A novel research tool for simultaneous measurement of liquid and ice soil water contents, soil thermal properties and electrical conductivity

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Soil water and heat are key variables in crop production, flooding, runoff, and greenhouse gas emission from soils. They also directly affect the pathway and fate of agrochemicals or wastes, such as runoff to rivers or lakes, leaching to groundwater, emission to the atmosphere, or uptake by plants. Generally, quantifying soil water and thermal regimes in non-level landscapes needs frequent measurements in space and time because of the transient nature of soil water and thermal regimes particularly during freezing and thawing. The lack of fast and efficient measurement methods hinders our understanding of soil water dynamics and thermal regimes in sloping landscapes. Further, in cold regions, freezing and thawing make liquid and ice water coexist in soil. The applicant has five stations for monitoring hydrological processes in the five typical landscape and hydrological units. However, there is a lack of facility for monitoring soil thermal properties regime that are intertwined with hydrological processes. Recently, a multipurpose heat pulse probe (MPHPP) was introduced. The MPHPPs can measure liquid soil water content, and ice content, as well as soil heat capacity, thermal diffusivity, soil temperature and soil electrical conductivity. MPHPPs allow tracking the transient changes in soil water, thermal regimes, and salt concentration in the same volume at the same time. The MPHPPs can be built in our laboratory with limited cost. However, because of a large amount of multi-component measurements to be taken in a short time, a rapid and multi-channel datalogger, CR9000XC, is needed in order to automate the MPHPP measurements at multiple depths.  The proposed research would be an important addition to the available hydrological monitoring infrastructure at the five landscape positions and hydrological units. The frequent and accurate measurement of soil water contents and thermal regimes is critical to understanding the mechanisms of hydrological processes that are critical for crop water use efficiency and wildlife habitats. An understanding of water dynamics, thermal regimes, is a prerequisite for improving the water use efficiency and environmental quality of agri-ecosystems, and consequently the health of Canadians.