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This article in SSSAJ

  1. Vol. 76 No. 6, p. 1938-1945
     
    Received: Feb 28, 2012
    Published: October 4, 2012


    * Corresponding author(s): kunio@bio.mie-u.ac.jp
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doi:10.2136/sssaj2012.0070

Micro-Chilled-Mirror Hygrometer for Measuring Water Potential in Relatively Dry and Partially Frozen Soils

  1. Kunio Watanabe *a,
  2. Megumi Takeuchia,
  3. Yurie Osadaa and
  4. Kazumasa Ibatab
  1. a Faculty of Bioresources, Mie Univ. 1577 Kurima-machiya, Tsu, 514-8507 Japan
    b Yamatake Corporation, 1-12-2 Kawana, Fujisawa, Kanagawa, 251-8522 Japan

Abstract

Estimating water potential in a relatively dry soil is fundamentally important, not only for predicting soil water flows in arid areas or during the evaporation process, but also for understanding soil freezing processes. A micro-chilled-mirror hygrometer (FINEDEW) that does not require a sampling chamber and has a rapid response time has recently been developed. The sensor head can be inserted into a soil sample. We confirmed that FINEDEW directly and quickly measures soil water potential in the range of less than −500 kPa in soil under near-equilibrium conditions and in the range of less than −1000 kPa in soil under evaporation at room temperature. The FINEDEW hygrometer was also applied to frozen soil at temperatures between −20 and −0.5°C. At equilibrium, regardless of soil type and freezing–thawing processes, the measured potential corresponded to the calculated potential determined using the Clausius–Clapeyron equation. Soil water potential was found to require time to reach equilibrium after a temperature change. This is thought to be because ice in the soil pores required time to acquire a new equilibrium geometry.

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Copyright © 2012. Copyright © by the Soil Science Society of America, Inc.