New time-domain response system calibration techniques are described for determining dry density and water content of soil based on electromagnetic wave propagation through it. For example, one disclosed technique use the ratio between V1, the voltage difference between the peak and trough of the response signal, and Vf, the long-term (i.e., steady-state) response of the system to the input pulse. These values are measurable, even for highly conductive soils, and calibration done in a laboratory can be applied to measurements taken in an uncontrolled field environment.