Using a Time Domain Reflectometry (TDR) probe (rod length 30 cm) to estimate the soil water content of a wet sandy loam soil. From the waveform we conclude that the two-way travel time of the electromagnetic wave along the rods in the soil is 10 ns (1 ns = 1?10-9 s). Calculate the volumetric wetness of the soil using the Topp and Davis (1985) equations. Approximate eqn is vv=c/(Er)^.5 Dielectric constant from inserting v=2L/t into above eqn. so Er=(ct/2L)^2