Soil Water Evaporation, Isothermal Diffusion, and Heat and Water Transfer1
- D. D. Fritton,
- Don Kirkham and
- R. H. Shaw2
Temperature and water distribution data were taken for a 9- by 11- by 20-cm soil column where wind was the evaporation agent and for a similar soil column where radiation was the evaporation agent. A Webster silty clay loam soil characterized by a soil-water retention curve and an inflow diffusivity versus water content curve was used in the experiments. The experimental results were compared with results calculated from a solution of the diffusion equation normally used to describe isothermal movement of soil water and from a heat and mass transfer solution which accounted for temperature effects. It was found that the isothermal diffusion equation would describe the cumulative evaporation for the wind and for the radiation treatments. The isothermal diffusion equation did not predict the formation of a surface layer of dry soil, and thus, did not describe the water distributions for the radiation treatment for times greater than 20 hours or for the wind treatment for times greater than 200 hours. A heat and mass transfer equation did predict the development of a dry surface layer and did describe the water distribution where temperature gradients were important.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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