Still, I don't have a clear idea about TDR and its circuit.
Do anyone know the circuit for a TDR for soil moisture content measurement.

 

I Googled the phrase "TDR for soil moisture content measurement" from your question and a link to this web page popped up:
https://labmodules.soilweb.ca/time-domain-reflectometry/

This paper was referenced in the paper that popped up in the seach:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3362958/

https://www.researchgate.net/publication/271003402_Determination_of_in_situ_moisture_content_in_soils_from_a_measure_of_dielectric_constant

That might clear things up a bit.

 

Only one thread per topic allowed. This thread is closed.
The duplicate thread is located at https://forum.allaboutcircuits.com/threads/time-domain-reflectometry-tdr.164124/#post-1443713