Bulk Density Effects on Soil Hydrologic and Thermal Characteristics: a Numerical Investigation
Date
Authors
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Research Projects
Organizational Units
The Department of Agronomy seeks to teach the study of the farm-field, its crops, and its science and management. It originally consisted of three sub-departments to do this: Soils, Farm-Crops, and Agricultural Engineering (which became its own department in 1907). Today, the department teaches crop sciences and breeding, soil sciences, meteorology, agroecology, and biotechnology.
History
The Department of Agronomy was formed in 1902. From 1917 to 1935 it was known as the Department of Farm Crops and Soils.
Dates of Existence
1902–present
Historical Names
- Department of Farm Crops and Soils (1917–1935)
Related Units
- College of Agriculture and Life Sciences (parent college)
Journal Issue
Is Version Of
Versions
Series
Department
Abstract
Soil bulk density (ρb) is commonly treated as static in studies of land surface dynamics. Magnitudes of errors associated with this assumption are largely unknown. Our objectives were to: i) quantify ρb effects on soil hydrologic and thermal properties, and ii) evaluate effects of ρb on surface energy balance and heat and water transfer. We evaluated six soil properties, volumetric heat capacity, thermal conductivity, soil thermal diffusivity, water retention characteristics, hydraulic conductivity, and vapor diffusivity, over a range of ρb, using a combination of six models. Thermal conductivity, water retention, hydraulic conductivity, and vapor diffusivity were most sensitive to ρb, each changing by fractions greater than the associated fractional changes in ρb. A 10% change in ρb led to 10-11% change in thermal conductivity, 6-11% change in saturated and residual water content, 49-54% change in saturated hydraulic conductivity, and 80% change in vapor diffusivity. Subsequently, three field seasons were simulated with a numerical model (HYDRUS-1D) for a range of ρb values. When ρb increased from 1.2 to 1.5 Mg m-3; 25% increase, soil temperature variation decreased by 2.1°C in shallow layers and increased by 1°C in subsurface layers. Surface water content differed by 0.02 m3 m-3 for various ρb values during drying events but differences mostly disappeared in the subsurface. Matric potential varied by >100 m of water. Surface energy balance showed clear trends with ρb. Latent heat flux decreased 6%, sensible heat flux increased 9%, and magnitude of ground heat flux varied by 18% with a 25% ρb increase). Transient ρb impacted surface conditions and fluxes, and clearly it warrants consideration in field and modeling investigations.
Comments
This is the peer reviewed version of the following article: Kojima, Yuki, Joshua L. Heitman, Masaru Sakai, Chihiro Kato, and Robert Horton. 2018. "Bulk Density Effects on Soil Hydrologic and Thermal Characteristics: a Numerical Investigation." Hydrological Processes, which has been published in final form at doi: 10.1002/hyp.13152. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.