Sensitivity of capacitance probes to soil cracks

Abstract

Capacitance probes are used in agriculture to allow the real time measurement of soil moisture to assist in irrigation scheduling. This type of frequency domain measurement system is fast replacing the older, neutron probe technology. Clay soils have a tendency to form cracks around the access tube as they dry. In dry conditions, these cracks may cause the sensors to give readings which could be lower than the actual moisture content. In wet conditions (immediately following a rainfall or irrigation event) the cracks could fill with water and cause the sensors to give a reading higher than the actual moisture content. Soil and water based experiments were undertaken in order to gain an understanding of the behaviour of a Sentek EnviroSCAN ® in terms of soil moisture, soil temperature, and salinity effect allows conclusions to be drawn on how these probes respond in cracking clay soils.