Submitted to: International Atomic Energy Agency
Publication Type: Other
Publication Acceptance Date: 9/1/2014
Publication Date: 9/8/2014
Citation: Evett, S.R., Schwartz, R.C., Casanova, J.J., Anderson, S. 2014. A new soil water and bulk eletrical conductivity sensor technology for irrigation and salinity management. International Atomic Energy Agency.
Technical Abstract: Many soil water sensors, especially those based on electromagnetic (EM) properties of soils, have been shown to be unsuitable in salt-affected or clayey soils. Most available soil water content sensors are of this EM type, particularly the so-called capacitance sensors. They often over estimate and sometimes underestimate water content in saline and salt-affected soils due to severe interference from the soil bulk electrical conductivity (BEC), which varies strongly with temperature and which can vary greatly throughout an irrigation season and across a field. Yet, the ability to be able to measure both the soil water content and BEC can be helpful for the management of irrigation and leaching regimes. A new technology that is promising is the waveguide-on-access-tube (WOAT) system based on time domain reflectometry (TDR) principles, recently developed by scientists at the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas. The system can be installed to depths greater than 3 m in 20-cm sensor segments to cover as much of the crop root zone as is needed for irrigation management or for determination of crop water use and water use efficiency. BEC can be easily measured with the WOAT design. The ability to measure soil BEC enables better management of salt affected soils and monitoring of environmental contamination. This system is less sensitive to interference from soil BEC than are conventional TDR systems and is much less sensitive to BEC effects than other EM systems. The WOAT sensor platform includes wireless communication that enables remote access to data. The WOAT will be a practical, multi-segment, down-hole access-tube-based system that uses new, relatively inexpensive TDR technology to accurately and automatically determine soil water content and BEC in 20-cm thick soil layers in undisturbed soil. This device will be useful in irrigation and salinity management, determination of crop water use and water use efficiency, and in watershed and environmental management.