Min Li1, 2 , Bingcheng, Si1, 2
1. College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
2. Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N5A8, Canada
In water-saving irrigation management, the water consumption is greatly reduced by avoiding evaporation and over-watering with water-efficient irrigation equipment and techniques. If soil water content (θ) distribution of the field can be accurately and continuously determined, the water can be further saved by applying different irrigation schedules at different locations. However, there is no instrument that can continuous measure θ both temporally and spatially at the field scale. The objective of this study was to evaluate the capability of the single-probe heat pulse (SPHP) method to determine θ, based on which the actively heated fibre optic-distributed temperature sensing (AHFO-DTS) technique can extend θ measuring scale from one single point to the field scale. This study experimentally determined soil thermal contact conductivity ( H ) of the single probe and estimated θ values from the H (θ) relations. Three different textured soils over a wide range of θ were measured by three single probes. The results showed that H values of the same soil increased with increasing θ. At the same θ, H values decreased as soil texture became finer. The H (θ) relations were linear fitted; however, the slopes and intercepts of three probes for the same soil were different. By unifying these differences, probes 2 and 3 provided satisfactory θ estimates for all soils (± 0.04 m3 m-3). This study proved the feasibility of the SPHP method on θ measurement and the potential of in situ θ monitoring at the field scale using the AHFO-DTS system.
