil bulk density (ρ _b ) is one of the most important parameters in the study of agriculture and geotechnical engineering. Time domain reflectometry (TDR) has been used to accurately determine ρ _b based on the relationships among ρ _b , θ _g , and dielectric constant (K). The objective of this study is to develop a simple and accurate TDR equation to measure soil bulk density. Laboratory measurements of soils with different textures were carried out to establish the TDR–bulk density equation, and then the performance of this improved equation was evaluated with independent soils in laboratory and field conditions. Results indicated that the established equation could provide accurate ρ _b estimation, where the TDR–bulk density equation was associated with <5% error both under laboratory and field conditions. It indicated that in the study of tillage management and geotechnical engineering, the established equation could be employed as a useful reference method for bulk density measurement when using TDR.

Keywords:

• Soil structure
• soil water
• testing methodology

Acknowledgments

This research was funded by the Innovation Knowledge Project of the Chinese Academy of Sciences (Grant No. KSCX2-EW-J-5) and the National Science and Technology Pillar Program (Grant No. 2006BADA3B04).