Thermal property values of a central Iowa soil as functions of soil water content and bulk density or of soil air content

Bing Tong, Dilia Kool, Joshua L. Heitman, Thomas J. Sauer, Zhiqiu Gao, Robert Horton

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Soil thermal properties play important roles in dynamic heat and mass transfer processes, and they vary with soil water content (θ) and bulk density (ρb). Both θ and ρb change with time, particularly in recently tilled soil. However, few studies have addressed the full extent of soil thermal property changes with θ and ρb. The objective of this study is to examine how changes in ρb with time after tillage impact soil thermal properties (volumetric heat capacity, Cv, thermal diffusivity, k, and thermal conductivity, λ). The study provides thermal property values as functions of θ and ρb and of air content (nair) on undisturbed soil cores obtained at selected times following tillage. Heat pulse probe measurements of thermal properties were obtained on each soil core at saturated, partially saturated (θ at pressure head of −50 kPa) and oven-dry conditions. Generally, k and λ increased with increasing ρb at the three water conditions. The Cv increased as ρb increased in the oven-dry and unsaturated conditions and decreased as ρb increased in the saturated condition. For a given θ, a larger ρb was associated with larger thermal property values, especially for λ. The figures of Cv, k and λ versus θ and ρb, as well as Cv, k and λ versus nair, represented the range of soil conditions following tillage. Trends in the relationships of thermal property values with θ and ρb were described by 3-D surfaces, whereas each thermal property had a linear relationship with nair. Clearly, recently tilled soil thermal property values were quite dynamic temporally due to varying θ and ρb. The dynamic soil thermal property values should be considered in soil heat and mass transfer models either as 3-D functions of θ and ρb or as linear functions of nair. Highlights: Thermal property values for a range of θ and ρb were measured on undisturbed soil cores. Freshly tilled soil thermal property values were quite dynamic temporally. The thermal property values of a tilled soil were described as 3-D surfaces with θ and ρb. The thermal property values of a tilled soil varied linearly with nair.

Original languageEnglish
Pages (from-to)169-178
Number of pages10
JournalEuropean Journal of Soil Science
Volume71
Issue number2
DOIs
StatePublished - 1 Mar 2020
Externally publishedYes

Keywords

  • air-filled pore space
  • bulk density
  • soil thermal property
  • soil water content
  • thermal conductivity
  • thermal diffusivity
  • tillage
  • volumetric heat capacity

ASJC Scopus subject areas

  • Soil Science

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