Calculation of soil water diffusivity using a model for soil moisture profile under different salinity conditions

Abstract EN

A closed formed model modified from that of van Genuchten (1980) was used to fit the data of soil moisture profile ( θ vs.

λ ) from which the slope dλ / dθ can be evaluated and then the soil water diffusivity [D(θ)] can be calculated.

Diffusivity was calculated for three soil textures under different salinity conditions.

The results showed that the model fitted the data very well with 1 % confidence level (R2 > 0.93).

D (θ) increased sharply with soil moisture for all soils but its values were lower when the texture got finer.

At a certain sodium adsorption ratio (SAR), D (θ) increase with the increase of salt concentration (C) of the water infiltrating.

Increasing SAR of water caused a decrease in D (θ) at any level of C.

Same trends were obtained for the values of weighted mean diffusivity.