GPR ground-wave parameters changes due to variation of soil moisture

The soil moisture distribution is important in terms of assessment of agricultural conditions for plant cultivations. The aim of this study is to develop methodology for monitoring soil moisture by the use of goundpenerating radar (GPR). This non-invasive geophysical method has been widely introduced for this purpose for the last decade. However, there is still lack of routinly application in agriculture. The main reasons are timeconsuming data processing and aqusition, particulary for multi-offset measurments. In order to fill this gap we tried to adapt single-offset measurment. Our field study contained several measurments for different time span after ground irrigation. We used 800 MHz shielded and 200 MHz unshelded antennas. We focused on ground wave which propagates just beneath the surface. We observed relative velocity and amplitude spectrum changes of air and ground waves after water irrigation. These changes has an explanation in electromagnetic wave propagation theory. Water irrigation causes the increase of ground wave time arrivals and shift of amplitude spectrum towards lower frequencies.