Water movement through soil in response to matric-potential and temperature gradients: I. Theoretical developments
2001
Ashraf, M. (On Farm Water Management, Bhalwal (Pakistan))
The theory of Philip and de Vries1 has been used extensively to describe water movement in response to water-content and temperature gradients. Their theory is applicable for homogeneous and salt free soils. The same theory is recast in terms of matric potential and temperature gradients to make it applicable in saline and heterogeneous soils. The theory is also extended to allow for the effects of temperature and osmotic potential on relative humidity. Thermal vapour diffusivity, with and without the temperature dependence of relative humidity, is discussed. It is concluded that the effect of temperature on relative humidity may be ignored in the temperature range (20-50 degree centigrade), generally encountered in agricultural soils. The isothermal vapour conductivity due to matric potential gradient in extremely small except at very low water contents and the isothermal vapour conductivity due to osmotic potential gradient (Kvo).is the smallest among the vapour conductivies. Salt concentration has negligible effects on Kvo.
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