Soil water content determination using network analyzer reflectometry methods

Time domain reflectometry (TDR) can be a good automated system for measurin g soil water content (theta(v)); however, TDR can yield noisy data and cann ot measure frequency dependence of the dielectric constant (K-a). Using a n etwork analyzer (NA) with a low-noise synthesized TDR, parallel-rod probes, and a resonant waveguide approach, theta(v) was measured from 0.02 to 0.25 m(3) m(-3) within the range of 50 to 900 MHz in sand. Below 100 MHz, K-a w as higher than it was within the range of 100 to 900 MHz; however, in the 1 00 to 900 MHz range K-a did not change with frequency. The NA compared favo rably with TDR.