Abstract
In order to understand the soil moisture conditions in fields, many soil moisture sensors have been developed in recent years. In this study, the range of influence of Profile Probe type PR1 soil moisture sensor (hereafter referred to as “PR1”,Delta-T Devices, Ltd) was measured and specific calibration equations were established for Kuroboku and Tachikawa Loam soils. The range of influence of PR1 was estimated to be 10 cm in both horizontal and vertical directions. Standard calibration equations (“Mineral equation”, proposed for mineral soil and the “Organic equation”, proposed for organic-matter rich soil) provided by the manufacturer were found to be invalid for Kuroboku soil. For Tachikawa Loam soil, the Mineral equation was found to be applicable. For precise water content determinations, however, we found that specific calibrations for each of the PR1 sensor may be required. A long-term field measurement indicates that PR1 may be a useful device for profiling soil water content and measuring changes in water content after rainfall events.
