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Soil Science Society of America Journal Abstract -

Some Aspects of the Kinetics of Moisture Flow into Unsaturated Soils1


This article in SSSAJ

  1. Vol. 24 No. 2, p. 81-85
    Received: Sept 18, 1959
    Accepted: Nov 19, 1959

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  1. J. W. Biggar and
  2. Sterling A. Taylor2



The movement of water into an air-dry silt loam soil was studied as a function of temperature. The results are interpreted with the use of the Arrhenius equation in terms of energy barriers, and the activation energies necessary to overcome the barriers were calculated from the experimental measurements. Activation energies of 1 to 3 kilocalories per mole of water taken up were found.

Qualitative relationships were observed between the energy barriers found in the system studied and the soil particle size, bulk density and wetting suction.

The rate of water entry into soil and the rate of advance of the wetting front was faster in soils at lower bulk density. This effect is about the same at all temperatures; consequently, the activation energies are not significantly different. Activation energies appear to be high for the finer size fraction of Millville silt loam. The barriers opposing water movement into soil appear to operate at the air-water-interface associated with the advancing water front.

Theoretical consequences of these findings provide a physical explanation of the wetting front, an explanation for hysteresis, and a basis for including shrinking and swelling as contributing factors in modifying the rate of flow of water through soil.

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