Soil moisture sensor systems and methods are disclosed. An exemplary soil
moisture sensor system includes a sensor configured to receive soil
between parallel plates. A capacitive measurement circuit is operatively
associated with the parallel sensor. A processor receives input from the
capacitive measurement circuit. The processor determines moisture content
of the soil between the parallel plates of the sensor based on the
flowing relationship:.times..times. ##EQU00001## where L is the length
of the sensor, H is the height of the sensor, and d is the separation
between the parallel plates of the sensor.